Structural Conformation of Single Storey Steel Buildings

STRUCTURAL CONFORMATION OF
SINGLE STOREY STEEL BUILDINGS
Tzanetis Vogiatzis
Structural Engineer, PhD
Guest Speaker
Norwegian University of Life Sciences
| TBA224 | Structural Design of Buildings II Winter Semester, 2021
ORCID iD: 0000-0003-3732-0174 www.linkedin.com/in/tzvogiatzis

Presentation Outline
A Single Storey Buildings
Α-1 Applications & Facilities
A-2 Construction Cost
A-3 Steel Construction Benefits
A-4 Design Decisions Hierarchy
A-5 Construction Programme
B Main Design Solutions
C Basic Structural Components
Dr. Tzanetis Vogiatzis
Structural Conformation of
Single-Storey Steel Buildings

o Commercial buildings account
for 20% of construction in the
EU, representing over 20 million
M2 of floor space per year.
75%
25%
EU buildings
Residential Non-residential
28%
23%
17%
11%
7%
4% 11%
Non-residential buildings
Wholesale & retail Offices
Educational Hotels & restaurants
Hospitals Sport facilites
Other
Source: “Europe’s buildings under the microscope”
(BPIE 2011) and IA EPBD, 2017
Single Storey Buildings (A-1)
Applications & Facilities

o Clients demand buildings that
are rapid to construct, of high
quality, adaptable in application,
and energy efficient in use.
Construction phase
Excavation phase

o Steel & composite construction
has achieved over 60% market
share in this sector in some
countries of Europe,
Single storey building: Structural design

o Steel & composite construction
has achieved over 60% market
share in this sector in some
countries of Europe,
o where the benefits of long
spans, speed of construction,
improved quality and reduced
environmental impact have
been recognised.
Single storey building: Members detailing

o This presentation is restricted to
single storey steel buildings with
spans from 15 m to 100 m.
o Typically applications for those
buildings are for:
Single storey building: Architectural design

Industrial facilities: Warehouse
buildings are for:
▪ Industrial facilities.

Office facilities
buildings are for:
▪ Office facilities.

Laboratory facilities
buildings are for:
▪ Laboratory facilities.

Storage facilities: Food
buildings are for:
▪ Storage facilities.

Storage facilities: Livestock
buildings are for:

Retail facilities
buildings are for:
▪ Leisure facilities.

Indoor sport facilities: Tennis court
buildings are for:
▪ Indoor sport facilities.

Indoor sport facilities: Swimming pool
buildings are for:

Aircraft hanger
buildings are for:
▪ Other facilities.

Helicopter hanger

Construction Cost
o An approximate breakdown for
construction costs for a typical
office building is presented

Construction Cost
o Site preliminaries can vary with
the scale of the project and a
figure of 15% of the total cost is
often allowed for steel intensive
construction reducing to 10%
for higher levels of
prefabrication.
Source: Access steel

Construction Cost
o The super structure/framework
cost is rarely more than 10% of
the total, but it has an important
effect on other costs.

(i) Speed of Construction
o All steel construction uses pre-
fabricated components that are
rapidly installed on site.
Steel Construction Benefits

o In commercial building projects,
construction can be reduced by at
least 30% in comparison to RC
construction, leading to:
✓ Savings in site preliminaries
✓ Earlier return on investment
✓ Reduced interest charges

o In commercial building projects,
construction can be reduced by at
least 30% in comparison to RC
construction, leading to:
✓ Savings in site preliminaries
✓ Earlier return on investment
✓ Reduced interest charges
o Those time-related savings amount
from 3 to 5% of the overall project
value, thus the client’s working
capital & cash flow is reduced.

(ii) Flexibility and Adaptability
o Steel constructions provide longer
spans in which the space can be
arranged to suit open plan facilities.
o All internal walls can be relocated
leading to gully adaptable buildings.

(ii) Flexibility and Adaptability
o Steel constructions provide longer
spans in which the space can be
arranged to suit open plan facilities.
o All internal walls can be relocated
leading to gully adaptable buildings.
(iii) Service Integration
o Steel structures can be designed by
integrating major services within the
depth of the structure.
o This is important in cases in which
the building height is restricted for
planning reasons.

