Modal Analysis Of RC Simple Supported Beam-Bridge In Attached Load

The load capacity of the reinforce-concrete beam-bridge is the necessary part during the course of bridge conservation maintenance and technical reconstruction of today, which is also one of the most heated problems that are being discussed by scientists in engineering area and scholars at home and abroad, and along with the increment of old bridges, the problem attracts more attention. The traditional static load test can not make sure the load capacity of the bridge and the damage position of the bridge, and it will take plenty of time and interrupt traffic. So it is an important realistic significance to explore a simple rapid approach to detect bridge load capacity and bridge damage. The paper's objective is to quest a proper approach to detect bridge load capacity bridge damage.The research of approach to monitor bridge state has become a hot spot in the engineering through the theory of dynamic of structures and the test technology. Structure mode parameters(vibration frequency, mode of vibration) are the functions of physical property parameters(mass, rigidity, damping). The damage of structures leads to the transformation of physical property parameters, and certainly leads to the transformation of structure mode parameters finally. So the damage and load capacity of the. bridge can be detected by the transformation of structure mode parameters with the modern technology of signal test. The vibration frequency is obtained easily in the measure, but it isn't sensitive to the transformation of mass and rigidity. So it is difficult to identify by test system when the damage of structure reach to the limit damage degree. The paper's main work is to solve the problem that the vibration frequency isn't sensitive to the transformation of mass and rigidity.Basing on RC simple supported beam the study of the paper is modal analysis using the finite unit software ANSYS, and the relationship among the transformation of vibration frequency, value of attached load, position of attached load , degree of damage, position of damage is discussed. The load capacity and damage degree of bridge are detected by the curve of the transformation of vibration frequency in different attached load and different damage. A conclusion that the attached load method improves the of vibration frequency sensitivity to the physical property parameters of bridge structure is drawn at last. And the same time the paperbring forward a new and convenient technique of dynamic load test--the attached loadmethod.