# Question 2

Posted in: Frames

No  calculations this week! Which BMD matches the load-case for the structure shown below ?

Choose  from the  following

What a week over 60 entries! Unfortunately only 50% of them correct ( BMD:4).

Quick Explanation: As the right hand support is a horizontal roller there is no horizontal reaction at this point – therefore there is no moment generated in the right hand column.
As there is no horizontal reaction at the right hand support, all of the horizontal applied force is taken by the left hand horizontal reaction, hence the left hand column behaves like a cantilever.

Posted in: Frames

• Dear All

What a week over 60 entries! Unfortunately only 50% of them correct ( BMD:4).

Quick Explanation: As the right hand support is a horizontal roller there is no horizontal reaction at this point - therefore there is no moment generated in the right hand column.
As there is no horizontal reaction at the right hand support, all of the horizontal applied force is taken by the left hand horizontal reaction, hence the left hand column behaves like a cantilever.

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• Dear All,

Interesting problem. At first glance we would assume that the bending moment diagram 4 is the correct answer assuming as explained briefly above that the base of the right hand column is a pinned roller and therefore cannot resist a horizontal reaction.

On closer inspection the denotation of the roller implies that it is a fixed roller, hence providing resistance to rotation therefore the bending moment diagram in this instance would be none of the above and based on a fixed roller I would be expecting a hogging moment to be generated at the right hand end of the beam. This would then induce an anticlockwise moment at the head of the right hand stanchion which would be balanced by a clockwise moment at the base of the stanchion due to the presence of the fixed roller. In this instance we would be expecting the moment applied across the full height of the column to be constant.

Thoughts/Views would be appreciated.

• Hi Serhan

It was intended that the right hand support is a pinned roller, the triangular icon always indicates a pinned support. The concept of fixed roller for a column allowing horizontal movement for a vertical member is quite odd ( if you have picture of one please send it through, i'm sure someone has built one somewhere). I have included a new page to the blog ( look at the top) which covers the drawing convention used.

Thanks for your comment. Mark