TB Manual 4

Manual 4
Design of
Clay Masonry
for Wind and
Earthquake
This publication updates and supersedes the publication
of the same name published by the Clay Brick and Paver
Institute in March 1999.
This manual is intended for use by a structural engineer.

While the contents of this publication are believed to be
accurate and complete, the information given is intended
for general guidance and does not replace the services of
professional advisers on specific projects. Local or State
regulations may require variation form the practices and
recommendations contained in this publication. Think Brick
Australia disclaims any liability whatsoever regarding the
contents of this publication.
This publication, its contents and format are copyright

©2020 of Think Brick Australia and may not be reproduced,
copied or stored in any medium without prior, written
authorisation from Think Brick Australia. ABN 30 003 873 309.
Published February 2013, revised 2020
The Standards referenced in this manual were current at the

time of publication.
Cover: ‘ROC’ by Jacobs in association with Smart Design

Studio.
Joint Winner - Horbury Hunt Commercial Award 2019
Manufacturer: Bowral Bricks
Builder: A W Edwards
Contractor: Favetti
Brick Used: Bowral Dry Pressed - Capitol Red
PO Box 275, St Leonards NSW 1590 Australia

Suite 7.01, Level 7, 154 Pacific Highway, St Leonards NSW 2065 Australia
Telephone +61 2 8448 5500
Technical hotline 1300 667 617
ABN 30003873309
www.thinkbrick.com.au
Contents
1 Introduction 7
2 Types of Construction 8
2.1 Housing 8
2.2 Multiple-occupancy domestic units 8
2.3 Low-rise commercial and industrial buildings 8
2.4 Multi-storey framed structures 8

3 Masonry Elements 9
3.1 Veneer walls 9
3.2 Cavity walls 10
3.3 Masonry Infill 10
3.4 Freestanding elements 11
3.5 Diaphragm Walls 11

4 Material Properties 12
4.1 Masonry units 12
4.2 Mortar 12
4.3 Masonry properties 12
4.4 Ties and connectors 13
4.5 Damp-proof courses, joints and other accessories 13
5 Loading Conditions 14
5.1 Wind loading 14
5.2 Earthquake loading 14
5.2.1 Domestic structures 15

6 General Design Aspects 17
6.1 Structural behaviour 17
6.1.1 Wind loading 17
6.1.2 Earthquake loading 17
6.2 Mechanism of Load Transmission 18
6.2.1 Housing 18
6.2.2 Framed structures 18
6.2.3 Loadbearing structures 19
6.3 Tying and Support of Elements 19
6.3.1 Slab/wall connections 20
6.3.2 Shear capacity of membranes and joints 20
6.3.3 Parapets and freestanding elements 20
Design of Clay Masonry for Wind and Earthquake / 3

7 Design of Walls for out-of-plane load 21
7.1 Introduction 21
7.2 One-way vertical bending 23
7.3 One-way horizontal bending 23
7.4 Two-way bending 24
7.4.1 Introduction 24
7.4.2 Virtual work method 24
7.5 Veneer walls 27
7.6 Cavity walls 28
8 Design of walls for in-plane load 29

8.1 Introduction 29
8.2 Shear wall design 30
9 Design of Wall Ties, Connectors and Joints 31

9.1 Introduction 31
9.2 Wall tie design 31
9.3 Design of Connectors 32
9.4 Seismic design of slip joints and joints
containing membranes 33
9.5 Durability of ties and connectors 33
10 Worked Examples 35
10.3 Two-way bending (single-leaf wall) 37
10.4 Veneer wall 39
10.5 Cavity wall 1 (No load sharing) 40
10.6 Cavity wall 2 (With load sharing) 41
10.7 Shear walls 42
11 Design Charts 44
11.3 Two-way bending without openings 46
11.3.1 110mm without openings
(no rotational restraint at the sides) 46
11.3.2 90mm without openings
4 / Design of Clay Masonry for Wind and Earthquake

11.4 Two-way bending with openings 48
11.4.1 110mm with openings
11.4.2 110mm with openings (partial rotational
restraint at the sides - factor 0.5) 50
11.4.3 110 mm with openings (full rotational
restraint at the sides – factor 1.0) 52
11.4.4 90 mm with openings (no rotational
restraint at the sides) 54
11.4.5 90 mm with openings (partial rotational
11.4.6 90 mm with openings (full rotational
12 References 60

Figures
1. Variation of Tie Forces for Flexible and Rigid Backups 12
2. Diaphragm and Shear Wall Action in a Loadbearing Structure 21
3. Idealised Crack Patterns for Various Wall Configurations 23
4. Wall with Opening Divided into Two Sub-panels 27
5. Shear Wall Behaviour 30
Tables
1. Maximum Wall Pressures (kPa) for Type A Ties at 600 mm Centres 33

1. Introduction
This manual provides guidance for the design of Unreinforced masonry construction generally has low
unreinforced clay masonry to resist wind and earthquake seismic resistance, because it is a heavy, brittle material
forces. It follows the procedures set out in the Masonry with low tensile strength and exhibits little ductility.
Structures Code (AS 3700)1. For any aspects not covered It is therefore unsuitable for areas of high seismicity.
here, reference should be made to AS 3700. Useful However, the level of earthquake forces experienced
guidance on the interpretation of AS 3700 can also be in Australia is moderate by world standards and
found in its commentary2. The standard Masonry in Small unreinforced masonry can be used in most instances,
Buildings – Part 1: Design (AS 4773.1)3 contains simplified provided the structure is designed and detailed for the
rules compatible with AS 3700 that can be applied to the appropriate earthquake forces and built to the required
design of small buildings. standard.
Most masonry construction in Australia is unreinforced This manual applies to all structural forms using
and non-loadbearing. The common definition of a masonry-veneer walls, cavity walls or single-leaf walls,
non-loadbearing wall is one that does not support any including single-occupancy housing, multiple-occupancy
significant vertical loads other than its self-weight. units and townhouses, industrial and commercial
Nevertheless, these walls are subjected to loading from buildings and multistorey, framed construction with
wind and earthquake, as well as overall requirements for masonry infill. It covers material properties for clay
robustness. Even internal partition walls are subjected masonry, general arrangement of structures, specific
to earthquake loading. Walls with a moderate level of design procedures for out-of-plane lateral loading and
vertical loading derive additional stability against face in-plane shear loading, and design detailing of ties,
loads and the most critical case for out-of-plane lateral connections and joints. It does not cover design for
loading is therefore a wall with no superimposed vertical vertical loading (see Manual 6).
load.
Worked examples for various cases and design charts
Wind loading in parts of Australia can be severe, and the for lateral loading (using equivalent static loads for both
magnitude of load from wind increases significantly in wind and earthquake) are included.
the upper stories of multistorey buildings.

2. Types of Construction
2.1 Housing 2.3 Low-rise Commercial and Industrial

Buildings
The most common form of domestic construction
in Australia is the single-occupancy house. The vast Where masonry panels are used as cladding for
majority of these are clad with clay masonry and brick- commercial and industrial buildings their structural
veneer is the most popular form in the eastern states. design is usually governed by resistance to wind and
Full-brick cavity construction is popular in Western earthquake forces. Economy in design is vital for these
Australia and single-leaf construction using hollow units walls. In these buildings, the frame of concrete or steel
is popular in North Queensland. Because the walls of provides the overall resistance to lateral forces and the
houses generally support only a light roof load or no load walls must have sufficient flexural resistance to span
at all, the critical design load is usually lateral load from between frame members and other supports. Deflection
wind or earthquake. compatibility between frames and walls is an important
consideration.
In a veneer-wall house, the frame (timber or steel) is
relied upon to resist the main forces, including vertical
forces from the roof and lateral in-plane shear. In a 2.4 Multi-storey Framed Structures
cavity-wall house and single-leaf construction, the
masonry walls must provide the resistance to all lateral Masonry cladding is popular for multi-storey structures
forces, including in-plane shear. The latter can be the where the frame is commonly made of reinforced
governing action where earthquake forces are high. concrete or steel. In these cases the walls provide the
envelope to protect the interior against the weather
and are only required to resist lateral out-of-plane wind
2.2 Multiple-occupancy Domestic Units and earthquake forces. Often, the inner leaf of the
external walls is an infill wall tied to the frame. This
Multiple-occupancy domestic units of loadbearing may then act compositely with the frame, however
masonry (commonly called three or four-storey walk-ups) design for composite action between frames and infill
are common in Australia and two-storey semi-detached walls is beyond the scope of this manual (for additional
townhouses are becoming increasingly popular. In these discussion, see Section 3.3). Where composite action
buildings, the masonry walls usually support concrete is not designed for, isolation of infill walls from frame
floor slabs and the roof structure and their sizes are movement is essential under heavy earthquake loads.
determined accordingly. However, especially in the upper The external leaf is usually a veneer, supported by angles
storeys and in townhouses, wall designs can be governed or nibs on the floor slabs.
by resistance to out-of-plane forces.
The external walls in the upper storeys of multi-storey
In these structures, the masonry walls must also provide buildings can be subjected to high wind loads because
the resistance to lateral in-plane (shear) forces, with the of their height above the ground and this will usually
floor and roof acting as diaphragms to distribute forces govern their design.
to the walls.
Internal walls are not subjected to wind loading but are
still required to resist out-of-plane earthquake forces,
which will also be highest in the upper storeys.

3. Masonry Elements
Various types of masonry elements are used to make that study, the veneer system comprised an external
up a typical masonry structure. These include walls 110 mm brickwork skin connected by medium-duty ties
(which might be of veneer, cavity, solid or diaphragm to either a flexible backup system (typically timber or
construction), piers and freestanding elements such as steel stud wall) or a rigid backup system (typically an
parapets and chimneys. These various types of elements internal masonry leaf). Both uncracked and cracked (at
behave in different ways and their design must take into mid-height) conditions were examined. The marked
account their particular characteristics. Detailed design difference in tie forces for the cracked and uncracked
of diaphragm walls is beyond the scope of this manual. states is shown in Figure 1.
Under wind loading, the force in each tie is directly

3.1 Veneer Walls influenced by the stiffness of the backup. The forces are
tensile in some locations for a flexible frame. Before the
Unreinforced masonry is widely used as a veneer in wall cracks, the top ties adjacent to the backup attract
residential, light commercial and multi-storey framed a much greater proportion of the load than would be
construction. Clay brick is by far the most common expected from their tributary area. This explains the logic
choice of masonry for these applications. Veneers are of deemed-to-comply rules, which require the number
non-structural elements and rely on the supporting of ties to be doubled in these locations if the backup is
backup frame or wall and the accompanying tying flexible. If the veneer cracks longitudinally at mid-height
system for stability. Although they are non-structural, along a bed joint there is a dramatic redistribution of
veneers are nevertheless subject to wind and earthquake load in the ties, with the ties near the mid-height of the
loading. In particular, the seismic performance of wall becoming heavily loaded. This is particularly the
veneers is important because of their widespread use and case when the backup is a flexible frame. It is clear that
the high cost of repair if their performance proves to be the ties play a crucial role in this interaction and their
inadequate. strength and stiffness are both important.
The behaviour of a veneer subjected to face loading is A veneer wall relies on flashing and damp-proof courses,
quite complex because it depends upon the relative in conjunction with weep-holes, to act as an effective
flexibility of the veneer and the backup system, as well as barrier to moisture entering the building. The presence
the stiffness and location of the wall ties. These factors of flashing and a damp-proof course will influence
affect the degree of load sharing between the veneer behaviour under lateral load.
and backup and the amount of redistribution of load
that can occur. There is also a substantial difference
in behaviour when the veneer is cracked rather than
uncracked, because, in its uncracked state, the veneer is
usually much stiffer than its backup. The masonry veneer
itself does not usually need to be designed. For design
purposes, it is sufficient to know the wall tie forces and
the corresponding loads on the backup frame or wall.
Typical distributions of tie force derived from an elastic
analysis4 are shown in Figure 1, where T indicates a tensile
force in the ties and C indicates a compressive force. In

