Analysis of the force distribution in bolts of a beam-to-column end-plate connection

<ns3:p>The article presents the results of a numerical analysis of a selected configuration of a bolted end-plate beam-to-column connection, with particular emphasis on the influence of the failure model on the values and distribution of axial forces in the bolts.A definition of the joint rotation capacity is given, based on the criterion of the maximum force a bolt can sustain in laboratory testing. For the average maximum force in bolts (M20, grade 10.9), a reduction factor BT of 0.90 was adopted to eliminate the occurrence of plastic strain. The force value BT = 240 kN was taken as a reference for determining the ultimate rotation angle u.The analysis involved a column with a HEB500 cross-section, connected to beams with cross-sections HEA280, HEA300, HEA320, HEA340, HEA360, and HEA400. Numerical simulations were performed using end plates with thicknesses of 12, 15, and 20 mm. The model was built based on the results of a calibration procedure involving multi-stage hierarchical validation. The force distribution in bolts was analyzed for the three different plate thicknesses (20, 15, and 12 mm), allowing for a detailed assessment of the influence of joint stiffness on the load transfer efficiency by individual bolt rows.In configurations characterized by dominant end-plate yielding and significant elastic-plastic rotation, a favorable redistribution of forces among bolts is observed. Connections that exhibit high load-bearing capacity do not show significant increases in rotation capacity. These are cases where the failure mode, governed by bolt yielding, becomes the decisive factor.The introduction of a joint rotation angle definition, based on laboratory test results of the ultimate bolt force (90% of the average failure load for M20 bolts, grade 10.9, ISO 4014), enabled the establishment of an objective criterion for evaluating the rotation capacity of the connection</ns3:p>