Resistant Buildings
Resistant Buildings
Resistant Buildings
Engineering Standard
JERES-M-009
Design Criteria for Blast Resistant
Buildings
Revision
1
Responsibility
JER Engineering Division
30 July
2008
30 July 2008
Revision Tracking
Revision
Revision Date
Scope of Revision
30 July 2008
Paragraph : 3.1,4.2, 6.1, 6.4.3, 6.5.2, 8.1.1, 8.1.3, 8.1.4, 8.2, Appendix A,
B- 6.1, B- 6.3, B- 7.4.1, B-7.5.2
29 April 2008
03
10 April 2008
02
31 March 2008
01
03 August 2007
00
30 January 2007
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Table of Contents
Section
Contents
Page
Scope
References
Definitions
General
10
Basic Requirements
12
Structural Design
18
Ancillary Items
27
Appendixes
A
30
Commentary
33
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Page 3 of 56
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Scope
1.1
This standard establishes mandatory structural design criteria for new blast resistant
buildings, including requirements for selection of structural systems, analysis
methods, and design of ancillary items such as doors and openings.
1.2
This standard also contains design criteria for non-structural items (e.g., architectural
or electrical items, HVAC ductwork, etc.) that could pose a hazard to the occupants
of blast resistant buildings.
1.3
Other design aspects such as architectural design and structural design for normal
(non-blast) loads and foundation design are covered in JERES-M-100 Building
Code, and JERES-Q-005 Concrete Foundations.
Commentary Note:
Building designs and construction types that are based on this standard and may
conflict with requirements in the Safety and Security Directives (SSDs), published by
the Saudi Arabian Government High Commission for Industrial Security (HCIS), will
require approval of a deviation request. The user of this standard is encouraged to
submit a deviation request to the Company Representative in compliance with the
procedures in JERES-O-100, for any design that could result in significant cost
savings.
2.1
Any conflicts between this standard and other applicable Company Engineering
Standards (JERES), Material Specifications (JERMS), Standard Drawings (JERSD),
Engineering Procedures (JEREP), Company Forms or Industry standards,
specifications, Codes and forms shall be brought to the attention of Company
Representative by the Contractor for resolution.
Until the resolution is officially made by the Company Representative, the most
stringent requirement shall govern.
2.2
Where a licensor specification is more stringent than those of this standard, the
Licensors specific requirement shall apply.
2.3
Where applicable Codes or Standards are not called by this standard or its
requirements are not clear, it shall be brought to attention of Company
Representative by Contractor for resolution.
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2.4
Direct all requests for deviations or clarifications in writing to the Company or its
Representative who shall follow internal Company procedure and provide final
resolution.
References
The selection of material and equipment, and the design, construction, maintenance,
and repair of equipment and facilities covered by this standard shall comply with the
latest edition of the references listed below as of the CUT-OFF DATE as specified
in the Contract unless otherwise noted.
3.1
Company References
Company Engineering Standards
JERES-A-112
JERES-A-113
JERES-A-204
JERES-B-014
JERES-B-055
Plant Layout
JERES-K-100
JERES-M-100
Building Code
JERES-O-100
JERES-O-126
JERES-P-100
JERES-P-119
Onshore Substations
JERES-Q-005
Concrete Foundations
JERES-S-060
Plumbing Code
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Page 5 of 56
3.3
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ACI 530
ACI 530.1
ASTM A82
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ASTM C90
TM5-1300
Definitions
4.1
Definitions presented in this Standard and other JER documents have precedence
over other definitions. Conflicts between various definitions shall be brought to the
attention of Company Representative by the Contractor for resolution.
Company: Jubail Export Refinery.
Company Representative: A designated person from the Company or an assigned
third party representative.
Company Inspector: A designated person or an agency responsible for conducting
inspection activities on behalf of the Company.
4.2
List of Definitions
Definitions of the key blast resistant design terminology used in this standard are
listed below. A more complete list of definitions can be found in the ASCE Report.
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Angle of Incidence: The angle between the direction of the blast wave travel and a
line perpendicular to the surface of a structure at the point of interest.
Blast Loads: The transient dynamic loads from the blast effects of an explosion,
usually stated in terms of peak pressure and impulse or duration.
Conventional Loads: Loads applied in the conventional (non-blast) design of
structures including dead, live, wind and seismic loads as required by JERES-M-100.
These loads are typically statically applied.
Dynamic Increase Factor (DIF): A multiplier applied to the static strength of a
material to reflect the increased effective strength due to fast strain rates caused by
rapidly applied blast loads.
Ductility Ratio: A measure of the degree of plasticity in a member at maximum
dynamic response, equal to the maximum displacement divided by the displacement
at yield. This value is a key measure of dynamic response.
Duration: The length of time from start of the initial positive phase of the blast
pressure to the return to ambient pressure.
Dynamic Reaction: The support reaction of a structural component to the dynamic
blast loading, taking into account inertia effects.
Engineer: The engineer with overall authority and responsibility for the structural
design of the blast resistant building.
Fragment Resistant: The resistance to high-speed fragments that are the result of
the break up of equipment or structures that are close to the explosion source.
Free-Field Pressure: The rise in pressure above ambient pressure produced by a
blast wave sweeping unimpeded across a surface not facing the blast source. Also
referred to as side-on pressure.
Impulse: A measure used, along with the peak blast pressure, to define the ability of
a blast wave to do damage. Impulse is calculated as the integrated area under the
positive pressure versus duration curve and is shown in units of MPa-ms (psi-ms).
Multi-Degree-of-Freedom (MDOF): Representation of a structure or component as
a spring-mass system with more than one degree-of-freedom.
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Multi-Unit Building: Building used for support of multiple process units, where loss
would adversely impact several, separate process units.
Negative Phase: The portion of the pressure-time history typically following the
positive (overpressure) phase in which the pressure is below ambient pressure
(suction).
Nonlinear Response: Deformation of a component or system beyond the elastic
limit.
OME/Team Building: An occupied in-plant building housing operations,
maintenance, and/or engineering personnel.
Owner: Jubail Export Refinery or a designated representative.
Period: The fundamental natural period of a structural component if modeled as a
single-degree-of-freedom (SDOF) system.
VCE: Vapour Cloud Explosion
PES: Potential Explosion Site is a congested/confined volume where a VCE could
occur. A PES is a potential blast source.
PIB: Process Interface Building
Positive Phase: The portion of the pressure-time history in which the pressure is
above ambient pressure.
Rebound: The deformation in the direction opposing the initial blast pressure. This
occurs after a component has reached a peak deformation and returns in the direction
of its initial position.
Reflected Pressure (Pr): The rise in pressure above ambient produced by a shock
wave or pressure wave striking a surface facing the direction of blast wave
propagation.
Response Range: The degree of structural damage permitted for blast resistant
buildings. The following descriptions apply to the response ranges mentioned in this
standard:
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Page 9 of 56
Low (L):
30 July 2008
Medium (M): Blast resistant Building shall withstand shock due to the
overpressure. Personnel remain alive and equipment sufficiently
serviceable. Repairing total cost is moderate.
High (H):
General
5.1
5.1.1
The following blast design requirements shall be included in the BDR Data Sheet:
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5.1.1.1
5.1.1.2
Performance categories (I - IV) (refer to Table 11) for blast resistant doors.
5.1.1.3
Blast loads specified as peak side-on positive pressure with corresponding impulse or
duration at the building (see Section 6.3).
5.1.2
5.1.2.1
5.1.2.2
Non-structural requirements:
5.1.2.3
5.2
Engineers Responsibilities
5.2.1
5.2.2
The Engineer shall be responsible for producing a design, using sound engineering
principles that meet the requirements of this standard.
