Multiparameter seismic behavior of castellated beam-to-column connections based on stress migration

Abstract

This paper presents a study on the castellated beam-to-column connections with four regular hexagonal web openings and one solid web beam-to-column connection that considering the opening rate and whether there is a combination of floor slabs (composite action) while subjected to the cyclic loading. Furthermore, the initial geometric imperfection was carefully incorporated in the FE model and the models have been validated against published experimental results. There is a slightly different about 5% between FE and test results including ultimate bearing capacity and other hysteresis behaviors. Investigation of 38 FE models subjected to cyclic loading focuses in the variation regularity of the failure mode, plastic development, stress migration, and seismic behaviors under the coupling effect of various factors, including the composite action of the floor slab, opening rate, the distance from the first opening to the face of the column, depth-to-thickness ratio of the web, and opening spacing. It is found that the composite action can improve the stress distribution around the first opening and raise the bearing capacity and ductility of the connections to a certain extent. Further, when the opening rate is either smaller than 0.5 or higher than 0.7, the plastic hinge of the connections with the floor slab occurs at the beam-to-column connection weld, which is completely different from the failure mode that without composite action. When the distance from the first opening to the face of the column is equal to or greater than 1.375 times the depth of beam, the plastic hinge formed in the beam-to-column weld while the composite action is taken into account; when disregarding the composite action causes the plastic hinge emerged in the beam section. Also, the ultimate bearing capacity of the castellated beam-to-column connections with closely spaced web openings significantly decreases; however, widely spaced web openings make stress concentration around the first opening and hinder the migration of stress to other openings, which has an adverse effect on the ultimate bearing capacity and ductility of the connections. The depth-to-thickness ratio of the web is also an important factor affecting the damage mode either web buckling or beam plastic hinge.