UNIT-III

CONSTRUCTION METHODS
FOUNDATIONS IN CONSTRUCTION:

Foundation is the lowest part of the building or the civil structure that is in direct contact with the soil which
transfers loads from the structure to the soil safely. Generally, the foundation can be classified into two,
namely shallow foundation and deep foundation. A shallow foundation transfers the load to a stratum present in a
shallow depth. The deep foundation transfers the load to a deeper depth below the ground surface. A tall building
like a skyscraper or a building constructed on very weak soil requires deep foundation. If the constructed building
has the plan to extend vertically in future, then a deep foundation must be suggested.

To construct a foundation, trenches are dig deeper into the soil till a hard stratum is reached. To get stronger base
foundation concrete is poured into this trench. These trenches are incorporated with reinforcement cage to increase
the strength of the foundation. The projected steel rods that are projected outwards act as the bones and must be
connected with the substructure above. Once the foundation has been packed correctly the construction of the
building can be started. The construction of the foundation can be done with concrete, steel, stones, bricks etc. The
material and the type of foundation selected for the desired structure depends on the design loads and the type of
underlying soil. The design of the foundation must incorporate different effects of construction on the environment.
For example, the digging and piling works done for deep foundation may result in adverse disturbance to the nearby
soil and structural foundation. These can sometimes cause the settlement issues of the nearby structure. Such effects
have to be studied and taken care before undergoing such operations. Disposal of the waste material from the
operations must be disposed properly. The construction of foundation has to be done to resist the external attack of
harmful substances. The foundation for each structure is designed such that:

 The underlying soil below the foundation structure does not undergo shear failure
 The settlement caused during the first service load or have to be within the limit
 Allowable bearing pressure can be defined as the pressure the soil can withstand without failure.

What is the Purpose of Foundation?

Foundations are provided for all load carrying structure for following purposes:

 Foundation are the main reason behind the stability of any structure. The stronger is the foundation, more
stable is the structure.
 The proper design and construction of foundations provide a proper surface for the development of the
substructure in a proper level and over a firm bed.
 Specially designed foundation helps in avoiding the lateral movements of the supporting material.
 A proper foundation distributes load on to the surface of the bed uniformly. This uniform transfer helps in
avoiding unequal settlement of the building. Differential settlement is an undesirable building effect.
 The foundation serves the purpose of completely distributing the load from the structure over a large base
area and then to the soil underneath. This load transferred to the soil should be within the allowable bearing
capacity of the soil.

Functions of Foundation in Construction

Based on the purposes of foundation in construction, the main functions of the foundation can be enlisted as below:

1. Provide overall lateral stability for the structure

2. Foundation serve the function of providing a level surface for the construction of substructure
3. Load Distribution is carried out evenly
 4. The load intensity is reduced to be within the safe bearing capacity of the soil
5. The soil movement effect is resisted and prevented
6. Scouring and the undermining issues are solved by the construction of foundation

Requirements of a Good Foundation

The design and the construction of a well-performing foundation must possess some basic requirements that must
not be ignored. They are:

1. The design and the construction of the foundation is done such that it can sustain as well as transmit the
dead and the imposed loads to the soil. This transfer has to be carried out without resulting in any form of
settlement that can result in any form of stability issues for the structure.
2. Differential settlements can be avoided by having a rigid base for the foundation. These issues are more
pronounced in areas where the superimposed loads are not uniform in nature.
3. Based on the soil and area it is recommended to have a deeper foundation so that it can guard any form of
damage or distress. These are mainly caused due to the problem of shrinkage and swelling because of
temperature changes.
4. The location of the foundation chosen must be an area that is not affected or influenced by future works or
factors.

DIFFERENT TYPES OF FOUNDATIONS:

Foundations are classified as shallow and deep foundations. Types of foundations under shallow and
deep foundations for building construction and their uses are discussed.

It is advisable to know the suitability of each type of foundation before their selection in any
construction project.
Types of Foundation and their Uses
Following are different types of foundations used in construction:

1. Shallow foundation
o Individual footing or isolated footing
o Combined footing
o Strip foundation
o Raft or mat foundation
2. Deep Foundation
o Pile foundation
o Drilled Shafts or caissons

Types of Shallow Foundations

1. Individual Footing or Isolated Footing
Individual footing or an isolated footing is the most common type of foundation used for building
construction. This foundation is constructed for a single column and also called a pad foundation.
The shape of individual footing is square or rectangle and is used when loads from the structure is
carried by the columns. Size is calculated based on the load on the column and the safe bearing
capacity of soil.

Rectangular isolated footing is selected when the foundation experiences moments due to the
eccentricity of loads or due to horizontal forces.

For example, Consider a column with a vertical load of 200 kN and a safe bearing capacity of 100
kN/m2 then the area of the footing required will be 200/100 = 2m2. So, for a square footing, the length
and width of the footing will be 1.414 m x 1.414 m.
2. Combined Footing
Combined footing is constructed when two or more columns are close enough and their isolated
footings overlap each other. It is a combination of isolated footings, but their structural design
differs.

The shape of this footing is a rectangle and is used when loads from the structure is carried by the
columns.

3. Spread footings or Strip footings and Wall footings

Spread footings are those whose base is wider than a typical load-bearing wall foundations. The
wider base of this footing type spreads the weight from the building structure over more area and
provides better stability.

