Study On Influence Of Behavior Of Municipal Bridge Under Jam Vehicle

Vehicle jam impairs bridges health at different level. The basic characters of damaged bridge are increasing deflection,developing crack, breakdown of bearing and expansion joint. Influence of vehicle jam on behavior of bridge is studied in this paper, which is to analysis the law of inner force's variation and fatigue injury's development under the state of vehicle jam. The conclusion would give a scientific reference for bridge's maintenance appraising and reinforcement.Through analyzing the distribution of car flow in urban road, vehicle loading model for municipal bridge under the state of jam is simulated, which includes type of vehicle, gross rail load on aixe, axie base, clear distance of adjacent vehicle and so on. Then, load effect including moment and shear force of representative bridges under different jam load are calculated, which are compared to load effect under design condition in order to reflect and disclose bridges practical behavior. At last, based on S-N curve and cumulative injury theory, fatigue lifetime are calculated under different stress level of design condition and jam condition, which disclose the influence of vehicle jam on fatigue character of bridge.The study indicates that load effects caused by jam composed by car or bus only are less than which caused by design load. But load effects caused by jam containing heavy vehicle may be greater than which caused by design load. So the jam would affect bridge's safety directly and strongly. On another hand, frequent jam would result in fatigue breakdown of bridge, which result that the degree of damage may be off-rating in several years and reduce normal operational life greatly.