5.2.3
The Engineer shall be responsible for designing the facility to meet the performance
requirements specified in the Blast Design Requirements (BDR) Data Sheet.
5.2.4
The Engineer shall bring any items requiring clarification to the Owners attention.
5.3
Documentation
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5.3.1
The final design shall be prepared by the Engineer per JERES-A-204 and shall
include the following documentation:
5.3.1.1
5.3.1.2
Supporting calculations covering the design criteria, methodology, results, and the
references and tools used.
5.3.1.3
Basic Requirements
6.1
Building Performance
The degree of structural damage permitted for blast resistant buildings, known as
building response range, will be as specified in Table 1. The building shall be
designed to resist the applied blast loads in the BDR Data Sheet within the required
building response range.
Table 1 Building Blast Design Requirements
Building Type
Main Control Building
Response
Range
L
Door
Performance
Category(1)
I (4)
Permitted Structural
Systems (see Table 2 )
0
Multi-Unit PIB/SIH
0,1
Single-Unit PIB/SIH
0,1
Multi-Unit Substation
(5)
0,1
Single-Unit Substation
II
II
0,1
Warehouse/Storage
III
1,2,3,4,5,6
Maintenance Shop
III
1,2,3,4,5,6
0,1
Operator Shelter
0,1
Utility Building
Emergency Generator Building
Other Buildings
II
1,2,3,4,5,6
M(3)
II
1,2,3,4 & 6
(see note 2)
(see note 2)
(see note 2)
Notes:
1)
This performance category is required for doors that are designated as egress doors. All other doors shall be designed
to Door Performance Category III.
2)
For building types not shown, follow results of BRA and dedicated JSD or contact the Company Representative for
the design requirements.
3)
For generator facilities providing backup for multiple unites response range shall be L.
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Page 12 of 56
4)
5)
30 July 2008
Structural System
Cast-In-Place Concrete Frame
Cast-In-Place Concrete Frame
or Shear Walls
Cast-In-Place Concrete Frame
or Shear Walls
Hot-Rolled Steel Frame
Wall Cladding
Cast-In-Place Concrete
Precast or Cast-In-Place
Concrete
Solid-Grouted Reinforced
CMU
Precast or Cast-In-Place
Concrete
Roof Deck
Cast-In-Place Concrete
Precast or Cast-In-Place
Concrete
Precast or Cast-In-Place
Concrete
Precast or Cast-In-Place
Concrete
Load-Bearing, Solid-Grouted
Reinforced CMU or Precast
Concrete panels
Solid-Grouted Reinforced
CMU
Steel Single Sheet or
Sandwich Panel
Load-Bearing, Solid-Grouted
Reinforced CMU or Precast
Concrete panels
Precast or Cast-In-Place
Concrete
Steel Single Sheet or
Sandwich Panel
Precast or Cast-In-Place
Concrete
6.2
Building Configuration
6.2.1
6.2.2
The floor plan and elevation shall have a clean rectangular profile without re-entrant
corners and recessed areas.
6.3
Blast Loads
6.3.1
General
6.3.1.1
Each blast resistant building shall be designed for the dynamic blast loads provided
in the BDR Data Sheet.
6.3.1.2
Blast loads on individual building surfaces shall be calculated from the specified
side-on pressure using the methods described in Chapter 3 of the ASCE Report Design of Blast Resistant Buildings in Petrochemical Facilities.
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6.3.1.3
6.3.2
Component Loads
6.3.2.1
6.3.2.1.1 The direct tributary blast load applicable to the surface of the building on which it is
located
6.3.2.1.2 The dynamic reaction to the blast load on a supported component, as appropriate
6.3.2.1.3 The ultimate load capacity of the supported component.
6.3.2.2
6.3.3
Foundation Load
The foundation for a blast resistant building shall be designed per Section 7.7 and
JERES-Q-005 using any one of the following:
6.3.3.1
The peak dynamic reactions from the supported superstructure treated statically
6.3.3.2
6.3.3.3
The tributary area method. This method may be used in conjunction with the applied
blast loads to determine foundation response using a dynamic analysis method.
6.4
6.4.1
General
The structural system and materials shall be selected to provide the most economical
design that meets all performance requirements or as dictated by the Owners
specifications or architectural considerations.
6.4.2
Brittle Construction
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Void
6.4.4
Advanced Materials
Advanced materials, such as composites, may be used if adequate test data are
available to confirm their satisfactory performance for the intended application, and
with the prior written approval of the Company Representative. Such test data shall
include the ultimate capacity and behavior of the material under dynamic conditions
representative of blast loading. Satisfactory performance of the material under
seismic conditions is not sufficient to indicate blast capacity.
6.4.5
Fragment Resistance
Reinforced concrete or fully-grouted reinforced masonry of appropriate strength and
thickness shall be used as cladding where fragment resistance is required per the
BDR Data Sheet.
Commentary:
TM5-1300 contains design procedures for structures that are fragment resistant in the
BDR Data Sheet.
6.5
Material Properties
6.5.1
6.5.1.1
(1)
6.5.1.2
Dynamic Design Stress, Fds, used to calculate the dynamic capacity of structural
components shall be accordance with the values listed in Tables 6 and 7 for
structural steel and reinforcing steel, respectively.
6.5.1.3
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Page 15 of 56
Fdu = Fu * DIF
where,
6.5.2
30 July 2008
(2)
6.5.3
SIF
1.1
1.1
1.2
1.1
1.0
Other materials
1.0
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Table 4 Dynamic Increase Factors (DIF) for Reinforced Bars Concrete and Masonry
DIF
Stress Type
Reinforcing Bars
Concrete
Masonry
Fdy/Fy
Fdu/Fu
fdc/fc
fdm/fm
Flexure
1.17
1.05
1.19
1.19
Compression
1.10
1.00
1.12
1.12
Diagonal Tension
1.00
1.00
1.00
1.00
Direct Shear
1.10
1.00
1.10
1.00
Bond
1.17
1.05
1.00
1.00
Ultimate
Bending/Shear
Tension/Compression
Stress
Fdy/Fy
Fdy/Fy
Fdu/Fu
A36/A36M
1.29
1.19
1.10
A572/A572M,
A588/A588M,
A992/A992M
1.19
1.12
1.05
A514/A514M
1.09
1.05
1.00
A653/A653M
1.10
1.10
1.00
Prestress Reinforcement
1.00
1.00
1.00
1.18
1.15
1.00
Aluminum, 6061-T6
1.02
1.00
1.00
Where
Type
of
Stress
Maximum
Ductility
Ratio
Dynamic
Design
Stress (Fds)
All
< 10
Fdy
All
> 10
Fdu
Fdy
= ductility ratio
= dynamic ultimate strength
= dynamic yield stress
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Type of
Reinforcement
Tension
and
Compression
Maximum
Support Rotation
Diagonal Bars
Fdy
Fdy + (Fdu - Fdy)/4
(Fdy + Fdu)/2
Fdy
0<2
2<5
5<12
Diagonal Tension
Stirrups
0<2
2<5
5<12
all
Compression
Column
all
Structural Design
7.1
Dynamic Design
Stress (Fds)
Fdy
Fdy + (Fdu - Fdy)/4
(Fdy + Fdu)/2
Fdy
All blast resistant buildings and their structural components shall be designed in
accordance with the methods outlined in ASCE Design of Blast Resistant Buildings
in Petrochemical Facilities. Alternate design methods may be used only with prior
written approval of the Company Representative.
7.2
Load Combinations
7.2.1
(3)
where:
U(t) =
B(t) =
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7.2.2
The blast load combination shall consider either the direct loads or their effects. In
combining blast load effects with those from static dead and live loads, the time
dependence of the blast loading shall be considered.
