General Flashcards
What is the hierarchy of stiffnesses in stability calculations?
Axial
Bending
Torsional
Why are end fixings important for long beams?
Bolt slippage can cause large deflection in longer beams
How are wind loads applied to a structural model?
As points on beam-column connections which represent the area around that point
What size of bolts are required for moment connections?
8.8
Why is there no k in PC1 & PC2 for prestressed concrete?
There are no losses at transfer
Which inequalities bound the profile of bowed reinforcement bars?
PC1 & PC4
What is the stiffness at the upper end of a column which is attached to two beams either side (bl & br) and a column above (cu)?
Ku = (Kc + Kcu)/(Kc + Kcu + Kbl + Kbr)
How does a plate girder bear loads?
Top flange takes compression moment
Web takes shear
Bottom flange takes tension moment
What are the limits of depth to web thickness ratio for plate girders?
100-250
How is a prestressed concrete beam analysed and what does this mean?
Serviceability limit state so no factors are used
What is the minimum limit for steel stress at the bottom of a composite beam?
165N/mm2
What must you remember when finding the stress in the top of the concrete?
Convert values back from steel to concrete
What must you do for a composite beam question?
Draw a diagram of all forces and lever arms
What is the limit for c in a plate girder?
Epsilon x flange thickness where epsilon is in the Eurocodes
What is depth d of a plate girder?
Height y - flange thickness
What must always be done for point loads on a plate girder?
Stiffeners are positioned under them
What is a in plate girder stiffener calculations?
Spacing between stiffeners
What is the approximation for the moment at the end and centre of a rigid portal beam?
M= wL2/16
What diagrams must be drawn in a rigid steel portal frame question?
A full dimensioned frame and a section of the bays with half of the columns above and below
If there is a wind load of 28kN per floor on a 6 storey building (including ground floor and roof), what is the total?
0 x 14 + 4 x 28 + 1 x 14 = 126kN
What is the short term concrete conversion factor for a composite section?
E of steel / E of concrete
What is the long-term concrete conversion factor of a composite section?
2 * E of steel / E of concrete
What must be found to compute the elastic stresses for short term and long term in a composite section?
The second moment of Area (I) for both short and long term
What moment is used to calculate the short-term elastic stresses?
Live load only
What moment is used to calculate the long-term elastic stresses?
Sum of dead load and self weight
In principle, what is the equation for elastic stress?
(Moment x distance of outermost fibre to n/a) / (second moment of area)
Divided by conversion factor if concrete
How do you determine the horizontal load on the mid height of wind loaded columns above a target floor?
Total wind load above target floor / number of half-beams
Inner columns have larger values to match the total wind load
How do you determine the horizontal load on the mid height of wind loaded columns below a target floor?
Total wind load above and including target floor / number of half-beams
Inner columns have larger values to match the total wind load
How does a rigid frame structure resist wind moment?
A force of
Total wind moment / width of frame base
Is carried in both outer columns, one upward, one downward
How is effective length of a column in a rigid steel frame determined
A chart gives the fraction Le/L from upper and lower limits of column stiffness
What is the lower limit for column stiffness if the base is fixed?
0.5
What is Wply of a plate girder?
Wply = Med/fy
How can you estimate the flange area for a plate girder?
Af = Med/(y * fy)
