Question

Why is that the diagonal cross bracing in the truss cannot support compression forces? I see problems like these in books. Thanks

Answer 1

Answer-

Cross bracings in trusses are X shaped bracing made with joining two braces diagonally, in truss system with diagonal bracing one of the braces in the X bracing is in tension for the sideways force in one direction of the frame. And when the force is reversed another brace of the X bracing will gets into the tension. Thus the whole diagonal bracing system always remains in tension, As we know steel cables are used in cross bracing as they can be stretched and bear tension but cannot squashed as they are poor in handling compression. Thus from the above discussion it is clear that both the braces in the cross diagonal bracing are in the tension and cannot support compressive forces due to lack of support in squashing.

In figure given below it can be seen that the internal tensile forces are being generated in both the diagonal braces of the X bracing system.