Fatigue Designed CL-cutting Shape: A new Economic Steel-concrete Connection System and some Applications for Bridges

Continuous shear connection, using a cut steel strip, is an upcoming solution for composite beams. With the activation of friction on the sides of the steel strip this method has already been used to design and build large durable bridges during the sixties. However direct shear transmission into the steel strip though teeth of the cut is also possible and has been scrutinized with the support of the European Research Fund for Coal and Steel. It is characterized by a high initial stiffness, bearing capacity and ductility. It allows new and economic construction methods, as the PreCoBeams (Prefabricated Composite Beam used as formwork).PreCoBeams are for instance composite beams associating steel T-sections acting as tension member with a concrete top chord acting as compression member. Steel parts are generally obtained from rolled steel profiles that are longitudinally cut in two identical T-sections. The cut is performed with a special shape to allow the shear longitudinal transmission between steel and reinforced concrete. In general, prefabricated, composite, longitudinal PreCoBeam bridge elements are produced in factory. They consist of at least one steel T-section associated to a precast first phase concrete flange. Second phase concrete layer is then completed in-situ after erection of the bridge elements on abutments. These PreCoBeam bridges are very economic in design and construction, though the main market drawback for PreCoBeams is the missing design rules for the shear connection.This paper introduces the static and fatigue design of continuous steel plate shear connections used for PreCoBeams derived from the recent research activities. The CL shape of the cutting has been tested in fatigue, ultimate and service limit states and validated in the scope of a bridge application. This concept aims at developing a competitive solution for small span bridges. The various solutions realized in the last years in many European countries, some of them presented in the paper, show clearly its interest.