7.2.3
Wind and seismic loads shall not be combined with blast loading.
7.2.4
Rebound effects shall be calculated and combined with the effects of negative phase
blast loads, if any, based on time dependent response.
7.3
Analysis Methods
The Engineer shall use analysis methods appropriate for the specific blast design.
The selected methods shall adequately model the dynamic response of the structure
to the applied blast loads and the structural component interaction. Except as
specified in Sections 7.3.1, 7.3.2 and 7.3.3, the analysis methods shall be in
accordance with ASCE Design of Blast Resistant Buildings in Petrochemical
Facilities, Chapter 6.
7.3.1
7.3.2
Single-Degree-of-Freedom (SDOF)
The required resistance for each structural component shall be based on the peak
blast pressure (or load) and duration, the natural period of the component, and the
maximum allowable response (deformation). An SDOF analysis can be used where
the connected components differ in natural period by a factor of two or more. The
formulas and charts provided in ASCE Design of Blast Resistant Buildings in
Petrochemical Facilities, Chapter 6, TM5-1300, or other similar references for the
approximate solution of the elastic-plastic SDOF system may be used in determining
the required resistance.
7.3.3
Multi-Degree-of-Freedom (MDOF)
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Deformation Limits
7.4.1
Response Parameters
Structural members shall be designed based on maximum response (deformation) in
accordance with the performance requirements or permissible damage level specified
in Table 1. Deformation limits shall be expressed as ductility ratio (), support
rotation (), or frame sidesway, as appropriate.
7.4.2
7.4.3
Response Limits
Maximum response shall not exceed the limits specified in Tables 8, 9, and 10 for
structural steel, reinforced concrete, and reinforced masonry, respectively.
Table 8 Deformation Limits for Structural Steel
Response Range(2)
Element Type
Low
Medium
High
10
20
12
1.5
1.5
1.75
1.25
1.5
Open-Web Joists
Plates
5
3
10
6
20
Notes Table-8:
(1) Sidesway limits for steel frames:
low
= H/50
medium = H/35
high
= H/25
2) Response parameter: = ductility ratio, = support rotation (degrees)
12
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Controlling
Stress
Beams
Slabs
BeamColumns
Shear Walls,
Diaphragms
Ductility
Ratio,
Flexure
Shear: (1)
- Concrete Only
- Concrete +
Stirrups
- Stirrups Only
Compression
N/A
Flexure
Shear: (1)
N/A
1.3
Flexure
Compression
Tension
Shear (1)
N/A
1.3
(3)
1.3
Flexure
Shear (1)
3
1.5
1.5
1.3
1.6
3.0
1.3
1)
Shear controls when shear resistance is less than 120% of flexural resistance.
2)
3)
Ductility ratio = 0.05 ( - ) < 10, where and are the tension and compression reinforcement
ratios, respectively.
Ductility
Ratio,
Low
One-Way
0.5
0.75
Two-Way
0.5
7.5
Component Design
7.5.1
General
Ultimate strength (limit state) methods shall be used for designing structural
components for blast resistance. The ultimate strength capacity shall be determined
in accordance with the applicable codes, practices and guides specified in Section 3,
subject to the following additional requirements:
7.5.1.1
In-plane and secondary bending stresses shall be accounted for in the design.
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7.5.1.2
7.5.1.3
Dynamic strength properties shall be used to reflect increased material strength under
rapidly applied loads.
7.5.1.4
Load and resistance factors shall be taken equal to 1.0 in all blast load combinations.
7.5.1.5
Composite sections can be used for design; however, adequate rebound resistance
shall be provided to ensure satisfactory response under rebound or negative phase
loads.
7.5.1.6
7.5.1.7
7.5.1.8
Design for compression elements, such as load-bearing walls and exterior columns,
should consider secondary bending effects including P-delta and slenderness.
7.5.2
Reinforced Concrete
Reinforced concrete components shall be designed, using ultimate strength methods,
in accordance with the provisions of ACI 318M and ASCE Design of Blast Resistant
Buildings in Petrochemical Facilities. The following specific requirements shall also
apply:
7.5.2.1
The strength reduction factor () shall be 1.0 for load combinations that include blast
loads.
7.5.2.2
Deformation limits for shear shall be used if the members shear capacity is less than
120% of the flexural capacity.
7.5.2.3
The design compressive strength of 28 MPa (4,000 psi) shall be used for the design
of concrete construction.
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7.5.2.4
Reinforcing bars shall conform to SASO SSA 2/1979 High Yield 420 MPa (grade
60), except that ASTM A706/A706M shall be used where welding of bars is
required. The maximum bar size shall be 32 mm (No. 10).
7.5.2.5
Minimum reinforcing requirements of ACI 318M apply, however, the option to use
one third more reinforcing than computed shall not be taken.
7.5.2.6
Wall and roof components shall be designed for in-plane and out-of-plane loads that
act simultaneously by using the following interaction equation:
= allowable deformation
= in-plane
= out-of-plane
7.5.2.7
Slenderness effects shall be included for load bearing walls and members with
significant axial loads.
7.5.2.8
Support shall be provided for roof slab to prevent failure during rebound. Headed
studs can be used for this purpose; however, unless composite action is required and
included in the design the studs shall be located and spaced to minimize composite
action.
7.5.3
Structural Steel
Structural steel components shall be designed in accordance with the provisions of
AISC LRFD, supplemented by the following requirements:
7.5.3.1
Materials with a specified yield strength of 345 MPa (50 ksi) or less shall be used for
flexural design. Higher strength materials may be used where ductile behavior is not
required.
7.5.3.2
Oversized holes shall not be used in connections that are part of the lateral forceresisting system.
7.5.3.3
7.5.3.4
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7.5.3.5
Column base plates shall be designed to develop the peak member reactions applied
as a static load. Dynamic material properties can be used for design of base plates.
7.5.3.6
7.5.4
Cold-Formed Steel
Cold-formed steel components shall be designed in accordance with the
AISI Manual, supplemented by the following specific requirements:
7.5.4.1
Ultimate resistance shall be determined using a factor of 0.9 applied to the plastic
moment capacity.
7.5.4.2
7.5.4.3
Tensile membrane capacity of cold-formed girts and purlins can be used in the
design if the girts and purlins are supported on the exterior face of a frame member
and are continuous over three or more spans.
7.5.4.4
Oversize washers shall be provided for wall panel anchorage screws to prevent
failure caused by rebound or negative phase loads.
7.5.5
7.5.5.1
Unless special provisions are made to enhance ductility of the joist, a 10% reduction
in ultimate moment capacity shall be used.
7.5.5.2
Lateral bracing shall be provided for the top and bottom chords as required to
provide the necessary rebound resistance and positive moment capacity.
7.5.6
Reinforced Masonry
Design of reinforced masonry shall be in accordance with the ultimate strength
method in ACI 530, ACI 530.1 and the IBC supplemented by the following specific
requirements:
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7.5.6.1
7.5.6.2
7.5.6.3
Joint reinforcing shall be in accordance with ASTM A82 with a minimum yield
stress of 485 MPa (70 ksi) and a minimum ultimate strength of 550 MPa (80 ksi).
7.5.6.4
Primary reinforcing bars shall be in accordance with SASO SSA 2/1979 High Yield
420 MPa (grade 60).
7.5.6.5
7.6
7.6.1
Static Analysis
Support members may conservatively be designed statically for the reactions due to
the ultimate resistance of the wall and roof components being supported or for the
peak dynamic reactions from the supported components treated as static loads. For
blast load combinations, factors of safety for overturning shall be 1.2, and 1.0 for
sliding.
