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

When should a portal frame be used for the gable frame?

When future extension is anticipated
For aesthetic reasons
To save weight
So that gable columns are not required

When verifying the rafter, which two zones are likely to be critical for lateral-torsional buckling?

Adjacent to the haunch, in the gravity combination of actions
Around the point of contraflexure
At the maximum sagging moment, near the apex
Adjacent to the haunch, in the reversal combination of actions

What is the primary objective for fire design if a portal frame is adjacent to a boundary?

To prevent loss of life
To prevent early collapse of the structure
To prevent fire spread to the adjoining property
To prevent the release of noxious fumes

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

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

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 does an 'unrestrained' column imply?

No intermediate restraints to the inside flange can be provided
There is no stiffener at the connection
There are no side rails
The bracing is attached in a different bay

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 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

If a member is not adequate when checking lateral-torsional buckling, what steps are effective in increasing the resistance?

Provide additional restraints
Reduce the spacing of the restraints
Select a larger and heavier member
Use higher grade steel

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