Finite element investigation of the cyclic behavior of bolted extended end plate connections strengthened with longitudinal plates
Abstract
The cyclic behavior of bolted extended end plate beam-to-column connections strengthened with longitudinal plates parallel to the beam web was investigated through three-dimensional nonlinear finite element analysis. Unlike previously studied methods such as haunches, end plate stiffeners, side plates, and internal reinforcement details, this strengthening configuration places the plates within the beam depth and parallel to the beam web, an arrangement that has not been systematically examined for this connection type. The finite element model was first validated using results from a benchmark experimental test reported in the literature. Following validation, six connection configurations were analyzed under the AISC cyclic loading protocol. These included a four-bolt unstiffened end plate (4E) reference model, a four-bolt stiffened end plate (4ES) model, and four models incorporating longitudinal plates with varying plate lengths and locations. The numerical results were assessed based on hysteretic response, cumulative energy dissipation, bolt force distribution, equivalent plastic strain development, and equivalent viscous damping. It was observed that the addition of longitudinal plates improved the global cyclic response by increasing the moment capacity while maintaining stable hysteresis loops. However, increasing the length of the longitudinal plates resulted in higher tensile force demands on the bolts, indicating the need for careful design to avoid brittle failure modes. Analysis of the equivalent plastic strain showed that the longitudinal plates reduced the peak strain in the beam-end region by up to approximately 64% relative to the unstiffened (4E) reference connection, whereas the conventional stiffener (4ES) shifted the plastic hinge away from the column face but produced the highest strain concentration. The results indicate that the longitudinal plate detail offers a practical strengthening approach for improving the cyclic response of bolted extended end plate connections, provided that the increased bolt tensile demand is explicitly considered in design.
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References
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