7.6.2
Dynamic Analysis
As an alternative to the simplified, but conservative, static analyses specified above,
a dynamic analysis may be performed to determine interaction of components,
sidesway, sliding and overturning response of the overall structural system to the
blast loading.
7.7
Foundation Design
Foundation design shall be based on a geotechnical report per JERES-A-113 and the
geotechnical data summarized in the Section A-4 of the Basic Design Requirements
(BDR) Data Sheet. Foundation components shall be designed per ASCE Design of
Blast Resistant Buildings in Petrochemical Facilities and JERES-Q-005 to resist the
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Page 25 of 56
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peak reactions produced by supported components resulting from the dead, live, and
blast loads, treated either statically or dynamically, as noted below.
7.7.1
Static Analysis
Static application of the peak dynamic reactions from the wall and roof components
can be used to design supporting members and to calculate overturning and sliding
effects. For blast load combinations, factors of safety for overturning shall be 1.2,
and for sliding shall be 1.0.
7.7.2
Static Capacity
Foundations shall be designed using vertical and lateral soil capacities as follows:
7.7.2.1
Vertical - 80% of the ultimate net soil bearing capacity for shallow foundations,
including footings and mats. For piles and other deep foundations 80% of the
ultimate static capacities in compression and in tension may be used.
7.7.2.2
Lateral - Passive resistance of grade beams may be used to resist lateral loads if
compacted fill is placed around the building perimeter. Frictional resistance of
spread footings and floor grade slabs shall be based on the coefficient of friction
determined by the geotechnical study. The normal force shall be the sum of the dead
loads and the vertical load associated with the ultimate resistance of the roof.
Frictional resistance of floating slabs shall not be used.
7.7.2.3
If only passive resistance, frictional resistance, vertical piles, or battered piles are
used to support the lateral blast loading, the design resistance shall be 80% of the
ultimate static value. However, if two or more of these resistances are used to
support the lateral blast loads, the lateral capacity shall be limited to 67% of the
combined ultimate static resistance.
7.7.2.4
Foundation sliding can be permitted but limited to 10mm if demonstrated that all
underground and aboveground utility, electrical, and instrumentation lines entering
and exiting the building have adequate flexibility to accommodate the slide.
7.7.3
Dynamic Analysis
To optimize the design, the foundation components can be analyzed dynamically for
the calculated reaction-time history of the supported components. The required
dynamic material properties of the foundation soils, including resistance and
stiffness, shall be determined based on an appropriate geotechnical investigation. No
deformation limits are specified for dynamic response of foundations. Based on the
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Page 26 of 56
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Ancillary Items
8.1
Blast Doors
Blast resistant doors shall be provided according to the following:
8.1.1
The performance category for the blast resistant doors shall be in accordance with
Table 1. The response limits and other requirements shall be as given in Table 11.
Table 11 Blast Door Performance Requirements
Ductility
Limit,
1.0
Edge
Rotation,
(deg)
1.2
Significant
damage
Prevent entrapment
Substantial
damage
10
Category
Hardware
Panels
Operable
Elastic
II
Operable
III
Inoperable
Door Function
Primary exit or
repeated blasts
8.1.2
In buildings large enough to require more than one egress door in accordance with
JERES-M-100 and the IBC, at least two doors shall be designated as egress doors for
the purpose of limiting the damage to these doors if subjected to blast loads.
Designated egress doors shall not be located on the same side of the building.
8.1.3
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Page 27 of 56
30 July 2008
THE doors shall be preferably on all four edges. Allowance should be made for the
provision of at the bottom edge. Alternatively a design for door leafs principally
supported on three edges may be acceptable if the provision of a step is not
practicable.
Double leaf doors (or 1% leaf doors) necessary for plant/equipment access, shall
have removable central step posts bolted to the door frame to support the door leafs.
Such doors shall not have window/vision panels, shall remain closed during normal
plant operations and the design shall discourage unauthorised used.
The doors shall be designed to facilitate easy operation under normal loads. Manual
operation is preferred but if power assistance is required, overload/proximity trips
shall be specified.
The doors shall be readly operable after a blast and remain functional. The doors
shall be designed for the lesser of ductility ratio of 5 and peak support rotation of 1.
8.1.4
8.2
Windows
When exterior windows will be used, as per JERES-B-014, they must resist to the
same blast load of the wall in which they are located.
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Page 28 of 56
8.3
30 July 2008
Openings
Large openings in the building envelope, such as intake ducts, shall be designed to
prevent entry of blast pressures.
8.3.1
Blast valves, blast attenuators, or other devices shall be used to limit blast pressure
entry into the structure. Performance of the blast valve or attenuator shall be
substantiated by test data and calculations.
8.3.2
Blast valves shall be provided for openings greater than 1000 cm (150 in) in any
surface in which the peak applied blast pressure is greater than 0.07 MPa (10 psi).
Blast attenuators can be used for openings greater than 1000 cm (150 in2) if the peak
applied pressure is not greater than 0.035 MPa (5 psi).
8.4
Penetrations
8.4.1
Wall and roof penetrations in reinforced concrete and masonry shall be sleeved.
Sleeves shall be anchored with a minimum of 2 each 12 mm diameter x 100 mm (
x 4) long headed studs.
8.4.2
8.5
Suspended Items
Equipment and furnishings such as ceilings, HVAC ductwork and light fixtures
suspended from the roof inside the building shall be secured to structural framing
members. Anchorage shall be designed to resist a statically applied force equal to the
mass of the item times the maximum acceleration of the roof or five times the weight
of the item, whichever is less.
8.6
8.6.1
To avoid the potential for hazardous debris, large non-structural features such as
canopies and post-mounted signs on the building exterior shall not be permitted.
However, small items such as instruments, fire alarms, lights, strobes and beacons
can be mounted on the exterior walls.
8.6.2
Roof and wall mounted equipment (e.g., HVAC equipment) shall not be used
without prior written approval from the Company Representative. If approved, such
equipment shall be securely anchored, and the supporting structural components
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Page 29 of 56
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shall be specifically designed for actual equipment dynamic loads if subjected to the
blast.
8.6.3
Equipment and other items mounted on the exterior surfaces (walls or roof) of the
building shall be designed similar to the structural components if they are to
withstand the applied blast loads. The reactions from such items shall be considered
in the design of the supporting structural components. If the externally mounted
items are not required to resist the blast loading, the supporting components shall be
designed for the failure, or ultimate resistance, loads from these items.
8.7
8.7.1
8.7.2
All fixed floor supported items (e.g., lockers, electrical cabinets, racks, etc.), shall
have a minimum clearance from exterior walls equal to the maximum calculated
lateral blast load deflection. The maximum deflection shall consider both the overall
building sidesway and the deflection of any wall component(s) and shall be
calculated based on the maximum blast loads defined in the BDR Data Sheet.
Supports and anchorage for such equipment shall be designed to resist a lateral force
equal to 20% of the equipment weight.
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Page 30 of 56
30 July 2008
Facility Name/Location:
Unit:
Job Number:
Building Name:
Building Number:
AA-1.
A-1.1
A-1.2
A-1.3.
Yes
No
PES Description
Reflected
Wall (3)
(N, S, NE,
SW, etc.)
(4)
Peak Side-On
Pressure (2)
unit: (5):
P1
P2
Duration (6)
msec
T1
T2
T3
T4
Notes:
(1) A PES (Potential Explosion Site) is a congested/confined volume where a VCE could occur. A PES is a potential blast source.
(2) Side-on pressure shall be computed at the wall nearest to the blast center.
(3) The reflected wall(s) may be different for each PES. Indicate the reflected wall(s) (N, S, NE, SW, etc.) facing the blast center.
(4) Indicate angle of blast center (in degrees) measured from a line normal to reflected wall. See Figure A1 on next page.
