Would you discuss the solution to the problem of crack control by suitable spacing of control joints or sawed joints in the slab, particularly when the slab is assumed to provide bending resistance to the longitudinal girders spanning between columns and also cross beams spanning between longitudinal girders?
Control of cracking in slabs that are part of composite construction is difficult to attain. Shrinkage cracks will often occur when the slab is tied into the flanges of the steel girders or beams, thus preventing free length changes due to drying or temperature changes. These cracks appear parallel to the girders near midspan of the slabs. Eliminating tieing into the flanges of girders or beams will be a decided help toward crack reduction. Other cracks might occur over the flanges of girders or beams when insufficient top steel is placed in the slabs to take care of negative movements.