Portal Frame Construction: Structural, Footing, Wall, Floor, Roof and Service Systems

This paper discusses the technical aspects of portal frame construction including structural, footing, wall, floor, roof and service systems. It provides insights into the design and construction of portal frames for low-rise structures like factories, warehouses, and barns. The paper is based on the investigation of Industrial unit 6D,1-3 Endeavour road and includes photographs for clarification.

Portal frame construction 1
PORTAL FRAME CONSTRUCTION
By Name
Course
Instructor
Institution
Location
Date

Portal frame construction 2
Table of Contents
1.0 Introduction.........................................................................................................................................3
2.0 Background.........................................................................................................................................4
3.0 Footing system....................................................................................................................................5
4.0 Structural system................................................................................................................................7
4.1 Fly bracing..........................................................................................................................................8
4.2 Column and rafter...............................................................................................................................9
4.3 Endwall column................................................................................................................................11
4.4 Girts and purlins...............................................................................................................................12
4.5 Bracing..............................................................................................................................................13
5.0 Floor system......................................................................................................................................13
5.1 Surface treatment..............................................................................................................................14
5.2 Floor joints.......................................................................................................................................16
5.21 Contraction Joints...........................................................................................................................16
5.22Construction joints..........................................................................................................................16
5.23 Isolation joints................................................................................................................................17
5.24 Expansion joint...............................................................................................................................18
6.0 Wall sytems.......................................................................................................................................18
6.1 Connctions and fixtures...................................................................................................................19
7.0 Roof stsem for portal frame systems..............................................................................................19
7.1 Roof cladding....................................................................................................................................20
7.2 Gutter and flashing details...............................................................................................................21
8.0 Service systems.................................................................................................................................22
8.1 Electricity and telecommunications...............................................................................................22
8.2 Sewage and water.............................................................................................................................22
8.3 Fire protection...................................................................................................................................23
9.0 CONCLUSION................................................................................................................................24
10. 0 Reference.......................................................................................................................................26

Portal frame construction 3
PORTAL FRAME CONSTRUCTION
1.0 Introduction
Portal frame construction refers to the technique of designing and constructing structures,
whereby two-dimensional rigid frames with basic characteristics of the rigid joint are between
the beam and the column are utilized (Hiriyur,2010). The main aim of using this method of
designing and construction is to reduce the bending moments in the beam in order to allow the
frame to act as one structural unit. With that, the size of the structural element can be reduced or
at the same time, and the span can be increased for the same size of the structural elements. Due
to that, the portal frames are considered to be very efficient and reliable construction method to
be used for the buildings with long span.
Portal frames are generally being used in the low-rise structures, which are comprised of beams,
columns or pitched rafters that are connected by the moment resisting connections. The
resistance to vertical and lateral actions is offered by a suitable haunch, or the deepening of the
rafter sections This type of continuous frame structure is usually stable in its plane, and it offers
clear span which is not obstructed by the bracing. In most cases, the portal frame construction is
used in the construction of single-level structures, and it is usually seen in the construction of
factories, warehouses, barns and other areas where large open spaces are needed at low cost and
a pitched roof is also accepted.
A portal frame structure usually comprises a series of transverse frames which are braced
longitudinally. The primary steelwork is made up of rafters and columns, which makes the form
portal frames and bracing. The gable frame can be either a portal frame or a braced arrangement
of columns and rafters.

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The light gauge secondary steelwork is made up of the side rails which are used for the walls and
the purlins that are used for the roof. The secondary steelwork offers support to the building
envelope, but it also plays a very significant role in restraining the primary steelwork. The wall
cladding and the roof separates the building envelope from the external environment as well as
offering acoustic and thermal insulation. The function of cladding is to transfer the loads to the
secondary steelwork and at the same time to restrain the flange of rails or purlins to which it is
attached (Paolacci and Giannini 2012). The figure below shows the anatomy of a typical portal
frame.
Fig 1: A cross-section showing portal frame and its restraints

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Fig 2: Principal Components of a portal framed structure.
The key focus of this paper provides a discussion of the technical aspects of the portal frame
construction. The area which is analyzed in this paper include; structural system, footing system,
wall system, floor system, roof system, and services. The information which is contained in this
paper is based on the deep investigation of Industrial unit 6D,1-3 Endeavour road. The
photographs are included in the discussion part to over clarification. The areas which were
mentioned in the assignment brief have been covered for simplicity.
2.0 Background
The industrial unit is located within the center of the Sutherland Shire’s Industrial Precinct. It has
a total area of approximately 850 m2. The ground floor is typically a warehouse of

