Seismic analysis of skewed highway bridges with intermediate supports

DUE TO THE DAMAGE SUFFERED BY MANY SKEWED HIGHWAY BRIDGES DURING THE SAN FERNANDO EARTHQUAKE, 1971, A STUDY IS MADE ON THE DYNAMIC RESPONSE OF THIS TYPE OF BRIDGE. USING A BEAM MODEL CAPABLE OF FLEXURAL AND TORSIONAL DEFORMATIONS, THE MODE SHAPES AND FREQUENCY EQUATIONS ARE PRESENTED. DUE TO THE SKEWNESS OF THE SUPPORTS, COUPLED FLEXURAL AND TORSIONAL VIBRATION WILL BE INDUCED ON SKEWED HIGHWAY BRIDGES. THE NATURAL FREQUENCIES OF THESE VIBRATIONS ARE GENERALLY FAIRLY HIGH (ABOVE 4 CPS) AS A RESULT OF THE TYPICAL DIMENSIONS OF THIS TYPE OF BRIDGE. HOWEVER, IF THE BRIDGE IS LOCATED CLOSE TO THE FAULT, THERE WILL BE SUFFICIENTLY STRONG HIGH FREQUENCY COMPONENT IN THE VERTICAL GROUND MOTION TO EXCITE THE COUPLED FLEXURAL AND TORSIONAL VIBRATIONS IN THE BRIDGE. /AUTHOR/