The Inelastic Response of Multiple-degree-of-freedom Systems Joseph M. Sussman Chairman, Departmental Committee on Graduate Studies the Inelastic Response of Multiple-degree-of-freedom Systems Title: Professor of Civil and Environmental Engineering

In earthquake-resistant design it is usually assumed that the structure is linearly elastic and remains linearly elastic throughout the duration of the seismic activity. This is not always a realistic assumption. Indeed, even well designed structures will yield during very strong shaking and endure stresses well beyond the elastic limit of the design material. It is neither necessary nor economical to design structures to resist very strong shaking within the elastic limit of the construction materials used. Some damage can be tolerated, provided that there is no undue hazard to the occupants of the building. This idea is reflected in modern building codes. The accepted philosophy is that structures should be designed to resist moderate shaking without damage, while permitting some yielding and limited damage in strong shaking. In seismic design beyond the material elastic limit, elastoplastic behavior is usually assumed. It is therefore of interest to the designer to study how a structure in which yielding is allowed to take place will behave under seismic loading. The aim of this research is to gain some insight into the inelastic behavior of a multistory building using finite element modeling. The finite element analysis software ADINA (Automatic Dynamic Incremental Nonlinear Analysis) is used to obtain the 'true' structural response of a structural system with inelastic material properties. The results of any finite element analysis are only as accurate as the mathematical model used. Therefore, part of this work is devoted to assuring that the model used would indeed give as accurate a representation of the true response of the structure as possible.