Fatigue Performance Analysis Of Precast Segmental Concrete Beam

Assembly is the main feature of bridge industrialization and the development direction of China’s transportation construction transformation and upgrading.At present,the fatigue performance of assembling girder bridge is mainly studied for the transverse connection of multi-piece joint girders,while the fatigue performance of longitudinal precast segmental assembling bridge is relatively little studied.In this paper,based on existing tests,a fatigue benchmark finite element analysis model for precast segmental assembling concrete beam is established,and through experimental verification,a numerical simulation analysis of the whole fatigue process is carried out.A probabilistic model for fatigue life prediction of concrete in precast segmental concrete assembling beam juncture is also established.The main contents are as follows:(1)The fatigue constitutive model and fatigue parameter degradation model of reinforcement and concrete are analyzed.The existing concrete compressive fatigue constitutive model and the fatigue strength degradation formula of reinforcement are improved.Based on large sample test data and classical fatigue S-N curves,fatigue S-N suggested curves for ordinary steel bar and concrete are given,and their accuracy of predicted fatigue life is examined by test data,respectively.A static load finite element model of the precast segmental assembling concrete beam is established,the optimal fatigue constitutive model is selected by the arrangement and combination of fatigue parameter degradation model,and then the fatigue benchmark finite element model is established.The whole fatigue process is numerically simulated and analyzed through experimental verification.(2)Based on the fatigue reference finite element model,the changes of concrete stresses and reinforcement stresses in the precast segmental assembling concrete beam under cyclic loading at various levels were analyzed.The results show that with the increasing of cyclic loading times,the stress of prestressed steel bar and ordinary steel bar increases gradually,the initial growth is faster,and it is smooth after stabilization.The concrete compressive stress is small during fatigue loading,and the concrete tensile stress near the joints shows an overall trend of gradual increase.(3)Based on the concrete plastic damage model,the fatigue damage of precast segmental concrete assembling beam was analyzed.The results show that at the initial stage of fatigue loading,cracks appear at the location of the bottom of the beam in the span.When the fatigue loading increases to a certain number of times,cracks are produced near the juncture and extend toward the loading point with the increase of fatigue times.The damage factor in the compression zone was small and no fatigue damage occurred.(4)Considering that the concrete near the juncture of precast segmental assembling concrete beam is susceptible to damage and there is dispersion in its fatigue life distribution,a method is proposed to predict the fatigue life of concrete in the juncture of precast segmental concrete assembling beam and obtain its failure probability distribution based on the fatigue residual strength probability distribution.According to the probabilistic statistical method,the fatigue life is predicted by using the residual strength distribution under low cyclic loading times of several groups,and the fatigue life failure probability distribution is obtained,and the validity of the method is verified by combining with existing tests.