Figure 1. Variation of Tie Forces for Flexible and Rigid Backups 3.3 Masonry Infill
Unreinforced masonry infill

panels have the potential to add
considerably to the strength and
rigidity of a framed structure if
they are designed and detailed
for composite action. Interaction
between infill and frame depends
on the contact area at the interface
of the two components. The extent
of composite action will depend on
the level of lateral load, the degree of
bond or anchorage at the interfaces,
and geometric and stiffness
characteristics of the frame and
infill masonry. The possibility of the
mobilisation of the infill, especially to
3.2 Cavity Walls resist seismic loads, should be considered at the design
stage. However, in Australia it is good practice to leave
Cavity walls are constructed of two leaves of masonry gaps at the vertical edges and top of infill panels to allow
separated by a cavity, typically 50 mm in width, intended for long-term moisture expansion of clay bricks. The infill
primarily to prevent water penetration into the building. panels are secured to the frame by ties, which permit
This form of construction has been popular in Australia the desired relative movements, and flexible sealant
and other parts of the world since the early twentieth fills the gaps. In these cases, composite action will not
century because it provides a wall having good thermal occur until large frame deflections have taken place.
and strength properties, without the need to maintain Consideration of composite action between masonry
an external coating. infill and frames is beyond the scope of this manual.
In resisting applied loads normal to the face, cavity walls Design of infill panels that are isolated from the frame are
rely on the interaction between the two leaves through usually governed by flexural action to resist lateral out-of-
the ties. Behaviour of the whole system is complex and a plane forces. If there is the possibility of a shallow arch
detailed structural analysis would be required in order to developing within the thickness of the wall as it deflects,
predict accurately the forces in individual components. that should also be considered. However, this arching
This is usually impractical and simplified rules are action is unlikely if expansion gaps are left between the
employed to design the masonry leaves and the ties. wall and the frame and design for this action is difficult
because of the uncertainty of its extent. Consequently,
Proper detailing of flashings, damp-proof courses and AS 3700 does not give design rules for this arching. Infill
weep-holes is essential to ensure that a cavity wall wall panels are usually designed as one-way or two-
remains an effective waterproof barrier. As in the case of way spanning plates of masonry with simple supports
veneer walls, the presence of flashing and a damp-proof provided by the framing members.
course will affect behaviour under lateral load.

3.4 Freestanding Elements
Parapets and other freestanding elements are commonly

used in unreinforced masonry structures. Because of
the low flexural strength of the masonry, these elements
have little resistance to lateral load and must rely on
gravity for stability. The presence of a flashing or damp-
proof course at the base exacerbates the situation. In
addition, these elements are usually located at or near
the top of the structure where the wind loading is
highest and the effects of seismic ground motion are
magnified by the dynamic response of the building.
It is desirable to avoid the use of freestanding elements,

or, if they must be used, for them to be supported or
locally reinforced to provide flexural strength (see Section
6.3.3).
3.5 Diaphragm Walls
Diaphragm walls are a form of construction that offers

high resistance to lateral out-of-plane load. They are
formed of two leaves, separated by a substantial distance
and joined by webs of masonry that are fully bonded
into the leaves. These webs transfer shear between the
two leaves, allowing the wall to act in flexure as a fully
composite member rather than two separate leaves. The
lateral resistance of a diaphragm wall depends primarily
on the separation between the two leaves and the webs
joining the leaves must be specifically designed to resist
the forces imposed on them.
The detailed design of diaphragm walls is beyond the

scope of this manual. Design rules are given in AS 3700
and further guidance is available in the Australian
Masonry Manual5.

4. Material Properties
Fired clay bricks have been in use for at least 5,000 years. tensile bond strength. Mortar mix proportions are
Clay masonry is particularly noted for its attractive specified as cement:lime:sand by volume. Further
appearance, long life and good loadbearing qualities. information on mortar composition and admixtures
When properly constructed and detailed it provides one is given in Manual 10, Construction Guidelines for Clay
of the most functional walling systems ever developed. Masonry8.
4.1 Masonry Units It is essential for the job specification to refer to

either the class of mortar or the mix proportions (and
The applicable Australian standard governing the ideally both). AS 3700 no longer requires different mix
manufacture of masonry units is AS/NZS 4455.16. Units proportions for GP (Portland) and GB (blended) cements.
for use in masonry construction are required by AS 3700 For example, AS 3700 classifies the following three
to satisfy that standard. Test methods are specified in mortars as M3:
a companion standard AS/NZS 44567. Not all the tests
described in this standard are required to be specified; • 1:1:6 using GB or GP cement
AS 3700 clearly sets out which tests and properties are
required in each particular case. • 1:0:5 using GB or GP cement
While durability classification, dimensions and aesthetic • 1:0:4 using masonry cement.
requirements must always be considered, the important
properties of masonry units for walls designed to resist
wind and earthquake loads are: 4.3 Masonry Properties
• Absorption characteristics compatible with the By definition, masonry is a composite material

mortar to be used, so that the required flexural consisting of masonry units set in mortar. Because the
tensile bond strength is achieved. units and mortar have different characteristics, masonry
exhibits distinct directional properties with potential
• Lateral modulus of rupture sufficient for the required planes of weakness being created by the low tensile
flexural strength. strength at each unit/mortar interface. For resistance to
wind and earthquake forces it is this bond strength at the
4.2 Mortar interface that is important, both in flexure and in shear.
Mortar is an important ingredient in masonry Flexural tensile strength ( ) is required by AS 3700

construction because its characteristics have a strong to be at least 0.2 MPa for all masonry. This is a 95%
influence on both the strength and durability of the characteristic value, which means that 95% of all
masonry assemblage. It is also the component most masonry in the building should be stronger than this
susceptible to site problems related to mixing and design value and only 5% of the masonry is weaker. This
batching. Mortar must be workable when wet and bias is taken into account in setting the required safety
have sufficient strength and be adequately bonded to factors. Design values as high as 1 MPa can be taken, but
the masonry units when set. The tensile bond strength only if site control testing is carried out as part of the
of masonry can vary from zero to more than 1.0 MPa construction to verify that the required strengths are
depending on the correct match of mortar and unit being achieved. Any masonry where strengths higher
properties, in particular the match between mortar than 0.2 MPa are used and the specification calls for
consistency and unit suction. quality control testing is classified as Special Masonry.
The designer should be quite sure about the materials
Selection of sand, cement, mix composition and specified and the potential strength before using a design
admixtures such as air entrainer (when appropriate) is strength higher than the minimum value.
of vital importance for the achievement of the required

Shear strength on horizontal planes in clay masonry 4.5 Damp-proof Courses, Joints and Other
( f 'ms) is defined by AS 3700 as 1.25 f 'mt but not greater Accessories
than 0.35 MPa nor less than 0.15 MPa. This property
is therefore also related to the basic bonding between Damp-proof courses (DPC) must comply with the
masonry units and mortar. Additional shear resistance Australian standard AS/NZS 290411. Most loadbearing
is provided by the friction effect of vertical load, which is masonry structures subjected to earthquake forces rely
accounted for by a shear factor prescribed in AS 3700 (see to some extent on the transfer of shear across the DPC
Section 8.2). to develop the necessary resistance. AS 3700 provides
friction shear factors for the common DPC materials to
4.4 Ties and Connectors allow these calculations to be made (see Section 9.4). If
shear resistance on a damp-proof course or other joint
Masonry wall ties are a structural component of the wall, is a critical design factor, the documents should clearly
not an optional accessory. It is most important that ties indicate the type of material that is required to satisfy
should be appropriately designed and specified, should the design assumptions.
have the necessary durability and should be properly
installed. The standard covering wall ties is AS 2699
Part 19 and for other connectors and accessories AS 2699
Part 2 governs10. Rarely, if ever, should the designer
need to refer to these standards, as they are intended
to control the manufacture of the ties and accessories,
not their use. AS 3700 gives everything necessary for
the specification and use of these components. Design
capacities of connectors should be obtained from the
manufacturer.
Ties are classified based on strength and stiffness as

light duty, medium duty and heavy duty. This rating is
determined by tension and compression tests on small
tie/masonry assemblages, with the test results reflecting
both the behaviour of the tie itself and its attachment
to the masonry and the frame. Designers should use the
procedure in AS 3700 to determine the grade required for
each particular loading situation (see Section 9.2). This
required grade should then be clearly specified on the
documents.
Ties and connectors are commonly made from steel with

a protective coating. Where a high level of durability
is required, stainless steel or polymer ties can be used.
AS 3700 gives the requirements for durability in terms
of a rating from R1 to R5 (see AS 3700 Table 5.1). The
means of satisfying these rating requirements are given
in AS 2699.1. The designer should specify the durability
requirement for ties and connectors on the documents.

5. Loading Conditions
Wind and earthquake produce horizontal lateral forces bending, in-plane shear and uplift causing direct tension.
on a structure, which generate in-plane shear loads and Design for the first two is covered in Section 7 and
out-of-plane face loads on individual members. While Section 8. The effect of the third should be considered
both wind and earthquake generate horizontal forces, for individual members when they are designed for
they are different in nature. Wind loads are applied flexure and shear. Net direct tension on the cross-section
directly to the surfaces of building elements, whereas of a masonry member must be avoided for design in
earthquake loads arise due to the inertia inherent in the accordance with AS 3700, as the tensile strength of the
building when the ground moves. Consequently, the material is considered to be zero in such circumstances.
relative forces induced in various building elements are
different under the two types of loading.
5.2 Earthquake Loading
5.1 Wind Loading Earthquake loading is the force generated by horizontal

and vertical ground movements caused by earthquake.
Wind load is often the most important load acting on a These movements induce inertial forces in the structure,
structure. Levels of wind loading vary greatly throughout related to the distributions of mass and rigidity, and the
Australia, from moderate in the interior to very high in overall forces produce bending, shear and axial effects in
the cyclonic regions of the north. There are also local the structural members. Earthquake loads are different
factors to consider, such as topography, surrounding in nature to wind loads and can produce different effects
shelter and height above ground. in some cases. Earthquake loading is governed by
AS 1170.414.
Basic wind speeds and the numeric multipliers for
dealing with factors such as topography are given by The 1989 Newcastle earthquake highlighted the need for
the wind loading standard (AS 1170.2)12. This standard seismic design in Australia and, with the incorporation
is designed for use by structural engineers and detailed of AS 1170.4 into the Building Code of Australia,
illustration of its use is beyond the scope of this guide. consideration of seismic effects is mandatory for all
structures except Importance Level 1 (minor structures)
For housing structures, wind loads are determined from as defined in AS 1170.015 Appendix F.
a classification system given in the relevant standard
AS 405513. This system uses a wind classification based Because of the low levels of Australian seismicity, it
on regions, terrain categories, topographic classes is feasible to use properly detailed and constructed
and shielding classes. Provided the structure is within unreinforced masonry in most areas. For domestic
certain restrictions on height, shape and slope of structures within certain limits, the lateral racking forces
roof, it is classed as N1 to N6 for non-cyclonic regions from earthquake loading are given in AS 1170.4 Appendix A
and C1 to C4 for cyclonic regions. This wind class then (see Section 5.2.1 below).
determines the design wind speeds for the serviceability
and ultimate limit states. For the ultimate limit state Masonry veneer attached to a ductile frame of timber
these range from 34 metres/second to 86 metres/ or steel is considered non-structural and requires no
second. These wind speeds are used to derive forces on specific design for earthquake if it complies with AS 3700.
the structure by considering pressure coefficients based Other unreinforced masonry (in solid or cavity walls) is
on the shape and size of the structure and the presence classed as non-ductile and must be designed to remain
of openings. AS 4055 Section 3 tabulates the resulting essentially elastic. A non-ductile structure is required
pressures for ultimate and serviceability conditions. to carry a higher level of applied load than a ductile
structure. Ductility factors for masonry are given in
Wind acting on a structure causes three main effects that AS 3700 Section 10. As for all seismic design, clear load
must be accounted for in design. These are out-of-plane paths must be established and irregularities in plan