(iv) Locality Reduced Disruption
o In many inner city projects, it is
important to reduce disruption to
nearby buildings and roads by:
▪ Timing deliveries to site to suit
traffic conditions.
▪ Reducing materials use and
waste creation
▪ Reduced material storage on site.
▪ Minimising noise and dust.
▪ Reducing the construction period.
o Steel constructions can
dramatically reduce the impact of
the construction operation on the
locality.

(v) Quality
o Off-site prefabrication improves
quality by factory-controlled
production, and is less dependent
on site trades and the weather.
o Also, steel does not suffer from
creep or shrinkage.

(v) Quality
o Off-site prefabrication improves
quality by factory-controlled
production, and is less dependent
on site trades and the weather.
o Also, steel does not suffer from
creep or shrinkage.
(vi) Safer Construction
o Working in a controlled,
manufacturing environment is
always safer than working on site.
o Using pre-fabricated components
can reduce site activity for frame
construction by up to 75%, thereby
contributing to construction safety.

(vii) Environmental Benefits
o The steel structure is 100%
recyclable. The steel incorporated
into the structure contains up to
45% recycled material.
o The speed of construction and
reduced disruption of the site gives
local environmental benefits.
o Their flexibility & adaptability
maximise the economic life of the
building as it can accommodate
radical changes in use.
o Steel production & fabrication are
both efficient processes with
minimum waste.

Design Decisions Hierarchy
o Design decisions must begin
with the clearest possible
understanding of the client
requirements and of local
conditions and regulations.

o It is this early interactive stage
where the important decisions
are made that influence the cost
and value of the final project.

o Once the concept design is
agreed, the detailed design of
the building and its components
may be completed, with less
interaction with the client.

Construction Programme
o A construction programme for
medium-sized office buildings is
shown as shown in side figure.

o The installation of the primary
structure & floors takes about
20-25% of the total construction
period but its completion
permits an early start on
cladding and servicing.

o A construction programme for
medium-sized office buildings is
shown as shown in side figure.
o The installation of the primary
structure & floors takes about
20-25% of the total construction
period but its completion
permits an early start on
cladding and servicing.
o The main benefit relative to
concrete construction is the
creation of a water-tight building
envelope early in the
construction progress.

B-1 Portal Frame Buildings
B-2 Latticed Framed Buildings
B-3 Suspended Buildings
B-4 Arched Buildings

(i) Principal Types
o Portal frame is by far the most
common form for steel buildings.
Portal frame principal types: Single-bay Portal frame building
Portal Frame Buildings
Main Design Solutions (B-1)

(i) Principal Types
o They are constructed with:
▪ either a flat roof,
Portal frame principal types: Single-bay Portal frame: Flat roof

(i) Principal Types
o They are constructed with:
▪ either a flat roof,
▪ or a pitched roof.
Portal frame principal types: Single-bay Portal frame: Pitched roof

(i) Principal Types
o When a flat roof is used the rafters:
▪ can be either straight,
Portal frame principal types: Single-bay Flat roof with straight rafters

(i) Principal Types
▪ or curved.
Portal frame principal types: Single-bay Flat roof with curved rafters

(i) Principal Types
▪ or curved.
o But for each case the design
methods follow the same principles.
Portal frame principal types: Single-bay Curved rafter portal frame

(i) Principal Types
o Curved rafter frames are used
mainly for architectural reasons.

(i) Principal Types
o Due to constructional limitation
(availability of steel sections length),
Portal frame principal types: Single-bay Curved rafter sections

(i) Principal Types
o Due to constructional limitation
(availability of steel sections),
o rafters longer than 12 m require
splices.

