Abutment stiffnesses are determined directly from the earthquake motions recorded at the US 101/Painter Street Overpass using a simple equilibrium-based approach without finite-element modeling of the structure or the abutment-soil systems. The calculated abutment stiffnesses, which include the effects of soil-structure interaction and nonlinear behavior of the soil, are used to investigate variation of the abutment stiffness with its deformation during the earthquake and torsional motions of the road deck. Also evaluated are the CALTRANS, ASSHTO-83, and ATC- 6 procedures for estimating the abutment stiffness. It is demonstrated that stiffness of the abutment depends significantly on its deformation during the earthquake: larger is the deformation, smaller is the stiffness. The road deck of this structure experienced significant torsional motions in part because of eccentricity created by different transverse stiffnesses at the two abutments. It is also shown that the CALTRANS procedure leads to good estimate of the abutment stiffness provided the deformation assumed in computing the stiffness is close to actual deformation during the earthquake, and ASSHTO- 83lATC-6 procedure results in stiffer initial estimate of the abutment stiffness.


Civil and Environmental Engineering


URL: http://digitalcommons.calpoly.edu/cenv_fac/74