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

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

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

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

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

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 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

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

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