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approximately 600m2 while the upper floor of 150m2 is for office. The warehouse has a parking
capacity of 10 vehicles. The main structure is a fixed structure of steel portal frame with a clear
span of 18m and a ceiling height of 7.0 m. The figures below are illustrations of the Industrial
unit 6D,1-3 Endeavour road.
Fig 3: Industrial unit 6D,1-3 Endeavour road.
Fig 4: 6D,1-3 Endeavour road interior

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3.0 Footing system
Footing refers to the components of the building which transfers the load from the build to the
foundation. The primary purpose of designing the footing is to ensure that the loads from the
structure are safely transmitted to the subsoil, economically and at the same time ensuring that
there is no unaccepted movement during the construction process and throughout the anticipated
lifespan of the structure.
The factors which are usually put into consideration during the design of the footing system are;
type of the structure, the soil conditions, economic factors, structural loadings, construction
problems and the proposed construction period. Of all these factors structural loading and the
soil condition are the most essential during the design process of the footings. The footing
system which is properly designed can significantly help to eliminate or minimize the differential
settlement which occurs when the weight of the structure stresses the soil. In the cases where no
settlement occurs, it must occur equally under the building.
According to the geotechnical report of the industrial unit above the site, foundation materials
are made up of sandy over the shale, having a high bearing capacity at a depth of about three
meters. According to this data, it is reasonable to assume that there is some soil movement on the
upper stratum of the foundation. Hence it is much safer to rest the footing at the shale level
which offers sound bearing pressure with very minimal movement. The engineer used two types
of footing during design. A 150mm thick structural raft shaft having stiffened edge and integral
beams over the piers were driven to the shale foundation. The main function of the raft is to
distribute the load both the live and dead load evenly over a large base in order to reduce the load
which is acting per unit area. The piers were used to bypass the reactive soil and at the same time

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transfer the superstructure load at the edge beam to the lower level of subsoil where suitable
ABP exist. The figure below shows the arrangement of this structural members.
Another appropriate kind of footing possibly is pad footing. This is the most common footing
style for the portal frame. A concrete pad footing is the easiest and cheapest type of footing used
in vertical support and transmitting of structure loads to the subsoil. A pad footing of adequate
size to stop uplift will be sufficient as long as it does not surpass an Acceptable Bearing Pressure
of 100kPa. Occasionally deep pad footing has to be used to reach the soil lay providing sufficient
APB, or a pedestal may be required to support the column base plate. The figure below shows
how the pad footing is connected to the frame.
Fig 5: pad footing connection
The images below which were obtained from the site shows a holding down bolt, a pad footing
having HD bolt that are cast in situ and a universal column set into the concrete pad footing. It
was observed that the holding down bolts were underneath the top layer of the additional
concrete grout over the footing.

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Fig 6: hold down bolts
4.0 Structural system
The common structural components of a portal frame system are as shown in the figure below.
Fig 7: components of a portal frame system

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Fig 8 : components of a portal frame system
Each componponent of thye portal frame systen are discussed into details in this section.
4.1 Fly bracing
A fly brace refers toa trap, bar or angle which runs from the flange of the rafter, endwall column
or central column to a wall or a roof batten and therefore refrains the section laterally. The top
flange of beams will possibly be under compression due to loads of gravity. As the roof purlins
try to restrain the top flange from buckling under the load, the system will then work efficiently.
The primary function of the fly brace is to prevent a rafter or column from rotating or twisting

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when under load. The pictures below show some of the fly braces.
Fig 9 :Fly brace for the rafters
Fig 10 :Fly brace for wall batterns
4.2 Column and rafter
The portal frame of the selected industrial unit is made from the 410UB54 column with
360UB56 rafters. The steel rafters were fabricated in a factory in that they are welded to the steel
plate, and later they were bolted to the UB column rafters.At the ridge of the Industrial Unit,
rafters are connected to each other with bolts. Steel fly bracing between steel purlins and purlins
also can be seen. The system of this industrial unit can be considered to be a rigid portal frame

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system which gives excellent resistance to side wind load, at the same time support roof load,
and it can be designed to carry the weight of the external wall cladding such as a precast concrete
panel. The image below shows the columns and rafters.
Fig 11: columns and raftes
The difference between the rafter and purlin
Rafters and purlins are the primary members of any given roof system. They are usually used to
transmit the load from the load to the walls and later on to the foundation. They transfer the dead
weight,live load, and wind load together with other loads which are acting on them. The rafters
and purlins are like a two-way reinforcement of the roof. The purlins are ones which are parallel
to the ridgeline or the ones which run along the span o0f the span of the roof while the rafters are
elements which are perpendicular to the ridgeline of the roof truss.

