Analysis Of Flexural Capacity Of Existing Prestressed Concrete Hollow Slab Beams

Prestressed concrete hollow slab girders are widely used in small and medium-span bridges in China because of their advantages such as convenient construction,simple manufacturing,saving engineering cost,and mass production.However,with the increase in service time and the increasing traffic volume,these bridges have caused some diseases under the combined effects of the external envirornment and overloaded vehicles.Therefore,the research work on the bearing capacity of existing bridges is particularly important.It has important theoretical value and practical significance for guaranteeing the safe transportation of transportation vehicles and advancing the steady and rapid development of China's highway traffic.In this paper,on-site destruction tests and modal tests of 4 prestressed concrete hollow slabs with a span of 16m have been conducted for 20 years and a nonlinear finite element model has been established.The finite element model of the elastic phase is modified using a neural network.The main research results can be summarized as follows:(1)The static displacement analysis values of the finite element model modified by BP neural network and RBF neural network are in good agreement with the experimental values.The elastic modulus of steel strands is basically the same as that of the tensile test.(2)The established nonlinear-finite element model better simulates the whole process of elasticity,cracking and failure of the test beam.The strain of steel strand increases linearly with the increase of load in the elastic stage,and the closer the strain is to the loading point,the greater the strain is.The strain at the same cross-section of the strand under the same load varies with the length of the effective segment.The longer the length of the effective segment.the greater the strand strain.(3)The theoretical calculation formula of the natural vibration frequency of simply supported beam with unequal prestressing tendon is deduced.Through the modal test and finite element simulation of PC hollow beam,it is verified that the formula is reasonable and accurate for calculating the first two-order natural vibration frequency.Analyze the relationship between the natural vibration frequency and bending stiffness of the test beam.Combining with theoretical calculation formula and finite element model,the influence of prestress value and eccentricity of prestressed tendons on the natural frequency and bending stiffness of such simple supported beams was analyzed.