Spread footings
Spread footings and wall footings are used for individual columns, walls and bridge piers where the
bearing soil layer is within 3m (10 feet) from the ground surface. Soil bearing capacity must be
sufficient to support the weight of the structure over the base area of the structure.
These should not be used on soils where there is any possibility of a ground flow of water above
bearing layer of soil which may result in scour or liquefaction.

4. Raft or Mat Foundations

Raft or mat foundations are the types of foundation which are spread across the entire area of the
building to support heavy structural loads from columns and walls.

Raft or Mat Foundation

The use of mat foundation is for columns and walls foundations where the loads from the structure
on columns and walls are very high. This is used to prevent differential settlement of individual
footings, thus designed as a single mat (or combined footing) of all the load-bearing elements of the
structure.

It is suitable for expansive soils whose bearing capacity is less for the suitability of spread footings
and wall footings. Raft foundation is economical when one-half area of the structure is covered with
individual footings and wall footings are provided.

These foundations should not be used where the groundwater table is above the bearing surface of
the soil. The use of foundation in such conditions may lead to scour and liquefaction.
Types of Deep Foundation
5. Pile Foundations
Pile foundation is a type of deep foundation which is used to transfer heavy loads from the structure
to a hard rock strata much deep below the ground level.

Pile Foundation
Pile foundations are used to transfer heavy loads of structures through columns to hard soil strata
which is much below ground level where shallow foundations such as spread footings and mat
footings cannot be used. This is also used to prevent uplift of the structure due to lateral loads such as
earthquake and wind forces.

Read More on Deep Foundations

Pile foundations are generally used for soils where soil conditions near the ground surface is not
suitable for heavy loads. The depth of hard rock strata may be 5m to 50m (15 feet to 150 feet) deep
from the ground surface.

Pile foundation resists the loads from the structure by skin friction and by end bearing. The use of
pile foundations also prevents differential settlement of foundations.

Read More on Pile Foundation

6. Drilled Shafts or Caisson Foundation
Drilled shafts, also called as caissons, is a type of deep foundation and has an action similar to pile
foundations discussed above, but are high capacity cast-in-situ foundations. It resists loads from
structure through shaft resistance, toe resistance and/or combination of both of these. The
construction of drilled shafts or caissons are done using an auger.

Fig: Drilled Shafts or Caisson Foundation (Source: Hayward Baker)

Drilled shafts can transfer column loads larger than pile foundations. It is used where the depth of
hard strata below ground level is located within 10m to 100m (25 feet to 300 feet).

Drilled shafts or caisson foundation is not suitable when deep deposits of soft clays and loose, water-
bearing granular soils exist. It is also not suitable for soils where caving formations are difficult to
stabilize, soils made up of boulders, artesian aquifer exists.

FORMWORK:
Formwork (shuttering) in concrete construction is used as a mold for a structure in which fresh
concrete is poured only to harden subsequently. Types of concrete formwork construction depends
on formwork material and type of structural element.

Formworks can also be named based on the type of structural member construction, such as slab
formwork for use in a slab, beam formwork, column formwork for use in beams and columns,
respectively, etc.
The construction of formwork takes time and involves expenditure up to 20 to 25% of the cost of the
structure or even more. The design of these temporary structures are made to economic expenditure.
The operation of removing the formwork is known as stripping. Stripped formwork can be reused.
Reusable forms are known as panel forms and non-usable are called stationary forms.

Timber is the most common material used for formwork. The disadvantage with timber formwork is
that it will warp, swell, and shrink. The application of water-impermeable cost to the surface of wood
mitigates these defects.

Requirements of Good Formwork

1. It should be strong enough to withstand all types of dead and live loads.
2. It should be rigidly constructed and efficiently propped and braced both horizontally and vertically, to
retain its shape.
3. The joints in the formwork should be tight against leakage of cement grout.
4. Construction of formwork should permit removal of various parts in desired sequences without damage to
the concrete.
5. The material of the formwork should be cheap, readily available, and should be suitable for reuse.
6. The formwork should be set accurately to the desired line, and levels should have a plane surface.
7. It should be as light as possible.
8. The material of the formwork should not warp or get distorted when exposed to the elements.
9. It should rest on a firm base.

Economy in Formwork
The following points are to be kept in view to effect economy in the cost of formwork:

1. The plan of the building should imply a minimum number of variations in the size of rooms, floor area, etc.
to permit reuse of the formwork repeatedly.
2. Design should be perfect to use slender sections only in the most economical way.
3. Minimum sawing and cutting of wooden pieces should be made to enable reuse of the material many times.
The quantity of surface finish depends on the quality of the formwork.
Formwork can be made out of timber, plywood, steel, precast concrete, or fiberglass used separately
or in combination. Steel forms are used in a situation where large numbers of re-use of the same
forms are necessary. For small works, timber formwork proves useful. Fiberglass made of precast
concrete and aluminium are used in cast-in-situ construction such as slabs or members involving
curved surfaces.
Types of Formwork (Shuttering)
1. Timber Formwork
Timber for formwork should satisfy the following requirement:

It should be:

1. Well-seasoned
2. Light in weight
3. Easily workable with nails without splitting
4. Free from loose knots
Timber used for shuttering for exposed concrete work should have smooth and even surface on all
faces which come in contact with concrete.