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The roof truss is usually supported at the columns, and the rafters are supported on the roof truss
upon which the purlins are welded or bolted and upon the purlins lies the roof covering materials
which may be asbestos sheets or any other roof covering materials.The figure below shows the
difference between purlins and rafters.
Fig12 :Rafters and purlins
4.3 Endwall column
An end wall column refers to the vertical member which is located at the end of any given wall
which offers support to the girts. In the beam and column end frames. The end wall column also
provides support for the beam which is also referred to as wind column. The figure below shows
the detailing of the end wall beam connected to a rafter.

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Fig 13: endwall column detail
In the Industrial unit which was under investigation, the end frames have additional columns
added to them. The end wall columns are also referred to as wind columns this is because they
transfer the lateral load of the wind to the roof members and then later on to the wall
members.With that, the weight is eventually distributed evenly in the entire structure. The extra
columns make the end wall frames not to be strictly portal frames as the additional columns
greatly help to share the load. Another function of the end wall columns is to offer to fix support
to the wall members.

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4.4 Girts and purlins
The Girts and purlins provide support for roof sheeting and cladding. The purlins are usually
cold steel sections and in most case are connected to the rafter with the use cleat which can be
bolted or welded on the rafter during the process of fabrication on site. The purlin is usually
bolted to the cleat. Sarking and safety mesh is located between purlins and roof sheeting.
Girts refer to the cold steel sections that are bolted to the cleats of the columns of the portal
rafters ensuring support for the wall cladding.The girts and purlins in the industrial unit are the
‘C’ sections.The ‘C’ sections are butt jointed.
The purlins depend on the cladding to offset the deflection and twisting due to the alignment of
the purlins, but a single row of the standard bridging pieces is usually required.
SAG RODS AND BRIDGING
Bridging is usually used between the sag rods and the purlins between the girts to overcome the
rolling and the excessive deflection. One row of the bridge is typically common through two
rows regularly are used and the bays where the girts or the purlins are transferring the lateral load
to the inner braced frame.
4.5 Bracing

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The portal frames are self-bracing in their plane, but the wind loads which are acting in right
angle to the portal must be solved by the use of wall or roof bracing. This is often in the form of
double diagonal bracing between the portal bays. Tubes, rods and the angles are very common
for bracing. In this industrial unit 75 × 75 × 6 mm mild steel angle bracing is usually used to
brace the roofing structure to help the structure to be stable when the lateral forces are applied on
the roof
.5.0 Floor system
The selection of the floor system to be used in the building should involve an extensive
consideration of all aspects of the building. Starting from the design of the structure, construction
and the future uses of the building. Sometimes it is essential to compromise since the final
selection of the floor system must meet some contradictory criteria.
Usually, the choice of the floor system has two meet two criteria. First, the finished flooring
must be able to serve its intended purpose. That means that floor system after completion should
behave well under the future service conditions, it should be free or minimal maintenance, be
appealing of the finishes, easy to install among others. Secondary, the floor system must be
structurally sound. It should have enough reserve of the strengthy against peak loadings and be
able to behave acceptably under the standard conditions and loads.
When one compares the domestic buildings .the floor system of the industrial unit will encounter
greater imposed loads such as forklifts and trucks which will be imposing rolling loads, and at
the same time, the machinery in the factory will be imposing static loads. With that, the slab for
the industrial unit must be able to support higher loads and tolerate less movement.

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The industrial unit under investigation has a stiffened raft lab which is supported on the
reinforcement concrete piers. It equivalents to the column-beam-two way slab system. The slab
is supported on four sides and the load the then to a carried in two different directions. Hence
this type of the design is adaptable to a wide range of different layouts and a wide range of
layouts.Well organized grids result in the more economical use of materials. Incorporating the
services within the floor slab is possible.The distribution of the suspended services can be taken
through holes that are cast in the web of the beams within the mid-third of the span.The figure
below indicates the layout of the floor slab, internal beams and piers(columns) of the selected
industrial unit.
Fig 15:floor slab layout
5.1 Surface treatment
The selected industrial unit has a concrete floor which is treated chemically. Through the
chemical reactions, the concrete floor hardened and a ‘case’ formed around the top of the
concrete slab. With that, it creates a more solid more durable and robust finish which also is
more appealing, resistant to the staining, deterioration and at the same time dust proof.
The product which was used in the industrial unit is Pentra-Sil (NL) which is a concrete sealer,
and hardener formulated to improve the overall integrity, strength and the lifespan of the

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concrete surface. The treatment to the floor offers long-term protection against abrasion, dusting,
efflorescence, waterborne contamination, alkalinity and harsh chemicals. The figure below
shows the surface treatment of the industrial unit under investigation.
Fig 17:Floor surface treatment
The product which was applied should only be applied when the temperature is above 20oC for not less
than 4hours after the application. The Concrete should be adequately trowelled or finished by use of
dry grinding, and be dry and at the same time to be clean.If the mentioned conditions are not met, the
petra won't be able to penetrate the surface equally. In case it is applied immediately after the finishing,
or shortly after the joints have been cleaned and cut or any other time afterward.

