The Research On Crake And Control Of The Prestressed Concrete Box Girder Bridge

With lots of advantages, the long-span pre-stressed concrete box-girder bridges are widespread used, which also makes it to be related with severe crack problem, so it takes the left line super-bridge over Jialing River as background to study the main influencing factors on the crack of concrete box-girder bridges. The dominating content is as below.(1) Based on a mass of literature materials, the crack of pre-stressed concrete box-girder bridge are classified and concluded to have clear understanding over the cracking problems of concrete box-girder bridges, to expatiate the reasons which possibly lead to the crack of concrete box-girder bridges and to set up foundation for the further study.(2) Analyzing the background bridge by midas/civil--the professional software of bridge, the text concentrates on studying the temperature gradient and vertical pre-stress which are the influencing factors of concrete box-girder bridges. Comparing with the computing result about mode of selected temperature gradient, which shows the importance of choice on the mode of temperature gradient and the computing results are much difference among every mode of temperature gradient. It indicates that the temperature stress makes great contribution to the stress state of bridge by comparing the temperature stress with the stress under live load and much attention should be paid to the factor. Meanwhile, It shows that vertical stress have much influence over the compressive stress storage along the principal tensile stress according to relation pictures between the loss of vertical stress and the principal tensile stress of web. With the inclination angle under some scope, inclination of the vertical pre-stress enhance the compressive stress storage along the principal tensile stress,which resulted from the process about inclining disposal of the vertical stress.(3) To study the dimensional forcing state of box-girder, large-scale analyzing software of finite element is used and the modeling process is also introduced in detail. Comparing the dimensional computing results with the plane computing results, It shows that the plane software about finite element is also available to the holistic computing of bridge. Once the key areas are related to, the analysis of dimensional stress should be progressed. And then the influence over box-girder’s dimensional forced state is analyzed, which is in accordance with the longitudinal loss of effective pre-stress from top flange, web and bottom flange. And the factors which longitudinal loss of pre-stress is prone to affect the box-girder dimensional forced state are found. In the meantime, it offers reference for the design and engineering.Finally,the elastic compression loss of the concrete are studied in order to offer something meaningful in the aspect of the calculation of the elastic compression loss.(4) Maintenance and reinforcement is also important after the cracks occur in the pre-stressed concrete box-girder bridge. Based on correlated literature, the text also expatiates the maintaining and reinforcing measures for box-girder in detail and offers reference for the homologous engineer.