COMPOSITE BEAM COMPOSED OF STEEL AND PRE-CAST CONCRETE. (MODULARIZED HYBRID SYSTEM, MHS) PART II: ANALYTICAL INVESTIGATION

This paper introduces the concept of a wide flange steel beam with the bottom flange encased in pre-cast concrete. These composite beams utilize the merits of both steel and concrete materials. The effective interaction between the two materials can reduce the size of the steel beams. The reinforcement and the concrete are pre-integrated with the bottom flange of the steel beam at a manufacturing plant. In this paper, the analytical investigation of the flexural moment strength of the composite beams at both the yield limit state and the maximum load limit state is performed and compared with the experimental results. The depth of the equivalent rectangular stress block of the beams is obtained using an equilibrium equation when both the compression steel reinforcements are present. The post-yield behaviour of the composite beams is also investigated based on the normalized effective stiffness (k/k(y)) versus the normalized drift ratio (Delta/Delta(y)). The stiffness of the composite beams degrades gradually with sufficient ductility and dissipating energy capability. A six-step procedure provides a fast, effective and accurate way of investigating the post-yield behaviour of the composite beams. Copyright (C) 2008 John Wiley & Sons, Ltd.