Analysis On Abnormal Vibration Of Luzhou Tuojiang Longxi Bridge's 100m Side Span

Reinforced concrete arch bridge has been used widely in our country's construction for its own virtue and can luckily make agreement with the factual situation of bridge engineering. Because a large number of arch bridge have been constructed in our country, and the bridge tends to have lighter and thinner structures, so its dynamic problem under vehicle moving loads should not be ignored. Predecessors have affirmed through both theory and practices that the vehicle moving loads would lead to more deformations and stress for bridge structures than the equivalent static loads. This dynamic effect should not be ignored, because large vibration can decrease the carrying capacity of structure, and affect the life-span of bridge.Along with the development of computer, it's easy to calculate the natural vibration frequency and vibration model through analyzing dynamical feature of structure with finite element software, and some powerful finite element software can provide the function to make the dynamic response analysis on structure, if choose some rational dynamical parameter, it can get a upper comparability of dynamic response feature between finite element model and actual bridge. In the thesis, aiming at the abnormal vibration that the impact coefficient of Longxi bridge's side span is too big, we use software ANSYS to establish 3-D finite element model of it to do a dynamical research, then get the natural vibration frequency and vibration model through analyzing its natural vibration feature. For the sake of finding out the reason that make the bridge vibrate abnormally, the central work of the thesis is the dynamic response analysis (the transient dynamic analysis) of structure, in view of the influence of the vehicle's vibration, we bring forward a method that we use the spring-mass to simulate vehicle, and the time history dynamic responses of the structure under uniform velocity moving load are analyzed. We get the impact coefficient of bridge through the calculation, then compare the calculated results with the experimental results, and it indicate that comparability of dynamic response feature between finite element model and actual bridge is satisfying. Based on this, we bring forward an idea that estimate bridge's vibration under vehicle in advance in design, then it can avoid a new bridge to vibrate abnormally. We change the influence factors such as rise-span ratio, length of crossbeam and vibration frequency of vehicle to discuss and study the reason that make Longxi bridge vibrate abnormally. Through the analysis, we get some useful conclusions, and the present results can provide a practical reference for the design.