NEES Collapse Project Summary…
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