2. Plywood Formwork
Resin-bonded plywood sheets are attached to timber frames to make up panels of the required sizes.
The cost of plywood formwork compares favorably with that of timber shuttering, and it may even
prove cheaper in some instances given the following considerations:

1. It is possible to have a smooth finish in which case on cost in surface finishing is there.
2. By the use of large-size panels, it is possible to affect saving in the labor cost of fixing and dismantling.
3. The number of reuses are more as compared with timber shuttering. For estimation purposes, the number of
reuses can be taken as 20 to 25.
3. Steel Formwork
This consists of panels fabricated out of thin steel plates stiffened along the edges by small steel
angles. The panel units can be held together through the use of suitable clamps or bolts and nuts.

The panels can be fabricated in large numbers in any desired modular shape or size. Steel forms are
largely used in large projects or in a situation where large number reuses of the shuttering is possible.
This type of shutter is considered most suitable for circular or curved structures.

Comparison between Steel and Timber Formwork

1. Steel forms are stronger, durable, and have a longer life than timber formwork and their reuses are more in
number.
2. Steel forms can be installed and dismantled with greater ease and speed.
3. The quality of exposed concrete surface by using steel forms is good and such surfaces need no further
treatment.
4. Steel formwork does not absorb moisture from concrete.
5. Steel formwork does not shrink or warp.
Order and Method of Formwork Removal
The sequence of orders and method of removal of formwork are as follows:

1. Shuttering forming the vertical faces of walls, beams, and column sides should be removed first as they
bear no load but only retain the concrete.
2. Shuttering forming soffit of slabs should be removed next.
3. Shuttering forming soffit of beams, girders, or other heavily loaded shuttering should be removed in the
end.
Rapid hardening cement, warm weather and light loading conditions allow early removal of
formwork.
The formwork should under no circumstances be allowed to be removed until all the concrete reaches
a strength of at least twice the stresses to which the concrete may be subjected at the time of removal
of formwork.

All formworks should be eased gradually and carefully in order to prevent the load from being
suddenly transferred to concrete.

WALL CONSTRUCTION METHODS:

Construction of concrete walls is a crucial phase in building construction. It is constructed as a load bearing structure

to transfers loads from floor to the wall below or to the foundation, in addition to divide spaces in multi-storey

buildings. Moreover, concrete wall is a desirable structural element in earthquake prone areas since it exhibit

satisfactory performance during earthquakes. Therefore, it greatly controls the safety of the building. That is why

considerable cautions shall be practiced during its construction. Finally, apart from proper construction process,

materials used for concrete wall construction play major role to improve the performance of the wall during its life

span.

Materials used in Concrete Wall Construction

There are different types of materials used in the construction of concrete walls. These materials need to be conform
with applicable codes and specifications like requirements of ACI 318-14:

1. Cements; different types of cements are available, and Portland cement is most famous one.
2. Aggregate
3. Sand
4. Admixtures
5. Steel Reinforcement
6. Formwork materials; wood, steel, aluminum, plastic, a composite of cement and foam insulation, or
composite of cement and wood chips
Equipment used in Concrete Wall Construction
1. Concrete Mixing and Delivery machinery
2. Concrete compaction and finishing equipment
3. Safety accessories for workers

Concrete Wall Construction Process

1. Reinforcement Placement
Generally, if wall thickness is smaller than 100 mm, then reinforcement bars are installed in one layer. However,

reinforcement bars shall be placed in two layer if wall thickness is greater than 200 mm. Steel bars are

placed horizontally and vertically in the wall in a grid pattern according to the design drawings. Designated steel bar

size, spacing, and concrete cover shall be provided with highest possible accuracy. Reinforcement bars are placed on

the tension side of the wall. After the reinforcement is completely placed then formwork fixing operation starts.

At construction joints, steel bars shall be extended for continuous resistance. Moreover, it splices with the rebar on
the other side, overlapping for a specified distance. Similar overlap should be provided for reinforcement bar ends
and steel bar that turns a corner.

Safety Tips Considered During Reinforcement Placement

here are certain advices which need to be considered during reinforcement placement for to maintain the saftety of
workers:

 Place caps or wooden trough on the protruding ends of reinforcement bars.

 Alternatively, Bend reinforcing steel so that extended ends are no longer upright.
 If labors work at a height above exposed rebars, then fallen prevention safety measures should be provided
to prevent loss of lives at construction site.
2. Formwork of Concrete Wall
 Fixing formwork is the next concrete wall construction process after the installation of reinforcements.
 Several formwork types are available to be used for wall construction such as wood, aluminum, and plastic
formworks.
 The quality of constructed wall shall be considered while formwork system is selected. However, good
quality construction should not reduce the project speed nor should it be uneconomical.
 Generally, wood formworks are installed onsite.
 Pre-fabricated formwork systems are also used for the construction of concrete walls.
 These formwork systems, which are manufactured from wood with a metal frame or entirely from metal,
are designed to attach to each other through a system of pins or latches.
 There are broad range of sizes and shapes of prefabricated fromwork sections, and sometimes custom sizes
are made for specific projects.
 Regardless of the formwork types and systems, it should be strong enough to resist the pressure of fresh
concrete, and adequate concrete cover shall be provided. In addition to prevent concrete leakage through
the formwork which can decline concrete wall quality.
3. Construction Joints in Concrete Walls
 Construction joints shall be made and located so as not to detrimentally affect the strength of the wall.
 Concrete at the interface of construction joints required to be roughened in order to create proper bond
between previous and newly poured concrete.
 ACI 350 specify maximum 12.19m spacing between construction joints, and 3.65m between wall corner
and closet construction joint.
 Minimum construction joint reinforcement embedment length of 305 mm shall be provided on both sides of
the joint.
4. Concrete Production
Concrete should be produced in batching plants under strict quality control, and convey it to site using suitable

transportation means like transit mixers.

