Serviceability of semi-continuous composite beams in buildings

Semi-continuous composite beams in buildings are constructed with longitudinal reinforcing steel over the column lines in a steel frame, which essentially is comprised of simple steel-connections. The ability of the longitudinal reinforcement to resist tensile forces in the slab, coupled with the ability of the steel beam-column connection in transferring compressive forces essentially creates a support which is partial strength for ultimate loads and semi-rigid for service loads. This paper provides an in-depth treatment of the modelling and detailing of semi-continuous composite beams for the serviceability Limit State. The paper will consider the in-plane finite element modelling of semi-continuous composite beams for determination of deflection and vibration behaviour. In addition to this comparisons with simplified methods are made. A parametric analysis is conducted to consider the effects of both the longitudinal reinforcement and steel connection on the static and dynamic service load behaviour. Furthermore, a qualitative study on the issue of minimum reinforcement requirements to provide adequate crack control in semi-continuous composite beams is also provided and compared with the results of both the deflection and vibration studies. The overall paper broadly highlights the approaches being considered for semi-continuous composite beams in the Draft Australian Standard for Continuous Composite Beams.