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 value of base stiffness is recommended when modelling nominally pinned bases?

Zero - it's a pinned base
Zero - at ULS
10% of the column stiffness when calculating frame stability
20% of the column stiffness when considering SLS

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

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

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 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 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

When might a Morris stiffener be required in a haunch connection?

When the vertical shear exceeds the resistance of the rafter web
When the panel shear exceeds the resistance of the column web
Whenever a compression stiffener is provided
To provide a fixing point for the vertical bracing and the eaves member