(5) Specify pressure unit (psig, MPa, millibar, bar, etc.).
(6) If rise time is a small percentage of the positive phase duration then use load shape A as shown in Figure A1. Negative phase pressure is
typically not considered, however if the explosion modeling software predicts a significant negative phase pressure it should be tabulated.
No.
Date
Description
By
Check.
App.
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Page 31 of 56
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Page 2 of 3
P1, T1
T1
Pressure
Pressure
P1
T3
Duration
T2
T4
Duration
P2, T3
P2, T2
Load Shape A
Direction of Blast
Load Shape B
Building
Plan View
Blast Door
ID or No.
Building Face
Door Location
( N, S, NE, SW, etc.)
Performance
Category (see Table 11)
(I, II)
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Page 32 of 56
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Page 3 of 3
A-4. Geotechnical Requirements (Refer to JERES-A-113)
A-4.1. Foundation Type (Select one and provide data in the appropriate section.):
Mat Foundation
Spread Footing
Pile Supported
A-4.2. Mat Foundation
Item
Ultimate Net Bearing Capacity
At Depth
Dynamic Modulus of Subgrade Reaction
Sliding Friction Coefficient
Passive Pressure Coefficient
Value
kN/m (psf)
m (ft)
kN (kips)
kN (kips)
kN/m (kips/in)
kN/m (kips/in)
( * ) Note: Choose unit from list or enter user-defined name under Special Unit.
A-5. Other Special Requirements:
Blast Valves
Blast Attenuators
Special Requirements:
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Page 33 of 56
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Appendix B Commentary
B-1
INTRODUCTION
B-1.1
Purpose
This Engineering Standard focuses on the structural design of blast resistant
buildings to be performed by a structural engineering professional (Engineer). The
requirements for the conventional and the non-structural (architectural, electrical,
HVAC, etc.) designs of such buildings are covered in other Jubail Export Refinery
standards as indicated in Section 5.1.2.
This commentary to the Standard provides additional information regarding the
selection and application of the blast design requirements. The commentary is not a
part of the design requirements but is intended to assist the Owner and Engineer in
applying the criteria during the course of the design.
B-1.2
Scope
This Standard is meant to cover new facilities when the Owner invokes it. It does not
specifically address existing facilities; however, the methods discussed are
applicable to analysis of existing buildings and the design of retrofits for such
buildings. The Engineer should refer to the ASCE Design of Blast Resistant
Buildings in Petrochemical Facilities (1) for specific guidance on analysis of existing
facilities.
Some buildings may not require design for blast for a variety of reasons, including
negligible blast loads levels or non-essential functions, or they may not be occupied
according to the Owners occupancy criteria. The Owner should determine whether
blast design is required for each facility and specify this in the project or job
specifications.
A common issue related to design of structures at petrochemical facilities is the
lower limit of overpressure below which blast resistant design is not required. Many
companies have cutoffs ranging from 0.5 psi (3.4 kPa) to 1.0 psi (6.9 kPa) side-on
overpressure. This load level will produce damage to conventional buildings, with
damage ranging from cosmetic to moderate requiring repair for continued use.
The most rational approach is to design each building at a site for the predicted blast
load predicted from Building Risk Assessment studies. However, this may not
always be practical, in which case an acceptable lower bound overpressure level
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Page 34 of 56
30 July 2008
must be established for conventional construction below which blast design need not
be considered.
Building occupancy may be used in determining the need for blast resistance in new
or existing buildings. However, this Standard does not cover occupancy criteria,
which are addressed in standard JERES-B-014 and other industry guidelines such as
API RP 752(2).
Application of this Standard for blast design may be influenced by future plant or
process unit development. A building may be at risk at some point in the future if a
process unit is modified or if a new unit is added that can produce higher
overpressures at a given structure. A master plan for facility siting is highly desirable
to address this issue.
B-3
References
The Standard is based primarily on the design methods and procedures provided in
ASCE Design of Blast Resistant Buildings in Petrochemical Facilities (1). However,
other similar references and guidelines may be used. There are a number of other
applicable references for design of blast resistant structures, including those
developed for U.S. Department of Defense purposes. One of the most widely used of
these references, TM5-1300(3), is also applicable to petrochemical facilities.
However, the ASCE Design of Blast Resistant Buildings in Petrochemical Facilities
(1) is a how to document, which covers all aspects of blast design for buildings at
petrochemical plants.
This commentary lists references relevant to blast resistant design some of which are
also included in the References Section of JERES-M-009.
1.
2.
3.
TM 5-1300 - Structures to Resist the Effects of Accidental Explosions, U.S. Dept. of the
Army, November 1990
4.
Siting and Construction of New Control Houses for Chemical Manufacturing Plants,
Safety Guide SG-22, Manufacturing Chemists Association, Washington, DC, 1978.
5.
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Page 35 of 56
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6.
Design of Structures to Resist Nuclear Weapons Effects, Manual No. 42, Committee on
Dynamic Effects, American Society of Civil Engineers, New York, NY, 1985.
7.
8.
Guidelines for Evaluating Process Plant Buildings for External Explosions and Fires,
Center for Chemical Process Safety of the American Institute of Chemical Engineers,
New York, NY, 1996.
9.
Guidelines for Evaluating the Characteristics of Vapor Cloud Explosions, Flash Fires
and BLEVEs, Center for Chemical Process Safety of the American Institute of
Chemical Engineers, New York, NY, 1994.
10. Method for the Determination of Possible Damage to People and Objects Resulting
from Releases of Hazardous Materials (CPR 16E), (Green Book), Committee for the
Prevention of Disasters Due to Dangerous Substances, The Director-General of Labour,
The Hague, 1992.
11. Structural Dynamics: Theory and Computation, third edition, M. Paz, Van Nostrand
Reinhold Inc., New York, NY, 1991.
12. Introduction to Structural Dynamics, J. M. Biggs, McGraw-Hill Book Company, New
York, NY, 1964.
13. Building Code Requirements for Structural Concrete (ACI 318-05) and Commentary
(ACI 318R-05), ACI Committee 318, American Concrete Institute, Detroit, MI, 2005.
14. Load and Resistance Factor Design Specification for Structural Steel Buildings,
American Institute of Steel Construction, Chicago, IL, December 27, 1999.
15. Specification for the Design of Cold-Formed Steel Structural Members, Load and
Resistance Factor Design, Cold-Formed Steel Design Manual, American Iron and Steel
Institute, 1997.
16. Standard Specifications and Load Tables for Steel Joists and Joist Girders, Steel Joist
Institute, August 2002.
17. Structural Welding Code - Steel, ANSI/AWS D1.1/D1.1M:2004, American Welding
Society, 2004.
18. Building Code Requirements for Masonry Structures, ACI 530-05/ASCE 5-05/TMS
402-05, American Concrete Institute, 2005.
19. International Building Code, International Code Council, Whittier, CA, 2003.
20. Design of Structures to Resist the Effects of Atomic Weapons, Technical Manual
5-856-1, Department of the Army, Washington, DC, January 1960.
21. Overturning and Sliding Analysis of Reinforced Concrete Protective Structures,
Technical Publication 4921, U.S. Army Picatinny Arsenal, Dover, NJ, 1976.
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any means without prior approval by the Company.
Page 36 of 56
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SG-22 and An Approach to the Categorization of Process Plant Hazard and Control
Building Design (commentary references 4 and 5, respectively) have been widely
used for a number of years. These documents provide requirements for design of
new facilities but are based on TNT-equivalent blast loads and the equivalent static
load design method. They do not cover the more accurate design methods, the more
complex forms of blast loads, or the structural design tools, which are now available
and commonly used.