(i) Principal Types
o Office accommodation is often
provided within a portal frame
structure using a partial width
mezzanine floor.
o The assessment of frame stability
must include the floor effect.
Portal frame principal types: Single-bay Portal frame with mezzanine floor

(i) Principal Types
o Where a travelling crane of relatively
low capacity (up to 20 t) is required,
brackets can be fixed to the columns
to support the crane rails.
o Tie member or rigid column bases
can reduce the eaves deflection.
Portal frame principal types: Single-bay Crane portal frame with column brackets

(ii) Hot-rolled universal sections
o The primary portal frame is typically
constructed using hot-rolled sections.
Portal frame with hot-rolled sections
Typical hot-rolled section profiles

o The primary portal frame is typically
constructed using hot-rolled sections.
o For the secondary components,
usually cold rolled sections are used.
Typical hot-rolled section profiles Typical cold-rolled section profiles

o As the name implies ’’hot rolled steel’’
refers to a steel rolling process carried
out with heat.
Hot-rolled steel

o As the name implies ’’hot rolled steel’’
refers to a steel rolling process carried
out with heat.
o This makes the steel easier to form, &
results with easier to work products.
Typical hot-rolled section profiles Hot-rolled steel

o Hot rolled steel is typically cheaper
than cold rolled steel due to the fact
that it is often manufactured without
any delays in the process, and
therefore the reheating of the steel is
not required (as it is with cold rolled).
Typical hot-rolled section profiles Hot-rolled steel

o When the steel cools off it will shrink
slightly thus giving less control on the
size and shape of the finished product.
Typical hot-rolled section profiles Hot-rolled steel UPE section

o When the steel cools off it will shrink
slightly thus giving less control on the
size and shape of the finished product.
o Compared to its counterparts, it has
less strength than cold rolled steel.
Hot-rolled steel I section

o ’’Cold rolled steel’’ is essentially ’’hot
rolled steel’’, that has had further
processing.
o This process will produce steel with
closer dimensional tolerances and a
wider range of surface finishes.
Typical cold-rolled section profiles

(iii) Fabricated Welded Sections
o Compared with traditional rolled
sections for medium spans, welded
members allow the sections to be
reduced by adjusting them precisely to
the internal forces.
Portal frame with fabricated welded sections

o While maintaining an identical external
size, web thickness may be reduced in
areas with low bending moments.

o This significantly reduces weight – at
the expense however, of having to butt
weld between the flange and web
plates of different thickness

o This significantly reduces weight – at
the expense however, of having to butt
weld between the flange and web
plates of different thickness
o The span/depth ratio is typically 20 to
25 for spans up to 30 m. Portal frame with fabricated welded sections

o The main type of built-up sections are:
▪ Uniform overall depth and width,
possibly with varying thickness.
Thickness may vary generally or
the changes may be limited to local
reinforcement at connections.
▪ Built up members with a gradually
tapering depth and, possible,
changes in flange width.
o Usually they are more expensive than
hot-rolled standard sections.
o Experience has shown that economy
for portal frames with welded sections
is achieved by using elastic theory.

(iv) Castellated & Cellular Beams
o Cellular beams are used for aesthetic
reasons or when providing long spans.
Cellular Beams in multistory buildings
Fabrication process

o They developed by cutting and
welding the web of a rolled I section.
Cellular Beams during fabrication
Fabrication process

o They developed by cutting and
welding the web of a rolled I section.
o Those sections cannot develop plastic
hinges at a cross-section, so only
elastic design is used.
Castellated Beams welded on site
Fabrication process

o Initially, the castelled beam with
hexagonal openings was used.
o Today, in common practice beams with
circular openings are used.
o The span/depth ratio is typically 30 for
spans up to 50 m.
Castellated Beams in single-storey buildings
Castellated beams

o In comparison with a solid web of
similar depth and bending resistance.
o Beams with web openings provide an
approximate 30% lighter structure.
o They are not suitable for roof beams
with heavy concentrated loads.
Cellular Beams in single-storey buildings
Cellular beams

(i) Typical Latticed Girders
o If the span range is larger than 45 m,
the latticed rafter layouts are used as
an effective and economic alternative.
Truss rafters in single-storey buildings
Typical arrangements for latticed girders
Latticed Framed Buildings

o If the span range is larger than 45 m,
the latticed rafter layouts are used as
an effective and economic alternative.
o If the rafters are to be latticed
structural steelwork, the span/depth
ratio is 15 to 20 for spans up to 100 m.
Typical arrangements for latticed girders Truss rafters in single-storey buildings

structural steelwork it is possible to
use different layouts of the internal
members.
‘‘Pratt’’ or ‘‘n’’ truss rafter in pitched roofs

