Abstract
The Great Hanshin Earthquake, which occurred in January 1995, damaged a
wide area. The structural design guidelines for buildings especially against
vertical seismic wave has been thoroughly reconsidered. Therefore, the
arrival of a convenient technique to analyse collapse modes of structural
objects under three-directional excitation, is now desired. However, generally
used finite element code needs some extra complicated processes to simulate
this kind of dynamic collapse problem which contain strong nonlinearity
and discontinuity, such as member fracture occurred in flexural damage
or shear damage in reinforced concrete members.
The Adaptively Shifted Integration (ASI) technique, which produces the
highest computational efficiency in the finite element analyses of framed
structures including static and dynamic collapse problems, is applied to
the seismic damage analysis of a reinforced concrete building. In this
technique, the numerical integration points in an elastically deformed
element are placed at the optimal points for linear analysis, while the
integration points are shifted immediately after the occurrence of a fully-plastic
section in the element to form a plastic hinge exactly at the position
of that section. Thus the technique produces higher computational accuracy
with fewer elements than the conventional finite element code. By expressing
an explosion or a fracture by a plastic hinge located at the exact position
with a simultaneous release of resultant forces on the element, discontinuous
problem such as this can be easily analysed even by the conventional finite
element code with the displacemental form. By using the ASI technique,
sufficiently reliable solution for the practical use has been obtained
in the seismic damage analysis of a five stories-five span reinforced concrete
building. The present technique can be easily implemented with a minimum
effort into the existing finite element codes utilizing the linear Timoshenko
beam element.