The load-bearing behaviour of the steel-concrete-steel composite (SCSC) plate

Abstract

The analysed innovative steel-concrete-steel composite (SCSC) plate has been researched at TU Wien, Institute of Structural Engineering, Research Unit Steel Structures. The aim of the investigations performed in the last years is to construct a load-bearing structure for single-track short-span railway bridges. The trough bridge system is developed for the Austrian Federal Rail Company (ÖBB) because numerous old railway bridges have to be replaced in Austria. The innovative SCSC plate is a special composite structure that is fabricated by connecting two 15 mm thick outer steel plates to a 170 mm thick concrete core. The steel and the concrete parts of the SCSC plate are connected by means of shear connectors. These composite dowels are welded alternately onto the bottom and top steel plates. Thus, the shear force resistant connection of the steel plates is reached through the concrete core, and the amount of welding work is minimalized.The presented doctoral thesis is divided into three blocks. In the first block the load-carrying mechanisms of the SCSCplate is presented comprehensively based on the results of finite element analyses. The load level used for fatigue limitstate (FLS) is examined. The second block introduces an engineering model of the SCSC plate which is appropriate to substitute the time-consuming numerical methods. Here, the structure of the developed two-dimensional spring framework model is explained, and the validation of the model is performed in the case of static loads. In the third block the effects from the cyclic loading is examined. In the case of high dowel forces, permanent displacement appears between the surfaces of the steel circular hole of the shear connector and the concrete part inside the hole. This permanent displacement in the composite connection is called in elastic slip. It is presented through the spring framework modelcalculation how the increasing inelastic slip due to the cyclic loading leads to a redistribution of forces as well as to the increase of deflection.Summing up, it is shown in this doctoral thesis that the SCSC plate can be analysed with a two-dimensional spring framework model which is also appropriate to model the cyclic behaviour of concrete. Thus, the presented dissertation isa preliminary step to derive the design models for the SCSC plate in the fatigue limit state.