75/2
structural steelwork it is possible to
use different layouts of the internal
members.
o However since the diagonals are likely
to be subject to stress reversal, due to
wind effects, the warren type truss is
generally preferred.
‘‘Pratt’’ or ‘‘n’’ truss rafter in pitched roofs

o Stability is generally provided by
bracing rather than rigid frame action.
Schematic side view
Latticed framed buildings with lattice columns

o Stability is generally provided by
bracing rather than rigid frame action.
o However, columns can also be
constructed in a similar way, in order
to provide in-plane stability.
Latticed framed buildings with lattice columns
Schematic side view

o In selecting the layout it is necessary
to decide on the purlins. If these are
located at node points then local
bending in top members is avoided.
Purlins location in truss rafters

o In principle, forces in all of the
members are either direct tensile or
compressive, with bending and shear
effects being secondary, as a result of
deformation of the truss.
Typical connections for ‘‘‘n’’ truss rafter

o In principle, forces in all of the
members are either direct tensile or
compressive, with bending and shear
effects being secondary, as a result of
deformation of the truss.
o For hand calculations analysis, it is
essential to assume that all joints are
pinned and preferably end support
conditions to the rafters are such that
the truss is statically determinate. Typical connections for ‘‘n’’ truss rafter

Typical connections for ‘‘‘n’’ truss rafter
Typical latticed framed industrial building

Hollow sections in three-dimensional trusses
(ii) Space Frames
o When hollow sections/tubes are used,
it is essential to ensure full welds.
Three dimensional triangular trusses

(ii) Space Frames
o When hollow sections/tubes are used,
it is essential to ensure full welds.
o Their specific advantage compared
with traditional sections are the high
strength to weight ratio, maximum
efficiency in tension, efficiency as
struts, good torsional properties,
appearance and maintenance.
Three dimensional triangular trusses

Space frames
(ii) Space Frames
o In space structures, the joints may be
very complex and more time
consuming to construct and install.

(ii) Space Frames
o The design must be aware of
problems which arise in the detail
design at the joints.

(ii) Space Frames
o Furthermore, the designer should
remember that some fabricators are
not fully equipped to use circular
hollow sections.

(ii) Space Frames
hollow sections.
o Used when the final decision is
influenced by aesthetics and not cost.

(ii) Space Frames
hollow sections.
o Used when the final decision is
influenced by aesthetics and not cost.
o The span/depth ratio for 3D trusses is
about 16 to 20 for spans over 50 m.

Suspended Buildings
Suspended structure Type 1
Principal Types
o Long span structures with columns
outside of the building envelope.
o The use of suspension cables or rods,
leads to reduced rafter sections.
o But, saving on material is not always
the way to economic solutions.
Main Configurations of Suspended Structures

Principal Types
o Complex joints need more time during
construction & installation.
o High maintenance costs and
waterproofing issues.
o Usually they are used for spans
between 30 m and 90 m.
Suspended Buildings

Principal Types
o The structure arrangement has direct
impact on the internal forces and
o therefore to the member sections.
o The suspension cables and rods are
obstructive to the use of the external
space.
Suspended Buildings

B-1 Portal Frame Buildings
B-2 Latticed Framed Buildings
B-3 Suspended Buildings
B-4 Arched Buildings

Arched Buildings
Curved Arch Structures
o Loads are distributed by compressive
arch members (parabolic or circular).
Methods of supporting arch members Arch structure during construction

o Their members are formed by cold
bending I-sections.
Methods of supporting arch members
Arched Buildings
Arch structure during construction

o Their members are formed by cold
bending I-sections.
o The span/depth ratio is between 60
and 75 for spans up to 50 m.
Methods of supporting arch members
Arched Buildings
Arch structure

C-1 Primary Structure
C-2 Secondary Members
C-3 Bracing Systems
C-4 Main Connections

(i) General Features
o A portal frame building comprises a
series of unbraced transverse
frames, braced longitudinally.
Multi-bay portal frame during construction
Multi-bay portal frame braced longitudinally
Primary Structure
Basic Structural Components (C-1)

(ii) Columns & Rafters
o The primary steelwork consist of
columns and rafters, which form the
portal frames, & longitudinal bracing.
Overview of structural components
Primary Structure

Primary Structure
(ii) Columns & Rafters
o The primary steelwork consist of
columns and rafters, which form the
portal frames, & longitudinal bracing.
o Those primary framing structural
members are generally fabricated from
hot rolled universal sections.
Principal building components
Columns
Rafters

