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Abstract

The damping ratio has a important effect on the dynamic behavior of the bridges. and it is customary when designing to assume it as a predetermined fixed value independent of the response amplitude and frequency of the structure . A lot of experimental research worked on identifying them, but the dependence of damping and other dynamic characteristics of vibration amplitudes and their impact on responses and the results of the analysis need more scrutiny and simulation due to the difficulty of conducting vibration experiments for structures of realistic dimensions and large weights such as a RC bridge, which necessitated a procedure Analytical process and computer modeling to study the responses of several seismic vibration amplitudes, based on the results of experiments to determine the mechanical properties of neoprene cushions and on prior experimental results of vibration tests on laboratory samples of RC bridge piers, since the accurate determination of the dynamic response essentially needs to determine the actual dynamic characteristics of the bridges, especially damping, by measuring their vibration and simulating numerical models in dynamic analysis provides a good visualization of the expected response, and as a result of analyzing the RC bridge damped with neoprene cushion in this paper It recognize that damping changes should be taken into account during dynamic analysis for seismic excitation amplitudes not exceeding (2 m/sec2). But for larger amplitudes than this value , it is recommended that damping is considered constant, and finally to adopt the dynamic characteristics of any structures , we need to give special concentration to the expected vibration amplitude before selecting design values .

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