and elevation must be considered. The establishment forces imposed on the structure. Design and detailing
of load paths includes the effective transmission of requirements become more stringent as the earthquake
seismic forces across the various connections and any design category increases from I to III. The design of the
other discontinuities in the structure, and to this end structure and its individual elements is covered by the
the influence of flashings, membrane-type damp-proof relevant material standards (e.g. AS 3700 for masonry).
courses and slip joints must be considered.
AS 3700 provides deemed-to-satisfy details for masonry
For simplicity, earthquake loading can be converted structures up to 15m in height. These are intended to
to equivalent static forces with appropriate allowance ensure that masonry elements have adequate support
for the dynamic characteristics of the structure, and tying into the structure to prevent collapse during an
foundation conditions etc. This approach is sufficient earthquake.
for most masonry structures, which normally have a
short fundamental period of vibration and low dynamic In addition, AS 3700 restricts the use of loadbearing
response. unreinforced masonry to buildings less than certain
heights limits, except for some very restrictive conditions
AS 1170.0 provides load combinations for seismic design that are intended to permit small plant rooms and the
against strength and stability limit states. Serviceability like on top of multi-storey structures with adequate
is not considered for seismic design, but must be framing systems to resist seismic loads. The height
considered when detailing connections for overall limits depend on the hazard factor and sub-soil class and
performance. are all less than or equal to 15m (see AS 3700 Table 10.3).
All loadbearing masonry structures in excess of the
In the application of AS 1170.4, four factors are considered height limits require the use of reinforced masonry for
in determining an earthquake design category: the structural system. The impact of these limitations
on current practice is small because the majority of
1. The structure importance level. unreinforced masonry is used in residential construction,
low-rise commercial and industrial structures. Most of
2. The combination of probability factor and hazard these structures are typically four storeys or less and the
factor. major population centres such as Sydney and Melbourne
are not located in severe earthquake zones.
3. The site sub-soil class.
4. The height of the building. 5.2.1 Domestic structures

Earthquake resistance of domestic construction depends
The structure importance level is related to the on good detailing more than on structural analysis.
consequences of failure. The probability factor is Domestic construction derives its resistance from
determined from the annual probability of exceedance overall system behaviour, which can only occur if all the
that is being designed for and the hazard factor is parts of the structure are adequately connected. The
determined by the geographic location of the structure. intention of the structural detailing requirements is to
Together, these generate an equivalent acceleration ensure that this connection is provided, so that all forces
coefficient. The site sub-soil class depends on the soil on the structure are transferred to the foundations. In
profile of the site, ranging from strong rock to very soft particular, the following are important:
soil.
• Horizontal resistance must be provided for
The resulting earthquake design category of I, II or connections of beams and trusses to their supports.
III determines the design principles and the type of
analysis (static or dynamic) required to determine the • External walls must be anchored to roofs and floors

for horizontal support and internal loadbearing walls
must be restrained at their top and bottom.
Other measures can be taken to improve horizontal

earthquake resistance, for example by incorporating sub-
floor braces for discrete footings.
Attention should be paid particularly to detailing of

unreinforced ‘non-structural’ masonry components, as
they are the elements most at risk during an earthquake.
Non-ductile components such as unreinforced masonry
gable ends, internal non-loadbearing walls, chimneys
and parapets require appropriate restraint.
AS 1170.4 makes special provision for domestic structures.

Within certain geometric limits shown in AS 1170.4 Figure
A1, and for a combination of probability factor and hazard
factor less than or equal to 0.11 (which covers most areas
of Australia) there is no specific earthquake design
required for masonry structures that are otherwise
designed in accordance with AS 3700. This is because the
system already in place to resist lateral wind load should
provide sufficient wall, floor and roof diaphragms to
resist horizontal earthquake loading.
Where the combination of probability factor and hazard

factor exceeds 0.11 the structure can be designed using
simplified calculation of racking forces and tying of
walls, chimneys, parapets and the like to resist specified
anchorage forces (see AS 1170.4 Appendix A). Otherwise
the structure must be designed as for other structures of
Importance Level 2.

6. General Design Aspects
6.1 Structural Behaviour Both plan and elevation symmetry is desirable to avoid
torsional and soft-storey effects during seismic activity.
6.1.1 Wind Loading Compact plan shapes behave better than extended
Traditional masonry structures were massively wings. If irregular shapes cannot be avoided, then more
proportioned to provide stability and prevent tensile detailed earthquake analysis may be necessary. In some
stresses. In the period after 1945, traditional loadbearing cases, it may be possible to separate wings by suitable
construction was replaced by structures using the isolation joints and thereby convert the structure into a
shear wall concept, where stability against lateral series of regular shapes.
loads is achieved by aligning walls parallel to the load
direction. Lateral forces are therefore transmitted to Recent research16 examined the earthquake resistance of
the lower levels by in-plane shear. This, combined with unreinforced masonry residential structures up to 15 m
the use of concrete floor systems acting as diaphragms, in height, with a view to identifying the critical actions
produces robust box-like structures with thin walls under a range of conditions. The study considered
and the capacity to resist lateral load. Loadbearing the wall forces and associated actions arising from
structures of this type offer an economical alternative to earthquake loads corresponding to AS 1170.4. The seismic
framed construction for low and medium-rise buildings, demands under various conditions were compared with
particularly for structures with repetitive floor layouts. the corresponding seismic capacities given by AS 3700.
For these structures, the walls subjected to face loading A parametric study was used to examine the effects of a
must be designed to have sufficient flexural resistance wide range of parameters, including number of storeys,
and the shear walls must have sufficient in-plane wall geometries, support conditions and openings. The
resistance. results of the parametric study indicate, for a typical
office building and a typical home unit building, the
The alternative structural form consists of a frame, range of conditions leading to earthquake failure using
usually of steel, timber or concrete, which resists the the current design criteria of AS 3700. The following were
lateral forces by bending (frame action). The masonry the main findings:
walls are attached to this frame as a cladding and
distribute the applied lateral forces into the framing • Out-of-plane bending tends to govern as wall length,
members. In this system, the masonry walls are designed site sub-soil class, hazard factor and the number of
for local flexural action only. levels increase. This applies for both office buildings and
home unit buildings. This finding is based on the failure
criterion of maximum flexural strength being reached.
6.1.2 Earthquake Loading
In buildings subjected to earthquake loading the walls • Out-of-plane shear governs in relatively few cases
in the upper levels are more heavily loaded by seismic and, when it occurs, it is in conjunction with out-of-
forces, because of dynamic effects, and are therefore plane bending and/or in-plane shear failure. There
more susceptible to damage caused by face loading. The is no difference in this respect between typical office
resulting damage is consistent with that due to wind or buildings and home unit buildings.
other out-of-plane loading. Racking failures are more
likely to occur in the lower storeys where shear forces • In-plane shear in the direction of the short plan
are greatest and are characterised by stepped diagonal dimension of a building is governed by the
cracking. This damage does not usually result in wall arrangement of the internal walls. For the assumed
collapse, but can cause considerable distress. Racking wall distributions used in this study, in-plane shear
damage can also occur in structures with masonry infill in the short direction was not critical for the office
when large frame deflections cause load to be transferred building and, for the home unit building, occurred
to the non-structural walls. simultaneously with in-plane shear failure in the
long direction.

• In-plane shear in the long direction is the most 6.2.1 Housing
significant mode governing structural performance The mechanisms of load transfer in masonry housing are
when the failure criterion of onset of sliding at the different for cavity construction and for masonry veneer.
base of the wall is used. The assumed layout of
internal walls was found to be a significant factor In the case of cavity construction, the inner leaf supports
influencing behaviour. However, the onset of sliding the vertical load of any upper floors and the roof, while
does not necessarily constitute failure under seismic the outer leaf provides the weather-resistant cladding.
action, as it often does not lead to collapse or provide Lateral out-of-plane forces are shared between the two
a risk to life. leaves in proportion to their respective stiffness. The
inner leaf is usually much stiffer, because of its load
supporting function, and therefore resists a larger
A follow-up study17 summarises the results of a portion of the lateral load. The extreme case is when the
displacement-based assessment (DBA) of the seismic outer leaf is attached only by the ties and is designed
capacity of typical loadbearing unreinforced masonry as a veneer on a stiff backup. Cross walls within the
buildings between two and five storeys in height across building, which might either be of masonry or of framed
a range of site sub-soil classes and earthquake hazard construction, act to transfer lateral shear forces to the
factors, covering all of the capital cities and major footings.
regional centres in Australia. This study found that the
DBA for out-of-plane bending of walls in the top storey For masonry veneer construction, the building frame
of buildings identified far fewer cases of failure than did supports all the applied forces (both vertical and
a traditional strength-based assessment. A similar trend horizontal) while the masonry cladding protects against
was observed for the DBA for in-plane shear of walls at the weather. The face loads applied to the walls are
the ground storey of buildings. The DBA implied, for transmitted to the backup frame through the ties. The
all practical purposes, that typical walls will have the framing members then transfer the forces to shear
in-plane shear displacement capacity to withstand the diaphragms such as floors, ceilings and the roof. Lateral
earthquake induced loads and displacements for any site shear resistance is provided by the frame, which must
soil conditions and earthquake hazard factor up to 0.12. be fitted with suitable bracing to transfer forces to the
This contrasts with the corresponding strength-based footings. It is only necessary to check the masonry
calculations, which identified significant numbers of veneer for its ability to span in flexure between ties and
cases where failure would occur. While current standards the tie spacing specified in AS 3700 will usually ensure
are based on strength-based analysis, there is scope for that this capacity is adequate. To limit the size of any
designers to use displacement-based methods (with due crack in the veneer, the deflection of the structural
caution) and for standards to be augmented along these backing is limited by AS 3700 (Clause 7.6.2(b)) to span
lines in the future. divided by 300.
6.2 Mechanism of Load Transmission

6.2.2 Framed Structures
The fundamental aspect common to both wind and In a framed structure, load is transferred from the face-
earthquake loading is that load imposed on the loaded walls to the framing members through their
structure must be transmitted through a load path to connections. The framing members then act together
the foundation. It is important for this load path to to resist the lateral force, either by sway action or by
be identified and the respective structural elements braced-truss action, thereby transferring the force to the
designed for the part they play in it. The load path is foundations. The important elements to be considered
different for structures that rely on masonry walls as by the masonry designer are the masonry walls (in out-
loadbearing elements and those where the masonry of-plane flexure) and the connections. Isolation of the
forms infill or veneer applied to a structural frame. masonry walls from any large frame sway movements
might also be necessary.

