Analytical Solution On Flexural Performance Of Composite Beams With Cast-in-Place Concrete Slabs On Precast Prestressed Concrete Decks

The research process of composite beams has been intense,and the theoretical development of corresponding composite beams is also vibrant.The main composite beam theories are divided into Euler-Bernoulli beam theory,Timoshenko beam theory and high-order beam theory.The Euler-Bernoulli beam theory is often used for steel-concrete composite beams.In addition,the commonly used models for predicting the combined structure are mainly divided into the numerical simulation,(semi)empirical formulas,and analytical solutions.A steel-prefabricated ribbed concrete composite slab is a new attempt at composite beams.It uses a prefabricated ribbed concrete floor and cast-in-place concrete to form a concrete composite slab,and the other parts are the same as the traditional cast-in-place concrete composite beam.The laminated composite beam not only has the advantages of conventional composite beams but also because of the use of precast concrete slabs.It has the advantages of saving high-altitude formwork and formwork and reducing on-site wet work.Through the test of steel-prefabricated ribbed concrete composite beams,it is found that the steel-prefabricated ribbed concrete composite beams have different mechanical performances from the traditional cast-in-situ composite beams.In this paper,11 full-scale steel-prefabricated ribbed concrete composite beams and one steel-full cast-in-situ concrete composite beam were loaded at two points.The bending moment-deflection curve at the mid-span of each group of specimens was obtained.The main test parameters in this test are the thickness of the laminated concrete slab,the shelving length of the precast concrete floor placed on the steel beam,the spacing of the shear studs,the diameter of the longitudinal reinforcement in the laminated concrete slab,and the placement direction of the ribbed concrete slab and whether it is a cast-in-place concrete slab.The bending moment-deflection curve of the composite beam,firstly,applies national codes to estimate the bending moment-deflection in the elastic phase.It is found that the Chinese standard,European standard and American standard all bias the rigidity estimation of the composite beam to the complete shear connection.For the rigidity of composite beams,the national codes only predict fully cast-in-place concrete slab composite beams.However,the national codes cannot make reasonable estimates for the composite slab composite beams after the above test parameters have been changed.In addition,OpenSees finite element simulation is carried out for the test.Since the concrete slab and the steel beam in the composite beam meet the assumption of the plane section of their respective sections,the two-layer nodes are designed according to their different sections.The difference between the different shear spring elements connecting the upper and lower nodes is analyzed.After comparing the ZeroLength,ZeroLengthSection and TwoNodeLink,the TwoNodeLink element is selected based on the OpenSees curve simulation results and the simplification of the command flow.The simulation results found that the OpenSees simulation results are only ideal for fully cast-in-place composite beams and can more accurately predict the flexural rigidity of fully cast-in-place composite beams.However,there is still a certain gap for the composite beam of the composite plate,and the variable changes in the composite beam of the composite plate cannot be adjusted.In studying the stiffness reduction method that considers slippage used in the Chinese code,it is found that it cannot be directly applied to composite beams of laminated slabs.This is equivalent to the European wooden structure standard used in wood joint beam and cross laminated timber(CLT).The stiffness method was studied again,and it was found that the direct application of these two theories could not describe the mechanical properties of composite beams.After reviewing the two theories that have analytic solutions to the previous composite beams,a segmented combination theory is proposed.It is assumed in the combination theory that the gradual decrease in the stiffness of the composite beam is caused by the gradual reduction of the combined action provided by the shear connectors.After applying the combination theory,it is found that the combination theory can be used not only for the composite beams with a complete shear connection design but also for the composite beams with a partial shear connection design.