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An HVLP sprayer often needs to spray Pentra-Sil equally on the surface.Spread out any pools
using smooth microfiber or a broom with soft bristles.The covers need to be maintained wet for
at least 20minutes, adding more materials where there is a need. Surface will then be ready for
use when it is already dry, but the complete reactions take up to two weeks to develop depending
on the site temperature and the conditions.
5.2 Floor joints
There are usually four joints which are commonly found in the concrete slab construction. They
include; contraction joints, construction joints, expansion joints and isolation joints. Nonetheless,
it was very challenging to locate all the four joints in the chosen industrial unit which was under
construction.
5.21 Contraction Joints
Usually, the concrete slab shrinks once it has dried or hardened, and it will never be the same
length as it was when it was constructed. The shrinkage leads to cracking.The construction joints
are weakened planes installed to predetermine the location of transverse cracks and at the same
time to ensure that they occur in straight lines. In the plastic concrete, the weakened planes can
be created by permanent or removable inserts or special tools. In the hardened concrete, they can
be formed by the sawing diamonds or carbide-tipped blades as shown in the figure below.

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Fig 18: contraction joints
5.22 Construction joints
Use of the chequerboard method poured the slab of the selected industrial Unit under
investigation. There were individual bays of approximately 6metres that can be cast alternatively
within the stop ends which forms the construction joints. Usually, the preplaced mesh
reinforcement continuous through splits form on all the sides of each of the bay. The benefits of
this technique are that they are very convenient construction method and they are easy to control
contraction and shrinkage. In the massive slab construction, there is need to have dowels which
should be placed across the construction joints. The dowel is required to be treated to allow
horizontal movement which is not restricted as the joint closes and opens. The primary function
of the construction joint is to facilitate easy and quick construction of large slabs.The figure
below illustrates the longitudinal construction joints in the industrial unit selected.

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Fig 19: construction joints

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5.23 Isolation joints
This type of the joints isolates the slab from the primary structure of the main structure of the
building. where the slab meets with the primary structure of the building, for instance, a pedestal
for the portal base, an isolation joint often required. The primary use of the isolation joint is to
allow movement of the slab and at the same time isolate the slab movement from the fixed
structure.
5.24 Expansion joint
This type of the joints is usually installed in the situations where the slabs are very large or in the
cases where the structural system varies.hence need for the articulation of the structure. For
instance, where part of the structure is on the good stable soil, and the other part is on poor
expansive soil, then in such a situation there should be two different types of footing forcing the
slab to be separated by use of a control joint. The joints are usually designed to allow movement
of the slab generally in the plane of the slab. In most cases, there are no expansion joints that are
required in the chosen industrial unit slab.
6.0 Wall sytems
All the external walls of the industrial unit that was selected for the study are made from vertical
precast concrete panels. The figure below shows the external walls of the selected industrial unit.

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Fig 20: external concrete panel walls
6.1 Connctions and fixtures
The details of the panels to the footings
The panes are normally supported on the seating which is in the direct bearing. Its weight in most
cases should be transmitted at one level by use of two seatings unless in the situations where the
wall is supported longitudinally by the use of ground seatings. Different fixing techniques are,
but the commonly used conncetion technique is the connection to the stepped footing.
load resistance
It is very essential that the walls of any given structure offer enough resistance mechanism from
the applied loads. In most structures, the roof can function as a diaphragm to transmit the applied

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lateral loads on one set of the walls to the ones at right angles. Then later acts as a shear wall to
resist all the applied loads.
7.0 Roof stsem for portal frame systems
The roof system of the portal frame systems is as shown below.
Fig 21:roof components for portal frame structures
7.1 Roof cladding
The roof of the Industrial unit which was selected for study is cladded by use of concealed fixed
Lysaght Klip-lok 406. This is durable, robust and versatile wall and roof cladding materials. This
type of materials usually combines the smart fluted pans, the strength of steel and the lock action
rib which work together with the fastening, enables its use on the applications from low pitched

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which is as low as 1-degree roofs to the horizontal and vertical ribbed walling. The figure below
shows the roof coverings that are used in the industrial unit under investigation
Fig 22: roof clading materials
lysaght Klip lok 406 specificationsLysaght Klip lok 406 usually exists in two grades. The first one is
typically the zinc/ aluminum alloy-coated steel. The second grade of Lysaght Klip lok 406 is the colour
bond prepainted steel.Both of this grades have a metal thickness of 0.48mm

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7.2 Gutter and flashing details
Fig 23: gutter and flashing details (Knudson and Flood 2010).

