The Study Of The Cause Of Girder Crack And Reinforcement Method In Collaborative Concrete Cable-stayed Bridge

The single tower prestressed concrete cable-stayed bridge becomes the preferred choose in the bridge design depending on its advantages of stability and economy. However, concrete girder cracking problem has become outstanding problems of hampering its development, and gets the academic and engineering concern. In order to analyze the cause of concrete cable-stayed bridge main beam crack, the paper completes the following work, taking a collaborative single-span cable-stayed bridge for example.(1)Elaborated the beam cracks distribution of west side 74.5m collaborate across, main span cable-free zone and east side 49.5m collaborate across, and preliminary analyze the causes of cracks. The analysis show that collection trucks and other heavy vehicles load, bearing tension and compression failure, and insufficient lateral rigidity of 49.5m across are the main cause of cracks.(2)Establish a full bridge model using finite element analysis software Midas/civil, and calculate the stress state of the main beam in bridge phase and operational phase. The results show that, although the stress state of the bridge meets the requirements, but crack resistance is small.(3)Considering the bridge has been operating since traffic congestion has been,and most arecollection trucks and other heavy vehicles, so the paper calculates the webs stress under the normal passage of trucks and traffic jam. The results show that the place of web overstress is consistent with the actual location of crack.(4)In view of tension and compression supports at 23 rd pier is crushed during operational process, and main beams status has changed. The paper contrast the effect of tension and compression supports on the stress state of the main beam taking collaboration across web principal stress, roof and floor stress for the study. The results show that crush of tension and compression supports causes the roof transverse crack at 24 rd pier.(5)Considering the single-beam model can’t reflect the spatial stress of girder, especially the transverse stress state, the paper establish the 49.5m cross solid element model, and calculate the lateral force of girder. The results show that the top and bottom principal tensile stress near vertical web is far exceeding the limit, and consistent with the actual distribution of crack.(6)Put forward four reinforcement measures of solid block demolition, additional stringers, transverse bulkhead and transverse prestressed tendons, to improve insufficient lateral rigidity of 49.5m span, and establish spatial finite element model after reinforcement, then compare the stress before and after reinforcement, thereby verify the effect of the reinforcements for controlling girder cracking. The results show that transverse rigidity is greatly improved and the stress meets the requirements after reinforcement.