Portal frames quiz

Please answer the following 10 multiple choice questions, then click 'submit' to check the result. The pass mark for a CPD certificate is 8 out of 10, and you may retake the quiz as many times as you wish, but the questions will vary! Please note that one, two, three or all of the possible answers presented for each question may be right, and to gain a mark for that question all correct answers must be identified.

Good luck

Portal frames

What steps are effective in reducing the calculated deflections at SLS?

Modelling the stiffness of nominally pinned bases
Using higher strength steels
Using members with a higher inertia
Adding restraints

How can second-order effects in portal frames be allowed for?

By using a second-order analysis
By amplifying the lateral loads
By using S355 steel
By down-rating member resistance by 10%

Which of the following combinations of actions should be verified for portal frames?

Permanent + Wind
Permanent + Snow
Permanent + Snow + Wind
Permanent + Wind + Imposed

How is a moment-resisting base commonly detailed for the fire condition, if necessary?

With a thicker base plate
With more holding down bolts
Set into a pocket cast in the base
Provided with stiffeners

What is the primary function of an eaves haunch?

To facilitate a bolted connection
To increase the shear resistance at the support
To increase the bending resistance of the rafter section
To reduce deflections

How long should the haunch be?

To the third purlin
Until the hogging bending moment is approximately the same as the sagging moment
Three times as long as its depth
One third of the column height

What best describes a portal frame structure?

Frames of simple construction
3-d continuous structures
Continuous frames in-plane, braced in the longitudinal direction
Continuous frames, braced in-plane

The adjustments to αcr in the calculation of αcr,est allow for what phenomena?

The high moment and shear combined
The flexibility of the structure
The axial load in the columns and rafters
The base fixity

How should purlins be located?

At spaces less than the maximum spaces specified by the cladding manufacturer
Spaced equally between the eaves and the apex
Judiciously, to suit the restraint to the rafter
At 1.75m centres

Which of the following situations should be verified as an accidental combination of actions?

Snow removed from one roof slope
Snow accumulating behind a parapet
Snow on the roof if the altitude is above 150 m
Snow accumulating in a valley