B-4
Definitions
The terminology used in this Standard is consistent with ASCE Design of Blast
Resistant Buildings in Petrochemical Facilities (1) and other blast design manuals
such as TM5-1300(3) and ASCE Manual 42(6). Some differences in definitions,
especially for symbols, may exist in blast load prediction manuals. The Engineer
should verify any conflicting definitions.
B-5
General
B-5.1
B-5.2
Engineers Responsibilities
The Engineer is responsible for designing a structure that provides protection in
accordance with the response criteria based on the building performance
requirements provided by the Owner or defined in this Standard. In situations for
which a particular blast protection requirement is not covered in this Standard,
conservative design assumptions should be made to ensure safety. The Owner should
cover topics or issues not addressed. The Engineer should bring items requiring
clarification to the Owners attention as soon as possible to avoid project delays.
B-5.3
Documentation
The BDR Data Sheet should completely describe the design criteria, blast loads,
structural system, and ancillary equipment. Material and section properties should be
tabulated to aid in future evaluation of alternate blast loads.
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Page 37 of 56
B-6
Basic Requirements
B-6.1
Building Performance
30 July 2008
Building
Response
Range
Low (L)
Medium (M)
High
The Owner should decide what philosophy is to be adopted in setting the response
range for evaluating and retrofitting existing buildings for blast resistance. In some
cases because it is normally much less costly to incorporate blast resistance into a
new facility than to retrofit a structure to increase its blast capacity, greater damage
to an existing facility may be more tolerable than would be permitted for a new
design.
B-6.2
Building Configuration
Blast resistant buildings should preferably be one-story construction with eave
heights ranging up to 6 m (20 ft). Two-story construction may be required but should
be used only when absolutely required. Two-story construction may be required if
limited plot area prevents the layout of a single-story building. The floor plan for a
building requiring blast resistance should be as simple as possible. A box type
structure is preferable, in which the shorter side is exposed to the larger reflected
blast load, and the longer side is exposed to the lower side-on blast load value. Roof
overhangs, canopies, and re-entrant corners should be avoided if possible to avoid
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Page 38 of 56
30 July 2008
additional blast wave reflections. Architectural items such as canopies and signs
should be designed with light construction materials, such as canvas, to avoid
creating a debris hazard for the structure.
B-6.3
Blast Loads
This Standard does not cover development of explosion scenarios or prediction of
blast loads, which therefore remain for the Owner to determine in accordance with
JERES-B-014. Methods for blast load prediction and considerations for determining
the design basis accident scenarios are provided in commentary references 6 through
10.
The Owner should specify the design blast load data in the Data Sheet (see Appendix
A). As a minimum, the side-on overpressure and duration at the building location
should be provided. The Engineer may use the procedures provided in ASCE(1) to
calculate the component blast loads on the basis of given side-on blast effects. The
Owner may also provide more detailed information from a site-specific study,
including the side-on or reflected pressure-time profile and orientation (angle of
incidence) of the blast loading on each surface of the building. In this case, the
Engineer should verify the location of the point of reference for the design blast
loads. If sufficient information is available, including the location of the explosion
reference point (epicenter) and the attenuation of the blast effects with distance from
this point, variation of the blast load over the surfaces of the structure may be
considered in the design.
Generally there are three approaches to specifying blast load for designing new
facilities:
1)
Using existing code/industry practice (default) values such as provided in SG22(4) and the UK CIA(5) Guide
2)
3)
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loads can only be approximated. In these situations, generic blast loads may be
appropriate. Such loads may be based on a building category or classification defined
by its occupancy or function following a blast and the separation distance from a
potential explosion hazard, as illustrated in Table B2.
Table B2. Building Classification Matrix
Building
Classification
Based on Blast
Severity or
Spacing
Separation
Distance
ft (m)
Minimum
Pressure
psi (kPa)
Impulse
psi-ms
(kPa-ms)
Maximum
Building Performance
Requirement & Damage Level
(H, M, & L)
Damage
Limiting
I (L, M)
Collapse
Limiting
II (H)
Hazard
Limiting
III (N/A)
A
B
C
D
For reference, both SG-22(4) and the CIA Guide(5) specify two sets of blast loads for
control buildings spaced 100 ft (30 m) to 200 ft (60 m) from a blast hazard (Building
Class A-I, per Table B2). The first set is based on a side-on overpressure of 10 psi
(69 kPa) for 20 msec, and the second on 3 psi (20.7 kPa) for 100 msec. The CIA
Guide(5) also specifies that such building should not collapse (that is, Class C-II) if
subject to a worst-case blast load corresponding to 14.5 psi (100 kPa) side-on
overpressure for 30 msec.
B-6.3.2
Component Loads
The blast load on each component of a building depends on the orientation of the
building surface on which it is located. The following is a discussion of the blast
loads for the main building components:
1)
Wall Load
Normal reflection may be assumed without consideration of the angle of
incidence of the blast wave. Clearing effects of the reflected blast wave may be
considered by using the approach described in ASCE(1) or TM5-1300(3).
2)
Roof Load
Roof load should be calculated using the methods provided in ASCE(1), on the
basis of the blast wave direction, component span, and spacing. For a flat roof
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Page 40 of 56
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(slope less than 20 degrees), roof load may be conservatively taken as the sideon value unless otherwise specified. For roofs sloped more than 20 degrees, the
effects of blast wave reflection should be considered.
3)
4)
5)
B-6.4
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components can develop tensile membrane action, which significantly increases their
capability to resist load.
B-6.4.1
General
Brittle structures, such as unreinforced masonry, have little ductility and can fail
under very low blast loads. Failures of brittle structures are sudden and should be
avoided in all cases. For this reason, unreinforced masonry construction is not
permitted for design of blast resistant structures.
Redundant construction is also desirable for blast design. Redundancy is
accomplished by providing alternate load paths and designing the structure to
redistribute loads if a single component failure occurs. In metal frame buildings,
where resistance to lateral loads is provided by girts and main frames, redundancy
may be provided by strengthening the roof deck to act as a diaphragm and to
distribute the load to other frames. Specific provision for redundancy is not required
for design; however, redundancy should be provided where feasible and cost
effective.
Metal frame, metal clad construction is commonly used in petrochemical plants for
warehouses, maintenance shops, and process support office buildings. This type of
construction is appropriate for relatively low blast overpressures and should typically
be located several hundred feet from major process units.
Moment-resisting frames are typically used in a metal building to resist the lateral
load applied on its long side. Vertical bracing is typically used between frames to resist
loads applied to the end or short walls of the building. However, the Engineer should
be aware of special considerations for blast resistant design including the following:
Frame spacing must typically be closer, on the order of 20 ft (6 m), than for
conventional construction, where frame spacing may exceed 30 ft (10 m).
Heavier gage wall panels and closer girt spacing are typically required to develop any
significant blast resistant capability.
It may also be necessary to provide bracing for flexural members to develop a full
plastic moment capacity for loads in both directions. This is a departure from typical
construction, where bracing is normally required for a load in one direction only.
Cladding fasteners should also be detailed to ensure proper resistance to rebound and
negative phase blast loading.
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Masonry buildings used for conventional construction can be classified as load bearing
or non-load bearing. The response for the load-bearing construction is limited to
ensure adequate safety against collapse under blast load. If a steel or concrete frame is
provided, infill masonry walls can be permitted to suffer significantly more damage
without risk of collapse. This non-load-bearing construction is preferred because it
provides better redundancy and overall safety. Unreinforced masonry load-bearing
construction may be adequate for relatively low blast overpressures (i.e. less than 1 psi
(7 kPa)).
