Static Flexural Behaviour of Externally Post-Tensioned Steel-Concrete Composite Beams

Abstract

Composite steel-concrete beams are used widely in bridge and building construction as the main structural elements in flexure. Bridges, throughout the world have a design life and this may be reduced if traffic flows are increased or environmental degradation occurs. Similarly, building beams may become compromised for serviceability or strength when loads on floor systems are increased. These changes may reduce the design life and strength of such members and thus replacement or retrofitting may need to be considered. One method of retrofitting (stiffening and strengthening) a composite steel-concrete beam is to externally post-tension the beam. The application of external post-tensioning also has the effect of increasing the fatigue life of such members. This paper provides a set of detailed experiments on both a conventional and prestressed composite steel-concrete beam. A numerical model is then developed for the load-deflection response and this is calibrated with the test data. An extensive parametric study is then conducted to consider the influence of various parameters on the behaviour of these beams. Finally a rigid plastic analysis procedure is presented and calibrated with the test results with good effect. This procedure is considered to be amenable for design in assessing the flexural strength.