Finite Element Study of Unstiffened Extended Single Plate Shear Connections

Abstract

Steel shear tabs are commonly used in beam-to-girder and beam-to-column connections where a vertical plate is welded to the column or girder web, and bolt connected to the web of the in-framing beam. The extended shear tab (EST) is one increasingly popular option when it is necessary to bring the bolt line outside of shop applied coatings or encasement. The effect of greater eccentricity resulting from extending the bolt line needs to be accounted for in design.

The current Canadian steel design standard CSA S16-09 does not contain guidelines for design of EST connections. The AISC Manual 2011 provides a design procedure for EST connections based on the bolt effective eccentricity. The effective eccentricity values based on this method have been shown to be overly conservative in some cases, which ultimately leads to underestimation of the connection capacity

This research presents results of a numerical study on the behaviour amd strength of EST connections using finite element modelling. The model is verified with experimental results reported in literature. The parameters studied include the web slenderness ratio of supporting column, distance ‘a’, plate thickness, double-row of bolts, beam lateral restraint, beam length-to-depth ratio and number of bolts. The effects of these parameters on the behaviour and bolt shear strength are presented and discussed. Results are also used to assess the effectiveness of the AISC design provisions. It shows that in general, the AISC 2011 design procedure is overly conservative in predicting bolt shear for parameters studied. The overall underestimation on the capacity is around 60 to 65% when compared with finite element results. The finite element determined eccentricity is markedly lower than the AISC specified value. If the AISC 2011 design procedure is used but in combination with the finite element determined effective eccentricity, the estimate on bolt shear strength can be improved by approximately 30% for EST coonetions with 3 and 4 bolts. But for higher number of bolts, the AISC design procedure seems to provide adequate bolt strength estimate.