6.2.3 Loadbearing Structures Figure 2. Diaphragm and Shear Wall Action in a Loadbearing Structure
The basic mechanism of lateral
load transmission for a loadbearing
structure is shown in Figure 2. Walls
aligned in a plane normal to the load
are subjected to face loads and span
vertically between the floors and, in
some cases, horizontally between
loadbearing walls. The concrete floors
then act as rigid diaphragms and
transfer the load to the shear walls,
which in turn transmit the forces to the
ground by in-plane shear.
The resulting structures are usually

quite robust, with relatively short-
span concrete slab systems supported
by numerous walls running in both
principal directions. The effective
performance of this system depends on
the ability of the individual masonry
elements to sustain their share of the
load, as well as the capability of the
connections between the elements
to transmit the appropriate forces.
The elements to be considered by the
masonry designer are the out-of-plane
flexural action, the in-plane shear
action and the connections between
structural elements. • Connectors between the edges of a non-loadbearing
wall panel and its supports.
6.3 Tying and support
of elements • Connectors attaching masonry infill to a structural
frame.
The correct performance of ties and connections between
structural elements is just as important as the behaviour • Connections providing support for non-structural
of the elements themselves, especially under earthquake components such as parapets and gables.
loading. Any failure or inadequacy of the connections can
lead to catastrophic collapse of the structure. Important • Slip joints, DPC membranes and flashings.
connections include the following:
It is important to remember that ties and connectors
• Ties between the leaves of a cavity wall. are usually required to provide resistance in only one
direction, and they must not unduly restrain movement
• Ties between a masonry veneer and its backup. in other directions. These considerations lead to the test
requirements for obtaining wall tie ratings, where they
• Roof tie-downs. must be subjected to a significant lateral movement

prior to application of the compressive or tensile force. slip joints. The use of these membranes in masonry walls
Similarly, in the case of slip joints and DPC membranes, has significant structural implications, as both in-plane
movements due to thermal and moisture strains and and out-of-plane forces must be transmitted across the
long-term expansion or shrinkage of the masonry units joint containing the membrane. Design of these joints is
must be allowed to occur without causing distress in the covered in Section 9.4.
structure. Under earthquake loading, the behaviour of
ties, connectors and joints under cyclic reversing load 6.3.3 Parapets and Freestanding Elements
must also be taken into account. Freestanding elements such as parapets must be
adequately supported and tied to the structure. They
6.3.1 Slab/Wall Connections can be subjected to high loads, especially from seismic
A slab-wall connection must be capable of transmitting action, where the dynamic response of the building can
the horizontal force induced in the wall to the slab. magnify the force. The provisions of AS 1170.4 allow for
For unreinforced masonry this requirement creates this effect by the application of a height amplification
potential serviceability problems, since if a positive form factor, which has a maximum value of 3.0 (see Clause 8.3
of attachment is adopted, the long-term movements of AS 1170.4). This is a simplification of what is quite a
mentioned above will be restrained, thus inducing complex phenomenon.
cracking in the masonry. If a positive form of connection
is not adopted, then reliance must be placed on the Grouted and reinforced cavity construction or grouted
transfer of the seismic force by friction. Design for reinforced hollow clay units can be used to provide
friction is covered in Section 9.4. sufficient resistance for this purpose. Alternatively,
unreinforced parapets can be tied to the main structure
6.3.2 Shear Capacity of Membranes and Joints or proportioned to span horizontally between returns
Membrane-type damp-proof courses are widely used in or piers that are designed to provide overall stability.
Australia as a barrier at the base of walls to prevent the Examples of details for tying parapets and chimneys back
passage of moisture from the ground to the structure. to a roof structure are shown in AS 382618.
These same membranes are also used for flashings and in

7. Design of Walls for Out-of-Plane Load
7.1 Introduction also has a strong influence on the behaviour. For veneer
or lightly-loaded panels where the level of compressive
For lateral out-of-plane loading, whether it arises from stress is low, flexural tensile strength is particularly
wind or earthquake, the response of the structural important. Determination of design loads for wind and
element is usually calculated by considering the load as earthquake is discussed in Section 5.
an equivalent static uniform pressure. Although there
is a fundamental difference in the type of load caused by Masonry walls behave differently under simple bending
wind and earthquake, there is no difference in design in one direction (for example between top and bottom
procedure between the two in most cases. supports) and bending in two directions (such as
when the wall has support on at least two adjacent
Masonry elements subjected to out-of-plane loading edges). This is a result of the flexural action of plates
resist the load by flexural action. The load capacity under distributed loading and also the different flexural
of unreinforced masonry wall panels depends upon properties of masonry normal to and parallel to the
the dimensions and support conditions, the level of bed joints. Most walls are designed to have support
compressive stress in the wall and the tensile strength of conditions that result in two-way bending because this
the masonry. The presence of door and window openings action is much stronger than simple one-way bending.
Figure 3. Idealised Crack Patterns for Various Wall Configurations
Walls without openings:
H V
Supports
1 D1 2 D2
3 D3 4 D4
Walls with openings: Typical opening
5 D5 6 D6

The design charts given in this manual give design rotation. This condition can occur when a wall
lengths and heights for walls with a range of support extends continuously past a support for a sufficient
conditions, for various wind pressures. Masonry distance or where a wall returns for a sufficient
walls crack in particular patterns under face loading, distance around a corner. The standard AS 3700 does
depending on the support conditions and the not give any guidance as to what return distance
dimensions. Figure 3 shows the idealised cracking around a corner to the edge of the nearest opening
patterns that occur for various wall configurations, or end of the wall is sufficient for this purpose. In
with edge supports indicated by dark lines. The crack the absence of other guidance, a distance of at least
lines shown, together with cracks along continuous or ten times the wall thickness can be considered a
restrained edges, allow a mechanism to form, at which reasonable minimum. Commonly, where there is
point the wall is considered to have failed. some degree of rotational restraint but it cannot be
considered as full restraint, a rotational restraint
Wall edges can be free of any support or subjected to factor of 0.5 or some other value between 0 (no
two types of edge restraint, namely lateral restraint and restraint) and 1 (full restraint) is used. Charts are
full rotational restraint. The latter can be referred to as provided later in this manual for partial as well as
a fixed edge. These two types of restraint are defined as full restraint (see Section 11.4). It should be noted
follows: that it is difficult to achieve full rotational restraint
by building the edge of a wall up to a supporting
• Lateral restraint occurs when the edge of the masonry member and incorporating metal ties. Such a
wall has only restraint in the lateral (out-of-plane) condition should usually be considered as providing
direction and there is no capacity to transmit a lateral restraint only.
moment across the edge. Control joints or isolation
joints where the masonry is tied to a support provide The top of a masonry wall might be considered either to
such a case and the bed joint at the base of a wall is have lateral restraint or to be a free edge. The base of a
also considered to be of this type. wall is considered to have lateral restraint only.
• Edge fixity occurs when the edge of the wall is

restrained against both lateral movement and

7.2 One-Way Vertical Bending However, the amount of vertical compression force
that can be used to enhance the bending resistance is
The simplest and most common form of one-way limited to 2 f
which is 0.24 MPa for most masonry
bending is simple vertical bending. In this mode, the (see AS 3700 Equation 7.4.2(3)).
wall panel acts as a simple beam between top and
bottom supports, with the main flexural stresses acting For a case where the flexural tensile strength is zero
across the bed joints. This is a simple mechanism and (for example at a damp-proof course or slip joint) the
results in a brittle failure. When a bed joint crack occurs moment of resistance is:
in masonry acting in this way the joint is assumed to
have no further resistance to applied moment.
Mcv = fd Zd
.................................................................. (2)
Resistance to vertical bending is only provided by the
flexural tensile strength of the masonry, although it is Where is limited to 0.36 MPa.
enhanced by any superimposed vertical load on the wall.
This superimposed load, if any, is taken into account The use of this design procedure is illustrated with a
in the design procedure by considering the resulting worked example in Section 10.1 and a design chart is
compressive stress as acting uniformly on the bed joint given in Section 11.1.
and partially relieving the tensile stress due to bending.
Because a wall under pure vertical bending fails in
a brittle manner and the flexural tensile strength of 7.3 One-Way Horizontal Bending
masonry is usually quite low, there are few cases where
one-way spanning walls can be justified. Wherever It is possible for portions of a wall to act in what is called
possible, walls should be provided with additional one-way horizontal bending. In these cases, the section
support along one or both the vertical edges or, if this is of masonry is supported at the two sides, but not at
not practical, the use of reinforced elements should be the top and bottom. This might occur for example in a
considered. strip of masonry over a window or door opening, where
the top of the wall is not supported. Such cases can be
The design procedure for vertical bending is based on the designed using the AS 3700 provisions for horizontal
moment of resistance Mcv, which is calculated as follows bending.
Mcv = φ f 'mt Zd + fd Zd The design procedure for horizontal bending is based on

.................................................(1)
the moment of resistance Mch, which is given by the lower
of two expressions:
Where
fd
Mch = 2φ k p f 'mt (1 + )Z d ..................................(3)
f = Capacity reduction factor (0.6 for f 'mt
bending). Mch = φ(0.44 f 'ut Zu + 0.56 f 'mt Z p ) ...........................(4)

= Characteristic flexural tensile strength Where
of the masonry (0.2 MPa except in the
case of Special Masonry). kp = A perpend spacing factor (1.0 for
traditional stretcher-bonded brickwork).
= Section modulus of the bedded area.
ut
= The characteristic lateral modulus of
= Minimum design compressive stress rupture of the masonry units (0.8 MPa in
due to superimposed vertical load. the absence of test data).

Zu = The lateral section modulus of the is sufficient to cause collapse. This pseudo-ductile
masonry units. behaviour is the basis of the virtual work method of
analysis adopted in the AS 3700 design provisions20.
Zp = The lateral section modulus based on The moment capacities of these potential crack lines
the bedded area of the perpend joints. are derived from the vertical and horizontal moment
capacities considered in Section 7.2 and Section 7.3,
The other symbols are as defined above. Note that Zp is along with consideration of the diagonal bending
less than Zu if the perpend joints are not completely filled; capacity (see below). More recent work has extended
otherwise they will be equal. The lateral section moduli our understanding of flexural behaviour but is not yet
and the lateral modulus of rupture are determined about incorporated into the design standard21,22.
the axis of bending in the wall, that is, a vertical axis.
The idealised cracking patterns are shown in Figure 3.
The first expression is derived from an empirical fit of The cracking pattern is always consistent with the shape
test results; the second expression is based on a model and boundary conditions of the panel. When the top of
of failure through units and perpends. A third expression a wall is supported, the first crack to develop is usually
given in AS 3700 (Equation 7.4.3.2(3)) has the effect of a horizontal crack in a bed joint at approximately the
limiting the amount of vertical compression force , mid-height of the panel. This crack is difficult to detect
used to enhance the bending resistance, to i.e. 0.2 and will almost disappear if the wall is unloaded. When
MPa for most masonry. adjacent vertical and horizontal edges are supported,
diagonal crack lines form and radiate out from at or near
The use of this design procedure is illustrated with a the corners. These cracks form in the bed and perpend
worked example in Section 10.2 and a design chart is joints and their angle is therefore governed by the length-
given in Section 11.2. to-height dimensions of the masonry units. These cracks
extend until they reach an edge or another failure line.
7.4 Two-Way Bending When a panel is high, compared to its length, a vertical
crack develops at approximately the mid-length. This
7.4.1 Introduction failure line extends to the top of the wall if unsupported
Wall panels with support on at least two adjacent or to the intersection of the diagonal failure lines at both
sides undergo a combination of vertical and horizontal top and bottom. When vertical edges have rotational
bending. This action provides more opportunity for restraint (for example because of continuity) they will
load sharing between various parts of the wall as crack either before, or at the same time as, the diagonal
cracks develop and leads to a less brittle behaviour. It is cracks develop.
therefore more desirable than one-way bending.
The presence of vertical load applied simultaneously with
Observations of cracking in numerous tests have led to the lateral load can enhance the strength of the panel
the identification of characteristic patterns that depend and this will be reflected in a higher value of Mch. When
on the wall support conditions19. Each of these cracking the load becomes substantial, such as where in-plane
patterns divides the wall panel into a number of sub- arching can develop due to the panel edges bearing
plates, which can be considered as being joined by hinges against the structural frame as the wall deflects, the wall
at their edges. While the exact distribution of moment strength can be substantially increased. However, there
along these crack lines is unknown, the total residual is no reliable design method for this action.
moment capacity of a crack line has been shown to relate
to the shape of the units and the basic bond strength 7.4.2 Virtual Work Method
. The collection of sub-plates in the cracked wall The lateral load design method used in AS 3700 is based
forms a mechanism that allows the wall to deflect, on the virtual work approach. This semi-empirical
at almost constant load, until the total deflection method relies on the identification of a particular

