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 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 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

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

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 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

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 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%