Discussion of an algorithm to transfer arbitrary shear connector load-slip curves into an effective shear resistance

The RFCS research project REDUCE (Project No. 710040) investigated dismountable shear connections with preloaded bolts. These connectors have in most cases a slip capacity greater than 6 mm and show a monotonic increasing nonlinear load-slip behaviour without plastic plateau and failure of the bolt in shear. Current design procedures of steel-concrete composite beams are largely based on the implementation of headed shear studs, which exhibit a rather different load-slip behaviour with a pronounced plastic niveau. Thus, a question turned out, which compression force can be activated by the shear connection in the concrete girder of a composite beam and how can the respective ultimate bending capacity be determined. Hence, this contribution presents an analytical algorithm to estimate the occurring compression force in the concrete girder when demountable shear connectors are used. The proposed algorithm bases on the actual measured load-slip curve of the shear connection and the expected slip along the beam, which is estimated for each single connector to later determine the compression force in the concrete girder. In addition to the explanation of the “general algorithm”, assumptions for practical use have been made for the slip distribution to simplify the calculation of the compression force and an effective shear resistance P_Rd,eff.