Secondary Members
(i) Purlins & Side Rails
o The cladding system spans between
the main frames & is supported directly
on them or a purlin and rail system of
secondary members is used.
Typical transverse frame - Cross-section Principal building components

o The cladding system spans between
the main frames & is supported directly
on them or a purlin and rail system of
secondary members.
o Those secondary members also
transfer the loads to primary structure.
Typical transverse frame - Cross-section Steel building under construction
Side Rail
Purlins
Secondary Members

o For economic reasons those are
usually cold formed sections that are
variants on Z or channel shapes.
Typical transverse frame - Cross-section Typical cold-rolled section profiles
Secondary Members

o For economic reasons those are
usually cold formed sections that are
variants on Z or channel shapes.
o They are produced in a range of sizes
and thicknesses to cover economically
the loads & span ranges in Europe.
Typical transverse frame - Cross-section Steel building under construction
Secondary Members

o The secondary steelwork consists of:
▪ Side rails (girts) supporting the wall
claddings and
Wall cladding supported by side rails
Side Rails typical cold rolled Z section
Secondary Members

▪ Purlins for supporting the roof
cladding.
Roof cladding supported by purlins
Purlins typical cold rolled Z section
Secondary Members

▪ Purlins for supporting the roof
cladding.
Roof cladding support
Typical cold rolled Z section profile: Side rails
Secondary Members

o Purlins are generally designed as
continuous members, over two or
more spans, supporting uniformly
distributed loads.
purlin system
Secondary Members

(ii) Anti-sag bars
distributed loads.
o Usually for spans larger than 3.0 m,
the effective length of purlins is
reduced by the use of anti-sag bars.
Sleeved purlin system
Secondary Members

(ii) Anti-sag bars
distributed loads.
o Those are provided between adjacent
purlins to extend lateral support for
purlins in their weaker direction.
purlin system
Secondary Members

(ii) Anti-sag bars
distributed loads.
o Those are provided between adjacent
purlins to extend lateral support for
purlins in their weaker direction.
o An anti-sag bar is designed as a
tension member to resist the tangential
component of the resultant of the roof
load and purlin dead load. purlin system
Secondary Members

(iii) Roof Monitor
o A roof monitor is a structure mounted
on the ridge of the building and is used
for ventilation purposes.
Single-bay portal frame during construction
Typical section of a monitor roof
Secondary Members

(iii) Roof Monitor
o A roof monitor is a structure mounted
on the ridge of the building and is used
for ventilation purposes.
o It is fabricated from either cold formed
channel sections or hot rolled I-
sections.
Multi-bay portal frame during construction
Typical section of a monitor roof
Secondary Members

Bracing Systems
(i) Vertical (Longitudinal) Bracing
o Vertical bracing in the side walls is
required to resist longitudinal actions
on the building and provide
longitudinal stability.

o Side wall bracing functions are:
▪ To transmit horizontal forces to the
foundations.
▪ To provide stability during erection.
Bracing Systems
Inverted V-Bracing Systems

o Side wall bracing functions are:
▪ To transmit horizontal forces to the
foundations.
o The bracing may be located:
▪ At one or both ends of the building.
▪ Within the length of the building.
▪ In each portion between expansion
joints (where these occur).
Bracing Systems
X-Bracing Systems

o (i) Initial horizontal loading conditions.
Structural behaviour
Bracing Systems
Common Bracing Systems

o (ii) Strut (red) and tie (blue) members.
Bracing Systems

o (ii) Strut (red) and tie (blue) members.
o (iii) Only the tie members participate
within the structural system behaviour.
Bracing Systems

CBF Typical connection - Λ1
Λ1
Bracing Systems

Portal frame with X-Brace
CBF Typical connection - Λ1
Bracing Systems

CBF Typical connection – Λ3
Λ2
Bracing Systems

Bracing Systems

Λ3
Bracing Systems

Bracing Systems

Portal frame with Inverted V-Brace
Bracing Systems
Section view

Portal frame with Inverted V-Brace
Bracing Systems
Vertical inverted V-Bracing system

