Effective breadths of concrete slab and effect of slab on steel connections

To study the effect of concrete slabs on structural behaviors of steel frame structures, three-dimensional finite element models of beam-to-column joints were established. Based on analyses of effect of concrete slabs on the stress in beam flanges, the effect of concrete slabs on the fracture of beam-to-column joints was studied. The effect of loadings on the effective breadth of slabs was also studied. Results show that slabs have active effects on the failures of both the top beam flange and the bottom beam flange under the same moment load. The effective breadth of the concrete slab is relative to the loadings. If the concrete slab is in compression, the effective breadth decreases rapidly with the increase of loading at first and then decreases slowly. If the concrete slab is in tension, the effective breadth decreases with the increase of loading at first and then increases with a slow rate.