Study On Prestress Loss Detection And Damage Identification Of Continuous Beam

In the bridge operation,due to the overloading of the vehicle,the aging of components,acid rain and other extreme weather conditions,as well as bridge fatigue and other adverse conditions and factors,the bridge may have varying degrees of damage.In order to ensure the safety of the normal operation of the bridge,the need to understand the health status of the bridge in real time,grasp the structural damage may exist,and detect the damage already exist,provides the basis for the bridge reinforcement so as to repair.Therefore,it is very necessary to study the damage identification of bridge structures,and the research results have direct or indirect application prospects.In this paper,aiming at the problem of girder prestress loss and structural damage detection,the prestressed concrete beam and prestressed steel beam were set as research objects.The test data were analyzed by fast Fourier transform method,to explore the relationship between the natural frequency and the damage degree of prestressed beam.The main experimental contents and results are as follows:(1)3 non bonded prestressed concrete beams are produced,the form of which is divided into the bottom of the eccentric cloth,the bottom of the flexural and axial reinforcement,different prestress are apply to the beam continued with vertical reciprocating load until the beam yield.The test results show that the influence of the form of the reinforced concrete beams on the deflection of the beam is obvious,and the influence factors of the prestressing tendons can not be ignored when the dynamic characteristics of the prestressed concrete beams are analyzed.The natural frequency of the beam is gradually reduced with the loss of the prestress value and the trend is opposite when the bottom is eccentric and the bottom is bent.The change tendency of the natural frequency of the beam is the same in the 3 prestressed concrete beams,and the natural frequency of the beam is gradually reduced along with the damage degree.(2)The prestressed steel beams are fabricated,which are subjected to eccentric reinforcement,bending and axial reinforcement,and by cutting the edge of the lower flange to simulate the damage.Experimental results show that the natural frequency changes of 3 kinds of steel reinforced form is the same,with the deepening of the degree of damage of prestressed steel beam,the beam natural frequency decreases gradually.The same rules go with prestressed concrete beams.(3)Numerical simulation of prestressed concrete continuous beams are established using ABAQUS,The result shows that the natural frequency of continuous beam is gradually reduced along with the loss of prestress,and the natural frequency is gradually decreased with the increasing degree of damage.This rule is consistent with the experimental results.