EXPERIMENTAL STUDY OF THE SEISMIC BEHAVIOR OF AN EXISTING BRIDGE ABUTMENT LOCATED ON SOFT CLAY DEPOSITS

Abstract

IN THIS STUDY, A DYNAMIC CENTRIFUGE EXPERIMENT IS DESIGNED TO INVESTIGATE THE SEISMIC BEHAVIOR OF AN EXISTING BRIDGE SUBJECTED TO THE EARTHQUAKE-INDUCED LATERAL MOVEMENT OF SOFT CLAY SOIL . THE PILE-SUPPORTED BRIDGE ABUTMENT AT THE MOVABLE BEARING SIDE IS MODELED AT THE 1/75 SCALE. THE MATERIAL AND THICKNESS OF THE SOFT CLAY LAYER ARE SET AS THE EXPERIMENTAL PARAMETERS. UNDER THE EFFECT OF THE LATERAL MOVEMENT OF THE SOFT CLAY LAYER DURING BASE SHAKING, A COLLISION BETWEEN THE BRIDGE ABUTMENT WALL AND THE GIRDER OCCURS, AND THE BRIDGE ABUTMENT WALL IS RESTRAINED AT THE TOP; HOWEVER, THE FOOTING LARGELY MOVES FORWARD, RESULTING IN THE LARGE BACKWARD INCLINATION OF THE BRIDGE ABUTMENT WALL. IN ADDITION, IT IS CONFIRMED THAT DURING BASE SHAKING, THE PILE BENDING MOMENT LARGELY INCREASES DUE TO THE GROUND LATERAL MOVEMENT AND THEN REMAINS NEARLY CONSTANT, EVEN AT THE END OF THE BASE SHAKING PHASE. FURTHERMORE, IT IS FOUND THAT WHEN THE SOFT CLAY HAS A HIGH SHEAR STRENGTH, THE GROUND LATERAL MOVEMENT MAY CAUSE A HIGH PILE EARTH PRESSURE, RESULTING IN THE LARGE CORRESPONDING INTERNAL BENDING MOMENT ON THE PILE SECTIONS; HOWEVER, WHEN THE SOFT CLAY LAYER IS VERY THICK, THE HIGH PILE EARTH PRESSURE GENERALLY OCCURS LOCALLY, INSTEAD OF ALONG THE WHOLE PILE LENGTH.