A metal deck can be used as a roof diaphragm for relatively low blast overpressures. A
poured-in-place concrete deck is typically used for masonry construction that is
subjected to blast loads. A concrete deck provides significantly more lateral capacity
than does a metal roof deck. A substantial bond beam at the top of the wall or secure
ties into a concrete roof deck should be provided for wall rebound.
Precast concrete construction is widely used in petrochemical facilities for control
rooms, plant offices, and process support buildings. Precast (non-prestressed)
construction can be completed quickly and can provide significant blast resistance.
The most significant consideration for blast resistant design is detailing of connections.
Precast panels for conventional loads can have minimal blast capability if a small
number of connectors are provided. For blast design, the number of connectors should
be significantly increased and should be able to develop the full flexural capacity of
the panel. If panel thickness is governed by architectural or mechanical considerations,
the Engineer should ensure that connections are designed on the basis of the panel
capacity rather than the required resistance for the blast.
Precast construction, like masonry, can be classified as a load-bearing or non-loadbearing structural system. For load-bearing construction, detailing of connections to
develop moment capacities is especially critical. Secondary bending effects, P-,
caused by in-plane vertical loads should also be considered. For non-load-bearing
construction, steel frames are used to support the vertical loads. The frames should
be recessed from the interior face of the wall panels to avoid applying lateral loads to
the columns.
Cast-in-place reinforced concrete construction is typically used to provide resistance
to severe blast loads. Wall thicknesses for structures in or immediately adjacent to
large process areas are typically 8 inches (200 mm) to 12 inches (300 mm) but can
be thicker for some special cases. Reinforced concrete is especially appropriate for
short duration loading that produces an impulsive response. Its large mass, relative to
the surface area, is especially effective in resisting these types of loads. Reinforced
concrete construction is typically used if a protective structure is needed around an
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Page 43 of 56
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existing structure to resist large blast loads because of close proximity to a blast
source.
B-6.4.5
Fragment Resistance
Buildings that are required by the BDR Data Sheet to have fragment resistance shall
be designed in accordance with TM5-1300(3) design procedures. Building with
minimum wall thickness required by SSD/9 will provide a significant level of
protection against fragments.
B-6.5
Material Properties
B-6.5.1
Fds
Fdy
Es
Strain
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B-6.5.2
30 July 2008
B-6.5.3
B-7
Structural Design
B-7.1
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30 July 2008
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30 July 2008
Load Combinations
Most design codes for conventional buildings have provisions for combination of
design loads such as live, wind, seismic, snow, etc. For blast design, a decision
should be made about which of these loads to include simultaneously with blast
loads. Dead loads are always included, but most other transient live loads are not,
although roof live loads (full or partial) are typically included.
The portion of live load to be applied in combination with blast load should be
determined by the Engineer on the basis of the amount of load that could reasonably
be expected to occur at the same time as the blast load. This should include roof live
loads, and floor loads. The full floor live load should not normally be used because
of the low probability of blast occurring during application of the full floor live load.
It is not normal practice to combine blast loads with extreme environmental loads
such as wind or earthquake. In rare situations, it may be appropriate to analyze
structural response for the blast load following application of seismic loads (for
example, where an earthquake causes damage to a process unit, which leads to an
explosion).
Most conventional design codes specify load factors to be applied to provide a factor
of safety in the design. These load factors are typically set at 1.0 for blast design
because a blast load is an extreme event.
B-7.3
Analysis Methods
B-7.3.1
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Use of the equivalent static load method requires iteration. Initial properties for the
member are selected to define the period of vibration. When the static equivalent
load is calculated and applied, a new section is selected on the basis of calculated
resistance. This new section can have different properties than originally assumed,
which can change the equivalent static load. If a new equivalent static load is not
calculated, subsequent calculations for member end shear and connection design may
not be correct. The equivalent static load method does not directly calculate the
dynamic shears and reactions of the member. The equivalent static load is used to
determine these parameters, and in some cases may underestimate these items and
thus the connection requirements. Another drawback of this method is that it cannot
model the interaction of connected components.
The equivalent static load method should be used only for analysis of a linearly
decaying blast load without a negative phase. This method should not be used for
non-ideal resistance functions nor for modeling differences in resistance for the
positive response phase and the rebound phase.
B-7.3.2
Single-Degree-of-Freedom (SDOF)
The Single-Degree-of-Freedom method is the most commonly used method for blast
resistant design. This method allows most structural components to be modeled as a
single, spring-mass system, which greatly simplifies the analysis of the time-history
response. This method can be used to model non-linear resistance functions and the
differences in resistance in the positive and rebound phases. The Single-Degree-ofFreedom method can also be used to model complex pressure-time histories
including negative pressure effects.
The time-varying end reactions can be calculated using the SDOF method. These
reactions can then be applied to supporting members to model component
interaction. Special consideration needs to be given to selection of the appropriate
mass to be applied to supporting members, based on the relative time to maximum
response of the member being supported.
Additional guidance is given in ASCE(1) and in references 11 and 12 of this
commentary for modeling and analyzing the response of structural components as
SDOF systems.
Pressure-impulse (P-I) curves, denoting lines of constant damage corresponding to a
particular response limit, may be used to evaluate the response of a structural
component to a number of blast loads. This approach is described in ASCE(1) and in
other References (7, 8, and 10).
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B-7.3.3
30 July 2008
Multi-Degree-of-Freedom (MDOF)
The multi-degree-of-freedom (MDOF) analysis method can be used to determine the
dynamic response of interconnected members. Each component should be modeled
as a one-degree-of-freedom spring mass system. Several SDOF systems can be
combined numerically to produce a MDOF model. The MDOF method can models
mass and dynamic reaction effects on supported members. A typical system for a
wall design can be modeled as a three-degrees-of-freedom system consisting of a
wall panel, girt, and frame column. MDOF analysis can result in a much lower
maximum deflection than a SDOF analysis if the periods of vibration of the
connected members are fairly close.
The MDOF method can be used to model non-rigid (spring) supports, which can
reduce the required resistance of certain components. A spreadsheet can be used to
perform numerical integration of simple models consisting of two or three degrees of
freedom. Beyond this, a computer program is more appropriate. A limited number of
special purpose computer programs are available that are suitable for this type of
analysis although most of these programs have been developed for defense-related
applications. Also a commercially available general purpose finite element program,
that employs general spring elements to model and analyze non-linear MDOF
systems subjected to transient blast loads, may be used.
Finite element analysis (FEA) can be used for analyzing a large system of
components that cannot be accurately modeled using SDOF or MDOF methods.
MDOF and FEA are essentially the same methods; however, FEA is usually
distinguished as capable of modeling complex elements, whereas an MDOF method
is based on equivalent spring elements. FEA is typically used to model response of a
three-dimensional frame structure if biaxial bending and other three-dimensional
effects are important.
A number of commercially available computer programs, referenced in ASCE(1),
provide general FEA capability and can predict dynamic response to transient loads.
These programs are therefore suitable for blast resistant design. It is important to use
an FEA program that can accurately model non-linear effects, both material and
geometric, and that can incorporate the effects of increased material strength under
rapidly applied loads.
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B-7.4
Deformation Limits
B-7.4.1
Response Parameters
30 July 2008
For blast resistant design, the adequacy of the structural response is determined in
terms of maximum deflection rather than stress level because the response typically
will be in the plastic region of the stress-strain curve. It is normal practice to design
blast resistant structures for plastic deformation if subjected to the extreme blast
loads from accidental explosions. It is not cost effective to design such structures to
remain elastic.
The two key parameters for evaluating structural response are support rotation ()
and ductility ratio (). Support rotation is a function of the maximum deflection to
span ratio. Figure B3 illustrates support rotation for a simple beam.
