nonlinear dynamic analysis of semi-rigid frames with bolted angle connections

in this paper, a parametric study was conducted to investigate the moment-rotation behavior of top and seat angle connections using nonlinear finite element (fe) method. based on the experiments carried out by preceding researchers, several refined fe models were cre ated in which the geometrical and mechanical properties of connections were as parameters. eight node solid elements were used to model all of the connectioncomponents such as beam, column, angles and bolts. the effect of interactions, such as slippage of bolts and frictional forces, were modeled using surface contact algorithm. to evaluate the connection behavior more precisely, pre-tensioning forces were also applied on bolt shanks as the first load case. comparing the results of numerical modeling and test results, good agreement was observed, especially in linear range of moment-rotation curves. to study the efficiency of the adding double web angles to enhance the rotational stiffness and moment capacity of bolted top-seat angle connections, models were created with different size and properties and the effect of each parameter on connection behavior was studied. then the study was extended by evaluating the role of the web angles on seismic performance of a selected semi-rigid frame. the frame was modeled using bar elements and relative stiffness of connections was considered and modeled using zero length joint elements. the result of nonlinear time-history analysis showed that adding web angles to frame connections will reduce the story drift and increase the energy absorbance capacity of the structure.