| Bridge structure is an indispensable key link of the transportation network.In the longterm operation process,it is under tremendous traffic pressure.Meanwhile,under the influence of various factors,some components of the bridge are gradually aging,and the internal structure of the bridge is damaged,which greatly reduces its durability or even fails.To alleviate the problem of structural durability degradation,in addition to regular inspections,maintenance and other measures,strengthening the bridge structure is also a very necessary and reliable means.A new bridge strengthening technology,externally prestressed-truss composite system(EPT),is proposed in the present study.And this paper is focused on the flexural behavior and the bearing capacity calculation method of damaged beams strengthened by externally prestressed-truss composite system.The main research works are as follows:(1)The flexural behavior of damaged concrete T-beams strengthened by externally prestressed-truss composite system are carried out.Based on the prefabricated method,the flexural behavior of the structures is improved through the combination of external prestress and a controllable deformation truss.The pre-damage test and the secondary load-bearing test after reinforcement are carried out on five reinforced concrete T-beams.The failure mode,bearing capacity,load-deflection curve and strain variation law of concrete of damaged strengthened beams under static load are researched.The reinforcement effect of the externally prestressed-truss composite system is revealed.And the results show that the strengthening system has a significant reinforcement effect.(2)A theoretical method for calculation of ultimate bearing capacity of composite strengthened beams considering the influence of damage factors is proposed.Based on the externally prestressed concrete beam bearing capacity model and the truss model,the effects of the external-prestress reduction factor,the damage residual stress,the secondary force calculation of the strengthened beam,and the truss calculation under oblique external force are integrated.By introducing the truss coupling factor,the calculation method for the flexural bearing capacity of the damaged concrete T-beams strengthened by the EPT is deduced.This method can be used to predict the bearing capacity of externally prestressed-truss composite beams.And the calculation accuracy is higher when the damage degree reaches about 50%.(3)A finite element model is established of the damaged T-beam strengthened by the EPT.The finite element software ABAQUS is used to numerically simulate the strengthened structure.The coupling relationship among prestressing strand,steel truss,and reinforced concrete is considered.And the simulation of beam damaged is also introduced.The loaddeflection curves of the finite element models are obtained by controlling the displacement,and the results are compared with the test values to verify the accuracy of the finite element models. |
