Study On The Technique Of The Old Bridge Strengthening With External Pre-stressed Force

Along with time pass and economic development more and more bridges do not meet the needs of the traffic. Bridge consolidating is a good solution for solving these problems. The technique of the old bridge strengthening with external pre-stressed force is studied in this paper. This method is put pre-stressed external tendons outside the bridge's body, tendons anchor firmly in bridge beam two ends and exert axial pressure and moment of flexion to beam. Because moment of flexion by the tendons is opposite to the original beam adverse moment of flexion in direction, can offset stress of deadweight and reduce the stress of changing load, and raise the bearing capacity of beam. This text did structure analysis and mechanic analysis for pre-stressed external tendons bridges consolidate method; presented the calculation method of force method for endogen force; presented the calculation method for stress, deflection and calculation method for ultimate strength of consolidate system. As a result of quadratic effect existences, In external pre-stressed beam's carrying capacity, the rigidity, the frequency is different has the unbonded or interior pre-stressed structure.Aiming at project of the Ganjiang bridge in Ji'an, V shape pier and Yaohu trestle strengthening, the theme has conducted the research in prestressed tendon simulation of prestressed bridge and obtained a method of simulating prestressed tendon by the basic function of ANSYS. A Spatial model of V shape pier of Ganjiang bridge has been established by useing ANSYS. As is shown from analytic result, the loss of prestress of slab of V shape pier is between 30% to 40% and propose to avoid of structure resonates measure. This conclusion can offer guidance for strengthening of slab. In this study, elasto-magnetic(EM) stress sensors utilization on external steel cables of V shape pier of GanJiang bridge in Ji'an are discussed. Through measure strain and calculation in theory of bent cap in Yaohu trestle strengthening with external pre-stressed force, compare test value after strengthening with calculated value in theory before strengthening, this paper study and analyze the actual effect of bent cap strengthening with external pre-stressed force, experimental data manifest exerting external pre-stressed force can cancel out a part of permanent loading and live loading, it has a unloading effect, thus improve and adjust state of stress, enhance rigidity and carrying capacity of structure remarkably.