SEISMIC EVALUATION OF HORIZONTALLY CURVED BRIDGES SUBJECTED TO NEAR-FIELD GROUND MOTIONS

Abstract

HORIZONTALLY CURVED BRIDGES HAVE MORE COMPLEX SEISMIC BEHAVIOR THAN STRAIGHT BRIDGES AND HAVE BEEN MORE VULNERABLE TO EARTHQUAKES. THE PRESENT STUDY AIMED TO EVALUATE THE SEISMIC RESPONSE OF CONCRETE BRIDGES WITH STRAIGHT AND ARCHED BOX GIRDER DECKS IN ISOLATED AND NON-ISOLATED STATES. THE RESULTS INDICATED THAT INCREASING THE CURVATURE OF THE NON-ISOLATED BRIDGE COULD INCREASE THE IRREGULARITY. IN ADDITION, INCREASING THE CURVATURE OF THE DECK LEADS TO AN INCREASE IN SHEAR FORCE, BENDING MOMENT, AND DISPLACEMENT IN THE PIERS IN THE RADIAL DIRECTION OF THE ARC, AND CAUSES VULNERABILITY OF THE PIERS IN THIS DIRECTION. FURTHER, IN THE DECK OF THE BRIDGE, THE REDUCTION OF THE ARC RADIUS, ESPECIALLY IN THE NON-ISOLATED BRIDGES, CONSIDERABLY INCREASES THE RADIAL SHEAR FORCE, TORSION AND MINOR BENDING MOMENT OF THE DECK. IN BOTH ISOLATED AND NON-ISOLATED CASES, THE DEMAND IN THE PIERS AND DECK OF THE BRIDGE UNDER THE INFLUENCE OF NEAR-FAULT GROUND MOTIONS IS GREATER THAN THAT OF THE FAR-FIELD EARTHQUAKES. SEISMIC ISOLATION RESULTS IN REDUCING THE FORCE DEMAND IN THE PIER, AND THE DECK OF THE BRIDGE, LEADING TO A REDUCTION IN THE FORCE DEMAND RATE CAUSED BY INCREASING THE CENTRAL ARC ANGLE ON THE BRIDGE DECK.