Simulation Analysis And Construction Monitoring Of Pestressed Concrete Continuous Rigid-Frame Bridge Strengthened By External Prestressing

In recent years, a large number of prestressed concrete continuous rigid-frame bridges with long span have been built in China, a series of defects in such bridges have also occurred concurrently, e.g., cracking and excessive deflection, which has seriously affect their normal use. However the theory research on external prestressing technique applicable to the reinforcement of such bridges is becoming common now,the reinforcement theory is still immature.In addition, the system study on external pre-stress strengthening construction and the research on direction-changing blocks or anchoring blocks in the construction is still uncommon.In this paper, in combination with a practical project, the whole process of strengthening a prestressed concrete continuous rigid-frame bridge by external prestressing is simulated by means of finite element software SAP2000, on the basis of which the theory of finite element calculation and the practical modeling methods are discussed and the construction monitoring is measured. After the construction, the reinforcement effect is analyzed. At last, the stresses in direction-changing and anchoring blocks during or after strengthening construction are analyzed by using the integrated model for strengthening construction instead of analytical method of equivalent load.According to the comparison between the theoretical values and the measured values of the control parameters under various loading conditions during external pre-stress strengthening construction, the model of a real strengthening bridge jiontly simulated by shell elements and volume elements is effectively used not only in stress monitoring and deflection monitoring for the main girder, but also in stress monitoring for the direction-changing and anchoring blocks. It is confirmed by finite element analysis that external pre-stress strengthening is able to improve the excessive deflection at mid-span and flexural capacity of the old beam, but the improvement of shear bearing capacity is non-ideal.Therefore comprehensive reinforcement scheme with external prestressing and steel sticking technique used is suggested to be adopted when shear failure of the original beam is obvious. The local finite element analysis of direction-changing blocks or anchoring blocks can provide guidance for them.Besides this, the measures to improve anchoring block structure is put forward on the basis of stress distribution variation of the concrete under the anchoring blocks.