ARC 3422
Construction Structural System
Lecture 1: Structural system
by
Dr Maszura Abdul Ghafar
Structure of Course
• Attendance minimum 80% before you can sit
for exam
• Late attendance considered absent
• Late submission considered zero or deductible
• Marks
– Assignment – 60%
– Exam – 40%
– Attendance and participation – 10%
Architects, Engineers and Design
• Who did what?
• Determining strength, who? Engineer
• Determining beauty, who? Architect
Architect + engineer
=
(space)
(majestic appearance,
sophistication and
ingenious architecture)
(mechanical)
design
Stability and strength
• What is structure?
- satisfying of two basic conditions: stability
and strength
Stability: various FORCES that act on structure,
always in balance to avoid failure
Strength: physical make up of structural material
that are sufficient to withstand FORCES
Stability and strength
Lifter supporting Barbell and
weights
A Failure of Stability
A Failure of Strength
The potential for structure to enrich
architecture
• Structure shouldn’t be architecturally mute
– Give meaning, richness, metaphor and experience
– Eg. Crematorium, Baumschulenweg, Germany
Relationships between Architectural
and structural form
• Consonant forms
- structure system co exist
with architectural form
Tapalpa House
Relationships between Architectural
and structural form
• Contrasting forms
- structure system contrast
with architectural form,
material, geometry, scale
& texture
Heydar Aliyev Centre , Azerbaijan
Structural Design
• When designing a structure:
1) You need to know the functionality of the
structure- how it influence your building
stability, aesthetically and cost
2) Building function/ typologies
3) Affected forces, loads, environments and
dimension of structural elements
4) Good negotiation skill with structural engineer
Structural Design
• Rule of thumb in structural design for architect
– For tension forces: you will need high strength steel
cables to span in a longer distance such as bridges
– For compression forces: you will need arches
– For surface resisting tension: you will need 3D
membrane structure composting of 2D surfaces
resisting tension only
– For axial stresses (balance of tension and compression
forces): you will need 3D structure composting of 2D
curved surfaces.
Structural Design
• Structure elements: Common elements from
which structures are composed
Tie Rods
• Members that are generally vertical and
resist axial compression loads
• Subject to both an axial load and a
bending moment
Structural Design
• Structure elements: Common elements from
which structures are composed
Beam
• Beams are usually straight
horizontal members used
primarily to carry vertical loads
• Design to resist bending
moment, if they are short and
carry large loads, the internal
shear force may become quite
large
Structural Design
• Structure elements: Common elements from
which structures are composed
Column
• Structural members subjected to a
tensile force
• Due to the nature of this load,
these members are rather slender,
and are often chosen from roads
and bars
Structural Design
• Types of structure: Truss
• A truss is an assembly of beams or other
elements that creates a rigid and slender
element structure
• Planar trusses are composition of same
plane members that lies 2D flat in the same
plane. Joints are usually pin joint type, and
members are free to rotate around the pin.
• Space trusses are composition planar
trusses in 3D. Uses pined joint to allow
members to rotate freely about each other.
No restraint and no internal bending
moment
• Due to the arrangement, loads converted to
tensile and compression forces to members
Structural Design
• Types of structure: Cables and Arches
Cables
• Cable are usually flexible and carry loads in tensions
• Commonly used to support bridges. Always in tension, thus will
not become unstable and sudden collapse
Arch
• Arch achieves its strength in compression
• Reserve curvature to the cable
• Rigid, need secondary loadings (shear and moment) to main its
shape.
Structural Design
• Types of structure: Frames
-
Often used in buildings
Composed together with column with fixed connection
Can be 2D or 3D
Loading on frame causes bending of its members and if has
rigid joint connections (welding and bolting), it is generally
“indeterminate”.
- Members are subject to axial forces(tensile and compression)
Structural Design
• Types of structure: Surface structure
- Made from thin material.
- Usually acts as cables and arches to support tension and
compression load, with very little bending
Structural Design
• Idealized structure
Structural Design
• Idealized structure
Structural Design
• Type of support/ support connection
– Type of support: roller and frictionless surface,
pinned, fixed and hanger
– Support can be at the end or at any intermediate
points along a member
– Type of support affects how reactions will act on
members and the kind of movement that the support
will restrain.
– To facilitate structural analysis, the structure is
usually idealized by assuming the act of movement is
simplified and pure manner.
Structural Design
• Type of support/ support connection
– Roller and Frictionless-surface support (RFSS)
Roller joint
• Can be found on one end of bridges to allow thermal
expansion and contraction of the span.
• RFSS is in the form of rubber bearing that can be used in
foundations for limiting seismic (earthquake) movement.