cracking pattern (as outlined above) and certain segments of the products of load and deflection for each
assumptions about the material properties. The method segment centroid. Equating the internal energy and the
was developed by examining crack patterns of a large external work done results in an equation that can be
number of test panels and relating the ultimate load solved to derive the load resisted by the cracked panel at
capacity of the walls to the energy developed on the crack the time the mechanism is formed. This predicted load
lines. This was then calibrated to give the closest fit to capacity depends on geometrical factors for the wall
the results and applied to predict the behaviour of other and the material properties, which are expressed as the
cases. The calibration involved deriving an equivalent horizontal moment capacity Mch (see Equations (3) and
torsional stress, which is closely related to the basic (4)) and the diagonal moment capacity Mcd (see Equation
flexural tensile strength . This derivation is the only (5)).
empirical step in the development of the method.
The diagonal bending moment capacity is given in
The assumed behaviour of the three types of crack lines is AS 3700 as:
as follows.
Mcd = φ f 't Zt ............................................................(5)
• Horizontal crack line in a bed joint – assumed to have

no residual moment of resistance after cracking. Where
This type of crack has virtually no influence on the
overall strength. = The equivalent torsional strength
= 2.25 f 'mt .
• Vertical crack line – results from failure through

masonry units and perpends or from the stepped = The equivalent torsional section
shearing failure alternating between the mortar modulus, measured normal to the
joints and perpends. The moment capacity is diagonal crack line, as calculated by the
influenced by the lateral modulus of rupture of the expressions given in AS 3700 (Clause
masonry units and the flexural tensile strength of the 7.4.4.3).
masonry and is expressed by Mch.
Other symbols are as defined previously.
• Diagonal crack line propagating from a corner –
results from torsional shearing action in the mortar Treatment of Openings
bed joints and perpends. The geometry of the
masonry units determines the slope of the line and When a wall panel contains door and window openings
the tensile strength of the masonry determines the these will cause variations to the crack pattern (see
flexural strength along the crack, expressed as the Figure 3). The virtual work method can still deal with
diagonal bending capacity Mcd. This type of crack has these cases by considering sub-panels on each side of the
the greatest effect of the three in determining the opening and using the energy developed on the actual
overall strength. crack lines. Any influence of a frame around the opening,
or any other effect of a door or window structure is
The virtual work method can be summarised as follows. ignored. However, the load applied to the door or
A mechanism is postulated, based on the assumed crack window is taken into account as a part of the overall load
pattern for the given wall, and this mechanism is given on the wall. Whereas a rigorous analysis could consider
a unit (virtual) deflection. The incremental internal the resistance along the crack lines for the expected crack
energy (work done on the hinge lines) is the sum along pattern, the tabulated coefficients in AS 3700 are based
all crack lines of the products of moment of resistance on a simplification. For these purposes, the opening is
and angle of rotation. The incremental external work treated as if it extended the full height of the wall. There
done during this deflection is the sum over all panel is no account taken of contribution to the resistance

from any masonry between the edges of the opening. af = aspect factor depending on the
However, the load on the section between the edges of geometry
the opening is included for the calculation of the work
done. This is equivalent to designing the panel on each Ld = design length (see below)
side of the opening as an independent panel with a free
edge having a line load applied. k1 and k2 = coefficients depending on the edge
restraints and the geometry (AS 3700,
Figure 4 shows a panel with an opening and indicates Table 7.5)
how it is divided into sub-panels.
Mch and Mcd are as defined above
Application of the Method
The design length and design height both depend on
The general formula for the virtual work method is: the support conditions for the wall and the presence of
openings. They are found as follows:
............................................(6)
Design length – When only one vertical edge of a wall is
supported, the design length is the actual length of the
Where wall. When both vertical edges are supported, the design
length is half the actual length. If there is an opening in
w = predicted lateral load capacity of the the wall, the edges of the opening are considered as if
panel under two way bending they are free edges and the design length is the distance
from the edge of the wall to the edge of the opening.
Figure 4. Wall with Opening Divided into Two Sub-panels
Sub-panel with Sub-panel with

free right edge Opening free left edge

Design height – When the top edge of a wall is not laterally The use of this design procedure with the aid of the
supported, the design height is the actual height of the design charts is illustrated with a worked example in
wall. When the top edge is supported, the design height Section 10.3. The charts are given in Sections 11.3 and 11.4.
is half the actual height of the wall.
If an opening is not centrally located within the length
Expressions for the other parameters are given in AS 3700 of a panel, each side from the opening to the edge of the
Clause 7.4.4. However, for design using the design charts panel must be checked independently.
in this manual, the designer is not required to evaluate
these other factors.
7.5 Veneer Walls
Design Charts
In a veneer wall, the veneer itself does not require
The equations given are used as the basis for the design structural design but should be checked for its capacity
charts. Charts are given for cases with and without to resist the load applied to it by spanning between the
rotational restraint at the sides, including partial ties in flexure. For the tie spacing specified in AS 3700
rotational restraint (factor = 0.5). In the virtual work this will not usually be critical.
method, it is always assumed that horizontal edges,
if restrained at all, only have lateral restraint and no The structural backup to a veneer wall must be designed
rotational restraint. to resist the total load applied to the wall. AS 3700
defines a flexible backup as one with stiffness less than
Each of the design charts gives limiting values of design or equal to half the stiffness of the uncracked veneer. All
length and design height for a range of loading and other backups are classed as stiff. Examples of flexible
a particular set of support conditions. The following backups are steel frames and timber frames, whereas
procedure is followed in using the design charts: stiff backups include concrete and masonry walls. For a
flexible backup and a stiff non-masonry backup, design
1. Determine the type of panel to be used (the type of should be in accordance with the appropriate code and
masonry and its properties). is beyond the scope of this manual. When the backup is
a stiff masonry wall, it should be designed in accordance
2. Determine the support conditions. with this manual (see Section 7.4). For a flexible backup,
AS 3700 limits the allowable deflection under the
3. Calculate the face load on the panel from the wind serviceability wind load to the span divided by 300. This
and earthquake codes. is intended to limit the width of any crack occurring at or
about mid-height.
4. Use the appropriate chart to find an acceptable
combination of design height and design length. The primary design consideration for a veneer wall is
(Note: interpolation is permitted on the charts.) therefore the capacity of the wall ties, and this depends
on whether the backup is flexible or stiff. The strength of
Alternatively if the panel dimensions and support the wall ties is no longer covered by deemed-to-satisfy
conditions are known, ascertain the maximum face load provisions of AS 3700 and must always be justified (see
from the corresponding chart. Section 9.2).
The AS 3700 robustness requirements must also be A typical example of design for a veneer wall on a flexible
checked (see AS 3700 Clause 4.6 and Manual 7, Design of backup is shown in Section 10.4.
Clay Masonry for Serviceability23).

7.6 Cavity Walls
In many cases, the inner leaf of a cavity wall supports the

roof structure, upper floors or some other vertical load,
from which it derives additional stability, whereas the
outer leaf performs the function of a cladding. In these
cases, the outer leaf is treated by AS 3700 as a veneer with
a stiff backup and the two leaves have different design
criteria.
For cases where both leaves share the load, the principal
difficulty is to determine the relative distribution of
load between the two leaves and the forces in the ties.
AS 3700 permits a designer to assume that all loads are
taken by one of the leaves and to design accordingly.
Alternatively, the distribution of load can be assessed and
each leaf designed individually as set out in Section 7.4.
The 2011 edition of AS 3700 introduced an approximate

method of allowing for load sharing between the
leaves, the basis of which originally appeared in The
Australian Masonry Manual5. More precise calculations
are possible, but will not often be warranted. In this
approximate method, the proportion of load applied to
the inner and outer leaves is not taken into account and
the wall capacity is obtained by factoring down the sum
of the individual leaf capacities, allowing for the stiffness
of the wall ties and the amount of load they are required
to transmit.
The strength of the wall ties and their ability to transmit

load is no longer covered by deemed-to-satisfy provisions
of AS 3700 and must always be justified (see Section 9.2).
A typical example of cavity wall design is shown in

Section 10.5, including the option of distributing the load
between the leaves.

8. Design of Walls for In-Plane Load
8.1 Introduction Figure 5. Shear Wall Behaviour
The force in a particular shear wall

will depend upon its stiffness relative Vertical Load
to the other elements resisting
horizontal forces and in some Racking
cases on the flexibility of the floor Force
diaphragms connecting the shear Diagonal
Tension
walls. Determination of design loads Failure
for wind and earthquake is discussed in
Section 5.
The general principles of shear wall

behaviour are well known. However,
the stress distribution within a shear
wall is complex and depends, among
Tension cracking Biaxial compression
other things, on the geometry of the at the heel failure at the toe
wall, the nature of the load application
and the presence of openings. The
strength of masonry subjected to
biaxial stresses depends on the
magnitude and sense of the principal stresses and the tensile and compressive stresses with subsequent sliding
angle of inclination of these stresses to the bed and along the joints. The magnitude and inclination of the
header joints. The inclination is particularly critical if principal tensile stress is influenced primarily by the ratio
tensile principal stresses are present. of vertical load to horizontal racking load, with the ‘shear
strength’ of the wall increasing significantly with an
As well as sliding failure, shear walls can fail locally in increasing level of vertical load.
three ways, involving various conditions of biaxial stress.
These are crushing at the toe, tensile cracking at the heel Unless major openings or discontinuities are present,
and diagonal cracking within the wall. Consideration none of these local failures will cause collapse of the
of this local state of stress is necessary if local and wall, although its capacity might be impaired. Walls
progressive failures are to be predicted. subjected to seismic loading will progressively degrade
with repeated load reversal as all or some of these failures
Figure 5 shows the potential regions of local cracking occur in various locations depending on the direction of
and failure. Toe failure will occur by crushing under loading. In some cases of cyclic reversing load, a wall will
biaxial compressive stress and usually causes splitting rock on its base as uplift occurs alternately at each end
and spalling normal to the plane of the wall. Uplift at of the wall. This may correspond to gradual shedding of
the heel occurs when vertical loads are low in relation bricks from the tension end or progressive local crushing
to the racking load, resulting in the development of in the compression region (or both simultaneously).
tensile stresses normal to the bed joint and a consequent Because of this process, and the possibility of progressive
horizontal crack. This crack might be tolerated in diagonal failure, unreinforced masonry shear walls have
some circumstances, or tying might be incorporated to some capacity for energy absorption. For walls with
minimise its effect. Failure in the centre of the panel major openings, significant distress and failure can also
is commonly described as ‘shear failure’, and is typified occur in the masonry piers between openings.
by diagonal cracking. This failure actually occurs in the
bed and header joints under a combination of principal The presence of discontinuities in the wall, such as

damp-proof courses, slip joints and interfaces with other The superimposed compressive stress is calculated
materials such as concrete slabs, provide potential slip differently for earthquake and other loadings. In the
planes where failure can occur. case of other than earthquake loading, it represents
the non-removable dead load and is usually 0.9 times
From a practical point of view, local failure may have the total dead load. In the case of earthquake loading,
implications for serviceability, but overall failure of the it can include a portion of the live load (see AS 1170.4).
wall is the main interest. Consequently, design rules The friction component is further reduced by ten per
for ‘shear strength’ have been formulated from racking cent to allow for upward acceleration that might be
tests on masonry panels and the observed performance present in an earthquake. Where the vertical gravity
of the panels at failure. This has resulted in a simple load contributes to resistance but not the induced lateral
relationship expressed in the form of a Coulomb criterion earthquake load, the live load is ignored and 0.9 times
in terms of the average shear and compressive stresses in the dead load is used.
the wall.
As well as checking for shear failure on the bed joints
using the above expressions, the designer should check
8.2 Shear Wall Design for the possibility of local compressive failure at the toe
of the wall. Crushing under compressive stresses can be
Design of shear walls in accordance with AS 3700 uses checked using the appropriate parts of AS 3700, using
the shear capacity of the masonry, determined from a the compressive strength of the material. If cracking
Coulomb-type equation: occurs at the heel, this loss of section should be taken
into account in calculating the compressive capacity at
Vd ≤ φ f 'ms Ad + kv fd Ad ..............................................(7) the toe.

