Professor, Department of Civil Engineering and Construction
Bradley University, Peoria, Illinois 61625, USA.
Received 18 May 2001; revised 12 Oct 2001; accepted 27 Nov 2001.
This paper investigates the validity of seismic design force recommended
by AASHTO for single-span bridges. The prescribed force is equal to the products
of soil factor , acceleration and tributary weight of the structure. A three
dimensional finite element analysis of straight and skewed bridges with skew
angles varying from 0 to 60 degrees is used for this study. In the longitudinal
direction, the bridges are assumed to be supported either by elastomeric
bearings or a pinned support. In the transverse direction, the stiffness of end
cross-frames is considered in the analysis. AASHTO ‘s recommended seismic
design force for single-span bridges is compared with the El Centro time history
and response spectrum analysis. It is concluded that AASHTO’s
recommended design force for single-span straight and skewed bridges
could be unsafe in certain cases. An increase in the design force to a level
equal to response spectrum value is recommended for such cases.
Skewed bridge; slab-girder; seismic analysis; cross-frame; elastomeric bearing.