5. Pouring Concrete
 Concrete pouring begins after formwork and its ties, pins and wedges are adequately fixed.
 Suitable measures are considered to prevent leakages.
 After that, oil applied for the formwork surface.
 Then, fresh concrete is poured using pumps or any other appropriate techniques.
 Concrete need to be compacted during placement and shall be worked around embedded items and
reinforcement and into corners of forms.
 If stay-in-place forms are used, concrete shall be consolidated by internal vibration.

However, if self-compacting concrete is used, then only pin vibrator is employed for concrete compaction.

Therefore, no internal vibration is required to compact self-consolidated concrete.

6. Removal of Formworks
Formworks of concrete walls can be removed 1-2 days after the concrete placement is ended. The removal of

concrete wall formworks shall be performed carefully. In residential houses, early removal of formworks can be

obtained by hot air curing / curing compounds. This will increase the pace of construction.

7. Curing Concrete Wall

 Curing technique and period may vary based on the environmental conditions.
 If wood forms are used and left in place, the wall should be kept wet using sprinkling or any
other suitable approach. The formwork helps keep the moisture and improve curing
economy.
 Alternatively, remove the formwork and using suitable and practical curing method.
 For concrete temperature above 5°C, the curing process shall last for minimum 7 days.
SLAB CONSTRUCTION METHOD:

Concrete floor slab construction process includes erection of formwork, placement of reinforcement, pouring,

compacting and finishing concrete and lastly removal of formwork and curing of concrete slab.

Concrete Floor Slab Construction Process

1. Assemble and Erect Formwork
2. Prepare and Place Reinforcement
3. Pour, Compact and Finish Concrete
4. Curing Concrete and Remove Formwork
1. Assemble and Erect Formwork for Slab
The formwork shall be designed to withstand construction loads such as fresh concrete pressure and weight of

workers and operators and their machines. Guide to Formwork for Concrete ACI 347-04 shall be followed for the

design of formworks. Moreover, there are various construction aspects that need to be considered during the erection

of formworks. For example, it should be positioned correctly, lined and levelled, joints sealed adequately, and

prevent protruding of nails into the concrete etc... Furthermore, different materials such as wood, steel, and

aluminum can be used for the formworks of concrete floor slab.

Finally, there are several common formwork construction deficiencies that site engineer needs to be aware of and
prevent their occurrence otherwise formwork failure may occur. These construction deficiencies are provided below:

 Poor or lack of formwork examination during and after concrete placement to identify uncommon
deflections or other indications of possible failure that could be corrected
 Inadequate nailing, bolting, welding, or fastening
 Improper lateral bracing
 Construct formwork that does not comply with form drawings
 Lack of proper field inspection to ensure that form design has been properly interpreted by form builders
 Use of damaged or inferior lumber having lower strength than needed.
2. Prepare and Place Reinforcement for Slab
Prior to the placement of reinforcement for concrete floor slab construction, inspect and check forms to confirm that

the dimensions and the location of the concrete members conform to the structural plans. Added to that, the forms

shall be properly cleaned and oiled but not in such amount as to run onto bars or concrete construction joints. Design

drawings provides necessary reinforcement details, so it only needs understanding to use designated bar size, cutting

required length, and make necessary hooks and bents. After preparation is completed, steel bars are placed into their

positions with the provision of specified spacings and concrete cover. The concrete cover and spacing for floor slabs

can be maintained by introducing spacers and bars supporters. Wires are used to tie main reinforcement and
shrinkage and temperature reinforcement (distribution reinforcement). It should be known that incorrect reinforcing

steel placement can lead to serious concrete structural failures. Improper concrete cover exposes reinforcement bars

to danger and jeopardize concrete-steel bond. Finally, after all requirements of reinforcement placements (positions,

concrete cover, spacing, and correct bars size; length; hooks; and bending) are finalized, then site engineer can order

concreting.

3. Pour, Compact and Finishing Concrete Floor Slab

Mixing, transporting, and handling of concrete shall be properly coordinated with placing and finishing works. In

floor slab, begin concrete placing along the perimeter at one end of the work with each batch placed against

previously dispatched concrete. Concrete should be deposited at, or as close as possible to, its final position in order

to prevent segregation. So, Concrete placement in large and separate piles, then moving them horizontally into final

position shall be prevented. Moreover, site engineer shall monitor concreting properly, and look for signs of

problems. For example, loss of grout is the indication of improper sealing and movement of joints. Added to that,

cracking, excessive deflection, level and plumb, and any movement shall be checked and tackled to prevent further

problems.

Furthermore, fresh concrete should be compacted adequately in order to mold it within the forms and around

embedded items and reinforcement and to eliminate stone pockets, honeycomb, and entrapped air. Vibration, either

internal or external, is the most widely used method for consolidating concrete. Lastly, slabs could be finished in

many ways based on floor application.

4. Curing Concrete and Remove Formwork

After finishing ended, suitable technique shall be used to cure the concrete adequately. Slab curing methods such as

water cure; concrete is flooded; ponded; or mist sprayed. In addition to water retaining method in which coverings

such as sand; canvas; burlap; or straw used to kept slab surface wet continuously, chemical Membranes,and

waterproof paper or plastic film seal. Regarding curing, it is recommended to remove formworks after 14 days.