Where At bedding planes containing damp-proof course
membranes and at junctions with other materials such
Vd = The design shear force. as a concrete slab, the characteristic shear strength is
usually zero, although AS 3700 does include provision
f = Capacity reduction factor (0.6 for shear for obtaining values by test. When the strength is zero,
in unreinforced masonry). the resistance is provided solely by friction. Values for
the shear factor kv are provided in AS 3700 for various
ms
= Characteristic shear strength of the membranes and interfaces and apply to both wind
masonry (see Section 4.3). loading situations and reversing earthquake load
situations. Shear capacity on these planes must be
Ad = Design cross-sectional area. checked (see Section 9.4).
kv = Shear factor (0.3 for bed joints in clay A typical example of shear wall design is shown in
masonry). Section 10.7.
= Minimum design compressive stress on

the bed joint (not greater than 2 MPa).
The first term represents the shear bond strength of

the section and the second term is the shear friction
strength.

9. Design of Wall Ties, Connectors and
Joints
9.1 Introduction structural backup and the ties themselves, is complex.

AS 3700 deals with the fundamental difference in
The bulk of the design provisions in AS 3700 relate to behaviour between veneer and cavity walls by providing
overall structural behaviour. However, most failures are deemed-to-satisfy design forces. For veneer walls with
due to inadequate detailing and design of joints, wall ties flexible backup, the design force for each tie is 20% of
and connections. The importance of correct attention the total tributary load on a vertical line of ties. For
to detailing for masonry structures cannot be over- veneer walls with stiff backup, the design force for each
emphasised. tie is 1.3 times the tributary load on the tie. For cavity
walls, the design force is equal to the tributary load on
Since masonry is a brittle material with limited tensile the tie. However, if a cavity wall has only the inner leaf
strength, it must be supported by suitable tying systems supported, it must be designed as a veneer wall with stiff
to keep the flexural stresses within acceptable limits. backup, and is therefore subject to the more stringent
Wall ties are used to connect non-loadbearing veneer requirements for tie forces.
walls to a structural backup and to allow the leaves
of cavity walls to share in resisting the applied loads. In a departure from previous practice, both AS 3700
Various types of connectors are used to attach masonry and AS 4773.1 now base the strength design of ties
walls to structural frames and across joints. on the mean strength of the ties instead of the 95%
characteristic strength. This is to compensate for the
AS 3700 requires all connections and wall anchorages considerable redistribution of force that occurs in the
to be capable of transmitting a horizontal force of 1.25 ties supporting a masonry leaf before failure can be
times the induced earthquake force. In particular, roofs considered to have occurred.
must be positively attached with a suitable system and
many of the traditional wind hold-down details (such as An additional requirement, in consideration of the
strapping connections) are inadequate for this purpose. particular behaviour of veneer walls on flexible backup,
is that the top of a wall should have double the number
The following sections cover design of wall ties and of ties required elsewhere in the wall. To satisfy this
connectors and the design to resist seismic forces of slip requirement, it might be necessary to spread the top row
joints and joints containing membranes. of ties across two adjacent bed joints, within 300 mm of
the top of the wall. This requirement for additional ties
also applies immediately above and below the plane of a
9.2 Wall Tie Design horizontal floor support when the veneer is continuous
past the support.
AS 3700 contains rational provisions for the design
of wall ties and AS 4773.1 gives deemed-to-satisfy duty The number of ties should also be double in line with the
ratings for various wind categories applicable to veneer intersection of an internal wall support, both for cavity
and cavity walls. The overall maximum spacing is 600 and veneer walls. This is because the additional support
mm horizontally and vertically and the first row of ties stiffness will attract more of the lateral force than would
is required to be within 300 mm from any edge. These otherwise be carried by the ties.
requirements are primarily to ensure a satisfactory
distribution of ties in the wall. They are set out in AS 3700 Table 1 shows the maximum wall pressures, calculated
Clause 4.10. using the AS 3700 design forces, for Type A ties spaced
at 600 mm in both directions. For a veneer wall with a
As well as satisfying the overall limits on spacing, the flexible backup, the maximum pressure depends on the
ties must be designed to resist the applied forces. A full wall height and values are only shown for a 2.4 m high
analysis to determine the tie forces, which considers the wall. Strength design of the masonry might result in
properties of the masonry (before and after cracking), the lower wall capacities than those shown in the table.

Table 1. Maximum Wall Pressures (kPa) for Type A Ties at 600 mm Centres.
Tension Compression
Light Med. Heavy Light Med. Heavy

Construction
Duty Duty Duty Duty Duty Duty
Veneer with Flexible Backup

0.99 1.98 4.95 1.19 2.38 5.94
(2.4 m wall height)
Veneer with Stiff Backup 0.61 1.22 3.04 0.73 1.46 3.65
Cavity Wall
0.79 1.58 3.96 0.95 1.90 4.75
(both leaves supported)
Note that for a flexible structural backing, the for control joints, where they limit movement in the
serviceability deflection of the backing must also be direction normal to the plane of the wall while allowing
checked, using the appropriate material standard. movement in the plane of the wall caused by shrinkage or
expansion.
In all situations, it is essential that ties be properly
installed. They will not perform to their full rated Where monolithic structural action is required across a
strength unless they are properly embedded in the vertical interface between two leaves of a solid masonry
mortar joints and properly attached to the frame or wall, or between a masonry wall and a supporting
backup (for veneer walls). They must also be installed in member, it must be designed in accordance with
the correct orientation and without a backward slope, AS 3700 Clause 4.11. If ties are used between the leaves
so that they shed water properly to the outside of the in solid masonry construction they must be rated at
wall. For face-fixed ties in masonry veneer more than least medium duty, spaced at no more than 400 mm in
3 m above ground, AS 3700 requires screw-fixing. Typical each direction. For other interfaces, the spacing must
examples of wall tie design are shown in Sections 10.4 not exceed 200 mm horizontally and 300 mm average
and 10.5. (400 mm maximum) vertically, unless substantiated
by calculation or test. The vertical joint must be filled
with mortar. Other connectors of equivalent strength
9.3 Design of Connectors (characteristic tensile capacity of 0.4 kN) can be used
within the same spacing limits.
Connectors used to tie masonry walls to frames and other
supporting elements must be designed to resist 125% of A special case occurs for diaphragm walls and walls of
any calculated load normal to the plane of the wall. The geometric section, where shear forces are often of much
minimum level of forces is specified by AS 3700 in Clauses larger magnitude. For these cases, connectors across a
2.6.3 and 2.6.4. When the forces arise from earthquake vertical interface in masonry are designed in accordance
action, the calculated horizontal force must similarly be with AS 3700 Clause 7.5.6. This clause provides equations
increased by a factor of 1.25 (see AS 3700 Clause 10.2.5). for steel connectors of rectangular and circular cross-
This applies to non-structural as well as structural sections, based on the dimensions and the yield stress
components. Characteristic strength values for these of the steel. These properties should be provided by the
connectors should be provided by the manufacturer, after manufacturer. For the shear strength of connectors
determination in accordance with AS 2699.2. Connectors between masonry and other structural members, the
must also comply with the durability requirements manufacturer should provide characteristic strengths
(see Section 9.5). Special connectors are available determined by test.

9.4 Seismic Design of Slip Joints and provide the shear transfer.
Joints Containing Membranes
AS 3700 uses the Coulomb-type shear equation (see
Slip joints are commonly placed between the edges Section 8.2) with a shear factor kv. For the joints being
of concrete slabs and the tops of the masonry walls considered here, the shear bond strength ms is zero
on which they sit, to permit differential movement and the equation for earthquake loading reduces to the
from sources such as shrinkage. These joints usually simple friction equation–
consist of two sheets of galvanised steel with a layer of
grease between, or a double layer of damp-proof course ................................................................(8)
material. In conditions of earthquake loading, these
joints are likely to be required to transmit shear forces Where
from the floor slab to the wall and their shear capacity
under transient loading is therefore important. kv = Shear factor
Damp-proof courses are used at the bases of walls to = The minimum design compressive stress
prevent moisture rising. They are usually formed by (see Section 8.2)
embedding a layer of embossed polythene or light-gauge
aluminium sheet with bitumen or polythene coating Ad = Design cross-sectional area
in the mortar joint. Recommended good practice is to
place the damp-proof membrane within the mortar joint, This equation applies to both in-plane and out-of-
rather than sitting it on the masonry units and placing plane shear. Values of kv have been investigated
the mortar on top. However, this is often not done and experimentally for membrane-type damp-proof
there is some evidence that the best performance under courses under static loading25 and dynamic loading26.
serviceability conditions comes from the damp-proof Design values are given in AS 3700 Table 3.3 as 0.3 for
course material being placed directly on the masonry bitumen-coated or embossed polyethylene and 0.15 for
units. These joints are also usually required to transmit polyethylene-coated and bitumen-coated aluminium.
shear forces under earthquake loading and therefore For properly designed slip joints using a greased
must have some shear resistance. sandwich of metal sheets, the appropriate value of
shear factor is zero, meaning that these joints cannot be
AS 3700 Section 10.3 provides various details that are relied upon to transmit shear forces under earthquake
deemed to be adequate for connecting masonry to loading.
supporting elements under earthquake loading.
Where no positive connectors are used the capacity of
the joint to transmit the necessary forces by friction must 9.5 Durability of Ties
be checked. Where positive connections are used their and Connectors
capacity must be checked using the relevant provisions
(see Section 9.3). Typical roof connection details are As pointed out above, ties and connectors are structural
shown in Manual 9 Detailing of Clay Masonry24. components and their integrity must be maintained
for the life of the structure. When ties and connectors
The serviceability requirements for damp-proof course corrode they are usually hidden in the wall and the
membranes and slip joints to prevent distress in the damage does not become evident until it is advanced.
masonry seem to conflict with the requirement for shear The consequences then are severe. The cost of replacing
transfer under earthquake load conditions. It is thus an corroded ties and connectors is vastly greater than the
important matter of design to ensure that the joints have incremental cost of providing enhanced protection when
sufficient freedom to accommodate the serviceability a structure is first built. Designers should consider this
requirements while having sufficient friction capacity to carefully.

All ties and connectors used with masonry are required to location requires an appropriate durability rating. The
meet durability requirements set out in AS 3700 Section 5 performance requirements and deemed-to-satisfy
or AS 4773.1 Section 4 (for small buildings). These provisions for durability of ties and connectors are given
requirements are expressed in terms of a classification in AS 2699.1 and AS 2699.2 respectively.
of exposure environments, ranging from mild to severe
marine, and the location within the building, comprising There are many reports of ties deteriorating markedly
interior, exterior and exterior-coated. The last of these after only a short time in the structure, the most notable
covers components that are in masonry exposed to the example being after the Newcastle earthquake27. In
exterior environment but which relies for protection on a recent years, stainless steel ties have become more
compliant weather-resistance coating. common and polymer ties have been developed.
The availability of an improved range of products,
The accessories are given a rating from R0 to R5, combined with an increased awareness by designers of
depending on their materials and other characteristics, the importance of tie durability, should lead to fewer
and each combination of exposure environment and problems in the future.

