The Monitoring Test Analysis Of Hoisting Construction Of Large Tonnage Asymmetric Prefabricated Box

Base on the investigation of the PC continuous girder bridge in operation status, the cracking problem of concrete structure is more prominent, these cracks severely reduces the bridge bearing capacity and durability, and with a large number of bridge construction and the increasing of highway construction, the various accidents in bridge engineering is becoming more and more serious.This thesis is based on Highway Project Hangzhou-Ningbo Connections engineering, the beam element finite element model and solid element finite element model are established respectively, to move the provided conditions of box girder under the overall and local stress of key conditions of the box girder of whole body and local stress conditions were simulated and calculated. At the same time, the stress and strain state of the key section and the suspension point in the process of transporting the precast box girder were monitored. The calculated data through the test data and theory of box girder in the process of stress analysis, the main research results are as follows:(1) Compared with the experimental results, the stress value and the allowable stress are compared and analyzed. It can be seen that the measured stress value is in good agreement with the theoretical calculation. This suggests that the two kind of elements is used to build the finite element model can meet the needs of the stress calculation. And the lifting construction technology can guarantee the construction safety, to meet the requirements of box girder structural safety.(2)Stress analysis of the observed data can be drawn, in thehoisting process, the ends of the beam height difference emerged, causing asymmetric longitudinal beam stresses. Therefore, the proposed attention in the construction process control box girder at a height difference, to prevent stress concentration condition, caused by beam cracks.(3)As the project cantilever box girder asymmetric characteristics, resulting in stress distribution in the transverse box beam asymmetry may cause danger to the box beam construction. Thus, in addition to construction should pay attention to the stress spreader real-time monitoring, the proposed lifting point centerline can be offset a certain distance to the long side or the short flange flange side counterweight way of box beams eccentric adjustment, prevent overturning box girder.(4)In the hoisting process, the top and the web at both ends of the box girder with variable cross section is larger than the difference between the top and the web, which is combined with the previous construction experience. If the box girder is carried out several times, the longitudinal cracks and inclined cracks are easy to be produced. Therefore, in the design and construction of the whole bridge construction process, we should pay attention to optimize the structure of the reinforcement layout and in the construction of the simulation analysis.