State of the art on the time-dependent behaviour of composite steel–concrete structures

Composite steel–concrete structures represent an efficient and economical form of construction for building and bridge applications. This paper presents the current state of the art on the time-dependent behaviour of composite steel–concrete members, i.e. columns, slabs and beams, and how this influences both service and ultimate conditions. In the case of beams, only H-shaped or box steel sections with solid and composite slabs have been considered. In the initial part of the paper, a brief outline of the main aspects related to the time-dependent behaviour of the concrete is provided. This is followed by the description of the work carried out to date on the long-term response of composite columns, slabs and beams considered separately. In the case of composite columns, particular attention has been devoted to the influence of time effects on the ultimate response, role of confinement at service conditions and possible occurrence of creep buckling. Very limited work has been carried out to date on the long-term response of composite slabs. Because of this, only brief considerations are provided on this solution while still presenting recent research dealing with the development of shrinkage gradients through the slab thickness when cast on steel decks. The work outlined on composite beams has been categorised according to different design issues, which include shear-lag effects, the shear deformability of the steel beam, influence of time effects on the ultimate response, prestressing, time-dependent buckling, and sequential casting of the slab. Recommendations for possible future research work are provided in the concluding remarks.

► Influence of the time-dependent behaviour of concrete on composite members ► Service and ultimate response of composite systems affected by time effects ► Research needs on time effects in composite construction