TIME-DEPENDENT ANALYSIS OF PRESTRESSED COMPOSITE BEAMS

The viscoelastic analysis of composite steel-concrete continuous beams , with prestressed slab and flexible shear connectors, is presented. T wo prestressing systems, involving the application of prestressing for ces before or after the connection of the concrete slab to the steel b eam, are considered. The mathematical formulation of the problem invol ves internal compatibility equations between beam and slab and between slab and prestressing cables. Such conditions are formulated taking i nto account the integral-type creep law for the concrete slab. With th e model proposed, some relevant examples were investigated and discuss ed. Partial longitudinal prestressing of the slab, performed using cab le with length less than the whole structure, is also analyzed. Partic ular attention is paid to examining the ''primary'' and the ''secondar y'' effects of the prestressing, and the shear force distribution at b eam-slab interface. A parametric study is then performed by varying th e stiffness of shear connectors and the combining time between slab an d beam.