10. Worked Examples
10. Worked Examples

10.1 One-Way Vertical Bending
Design a section of wall 2 m wide, spanning between top and

bottom supports at 2.7 m spacing, carrying no vertical load and an
applied lateral load of 0.5 kPa.
Procedure using AS 3700 (Clause 7.4.2) –
Bending moment:
%&' ).+×-..'
M"# = (
= (
= 0.46 kN.m per metre width
For a single leaf of 110 mm units, fully bedded –
34' 6)))×66)'
Z" = 5
= 5
= 2.02 × 105 mm3 per metre width
Density for clay masonry = 0.19 kN/m2 per 10 mm thickness (AS 1170.1).
Therefore, compressive stress at mid-height due to self-weight (based on 90% dead load) –
).:×[().6:×66)×6.>+]×6)))
𝑓𝑓" = 66)×6)))
= 0.023 MPa
Vertical bending capacity –
D
MA# = ϕ𝑓𝑓C4 Z" + 𝑓𝑓" Z"
= [0.6 × 0.2 × 2.02 × 105 + 0.023 × 2.02 × 105] × 10G5
=0.29 kN.m per metre width (One leaf of 110 mm masonry)
For two leaves of 110 mm masonry (assumed to be connected by heavy duty ties and
therefore to share the load equally) –
Moment capacity = 0.58 kN.m per metre width, which is greater than the applied bending
moment of 0.46 kN.m per metre. \OK
Procedure using the design charts (Chart 11.1) –
Assume a leaf thickness of 110 mm.
For a height of 2.7 m, the load capacity of a single leaf is 0.28 kPa, so for two leaves the
capacity is 0.56 kPa. \ OK

10.2 One-Way Horizontal Bending
Design a section of wall spanning horizontally 2.4 m between supports, for an

Bending moment –
%I' )..×-.J'
M"H = = = 0.50 kN.m per metre width
( (
For a single leaf of 230 mm x 110 mm x 76 mm units, fully bedded –
Z" = 2.02 × 105 mm3 per metre width (see Example 10.1),
and Zu, Zp and equal to Zd for full perpends and no joint raking.
Perpend spacing factor kp is the lesser of (see AS 3700 Clause 7.4.3.4) –
LM 66) LM 66)
4N
= 66) and HN
= .5
and 1.0
Ignoring the self-weight effect (which is negligible for small sections):
Horizontal bending capacity –
D
MAH = 2.0ϕk S T𝑓𝑓C4 Z"
= U2.0 × 0.6 × 1.0 × √0.2 × 2.02 × 105 W × 10G5
= 1.08 kN.m per metre width (Equation 3)

OR
D D
MAH = ϕU0.44 𝑓𝑓Y4 ZY + 0.56 𝑓𝑓C4 ZS W
D
Taking 𝑓𝑓Y4 as the default value of 0.8MPa in the absence of test data –
MAH = 0.6 × (0.44 × 0.8 × 2.02 × 105 + 0.56 × 0.2 × 2.02 × 105 ) × 10G5
= 0.56 kN.m per metre width (Equation 4)
Therefore, the governing value = 0.56 kN.m per metre width, which is greater than the applied
bending moment of 0.50 kN.m per metre. \OK
Procedure using the design charts (Chart 11.2) –
Assume a 110 mm wall.
For a length of 2.4 m, the load capacity is 0.78 kPa, which is greater than the applied load of
0.7 kPa. \OK

10.3 Two-way Bending (Single-leaf Wall)
Design a wall panel 4 m long and 3 m high

with simple supports on all sides, for an
For the virtual work method –
Design length
Ld = 2000 mm (half the actual length).
Design height
Hd = 1500 mm (half the actual height).
For 230 mm x 110 mm x 76 mm solid or cored units –
-UHN [4\ W -×(5

Crack Slope G= ]N [4\
= -J)
= 0.717
`Ia )..6.×-)))
Slope Factor α= = = 0.96
&a 6+))
Since there is no opening and both vertical edges are supported, use the first row in AS 3700
Table 7.5 –
6 6
Aspect Ratio ac = 6Gd = 6G).:5e = 1.47
e> >
Sides are simply supported, so restraint factors Rf1 and Rf2 are both 0, therefore –
k6 = 1 − α = 1 − 0.96 = 0.04
6 6
k - = α g1 + `'h = 0.96 g1 + )..6.' h = 2.83
MAH = 0.56 kN.m per metre width (see Example 10.2)
Equivalent torsional strength (ignoring the small effect of self-weight) –
𝑓𝑓4D = 2.25T𝑓𝑓C4
D
= 2.25 × √0.2 = 1.01 MPa
Height factor –
HN [4\ (5
B= = = 69.9 mm
√6[`' √6[)..6.'

Since tu = 110 mm > B, the equivalent torsional section modulus –
-j' 4'N
(>4N [6.(j)
Z4 = n
gUlY + t m W√1 + G - h
-×5:.:' ×66)'
(>×66)[6.(×5:.:)
= n
g(230 + 10)√1 + 0.717- h
= 879 mm3 per mm crack length
Diagonal moment capacity –
MA" = ϕ𝑓𝑓4D Z4
= (0.6 × 1.01 × 879 × 1000) × 10G5
= 0.53 kN.m per metre crack length
The wall load capacity is therefore –
-pq
w= (k6 MAH + k - MA" )
I'a
-×6.J.
= (0.04 × 0.56 + 2.82 × 0.53)
-.)'
= 1.12 kPa
Which is greater than the applied load of 1.0 kPa. \OK
Procedure using the design charts –
Assume a 110 mm wall, therefore use Chart 11.3.1 for four edges supported.
For a design length of 2,000 mm and design height of 1,500 mm, the load capacity is between
the curves for 1.0 kPa and 1.5 kPa. Interpolate a value of 1.1 kPa. \OK

10.4 Veneer Wall
Design a single-storey masonry veneer wall 2.7 m high supported on a timber frame. The
applied lateral load is 1.5 kPa suction on the wall. Assume ties at 600 mm centres in both
directions.
Using AS 3700 Section 7.6, design tie force based on 20% of the load on the tributary area for a
line of ties –
F4" = 0.20 × 2.7 × 0.6 × 1.5 = 0.49 kN tension
Capacity reduction factor = 0.95 (AS 3700 Table 4.1).
Load capacity for medium duty ties in tension = 0.60 kN (AS 3700 Table 3.5).
\ Tie capacity = 0.95 × 0.6 = 0.57 kN \OK
The top row of ties must be within 300 mm of the top of the veneer (AS 3700 Clause 4.10) and
spaced at an average of 300 mm horizontally. This can be achieved by placing two ties at each
stud (600 mm centres), either in the same bed joint or spread across two adjacent bed joints
within 300 mm of the edge. Ties in the remainder of the wall are spaced at 600 mm in each
direction.
Provided the tie spacing complies with AS 3700, the veneer skin itself will require no further
design.

10.5 Cavity Wall 1 (No Load Sharing)
Design a cavity wall 3 m long and 3 m high for a multistorey building. The inner leaf is tied to a
structural frame on all four edges and the outer leaf is supported on shelf angles attached to
the spandrels. The applied load is 0.5 kPa internal suction and 1.0 kPa external pressure.
Only the inner leaf is supported, so design as veneer on a stiff backup (AS 3700 Clause 7.7.4).
The force to be transmitted by the ties derives from the outer leaf and the design tie force is
based on 130% of the load on a tributary area for one tie (AS 3700 Clause 7.6.3).
Assuming ties are spaced at 600 mm centres in both directions –
F4" = 1.3 × 0.6 × 0.6 × 1.0 = 0.47 kN compression
Load capacity for medium duty ties in compression = 0.72 kN (AS 3700 Table 3.6).
Therefore the tie capacity = 0.95 x 0.72 = 0.68 kN, which is greater than the applied force of
0.47 kN. \OK
Ties throughout the wall are spaced at 600 mm in both directions, with the first row located
within 300 mm of all edges, supports and around openings (AS 3700 Clause 4.10).
For the design of the wall itself, the simplest approach is to assume that the entire load is
taken by the inner leaf. A leaf of 110 mm thickness, with both sides supported, a design length
of 1500 mm and a design height of 1500 mm has a load capacity exceeding 1.5 kPa (Chart
11.3.1). \OK
A more refined design could be carried out by assessing the load distribution between the two
leaves but this approach is unnecessary in this case. For an example of load sharing between
the leaves see the next example.

10.6 Cavity Wall 2 (With Load Sharing)
Design a cavity wall 3 m long and 3 m high for a multistorey building. The inner leaf is tied to
structural columns on both sides, with the top free. The outer leaf is supported on shelf angles
attached to the spandrels and is continuous past the columns at 3 m centres. The applied load
is 0.5 kPa internal suction and 1.0 kPa external pressure.
The force to be transmitted by the ties is based on the difference between external pressure
and internal suction i.e. 0.5 kPa. The force per tie is derived from the tributary area (AS 3700
Clause 7.7.4).
Assuming ties are spaced at 600 mm centres in both directions –
F4" = 0.6 × 0.6 × 0.5 = 0.18 kN compression
Load capacity for medium duty ties in compression = 0.72 kN (AS 3700 Table 3.6).
Therefore the design tie capacity = 0.95 x 0.72 = 0.68 kN , which is greater than the applied
force of 0.18 kN. \OK
Ties throughout the wall are spaced at 600 mm in both directions, with the first row located
within 300 mm of all edges, supports and around openings (AS 3700 Clause 4.10). The ties at
the vertical lateral supports (the columns) are required to resist 2 x Ftd = 0.36 kN compression
(AS 3700 Clause 7.7.4). \OK
For the design of the wall itself, the load is to be assessed as being shared between the two
leaves (AS 3700 Clause 7.7.3). A leaf of 110 mm thickness, with both sides supported and the
top free has a design length of 1500 mm and a design height of 3000 mm. The load capacity is
interpolated as 0.95 kPa (Chart 11.3.1). In this case the two leaves are of equal thickness and
equal load capacity, therefore the total load capacity is (AS 3700 Equation 7.7.3):
w = 0.9[0.95 + 0.95] = 1.7 kPa
This is greater than the total applied load of 1.5 kPa. \OK
Trial a design with an outer leaf thickness 90 mm and an inner leaf thickness 110 mm, using
medium duty ties as above.
The 90 mm thick leaf has a load capacity interpolated as 0.75 kPa (Chart 11.3.2). Therefore the
combined load capacity is (AS 3700 Equation 7.7.3):
:)
w = 0.9[0.95+
66)
0.75]= 1.4 kPa
This is less than the total applied load of wd = 1.5 kPa, therefore the outer leaf thickness of
110 mm is required.

