| Experience shows that buildings with irregularities are prone to earthquake loading, as demonstrated in many earthquake occurrences. This experimental study focused on the validation of the analytical tools for evaluation of seismic response of irregular structures, i.e. setback structures. A number of analytical studies had been carried out to evaluate such structures, but very few experimental works had been done on this subject.; A versatile model was developed to be used and reused with structures undergoing severe damage to sacrificial elements thus capable to be repaired and further tested to provide reference information for the required validations. The model is a one-third scale of a three-story three-bay steel structure. For the purpose of this study, the irregularity aspect was introduced to the designated model by having two unequal towers. From dynamic analyses of the analytical model, LA16 ground motion (Northridge 1996, Rinaldi RS), from the SAC project with 10% probability of exceedence in 50 years in Los Angeles, was found to be the most suitable ground motion for this study.; Prior to the experimental study on the model, several material and component tests were carried out. The actual properties obtained from the material tests were used to refine the analytical model. The gravity column and the beam-column connection components were also tested to better understand the behavior of the model structure. The gravity columns were equipped with special spherical attachments to enable them to act as pin-connected leaning columns, thus they can resist only vertical load. The beam-column connections were designed to resist only lateral loads, and the tests were conducted on a 'cruciform' specimen made of half-beams and half-columns to resemble a sub-assembly having half spans and half stories on each side. The component test results were subsequently used to refine the analytical model.; The experimental tests of the model structure were conducted by applying a sequence of increasing LA16 ground motions. Structural identifications using white noise excitations were made in-between the dynamic loadings to monitor changes in the dynamic properties. Experimental results and visual observation show that the model behaved elastically under minor earthquake loadings. The first yield occurred at a PGA = 0.25g, and at higher ground motion levels the model behaved inelastically. Damage were recorded in the forms of prying effect at the column end plates and a welding failure of a block joint located at the toes of the higher tower where force concentrations due to irregularities were expected. (Abstract shortened by UMI.)... |