MODULAR CONSTRUCTION:

What is Modular Construction? Types, Pros

and Cons, and Applications
21st July 2022
Modular construction refers to offsite building construction under controlled factory setting
conditions. Unlike a “stick-built” structure that is built piece by piece, modular structures are
produced in “modules” or separate sections. Permanent modular buildings and relocatable modular
buildings are the main types of modular construction buildings.

Although the modular construction concept has been around for over 100 years, the unique opportunities
of modular construction had been largely untapped until the revival of modular solutions, such as modular
apartment buildings, modular construction hotels, modular classrooms, and modular office buildings.

The modular construction method uses the same building codes, raw materials, and standards applicable
for traditionally built projects. Completed modules are transported to and assembled on site to fit with
each other, with the same design intent and architectural specifications of the most advanced site-built
facility.

What is Modular Construction?

The first documented modular construction example is a prefabricated home (the “Manning Portable
Cottage”) made in 1830 by a London carpenter named John Manning. Later, the rapid rebuilding of
homes and the growing popularity of prefab structures led to the widespread acceptance of the time- and
space-saving modular construction method.

Concrete, steel, and wood are commonly used modular construction materials. Modular building
manufacturers buy and recycle materials in bulk and maintain portable building and trailer fleets to create
cost efficiencies and ensure quick turnaround for projects.

Modular Buildings vs. Traditional Buildings

A traditional building is an example of on-site construction while a modular building represents offsite or
volumetric construction. Compared to traditional construction, modular construction is believed to be more
efficient as it saves money and assures the project stakeholders of improved workmanship and reduced
financial risk.

Research shows that a modular construction schedule can result in project completion in half the
time compared to a traditional method.

With an estimated 60%-90% of the work completed in a factory-controlled environment, a modular

building is ready either as a complete structure or as a set of modular subassemblies for a larger project.

However, the traditional method or linear construction requires every step to be completed before the
next step, which increases the time taken to occupy a building.

Moreover, inconsistent labor yield and weather conditions can affect the quality of construction that
largely occurs on the site. Do traditional construction methods have an advantage over modular
construction? Yes.
 A modular project is not flexible for late changes in design and may need early client sign-off unlike an
on-site project.

Modular Building Design

The modular sections are configured to match the building layout and maintain ease of transportation. As
individual modular building components cannot be easily realigned onsite, modular construction
architecture demands the inclusion of specific construction techniques and design practices.

Modular building design involves critical components, such as:

 Advanced building information modeling (BIM) to assess energy performance and
cost-effective measures
 Computer-aided design (CAD), additive manufacturing (3D printing), and
manufacturing control systems for modular component alignment
 Design for Manufacture and Assembly (DfMA) practices to control assembly
tolerances and misalignment

Modular construction software eliminates manufacturing errors and seamlessly integrates project
information, including cutting lists, material reports, and shop drawings for quicker project completion.

Modular Construction Types

Generally, a modular construction system consists of many FRP (fiber-reinforced plastic) composite
panels bonded together to form a membrane structure with complete structural integrity.

A modular manufacturer provides a wide range of residential, commercial, and industrial modular units in
compliance with building codes like the International Building Code (IBC) and a variety of floor plan
layouts.

Here are the main types of modular construction buildings:

Permanent Modular Construction (PMC)
Permanent modular construction (PMC) uses offsite, lean manufacturing techniques to prefabricate single
or multi-story buildings in deliverable modules. Integrating PMC modules into site-built projects or as a
stand-alone turnkey solution provides higher quality control and reduces waste unlike projects that
leverage only site-built construction.

Permanent modular buildings are also ideal for mixed-use applications. It is possible to integrate a PMC
building with a concrete tilt-wall or a pre-engineered steel building to yield a hybrid facility.

Relocatable Building (RB)

A Relocatable Building (RB) is built using a modular construction process and is partially or completely
assembled for reusing multiple times and transporting to different building sites.
 An RB meets the need for a temporary space and complies with the manufacturer’s installation
guidelines, local building code requirements, or state regulations. In addition, the versatility of an RB
makes it a good option for emergency and natural disaster relief services.

When there is a need for a fast, temporary space solution, an RB works well with complete MEP
(Mechanical, Electrical, and Plumbing), fixtures, and finishes. Relocatable modular buildings are ideal for
construction site offices, medical clinics, sales centers, restroom facilities, schools, etc.

Relocatable buildings offer a variety of benefits, including:

 Ease of relocation
 Fast delivery
 Greater flexibility
 Low-cost reconfiguration
 Accelerated depreciation schedules

Apart from the types mentioned above, an in-depth analysis of modular construction identifies the
following categories based on the modular construction method:
Closed modular construction
Closed construction involves designing, developing, and constructing entire rooms offsite, including
electrical wiring, plumbing, and HVAC. This prefabrication process installs and “closes up” all components
at the manufacturing facility before delivering the completed module at the job site.

Open modular construction

Open construction introduces more versatility and simplifies the inspection process because the building
components can be expanded, downsized, relocated, and visually inspected at the jobsite while
maintaining quality and engineering integrity.

With respect to modular construction, it is important to mention key modular building variations that are
widely used worldwide. These are modular trailers, modular containers, panel-assembled office systems,
and office complexes.

