Loading capacity of composite slim beam in the sagging moment region

Steel-concrete composite slim beams, with steel section encased in concrete slabs, provide a steel-concrete floor construction of minimum depth and high capability of fire resistance. Under vertical load, the moment at the midspan of framed beams is positive and under horizontal load, the sign of the moment depends on the position of the cross-section. Clearly understanding the capacity of composite slim beam in the sagging moment region is the basis of structural analysis. The bending capability and flexural stiffness of the composite sections in sagging moment region are investigated theoretically. A simply supported beam has been loaded in order to verify the theoretical result. The research shows that theoretical bending capability is well consistent with test result. A the theoretical flexural stiffness is well relatively conservative, for ignoring the contribution of the pre-cast concrete slab in the analysis.