Ductility ratio is a measure of the degree of plastic response. A ductility ratio of 2
means than the maximum deflection is twice the deflection at the elastic limit. Steel
members can achieve relatively high ductility ratios if buckling and shear modes of
failure are prevented. The limits on deformation provide some conservatism for these
effects.
Ductility ratio is an appropriate criterion for steel members, but it is a less reliable
performance indicator for reinforced concrete components. Concrete members tend
to be very stiff, which produces a very low elastic deflection. Therefore, small
dynamic deflections can produce large ductility ratios. Support rotation is a more
reliable measure of performance for concrete or masonry.
1
Xm
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B-7.5
Component Design
B-7.5.1
General
30 July 2008
Structural components designed using SDOF analysis should include in-plane loads
and secondary bending effects. These effects are typically incorporated as statically
applied loads together with the flexural response to the transient loads.
Components should be designed to develop the full flexural capacity to avoid brittle
failure modes. This type of response provides the maximum blast-absorbing
capability and results in a controlled failure mode. This type of response requires that
components have sufficient shear and connection capacities. The shear and
connection capacities of a component are typically based on the components full
flexural resistance. Adequate bracing should also be provided to prevent lateral
buckling, which can result in sudden failures.
The primary response for short span components is in shear, and thus it is not
feasible in many cases to develop the full flexural capacity. In these cases, the
maximum resistance produced by the transient load should be determined for the
entire response history. End shears and reactions should be based on 120% of the
maximum attained resistance applied as a uniform load on the member.
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B-7.5.2
30 July 2008
Reinforced Concrete
Design of reinforced concrete should be in accordance with the ultimate strength
method according to ACI 318-05(13) or comparable concrete design methods. The
customary strength reduction factor () should be 1.0, and a dynamic stress factor
(SIF * DIF) should be applied in accordance with Sections 6.5.2 and 6.5.3
respectively. In addition, because of the importance of adequate shear capacity to
develop ductile flexural behavior in reinforced concrete components, the minimum
static compressive strength for blast resistant design is set at 4,000 psi (28 Mpa). The
higher strengths assure a more reliable performance in shear. Compressive strength
less than 3,000 psi (21 Mpa) should not be permitted. A compressive strength of
5,000 psi (35 Mpa) is considered acceptable for concrete design. However,
compressive strengths above this value have not yet had adequate testing to assure
proper dynamic performance under blast load conditions.
Reinforcing steel higher than Grade 60 (420 Mpa) should not be permitted. In
addition, bar sizes above a #10 (32 mm) should not be used because of decreased
ductility for large bars. Use of a greater number of smaller bars is preferred to
decrease development length requirements.
Time phasing of the interaction equation may be used; however, because of
inaccuracies in load-time phasing and response, it is important to apply some
conservatism to the design.
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B-7.5.3
30 July 2008
Structural Steel
Methods in accordance with AISC Load and Resistance Factor Design Specification for
Structural Steel Building (14) or comparable limit state methods may be used for the
blast resistant design of structural steel. As in reinforced concrete design, should be
1.0 and the dynamic strength increase factors should be used. Steel materials with 50
ksi (345 Mpa) yield material should be used because of the wide variation in material
strength for A36 steel. Use of A36 material, which has an actual yield strength
significantly greater than 36 ksi, can result in an unconservative prediction of
reaction forces and required shear resistance.
B-7.5.4
Cold-Formed Steel
The load and resistance factor design (LRFD) method of AISI(15) or a comparable
strength limit state method may be used for the blast resistant design of cold-formed
steel members. A = 0.9 factor should be applied to plastic moment capacity when
computing an ultimate resistance to reflect the potential buckling of a section before
developing the full plastic moment. The dynamic strength increase factors in Section
6.5.3 of this Standard should be applied.
B-7.5.5
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B-7.5.6
30 July 2008
Reinforced Masonry
Only fully inspected reinforced masonry (concrete or brick) is appropriate for blast
resistant design. The ACI 530(18) and the IBC(19) requirements for ultimate strength
for reinforced masonry should be used for blast resistant design, particularly the
requirements pertaining to seismic design. ASCE(1)and TM5-1300(3) also provide
guidance specific to the design of reinforced masonry for blast resistance.
Masonry construction responds similarly to singly reinforced concrete. Fully grouted
cells normally provide adequate compression and shear capacity to develop flexural
strength. Horizontal truss or ladder type reinforcing provides minimal flexural
capacity and is not generally classified as reinforced masonry.
Connections at floor and roof are typically weak links in conventional reinforced
masonry construction. The connections should be capable of resisting inward and
rebound loads. Connections for load-bearing construction are especially critical.
Walls should be doweled into floor and roof slabs.
B-7.6
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B-7.7
30 July 2008
Foundation Design
Analysis of explosion accident data has shown that foundation failure is rare because
of the inability of the supported structure to transfer the entire blast load to the
foundation. Also, foundation members are typically massive compared with
superstructures and provide greater resistance to blast loads than does the supported
building. Usually foundation components are simply designed statically for the
capacities of the structural components they support. However, if this proves to be
too conservative or costly, a more accurate dynamic analysis of the
structure/foundation system can be performed.
B-8
Ancillary Items
B-8.1
Blast Doors
The Owner should specify whether blast doors are required for the building. Blast
doors are expensive, even for low blast loads, and may not be cost effective at low
risk levels. Conventional hollow metal doors may not be operational above
approximately 1.0 psi (7 kPa) applied peak pressure. If the blast pressure entering a
structure is not sufficient to cause damage, a conventional door may be acceptable.
Door hardware may not be required to remain operational if additional protected
exits are provided. This may be the case for doors on a wall receiving reflected loads.
It may be appropriate to permit these doors to be substantially damaged if a
sufficient number of doors are located in building faces receiving side-on blast loads.
The Owner should select an allowable response category for design of each door and
specify the categories on the BDR Data Sheet. Additional information regarding
door performance and design is provided in ASCE(1).
Support for blast door frames is very important. Typically, subframes are provided
by the building contractor during wall construction. This allows construction to
continue while blast doors are being fabricated, which may take several weeks or
months. Door framing should be provided by the manufacturer.
B-8.2
Windows
Windows should be avoided in buildings subjected to significant blast loads.
However, laminated glass and polycarbonate glazing can provide substantial blast
resistance if they are either:
Wet-glazed into the window frames using a structural sealant, or are equipped with a
large rebate (bite) to prevent the glazing from pushing through the frame.
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Openings
Small openings or low applied blast loads may not produce an appreciable increase
in pressure in the building. In these cases, blast valves or other pressure relieving
devices should not be required. For structures near a process unit, leakage pressures
through air intake openings can be significant and valves or attenuators are required.
Methods for predicting leakage pressure through openings should be in accordance
with TM5-1300(3).
Blast valves typically incorporate a moving disk that seals the opening and prevents
entry of blast pressures. Blast attenuators significantly reduce leakage pressures but
do not completely eliminate the blast.
Passive blast valves have no moving parts and reduce blast pressures by creating a
tortuous exit path rather than a seal.
B-8.4
Penetrations
Pre-manufactured multi-cable transits (MCT) for use in blast resistant buildings have
a frame that is anchored into the concrete or masonry. Flexible collars are placed
around pipes running through the MCT and are clamped down to prevent leakage of
the blast pressure into the structure. MCTs are available in a variety of sizes.
B-8.5
Suspended Items
Light fixtures in suspended ceilings can produce a serious hazard to occupants
during a blast. Ceiling grids, unless seismically rated, will not support fluorescent
light ballasts and ventilation dampers. These items should be anchored to the roof
framing with heavy gauge wire or threaded rod. Any item weighing more than 10
pounds (5 kg) should be independently anchored.
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