Understanding, predicting, and preventing
collapse have always been major objectives of earthquake engineering. Collapse is the main source of injuries and
loss of lives. Thus, it constitutes an
engineering limit state that needs to be predicted in order to evaluate, in a
probabilistic format, the life safety performance level, which is of primary
societal concern. In the context of
earthquake risk management, a process is needed that permits a rigorous
assessment of the probability of collapse to make informed decisions in the
best interest of society. In the context
of earthquake resistant design, this process needs to be simplified so that the
engineering profession can use engineering techniques, which are based on
parameters such as strength, stiffness, and ductility (deformability), to
derive structural properties that comply with specified targets for a required
level of collapse safety, or a tolerable probability of collapse.
This project will address both
contexts. It will provide a methodology
and reliable data for predicting a critical mode of collapse, namely that
associated with sidesway instability in which an individual story (or a series
of stories) displaces sufficiently so that the second order P-delta effects
fully offset the first order story shear resistance and dynamic instability
occurs, i.e., the structural system loses its gravity load resistance. Prediction of this mode of collapse is a challenging problem because structural components will
deteriorate in strength and stiffness before the collapse limit state is reached,
and great uncertainties are associated with the description of the seismic
input and of the parameters that control the response of structures close to
collapse.
The methodology will be based on a combination of analytical
and experimental simulations, with the former being carried out at