STRUCTURAL STEEL DESIGN EXAM | QUESTIONS AND ANSWERS |
VERIFIED ANSWERS (100% CORRECT) | LATEST EXAM UPDATE
why is steel framing the most common construction form in UK?
high strength to weight ratio and speed of erection
2 types of frame
with rigid connections or simple connections
rigid connection
moment carrying, fixed
simple connection
shear carrying, pinned
main components of plane frame
how to draw pinned connection
how to draw rigid connection
how to draw semi rigid connection
braced frame
-simple joints transmit shear but not moment
-bracing acting in tension resists lateral loads
continuous frame
rigid joints transmit moments which means the frame resist lateral loads in
bending
to be an effective brace
must reduce lateral flexibility by > 80%
Ultimate Limit State
point where structure collapses
serviceability limit state
,point where structure is no longer usable
partial safety factor for dead load
1.35
partial safety factor for live load
1.5
partial safety factor for failure by plastic yielding
1
partial safety factor for failure by buckling
1
partial safety factor for failure by tensile fracture
1.1
partial safety factor for bolts
1.25
partial safety factor for welds
1.25
hot rolled sections can be estimated as
elastic perfectly plastic
overview on design of frames
elastic analysis
based on assumptions of linear elastic behaviour
-reference stress is always lower than the yield stress
plastic analysis
assumes progressive yielding leading to plastic hinges
classification of sections
Class 1 - plastic
Class 2 - compact
Class 3 - Semi-compact
Class 4 - slender
Class 1 Plastic
, can sustain very large plastic deformations without local buckling
Class 2 Compact
can just achieve full plastic moment without local buckling
Class 3 Semi-compact
can reach yield at extreme fibres before local buckling but not full plasticity
Class 4 Slender
local buckling occurs before first yield
classification depends on
width to thickness ratio of parts subject to compression
analysis for class 1
plastic analysis
analysis for class 2
elastic analysis
class 3 analysis
elastic analysis
class 4 analysis
elastic analysis
analysis and checks of classes
imperfections include
residual stresses, eccentricities of load, lack of verticality, lack of linearity
in members
how is lack of verticality modelled
equivalent horizontal forces
lack of verticality can be neglected if
the applied horizontal force is > 0.15 applied vertical force
how to deal with initial bow imperfections
replace with equivalent horizontal force.
when can you use a first order analysis
VERIFIED ANSWERS (100% CORRECT) | LATEST EXAM UPDATE
why is steel framing the most common construction form in UK?
high strength to weight ratio and speed of erection
2 types of frame
with rigid connections or simple connections
rigid connection
moment carrying, fixed
simple connection
shear carrying, pinned
main components of plane frame
how to draw pinned connection
how to draw rigid connection
how to draw semi rigid connection
braced frame
-simple joints transmit shear but not moment
-bracing acting in tension resists lateral loads
continuous frame
rigid joints transmit moments which means the frame resist lateral loads in
bending
to be an effective brace
must reduce lateral flexibility by > 80%
Ultimate Limit State
point where structure collapses
serviceability limit state
,point where structure is no longer usable
partial safety factor for dead load
1.35
partial safety factor for live load
1.5
partial safety factor for failure by plastic yielding
1
partial safety factor for failure by buckling
1
partial safety factor for failure by tensile fracture
1.1
partial safety factor for bolts
1.25
partial safety factor for welds
1.25
hot rolled sections can be estimated as
elastic perfectly plastic
overview on design of frames
elastic analysis
based on assumptions of linear elastic behaviour
-reference stress is always lower than the yield stress
plastic analysis
assumes progressive yielding leading to plastic hinges
classification of sections
Class 1 - plastic
Class 2 - compact
Class 3 - Semi-compact
Class 4 - slender
Class 1 Plastic
, can sustain very large plastic deformations without local buckling
Class 2 Compact
can just achieve full plastic moment without local buckling
Class 3 Semi-compact
can reach yield at extreme fibres before local buckling but not full plasticity
Class 4 Slender
local buckling occurs before first yield
classification depends on
width to thickness ratio of parts subject to compression
analysis for class 1
plastic analysis
analysis for class 2
elastic analysis
class 3 analysis
elastic analysis
class 4 analysis
elastic analysis
analysis and checks of classes
imperfections include
residual stresses, eccentricities of load, lack of verticality, lack of linearity
in members
how is lack of verticality modelled
equivalent horizontal forces
lack of verticality can be neglected if
the applied horizontal force is > 0.15 applied vertical force
how to deal with initial bow imperfections
replace with equivalent horizontal force.
when can you use a first order analysis
