Study On External Prestressing Strengthening In Continuous Rigid-frame Bridge

In recent years,the transportation of China has been developed rapidly,and the number of bridges in the road traffic has also increased rapidly.However,with the increase of service life and load,the existing bridges expose a lot of defects and diseases,and become dangerous bridges and old bridges.The safety of the bridge and the use performance are not guaranteed,so it is necessary to strengthen them.External prestressing strengthening is an main strengthening method with placing prestressed tendons outside the beam.The principle of this strengthening method is to add prestress to the beam and it can improve the internal force distribution of the original structure and adjust the stress.Thus it will improve the bearing capacity of the structure and improve crack resistance and durability.Through searching a large number of domestic and foreign literature materials,and combining with the engineering example Lancang River bridge,the method of external prestressing strengthening is studied.Diseases,causes,the project of strengthening of the bridge are studied.In this thesis,the main contents are as follows:(1)The development and research status of the external prestressing technology at domestic and foreign,and the advantages and disadvantages of the technology are pointed out.(2)The system,the layout of external prestressing tendons and the materials of the external prestressing strengthening are expounded.(3)The calculation theory of external prestressing strengthening is systematically summarized.(4)The situation of Lancang River bridge with external prestressing strengthening is introduced.Through the analysis of the present situation of Lancang River Bridge,it is concluded that the bridge should be strengthened and the strengthening method is put forward.(5)Based on the test data,the finite element model established by the design drawing is corrected so that the model can reflect the actual situation of the bridge.The model is used to verify the strengthening effect of Lancang River Bridge,and its effectiveness is also studied.The results show that the external prestressing technology can improve the rigidity of the bridge and can restrain the development of cracks.