NONLINEAR DYNAMIC ANALYSIS OF TELESCOPIC MECHANISM FOR TRUSS STRUCTURE BRIDGE INSPECTION VEHICLE UNDER PEDESTRIAN EXCITATION

Abstract

NONLINEAR DYNAMIC ANALYSIS OF AN AXIALLY MOVING TELESCOPIC MECHA-NISM FOR TRUSS STRUCTURE BRIDGE INSPECTION VEHICLE UNDER PEDESTRI-AN EXCITATION IS CARRIED OUT. A BIOMECHANICALLY INSPIRED INVERTED-PENDULUM MODEL IS UTILIZED TO SIMPLIFY THE PEDESTRIAN. THE NONLIN-EAR EQUATIONS OF MOTION FOR THE BEAM-PEDESTRIAN SYSTEM ARE DE-RIVED USING THE HAMILTONÂS PRINCIPLE. THE EQUATIONS ARE TRANS-FORMED INTO TWO ORDINARY DIFFERENTIAL EQUATIONS BY APPLYING THE GALERKINÂS METHOD AT THE FIRST TWO ORDERS. THE SOLUTIONS TO THE EQUATIONS ARE ACQUIRED BY USING THE NEWMARK-β METHOD ASSOCIATED WITH THE NEWTON-RAPHSON METHOD. THE TIME-DEPENDENT FEATURE OF THE EIGENFUNCTIONS FOR THE TWO BEAMS ARE TAKEN INTO CONSIDERA-TION IN THE SOLUTIONS. ACCORDINGLY, THE EQUATIONS OF MOTION FOR A SIMPLIFIED SYSTEM, IN WHICH THE PEDESTRIAN IS REGARDED AS MOVING CART, ARE GIVEN. IN THE NUMERICAL EXAMPLES, DYNAMIC RESPONSES OF THE TELESCOPIC MECHANISM IN EIGHT CONDITIONS OF DIFFERENT BEAM-TELESCOPING AND PEDESTRIAN-MOVING DIRECTIONS ARE SIMULATED. COM-PARISONS BETWEEN THE VIBRATIONS OF THE BEAMS UNDER PEDESTRIAN EXCITATION AND CORRESPONDING MOVING CART ARE CARRIED OUT TO INVES-TIGATE THE INFLUENCE OF THE PEDESTRIAN EXCITATION ON THE TELESCOPIC MECHANISM. THE RESULTS SHOW THAT THE DISPLACEMENT OF THE TELE-SCOPIC MECHANISM UNDER PEDESTRIAN EXCITATION IS SMALLER THAN THAT UNDER MOVING CART ESPECIALLY WHEN THE PEDESTRIAN APPROACHES THE BEAMS END. ADDITIONALLY, COMPARED WITH MOVING CART, THE PEDES-TRIAN EXCITATION CAN EFFECTIVELY STRENGTHEN THE VIBRATION WHEN THE BEAM EXTENSION IS SMALL OR WHEN THE PEDESTRIAN IS CLOSE TO THE BEAMS END.