Now, let us look at modular construction pros and cons and major applications.

Modular Construction Advantages

Working on the modular structure offsite and simultaneously preparing the site reduce the lead time
required for project completion.

Here are some well-known benefits of modular construction:

Faster, greener, and safer construction
The primary benefits of modular construction are speeding up construction time and keeping the project
on schedule by providing significant time savings (around 30%-60%).

Unlike the high volume of waste generated by a regular construction site, a modular manufacturing facility
uses engineered construction materials and in-plant recycling to provide an environmentally friendly
construction process that minimizes waste and optimizes recycling.

Modular construction provides safe working conditions during production and assembly to workers and
tradespeople. In addition, storing materials and building modules in a factory help keep construction sites
clean and prevent theft concerns.

Lower construction costs

The cost of a modular construction project depends on several factors, such as design complexity, the
scale of the project, the types of materials, and the inclusion of internal fixtures and fittings. Modular
options provide the advantages of less labor, fewer materials, shorter construction times and more.
Contrary to site-built projects, modular projects’ improved overall costs minimize cost overruns.

Less waste and more savings

According to the UK-based climate action NGO named “WRAP” (Waste and Resources Action
Programme), a modular building equates to an estimated 90% reduction in material use compared to a
traditional build.

By limiting the amount of waste on projects and using precise modeling through modular construction
techniques, the modular construction industry is contributing to a greener world and an improved
construction industry.

Adaptability to remote locations

Whether you need a state-of-the-art biotechnology facility or a utility system module, modular construction
manufacturers provide a broad range of modular construction solutions for use in remote locations and
extreme weather conditions.

Better structural strength

In contrast to conventional construction, the module-to-module combination of units greatly increases the
structural strength of a modular unit. Furthermore, stricter quality control over assembly lines has enabled
modular manufacturers to ensure consistent quality in the manufacturing process.
Better thermal insulation and damp resistance
Due to little air infiltration of a modular unit such as a modular home, it reduces heat loss considerably
and ensures greater energy efficiency. As building supplies are stored in on-site warehouses, there is
virtually no risk of using wet materials in building a modular unit.

No weather-related delays
Climate-controlled factory production eliminates weather-related construction delays. As modular
construction continues offsite regardless of the weather conditions, it is easy to complete the project on
time without waiting for onsite construction activities.

Modular Construction Disadvantages

While there are various benefits of modular construction, there are certain disadvantages, such as:
Costly transportation
The cost of transporting modules from a factory to a construction site is higher, with inherent risks in
transporting large loads of modules. Costly transportation is the main disadvantage of modular
construction.

Complicated approval process

Modular building approval may require additional inspections for local and state building codes. The
complicated approval process may adversely impact the project timeline.

Design updates
While design updates can be made for a traditional build during construction, it is not easy to make
updates to pre-built modules once they leave a modular manufacturing facility.

Permit issues
The process of issuing permits varies from state to state. For example, state-level permits for module
interiors may be rejected at other locations.

Reduced resell value

Modular buildings still face a stigma surrounding the quality of the properties. It will take time to see a
change in the opinion that the quality of a modular property is not inferior to that of a traditionally built
property.

Site and size constraints

While modules are generally restricted to certain maximum dimensions, it is difficult to transport modules
in trucks with varying capability and size. Moreover, an irregularly shaped building site may pose design
challenges for rectangularly shaped modules that are the norm in modular construction.
 Applications of Modular Building Systems
Permanent and temporary modular building systems are available in attractive sizes, specifications, and
styles. For example, a general contractor may offer modular residential construction services for custom-
built homes—a factory-designed-and-built modular home that has the flexibility of high-quality
construction with wholesale pricing.

The notable applications of residential and commercial modular construction include:

 Cashier booths
 College dormitories
 Community health clinics
 Diagnostic imaging centers
 Distribution centers
 Equipment booths
 Mobile office trailers
 Multi-story office buildings
 Parking booths
 Pharmaceutical labs
 Portable classrooms
 Portable restrooms
 Retail shops and malls
 Screening booths
 Single-family homes
 Sports facilities

PRECAST CONSTRUCTION:

Precast concrete construction offers several key features such as dimensional accuracy, better
finishes, and faster erection, which is absent when other concrete construction methods are
considered. The design of precast structures involves:

1. The design of precast members for all the possible loads during various stages, storage to jointing, and
possible loads in the building lifecycle.
2. The design of joints/connections for all possible loads in the building lifecycle.

The following are the important design considerations that are used while designing precast
structures.

