Multi-span composite girders with composite dowels – Experimental investigations and design approach to account for the beneficial effect of shear force redistribution along the composite interface

The broad use of composite dowels as shear connectors in multi-span steel and concrete composite members is currently hindered by insufficient regulations for hogging moment regions, where the connectors are located in cracked concrete slabs and have reduced shear resistance. This paper reports on the results of three beam tests that illustrate the ability of continuous steel and concrete composite beams with composite dowels to redistribute shear forces from impaired connectors located in hogging bending regions to intact connectors in sagging bending regions. The effect of concrete cracking on the load-bearing behaviour of composite dowels is analysed with regard to their strength, stiffness and ductility by means of three full-scale member tests. This paper proofs the existence of a beneficial shear force redistribution process along the interface of multi-span composite members and quantifies the shear force transfer occurring between connectors in sagging and hogging bending regions. In addition, the paper provides an economical design method for continuous composite girders. Previously developed models regarding the shear resistance of single composite dowels in cracked concrete are refined aiming to provide both safety and ease of use. These models are subsequently extended into a comprehensive design strategy that allows us to consider the beneficial shear force redistribution processes along the interface when designing the shear connection of multi-span composite beams with composite dowels.