Typical connection – Λ1
Bracing Systems

Bracing Systems

(ii) Roof (or Plan) Bracing
o It is located in the plane of the roof
spanning between the outer frames &
it normally consists of diagonal
members between columns & rafters.
Bracing Systems

o It is located in the plane of the roof
spanning between the outer frames &
it normally consists of diagonal
members between columns & rafters.
o It can be single diagonal roof bracing.
Plan view with single diagonal roof bracing
Bracing Systems

o The roof bracing can be also designed
with cross members.
o If the former system is adopted the
members are designed to support
compressive and tensile loads.
o
Structural frame side view
Plan view with cros member roof bracing
Roof bracing
Bracing Systems

o When cross members are used only
the members in tension are assumed
to be effective,
o those in compression are designed to
satisfy the slenderness criteria.
Plan view with cross member roof bracing Portal frame with cross member roof bracing
Roof bracing
Bracing Systems

o The roof bracing primary functions are:
▪ To transmit wind forces from the
gable posts to the vertical bracing.
Horizontal loads
Bracing Systems

▪ To transmit any frictional forces
from wind on the roof to the vertical
bracing.
Bracing Systems

bracing.
Roof bracing
Bracing Systems

bracing.
▪ To provide a stiff anchorage for the
purlins which are used to restrain
rafters.
Roof bracing
Bracing Systems

bracing.
▪ To provide a stiff anchorage for the
purlins which are used to restrain
rafters.
o In modern construction, circular hollow
sections are generally used in the roof,
and are designed to resist both tension
and compression. Roof bracing
Bracing Systems

Structural frame side view
Typical connection - Λ1
Λ1
Bracing Systems

Roof bracing
Portal frame
Bracing Systems

Roof bracing
Bracing Systems

3D Model – Front view
Bracing Systems

3D Model – Back view
Bracing Systems

Roof bracing
Bracing Systems

3D Model – Front view
Bracing Systems

3D Model – Back view
Bracing Systems

Bracing Systems
Portal frame

Typical connection – Λ2 3D Model
Bracing Systems

153/2
C-1 Primary Structure
C-2 Secondary Members
C-3 Bracing Systems
C-4 Main Connections

Main Connections
General Features
o The three major connections in a
single portal frame are those at the
eaves, the apex & the column base.
Typical portal frame structure - Cross-section

Main Connections
General Features
o The three major connections in a
single portal frame are those at the
eaves, the apex & the column base.
o For economy, connections should be
arranged to minimise any requirement
for traditional reinforcement (stiffeners)
Typical portal framed building

(i) Eaves Connection
o The eaves connection in particular
must generally carry a very large
bending moment.
Main Connections
Typical bolted eaves connection

o The eaves connection in particular
must generally carry a very large
bending moment.
o Those connections are likely to
experience reversal in certain
combination of actions.
Main Connections

o For the eaves mostly bolted
connections are used with continuous
columns combined with beams having
end plates.
Typical design details
Main Connections

(ii) Apex Connection
o On-site apex connection is avoided for
span within transportation limits <16 m
Main Connections

o Typically they are bolted but they,
Design details: Bolted eaves connection
Main Connections

o Typically they are bolted but they
o could also be designed to be welded.
Typical welded eaves connection
Design details: Welded eaves connection
Main Connections

(iii) Column Base Connection
o The base of the frame column is often
kept simple with larger tolerances in
order to facilitate the interface between
the concrete and steel workers.
Main Connections

o In most cases it is designed as a pin to
keep the dimension of the foundation
as small as possible.
Pinned-based columns
Main Connections
Portal frame

o A pinned based column design doesn’t
transfer any moment, or bending, load
into the supporting foundations.
Pinned-based column: Design
Pinned-based column: Constructed
Main Connections

o Designing the steel building to a fixed
base connection makes each column
of a building like a flag pole.
Fixed-based column: Design
Main Connections
Fixed-based column: Constructed

o While this design makes for a cheaper
steel building, the support foundations
is required to be much more
substantial and more costly.
Fixed-base
Main Connections
Fixed-based columns

THANK YOU FOR
YOUR ATTENTION!
tz.vogiatzis@gmail.com

ANY QUESTIONS ?
tz.vogiatzis@gmail.com

Structural Conformation of Single Storey Steel Buildings

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