COMPARISON AND SELECTION OF REINFORCEMENT SCHEME FOR 32 M-SPAN GIRDER TO MEET REQUIREMENT OF TRAIN SPEED-RAISE

Research purposes: To avoid the existences of local fatigue damage of bridge structure and resonance vibration of train and bridge,to guarantee the integrated rigidity of bridge structure and its good working performance and to meet the requirement of comfortableness,it is necessary to reinforce the bridge. Research methods: Several different reinforcement schemes for bridge are proposed according to the influencing factors on natural vibration frequency of structure and in combination with the real situation of bridge. The comparison and selection of schemes are made and rational scheme is decided after the modal analysis is carried out by finite-element method and construction feasibility is considered. Research results: Bridge will vibrate with the effects of train dynamic load. The present dynamic design and evaluation are made to the bridges on existing railway lines based on the design speed per hour of train in construction time. After train speeds up,the shock excitation frequency of train changes,along with it the response of bridge structure also changes. After testing,it is found that the main problems of existing bridge are as follows:the univalent lateral natural vibration frequency is over low and the bridge lateral amplitude of vibration frequency is over low and the bridge lateral amplitude of vibration is over large. Research conclusions: It is known from the calculation made by finite-element method that enlarging cross slab and adding support are good ways to increase lateral frequency,aiming at influencing factors on fixed frequency of bridge structure. Generally speaking,the integrated reinforcement result of Scheme 2 is best. However,it is feasible to complete such reinforcement to existing bridge by replacing concrete support with angle steel-concrete support,which can meet the same requirements. Therefore,it is recommended to adopt Scheme 5 for reinforcement.