Expert: Arshad Khan - 9/17/2009

Question
Hi Arshad

I am currently studying for a distance learning HND in construction and am having serious headaches trying to answer aspects of a scenario based assignment.  I have read the study material, along with various Building Standard publications and have also scoured the internet for information yet I am still having trouble with this area.  I am not looking for someone else to do my diploma for me but I really have nowhere else to turn as there is no one to one teaching available.

The scenario is based on the construction of a large scale, modern block of flats being constructed by the coast in Poole (Dorset UK)  in Shrinkable Clay ground conditions.  

The question I am struggling with reads:

“On the rear elevation of the property (which is not required to be as aesthetically pleasing) there will be small balconies to each of the kitchens.  These will be just large enough for people to step out onto and can be approximately 2m x 1m plan size.  Consider the likely magnitudes of the dead load, live load and forces that would have to be taken into account on the design of these and suggest how the balconies might be framed in steel by either; cantilever from the external walls or by columns extending to the foundations.  Draw sketches, labeled showing the construction and provide structural diagrams and calculations showing the resolution of forces in beams, columns and frame members, a range of calculations for beam reactions, bending moments and shear force diagrams.”

Now I have read so, so much material on this subject and I basically understand the theory behind stresses, strains, moments, shear forces, youngs modulus, loads etc.  I just cannot work out how and which will apply to these type of balcony design.  

If anyone can please help shed some light or point me in the right direction of how to directly apply the theory into this scenario, I would be eternally grateful.  

Thanks you so much for your time

Nick m


Answer
Hi Nick,

This is quite an involved question, but you can break it down into steps and do the following:

1. Work out the loading and the platform span direction (could be parallel to wall or right angles).
2. Work out the loading as UDL on the supporting beams.

3. Work out the shear and BM in these beams (either as cantilevers or SS between the wall and the supporting columns).

4. Design the supports for the shear and moments.

5. Design the joints/connections.

Don't forget that you alos need to design the balustrade/hand-railing which should be able to resist a lateral load in accordance with code requirements.