10.7 Shear Wall
Design a shear wall 4 m long and 2.7 m high, subject to a wind shear force of 40 kN. The
D
masonry is constructed with clay units of 110 mm thickness and with an 𝑓𝑓C4 of 0.2 MPa. The
wall sits on a bitumen-coated aluminium damp-proof course and there is a uniform vertical
load on top of the wall comprising 50 kN/metre dead load and 15 kN/metre live load.
Shear strength –
𝑓𝑓CD L = 1.25𝑓𝑓C4
D
= 0.25 MPa (AS 3700 Clause 3.3.4)
Design cross-sectional area –
A" = 110 × 4000 = 0.44 × 105 mm2
Therefore, shear bond capacity –
Vu = ϕ𝑓𝑓CD L A"
= (0.6 × 0.25 × 0.44 × 105 ) × 10G>
= 66.0 kN
Shear factor at the mortar joints and at the damp-proof course kv = 0.3 (AS 3700 Table 3.3)
Vertical stress from imposed load (using 90% of dead load) –
+)×6)w
𝑓𝑓" = 0.9 × g
66)×6)))
h = 0.41 MPa
Therefore, shear friction capacity –
V6 = k # 𝑓𝑓" A"
= (0.3 × 0.41 × 0.44 × 105 ) × 10G>
= 54.1 kN
Total shear capacity Vd = V0 + V1 = 66.0 + 54.1 = 120.1 kN, which is greater than the applied
shear force of 40 kN. \OK
Sliding at the base of wall is OK because the shear friction capacity alone exceeds the applied
shear force, the shear factor is the same (0.3) and additional frictional resistance is present at
the base from self-weight.
Check for crushing at the toe –
Density = 0.19 kN/m2 per 10 mm thickness (AS 1170.1).

Stress due to compression (using 1.2 times dead load, including self-weight, plus 40% live load) –
+)×6)w [-..×).6:×66×6)w 6+×6)w

= 1.2 × g h + 0.4 × g h
66)×6))) 66)×6)))
= 0.66 MPa
Overturning moment due to wind = 40 x 2.7 = 108 kN.m
3×"' 66)×J)))'
Wall section modulus =
5
= 5
= 293 × 105 mm3
6)(×6)x
Therefore, bending stress = -:>×6)x = 0.37 MPa
Net stress at the toe from compression + bending stress = 0.66 + 0.37 = 1.03 MPa compression
D
With a capacity reduction factor of 0.75 (AS 3700 Table 4.1) this requires 𝑓𝑓C3 of 1.4 MPa,
which is satisfied by units of strength 5 MPa and M2 mortar (see AS 3700 Table 3.1). \OK
Check for tension at the heel –
Stress due to compression (using 90% dead load, including self-weight) –
+)×6)w [-..×).6:×66×6)w
= 0.9 × g 66)×6)))
h = 0.46 MPa
Net stress at the heel from compression – bending stress = 0.46 – 0.37 = 0.09 MPa
compression (i.e. no net tension). \OK
Check for overturning about the toe –
Overturning moment = 108 kN.m (see above).
Force resisting overturning (using 90% dead load, including self-weight) –
= 0.9 × (50 × 4.0 + 4.0 × 2.7 × 11 × 0.19) = 200 kN
Therefore resisting moment = 200 x 2.0 = 400 kN.m and this is greater than the overturning
moment. \OK

11. Design Charts
Limitations for all charts:
• They apply to single-leaf walls without engaged

piers, using solid or cored masonry units.
• No superimposed compression is taken into account.
• No joint raking is assumed.
• mt
is assumed to be 0.2 MPa (AS 3700 default).
• ut
is assumed to be 0.8 MPa (AS 3700 default).
• Robustness should be checked separately.
• All supports are simple (without rotational restraint)

unless otherwise indicated.
• The dimensions of masonry units have been taken as

230L x 76H for 110 mm units and 290L x 76H for 90 mm
units. This is conservative for other common sizes
of solid or cored units in horizontal and two-way
bending.

11.1 One-Way Vertical Bending
11.2 One-Way Horizontal Bending

11.3 Two-way Bending Without Openings
11.3.1 110 mm without openings (no rotational restraint at the sides)
Both Sides Supported
One Side Supported

11.3.2 90 mm without openings (no rotational restraint at the sides)
Both Sides Supported
One Side Supported

11.4 Two-way Bending With Openings
11.4.1 110 mm with openings (no rotational restraint at the sides)
900 mm Wide Opening (Any Height), Both Sides Supported


11.4.2 110 mm with openings (partial rotational restraint at the sides - factor 0.5)


11.4.3 110 mm with openings (full rotational restraint at the sides – factor 1.0)


11.4.4 90 mm with openings (no rotational restraint at the sides)


11.4.5 90 mm with openings (partial rotational restraint at the sides – factor 0.5)


11.4.6 90 mm with openings (full rotational restraint at the sides – factor 1.0)


12. References
1 AS 3700 – 2018 Masonry structures, Standards 14 AS 1170.4 – 2007 Structural design actions, Part
Australia, Sydney, 2018. 4: Earthquake actions in Australia, Standards
Australia, Sydney, 2007.
2 AS 3700 – 2011 Masonry structures – Commentary,
Standards Australia, Sydney, 2012. 15 AS 1170.1:2002 Structural design actions, Part O:
General principles, Standards Australia, Sydney,
3 AS 4773.1:2015 Masonry in small buildings – Part 1: 2002.
Design, Standards Australia, Sydney, 2015.
16 awrence, S.J., Willis, C.R. & Griffith, M.C.
L
4 age, A.W. Unreinforced masonry structures
P Earthquake performance of unreinforced masonry
– an Australian overview, Proceedings of the residential buildings designed to Australian standards.
Pacific Conference on Earthquake Engineering, The Australian Journal of Structural Engineering,
University of Melbourne, Melbourne, Dec. 1995, Vol.8, 2008, pp.49-61.
pp.1-16.
17 awrence, S.J., Willis, C.R., Melkoumian, N. &
L
5 aker, L.R.; Lawrence, S.J. & Page, A.W. The
B Griffith, M.C. Earthquake design of unreinforced
Australian Masonry Manual, Deakin University masonry residential buildings up to 15m in height.
Press, 1991. Australian Journal of Structural Engineering,
Vol.10, 2009, pp.85-99.
6 AS/NZS 4455.1:2008 Masonry units, pavers, flags and
segmental retaining wall units, Part 1: Masonry units, 18 S3826 – 1998 Strengthening existing buildings for
A
Standards Australia, Sydney, 2008. earthquake, Standards Australia, Homebush,
1998.
7 AS/NZS 4456:2003 Masonry units, segmental pavers
and flags – Methods of test, Standards Australia, 19 awrence, S.J. Out-of-plane lateral load
L
Sydney, 2003. resistance of clay brick panels. Proceedings of
the Australasian Structural Engineering Conference,
8 anual 10, Construction Guidelines for Clay
M Sydney: Institution of Engineers, Australia, 1994.
Masonry, Think Brick Australia, Sydney, 2018.
20 awrence, S.J. & Marshall, R.J. The New AS 3700
L
9 AS/NZS 2699.1:2000 Built-in components for Approach to Lateral Load design, Proceedings of
masonry construction, Part 1: Wall ties, Standards the Fifth Australasian Masonry Conference,
Australia, Sydney, 2000. Gladstone, 1998.
10 AS/NZS 2699.2:2000 Built-in components for 21 awrence, S.J., Willis, C.R. & Griffith, M.C.
L
masonry construction, Part 2: Connectors and Further developments in the design of masonry
accessories, Standards Australia, Sydney, 2000. walls in bending. Proceedings of the Australian
Structural Engineering Conference. Newcastle, NSW,
11 AS/NZS 2904:1995 Damp-proof courses and flashings, Institution of Engineers, Australia, 2005.
Standards Australia, Sydney, 1995.
22 illis, C.R., Griffith, M.C. & Lawrence, S.J.
W
12 AS 1170.2:2011 Structural design actions, Part 2: Moment capacities of unreinforced masonry sections
Wind actions, Standards Australia, Sydney, 2011. in bending. Australian Journal of Structural
Engineering, Vol.6, 2006, pp.133-145.
13 AS 4055 – 2012 Wind loads for housing, Standards
Australia, Sydney, 2012. 23 anual 7, Design of Clay Masonry for Serviceability,
M
Think Brick Australia, Sydney, 2019.

24 anual 9, Detailing of Clay Masonry, Think Brick
M
Australia, Sydney, 2019.
25 age, A.W. The shear capacity of damp-proof courses

P
in masonry. Civil Engineering Transactions,
Institution of Engineers Australia. CE37(1), Feb.
1995, pp.29-39.
26 age, A.W. and Griffith, M.C. A preliminary study

P
of the seismic behaviour of slip joints and joints
containing membranes in masonry structures. The
University of Newcastle Dep’t of Civil, Surveying
& Environmental Engineering Research Report,
Dec. 1997.
27 age, A.W. The design, detailing and construction of

P
masonry - the lessons from the Newcastle earthquake.
Civil Engineering Transactions, Institution of
Engineers Australia. CE34(4), Dec. 1992, pp.343-
353.

PO Box 275, St Leonards NSW 1590 Australia
Suite 7.01, Level 7, 154 Pacific Highway, St Leonards NSW 2065 Australia
Telephone +61 2 8448 5500
Technical hotline 1300 667 617
ABN 30003873309
www.thinkbrick.com.au

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Manual 4

This manual is intended for use by a structural engineer.

This publication, its contents and format are copyright

Published February 2013, revised 2020

The Standards referenced in this manual were current at the

Cover: ‘ROC’ by Jacobs in association with Smart Design

PO Box 275, St Leonards NSW 1590 Australia

Design of Clay Masonry for Wind and Earthquake / 3

8 Design of walls for in-plane load 29

9 Design of Wall Ties, Connectors and Joints 31

4 / Design of Clay Masonry for Wind and Earthquake

Design of Clay Masonry for Wind and Earthquake / 5

2. Diaphragm and Shear Wall Action in a Loadbearing Structure 21

3. Idealised Crack Patterns for Various Wall Configurations 23

4. Wall with Opening Divided into Two Sub-panels 27

5. Shear Wall Behaviour 30

6 / Design of Clay Masonry for Wind and Earthquake

Design of Clay Masonry for Wind and Earthquake / 7

2.1 Housing 2.3 Low-rise Commercial and Industrial

8 / Design of Clay Masonry for Wind and Earthquake

Under wind loading, the force in each tie is directly

Design of Clay Masonry for Wind and Earthquake / 9

Unreinforced masonry infill

10 / Design of Clay Masonry for Wind and Earthquake

Parapets and other freestanding elements are commonly

It is desirable to avoid the use of freestanding elements,

3.5 Diaphragm Walls

Diaphragm walls are a form of construction that offers

The detailed design of diaphragm walls is beyond the

Design of Clay Masonry for Wind and Earthquake / 11

4.1 Masonry Units It is essential for the job specification to refer to

• Absorption characteristics compatible with the By definition, masonry is a composite material

Mortar is an important ingredient in masonry Flexural tensile strength ( ) is required by AS 3700

12 / Design of Clay Masonry for Wind and Earthquake

Ties are classified based on strength and stiffness as

Ties and connectors are commonly made from steel with

Design of Clay Masonry for Wind and Earthquake / 13

5.1 Wind Loading Earthquake loading is the force generated by horizontal

14 / Design of Clay Masonry for Wind and Earthquake

4. The height of the building. 5.2.1 Domestic structures

Design of Clay Masonry for Wind and Earthquake / 15

Other measures can be taken to improve horizontal

Attention should be paid particularly to detailing of

AS 1170.4 makes special provision for domestic structures.

Where the combination of probability factor and hazard

16 / Design of Clay Masonry for Wind and Earthquake

Design of Clay Masonry for Wind and Earthquake / 17

6.2 Mechanism of Load Transmission

18 / Design of Clay Masonry for Wind and Earthquake

The resulting structures are usually

Design of Clay Masonry for Wind and Earthquake / 19

20 / Design of Clay Masonry for Wind and Earthquake

Figure 3. Idealised Crack Patterns for Various Wall Configurations

Walls without openings:

Walls with openings: Typical opening

Design of Clay Masonry for Wind and Earthquake / 21

• Edge fixity occurs when the edge of the wall is

22 / Design of Clay Masonry for Wind and Earthquake

2.1 Housing 2.3 Low-rise Commercial and Industrial

6.2 Mechanism of Load Transmission

= Minimum design compressive stress on