Construction Monitoring And Analysis Of I-beam Concrete Composite Continuous Beam

In this paper,the structural deflection,strain and temperature of the I-steel-concrete composite continuous beam are monitored in the construction stage and the time after the bridge is completed.The influence of temperature on the strain of the I-steel-concrete composite continuous beam is obtained.The effect of shrinkage and creep on the deformation and stress redistribution of I-steel-concrete composite continuous beam is obtained.After the bridge is built,the structural bearing capacity and finite element model are verified by static load test.Finally,the long-term performance of the composite beam is studied according to the effective modulus method adjusted by age.The main research work is as follows:(1)Through the monitoring of the I-steel-concrete composite continuous beam,the stress redistribution of the composite girder with early shrinkage and creep is obtained:With the influence of shrinkage and creep,the tensile stress of the concrete in the negative moment zone is gradually reduced,the compressive stress of the lower flange of the steel beam is gradually increased,and the steel beam bears more stress;the compressive stress of the concrete slab in the positive bending moment zone is gradually increased.The tensile stress of the lower flange of the steel beam increases,and the deformation caused by the shrinkage and creep increases the force of the concrete slab and the steel beam.(2)Through the monitoring of the I-steel-concrete composite continuous beam,the influence law of the temperature distribution law and the daily temperature variation structure of the composite beam is obtained:the temperature of each measuring point of the steel beam and the concrete slab changes obviously sinusoidal,and the change trend Consistent,there is no temperature lag.(3)Based on the modified ANSYS fine finite element model,the steel framwork is analyzed by the life and death element method:The steel formwork can effectively improve the longitudinal stiffness of the steel-composite beam,reduce the deflection deformation,and participate in the structural stress;the steel formwork can effectively improve the lateral stiffness,so that the steel beams on the inner and outer sides are more involved in the force.The effect of the permanent steel formwork on the structure increases as the load increases.With the increase of concentrated load,the stress of the concrete slab in the negative moment zone and the increase of the stress of the lower flange of the steel beam doubled.The stress of the concrete slab in the positive moment zone and the stress increase of the lower flange of the steel beam also doubled.(4)Through the design of the static load test of the I-steel-concrete composite continuous beam,the intermediate load and the eccentric load of the S2 section and the S6 section are respectively loaded with three stages,and the test load corresponding to the design load is obtained.The law of measured data of various working conditions:The main beam structure is in elastic working state under the action of design load,has a certain safety reserve,and the overall working performance of the bridge is good,and its strength and stifibess meet the design requirements.(5)Based on the creep data of the concrete test block,the creep function of the concrete is obtained by fitting.The creep of the composite beam is calculated by the effective modulus method adjusted by age.The numerical analysis results are basically consistent with the deflection monitoring results,which proves the correctness of the numerical analysis method.The numerical analysis method is used to analyze the stress variation of the cross-section of the I-steel-concrete composite continuous beam.The results show that under the action of creep,the tensile stress of the concrete slab in the negative moment zone is gradually reduced.The compressive stress of the lower flange of steel beam increases gradually;the compressive stress of concrete slab in positive bending moment zone increases gradually,the compressive stress of upper flange of steel beam decreases gradually,and the tensile stress of lower flange of steel beam increases.(6)Using the numerical analysis method to analyze the intermal force change of the I-beam-concrete composite continuous beam stud,the results show that imder the effect of self?weight,the bending moment of the stud is sinusoidal,and the bending moment value at the bearing is larger.The slip of the bearing section is larger;the bending moment of the 3/4 section is the largest and the slip is larger.Under the action of shrinkage and creep,the bending moment of the studs in the small area near the middle pier is gradually increased,while the bending moment of the other sections is gradually reduced.