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A gutter refers to the surface or rainwater collection channel system for a building. The water
from the pitched roofs usually flows into gutters whereby the water is further directed to the
downpipe which discharges the water into the storage tanks or the stormwater drainage systems.
In the selected industrial unit which was under study, the had a gutter which was connected to
the downpipe which was directing water to the stormwater systems.
8.0 Service systems
8.1 Electricity and telecommunications
The primary electricity distribution and other services are located next to the main entrance of
this industrial unit. Most of the electricity and services cables are laid underground, and in most
cases, they are within the slab of the industrial unit structure/. Most of the wiring cables in the
structure are surface mounted by use of bracket fix to the concrete panels directly.
8.2 Sewage and water
The industrial unit is supplied with the water and the sewage services. The water is obtained
from the city council and is well distributed with the industrial unit. In short water in the building
is sufficient to enable one to carry ou any industrial activity that may require plenty of water in
the selected building. The sewage is also well connected in the structure which makes it easy to
disposal any waste wastewater within the building. The images below show the sewage and
water within the building.

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Fig24:stormwater manhole
8.3 Fire protection
In the selected industrial unit some measures have been put in place to ensure that incidents of
fire are minimized for instance there are passive fire protection measures, active fire protection
measures and fire alarm and detection system.
The passive fire protection systems are the measures that have been put in place to ensure that
the spread of smoke and fire is controlled. That is achieved in most cases by the use of barriers
which have characteristics which do not allow further spread of fire.
The active fire protection systems are the ones whereby the firefighting equipment are put in
place to ensure that in case of incidents of fire. The fire can be quickly put off. In the selected
industrial building there were fire extinguishers, sprinklers and another mechanism which help to
fight the fire. The fire detection and alarm system is an active fire protection system which
automatically detects fire and alerts the occupant's use of alarms.

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Fig 26:Fire dectection sytem

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9.0 Conclusion
In conclusion, A portal frame structure usually comprises a series of transverse frames which are
braced longitudinally. The primary steelwork is made up of rafters and columns, which makes
the form portal frames and bracing. The gable frame can be either a portal frame or a braced
arrangement of columns and rafters.
The factors which are usually put into consideration during the design of the footing system are;
type of the structure, the soil conditions, economic factors, structural loadings, construction
problems and the proposed construction period. Of all these factors structural loading and the
soil condition are the most essential during the design process of the footings. The footing
system which is properly designed can significantly help to eliminate or minimize the differential
settlement which occurs when the weight of the structure stresses the soil.
The light gauge secondary steelwork is made up of the side rails which are used for the walls and
the purlins that are used for the roof. The secondary steelwork offers support to the building
envelope, but it also plays a very significant role in restraining the primary steelwork. The wall
cladding and the roof separates the building envelope from the external environment as well as
offering acoustic and thermal insulation.

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Rafters and purlins are the essential members of any given roof system. They are usually used to
transmit the load from the load to the walls and later on to the foundation. They transfer the dead
load, live load, and wind load together with other loads which are acting on them. The rafters and
purlins are like a two-way reinforcement of the roof. The purlins are ones which are parallel to
the ridgeline or the ones which run along the span o0f the span of the roof while the rafters are
elements which are
An end wall column refers to the vertical member which is located at the end of any given wall
which offers support to the girts. In the beam and column end frames. The end wall column also
provides support for the beam which is also referred to as wind column. A fly brace refers toa
trap, bar or angle which runs from the flange of the rafter, endwall column or central column to a
wall or a roof batten and therefore refrains the section laterally. The top flange of rafters will
possibly be under compression due to loads of gravity. As the roof purlins try to restrain the top
flange from buckling under the load, the system will then work efficiently.

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10. 0 Reference
Hiriyur, B. K. (2010). U.S. Patent Application No. 12/178,078.
Knudson, G. A., & Flood, P. D. (2010). U.S. Patent No. 7,752,812. Washington, DC: U.S. Patent
and Trademark Office
Paolacci, F., & Giannini, R. (2012). An experimental and numerical investigation on the cyclic
response of a portal frame pier belonging to an old reinforced concrete viaduct. Earthquake
Engineering & Structural Dynamics, 41(6), 1109-1127.