• Behave similar like other members n the structure.
Structural Design
• Type of support/ support connection
– Roller and Frictionless-surface support (FSS)
• Only support and accept perpendicular forces on a member
and away from the surface on which the member rest
• RFSS cannot prevent translational and rotation movement
in all direction.
Structural Design
• Type of support/ support connection
– Pinned/ Hinged support
• Used in bridges and certain type of trusses. Literally are pins
usually visible in the bottom chord of inserted
Structural Design
• Type of support/ support
connection
– Pinned/ Hinged support
• The steel connector
attaching web of beam to a
girder is called shear
connection
Shear connection of a steel beam
• A pinned support accept forces on a
member in any direction.
• A pinned support prevents
translation movement in any
direction but not rotational
movement.
Structural Design
• Type of support/ support
connection
– Fixed / rigid support
• Commonly found in beam to column
connections of moment-resisting steel
frames, beam cantilever, projection of
building etc.
• The steel connection
attaching the flange/ web
of girder is called moment
connection
Structural Design
• Type of support/ support connection
– Fixed / rigid support
• Can accept a force on a member in any direction and can
resist moment and translational moment in rotational
directions.
• Only have single fixed support but cannot resist deflection.
Possible reactions
Deformation of a member at a fixed support
No Movement
Structural Design
• Type of support/ support
connection
– Hanger support
• Can be found in suspension
bridges, canopies, signs etc
• Act only in tension and uses
steel cables, rods, and flat bars
for supports.
Hanger supports on the beam of the bridge
Hanger support
Hanger supports on a canopy
Structural Design
• Type of support/ support connection
– Hanger support
• Accept forces on a member acting away from the member in
the direction of the hanger
• Cannot prevent any rotational movement and translational
movement in any directions.
Translational Movement
Rotational movement
Structure Definition: Loads
• Gravity loads
Structure Definition: Loads
• 1- Lateral loads
– Caused by wind and seismic movement
– act in horizontally
a) Lateral wind load
Effect of wind load
Lateral load by wind
- Depend factors such as velocity,
shape and height of building,
geometry & proximity of adjacent
building
- - will cause to sway
Structure Definition: Loads
Effect of lateral wind load
Creates positive pressurepushing inwards buildings
exterior surface on windward
side
Creates negative pressurepushing outwards buildings
exterior surface on leeward
side
Note: for tall & irregular shaped structure use wind tunnel to test
Structure Definition: Loads
b) Lateral seismic load
Lateral load by seismic
- Created by random, variable,
erratic motion of the ground
- Cause to sway
Structure Definition: Loads
- Wind and seismic load
create uplift forces at
the base of the structure
and overturn it
- Communication towers
are lightweight
therefore susceptible to
uplift and overturn
Structure Definition: Loads
• 2-Dynamic loads
- changes rapidly, suddenly, amplified rhythmic
movement
- Effect of dynamic load →
increases its actual static
load
Constant movement of lift and
vehicles are dynamic loads
Structure Definition: Loads
• 3-Impact loads
- Result from sudden collisions or an explosion
- Blast resistant design must consider impact
force
Structure Definition: Loads
• 4-Load paths
- All loads applied eventually make their way
through structure components and down to
ground
Structure Definition: Loads
• 4-Load paths
- In framed building loads applied to roofs→ Floors
→ vertical supports →Structure → foundation
→ground
Structure Definition: Loads
Structure Definition: Stress
• 1- Tension
- Tendency of a body to be pulled apart.
- A pulling effect in a perpendicular direction to
its cross section
direct tensile stress
A rope in tension
Structure Definition: Stress
• 2- Compression
- Tendency of a body to be crushed.
- A downward force and the upward resistance
to ground
Direct compression stress
A post in compression
Structure Definition: Stress
• 3- Shear
- Tendency of a body to be sliced.
- A pulling force opposite each other in a
direction to its cross section
A bold under shear
Direct shear stress
Structure Definition: Stress
• 4- Torsion
- A type of shear which a body tends to be twisted
resulting shear stress
A pole sign under torsion
A spandrel girder under torsion
Structure Definition: Stress
• 5- Bending
- Tendency of a body to bow
therefore creating stress to
body
- The body compresses at one
edge and stretches along the
other
Horizontal shear parallel to the
length of a beam
Tension and compression in a beam
Vertical shear perpendicular to the
length of a beam
Structure Definition: Stress
• 5- Bending
- When load is at the centre of a span, max bending stress
occurs
Maximum bending
stresses at the centre of
a span
Maximum compression
and tensile stresses at
the edges of a beam
• Thank you