|
by R.
Goel and A. Chopra
March 1995, 70 pp.
Click on the link below for the full text:
Abstract
A procedure is developed to estimate the stiffness of abutment-soil systems directly from the
earthquake motions of small, well-instrumented bridges using a simple equilibrium-based approach
without finite-element modeling of the structure or the abutment-soil systems. This procedure
is used to estimate abutment stiffnesses of the US 101/Painter Street Overpass during past
earthquakes. The calculated abutment stiffnesses, which include the effects of soil-structure
interaction and nonlinear behavior of the soil, are used to investigate effects of abutment
deformation on the abutment stiffness during an earthquake and to explain the torsional motions
of the road deck. It is demonstrated that the abutment stiffness decreases significantly at
larger deformations. The torsional motions of the road deck resulted, in part, because of the
differences in transverse stiffnesses of the two abutments. Also evaluated are the CALTRANS,
AASHTO-83, and ATC-6 procedures for estimating the abutment stiffness. The CALTRANS procedure
leads to a good estimate of the stiffness along the abutment (transverse to the deck) provided
the deformation assumed in computing the stiffness is close to the actual deformation during
an earthquake. However, this procedure leads to overestimation of the stiffness normal to the
abutment (along the length of the deck). The AASHTO-83 and ATC-6 procedures give an initial
estimate of the abutment stiffness that is too high in both directions.
|