1. The precast structure should be analyzed as a monolithic structure, and the joints in them shall be designed
to take the forces of an equivalent discrete system.
2. The resistance to horizontal loading shall be provided by placing shear walls (in diaphragm braced frame
type of construction) in two directions at right angles or otherwise.
 3. Rotational stiffness is not taken into account if any of the floor-wall joints in the case of precast-bearing
wall buildings.
4. The individual components shall be designed considering the appropriate end conditions and loads at
various stages of construction.
5. The structure's components must be designed for loads in line with the requirements.
6. In addition, members shall be designed for erection, handling, and impact loads that might be expected
during handling and erection.
7. Adequate buttressing of external wall panels is essential since these elements are not fully restrained on
both sides by floor panels. Adequate design precautions must be taken into account while designing.
Multiple studies have shown that the external wall panel connections are the weakest points of a precast
panel building.
8. It is important to provide restraint to all load-bearing elements at the corners of the building. These
elements and the external ends of cross-wall units should be stiffened, either by introducing columns as
connecting units or by jointing them to non-structural wall units, which may support the load in an
emergency. Jointing of these units should be designed considering the need for support in an emergency.
9. The potential of gas or other explosions, which might destroy major structural parts and lead to the
structure's gradual collapse, must be considered in the design of prefabricated construction. As a result, the
potential of progressive collapse must be considered, in which the failure or displacement of one structural
element promotes the failure or displacement of another, resulting in the partial or entire collapse of the
structure.
10. A provision in the design to reduce the probability of progressive collapse is essential in buildings with
more than six storeys and is of relatively higher priority than for buildings with a lower height.
11. It is necessary to ensure that any local damage to a structure does not spread to other parts of the structure
remote from the point of mishap and that the overall stability is not impaired. Still, it may not be necessary
to stiffen all parts of the structure against local damage or collapse near a mishap unless the design briefs
specifically require this to be done.
12. Additional, protection may be required regarding damage from vehicles; further, it is necessary to consider
the effect of damage to or displacement of a load-bearing member by an uncontrolled vehicle. It is strongly
recommended that concrete kerbs or similar methods adequately protect important structural members.
13. In all aspects of erection that affect the structural design, the designer must maintain a close liaison with the
builder/contractor regarding the erection procedures to be followed.
14. Failures that have occurred during construction appear to be of two types:

1. Pack-of-Cards Collapse: In this type of failure, the absence of restraining elements, such as
partitions, cladding, or shear walls, means that the structure is not stable during the
construction/period.
2. Situational Collapse: In this type of failure, one element falls during erection and lands on an
element below. The connections of the lower element then collapses under the load of falling
element, both static and dynamic, and a chain reaction of further collapse is initiated.

SLIPFORM CONSTRUCTION METHODS IN TALL STRUCTURES:

Slipform construction technique is an alternative for conventional formwork system which helps in
continuous vertical and horizontal construction. The slipform helps to conduct continuous pouring of
the concrete to the moving formwork. The process stops only when the required length of casting is
completed. The features and advantages of slipform construction technique is explained in the below
section.
Development of Slipform Construction
The property of cement and concrete to gain sufficient strength to stay in shape once cast within the
initial setting time of 30 minutes lead to the development of slip form construction technique.
Engineers took this property to develop a moving formwork system so that the concrete can be
poured continuously.

The height of the formwork is designed such a way that, during the pouring of the upper level
formwork, the concrete poured in the below formwork would have gained initial setting. The
concrete exposed when the formwork moves up will remain firm.

Components of Slipform
The slipform system is designed with varied features. Generally, it consist of yoke legs. Yoke legs
are employed to lift and sustain the weight of the entire structure, so that it behaves as a single unit.
Yoke legs are also used to connect with the beams, scaffoldings and working platforms to serve the
supporting purpose.

To the yoke legs, walk-away brackets are connected. These walkway brackets will enable proper
placement of the concrete.

The whole slipform assembly is lifted by means of strand rods and lifting jacks. These primary
components are located at equal intervals so that the uniform and good distribution of weight is
performed. In some construction, lifting process are supported by means of hydraulic pump
components.

Features of Slipform Construction

The slipform construction technique is a rapid and a economic construction method compared to the
conventional formwork technique. This helps to achieve huge cost saving. The technique is best
suitable for large building structures and bridges. When small structures are concerned, the projects
with identical geometry can be easily completed by slipform construction.

Continuous movement of formwork in upward direction is performed in slip form technique. The
movement is facilitated by hydraulic jacks and jack rods. In the construction of vertical structures,
the rate of rising the formwork upwards will be almost in the rate of 300mm per hour. These rise
with the help of the supports from other permanent parts of the building.

The technique of slipform construction will vary based on the type of structure constructed. Based on
this the frameworks required to support the system will vary.

Applications
1. Construction of Regular core high rise structures
The slipform construction technique used in high rise building construction will be performed by
vertically extruding the reinforced concrete section. Regular shaped core structures and buildings are
easily constructed by this method.

2. Slipform Technique for Chimney Construction

The slipform technique used for the construction of large chimneys, cooling towers and piers are
called as tapered slipform. This technique is used for constructing vertical structures with varying
wall thickness, or shapes or diameters.

3. Construction of Steel Tanks

Slipform construction technique helps to construct the large volume cisterns in industries and
factories in a cost effective way.

4. Construction of Water Towers

The slipform technique helps to construct the walls of water tanks uniformly with better quality.
Tanks of thousands of litres are easily constructed by this method.

Advantages of Slipform Construction Technique

1. Non-stop Method of Construction
2. Increase rate of construction
3. Increase the productivity
4. Provide more working space
5. Creates safe work environment for the workers
6. Employs less accessory equipment
7. Increase flexibility in construction
8. Reduced Labor costs
9. Scaffolding and temporary works in construction is reduced
 10. Uniform wall sections and layouts are obtained

Disadvantages of Slipform Construction Technique

1. High –cost for initial setup
2. Requires Specialized workers and expertise
3. Need sophisticated Equipment
4. Dimensional Accuracy can go low in certain conditions

CONSTRUCTION METHODS FOR STEEL STRUCTURES:

There are three different methods for design of steel structure, i.e. simple design, continuous design and semi-
continuous steel design. Joints in structures have been assumed to behave as either pinned or rigid to render design
calculations manageable. In simple design the joints are idealised as perfect pins. Continuous design assumes that
joints are rigid and that no relative rotation of connected members occurs whatever the applied moment. The vast
majority of designs carried out today make one of these two assumptions, but a more realistic alternative is now
possible, which is known as semi-continuous design.

