Sketch a suitable arrangement of beams to show an example of compatibility torsion

Explain why this form of torsion can usually be ignored in design situations. 

(b) Sketch an arrangement of beams to demonstrate an example of equilibrium torsion.

Explain why this torsion type must be considered in design situations. 

(c) A bridge deck supporting an integral reinforced concrete slab spans 25 m and is 14 m wide

. The bridge will comprise a number of prestressed concrete beams. 

is an integral concrete diaphragm at either end of the bridge.