Beam-Column Subassemblages Under Repeated Loading

The behavior of two types of structural steel half-scale subassemblages of a multistory unbraced frame have been investigated experimentally. These subassemblages were subjected to simulated gravity and cyclic seismic loads. The results obtained in the tests of the upper story specimens show that the weakest element of the subassemblage was the panel zone, where large shear deformation and diagonal buckling occurred. The weakness of the subassemblages representing a lower story, was associated with lateral torsional instability of the beams, which was triggered by local instabilities. From the interpretation of the results, it is concluded that for an efficient design of earthquake resistant structure, it is advisable to have a design which provides a balance between the inelastic deformations, which may take place in each of the critical regions (beam ends and panel zone). It also appears that the energy absorption and dissipation capacity of properly designed steel subassemblages exceeded the required energy even for cases of extreme earthquakes.