Methods of Steel Structure Design

Following are the methods of structural steel design:

1. Simple Design of Steel Structure

Simple design is the most traditional approach and is still commonly used. It is assumed that no moment is
transferred from one connected member to another, except for the nominal moments which arise as a result of
eccentricity at joints. The resistance of the structure to lateral loads and sway is usually ensured by the provision of
bracing or, in some multi-storey buildings, by concrete cores. It is important that the designer recognises the
assumptions regarding joint response and ensures that the detailing of the connections is such that no moments
develop that can adversely affect the performance of the structure. Many years of experience have demonstrated the
types of details that satisfy this criterion and the designer should refer to the standard connections on joints in simple
construction.

2. Continuous Design of Steel Structure

In continuous design, it is assumed that joints are rigid and transfer moment between members. The stability of the
frame against sway is by frame action (i.e. by bending of beams and columns). Continuous design is more complex
than simple design therefore software is commonly used to analyse the frame. Realistic combinations of pattern
loading must be considered when designing continuous frames. The connections between members must have
different characteristics depending on whether the design method for the frame is elastic or plastic.

In elastic design, the joints must possess sufficient rotational stiffness to ensure that the distribution of forces and
moments around the frame are not significantly different to those calculated. The joint must be able to carry the
moments, forces and shears arising from the frame analysis.

In plastic design, in determining the ultimate load capacity, the strength (not stiffness) of the joint is of prime
importance. The strength of the joint will determine whether plastic hinges occur in the joints or in the members, and
will have a significant effect on the collapse mechanism. If hinges are designed to occur in the joints, the joint must
be detailed with sufficient ductility to accommodate the resulting rotations. The stiffness of the joints will be
important when calculating beam deflections, sway deflections and sway stability.
semi-continuous design is more complex than either simple or continuous design as the real joint response is more
realistically represented. Analytical routines to follow the true connection behaviour closely are highly involved and
unsuitable for routine design, as they require the use of sophisticated computer programs. However, two simplified
procedures do exist for both braced and unbraced frames; these are briefly referred to below. Braced frames are
those where the resistance to lateral loads is provided by a bracing system or a core; in unbraced frames this
resistance is generated by bending moments in the columns and beams.

The simplified procedures are: (i) The wind moment method, for unbraced frames. In this procedure, the
beam/column joints are assumed to be pinned when considering gravity loads. However, under wind loading they
are assumed to be rigid, which means that lateral loads are carried by frame action. A fuller description of the
method can be found in reference. (ii) Semi-continuous design of braced frames. In this procedure, account of the
real joint behaviour is taken to reduce the bending moments applied to the beams and to reduce the deflections.

CONSTRUCTION METHODS FOR BRIDGES:

Different Methods of Bridge Construction

Described below are the different methods employed in the construction of bridges.

1. Cast-in-situ Method of Bridge Construction

This method is a flexible method of bridge construction where complex and unusual geometrical shapes of dams can
be constructed easily. Situations when it is hard to transport pre-fabricated elements either due to size or
unreachability, this method is a good choice. Read More: Cast-in-situ Method of Bridge Construction

2. Balanced Cantilever Method of Bridge Construction

This method is used for constructing bridges with span 50 to 250m. The bridge constructed can either be cast-

in-place or precast. Here, the segments are attached in an alternative manner at opposite ends of the

cantilevers supported by piers. This is the best choice for the construction of long span length bridges,

irregular length, and cable-stayed bridges.

3. Precast Method of Bridge Construction
In this method, the bridge is constructed with the help of precast concrete elements. The prefabrication is performed
in different methods. The precast elements include:

 Precast Beams
 Precast Decks
 Precast Segmental Decks
4. Span by Span Casting method of Bridge Construction
This method is associated with cantilever construction method but with many advancements in the technique, it
is considered as most economic and rapid in construction. For long bridges and viaducts with an individual span
up to 60m, the method is feasible. Decks are begun at one abutment and constructed continuously by placing
segments to the other end of the bridge. Segments can be positioned by either a temporary staying mast system
through more commonly using an assembly truss.
5. Incremental Launching Method of Bridge Construction
The Incremental Launching Method (ILM) method of bridge construction is employed mainly for the
construction of continuous concrete bridges or steel girder bridges. The method performs the procedure in
increments. With this method of construction, the bridge deck is built in sections by pushing the structure
outwards from an abutment towards the pier. The ILM method can be used for bridge decks with a length
greater than 250m
6. Cable-Stayed Method of Bridge Construction
In the cable-stayed method of construction, cables are used to carry the bridge deck from one or both sides of
the supporting tower. The cables carry and transfer all the loads to the foundations. Cable-stayed method of
construction is used for constructing bridges that span more than 300m.
7. Arch Method for Bridge Construction
Arch shaped bridge construction is one of the most economical choices when the bridge under consideration is
required to cross over landscapes that are inaccessible. Many modern arch construction methods have made the
arch construction more economical. The arch construction can be built with concrete or pre-cast concrete. The
cast-in-situ free cantilever method and slip formed sections are two main construction techniques coming under
arch methods.