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

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

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

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

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%

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

Why are Anti-sag systems used with purlins?

To control the vertical deflection of the purlins
To control deflection down the slope, and assist the alignment of the purlins
To provide restraint to the bottom flange of the purlin in an uplift combination of actions
So that the manufacturer's warranty is not invalidated

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

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

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

When should the junction of the inside face of the column and the underside of the haunch be restrained?

Only in the gravity combination of actions
Always
If there is not a side rail and compression stiffener at that level
If a side rail can be provided at that level