Research On Mechanical Properties And Construction Process Control Of New Cast-in-place Prestressed Composite Sla

With the continuous improvement of China’s social living standards,higher requirements have also been put forward for the construction industry.The prefabricated building adopts modern manufacturing and assembly technology,which makes the building modular,standardized and industrialized,improves the production efficiency and replaces the backward production mode in the past.Prefabricated building adopts a series of processes such as digital design and manufacturing,on-site simplified construction,etc.which reduces the construction cost and carbon emissions at the same time.Therefore,prefabricated building are of great significance for protecting the environment,improving building performance and promoting green and sustainable development.The cast-in-place layer prestressed composite plate is a new type of floor structure composed of cast-in-place concrete composite layer,truss reinforced concrete composite plate,low relaxation prestressed steel strands,and ordinary steel bars.It is equipped with bidirectional low relaxation prestressed steel strands below the neutral axis,and the cast-in-place layer concrete forms a whole with the prefabricated bottom plate to jointly bear the upper load after setting and hardening.When the prestressed reinforcement is tensioned to the controlled stress,it increases the overall stiffness of the structure,making it characterized by high overall stiffness,good crack resistance,and high bearing capacity.In this thesis,static load test was concucted on prestressed composite plates and concrete composite plates applied to cast-in-place layers in practical engineering,and the deflection,crack development law,concrete surface and reinforcement strain were analyzed.Studied the mechanical performance of laminated plates and cast-in-place layers with pre-stressed laminated plates.The finite element software ABAQUS was used to simulate and analyze the prestressed composite plates with cast-in-place layers under load.Based on the strip method and short-term stiffness method,the construction process of applying prestressed composite plates to the cast-in-place layer was analyzed.The main content is as follows:(1)Through the comparative test,it is found that the prestressed composite slabs of cast-in-place layer have good mechanical performance under the action of load,and the bearing capacity meets the requirements in the normal use stage.(2)The variation and development characteristics of cracks,deflections,upper and lower surface strain of concrete and reinforcement strain of composite slabs under load are studied.The test shows that the prestressed composite slabs of cast-in-place layer are in an elastic state before cracks appear in the concrete floor.When the first crack appears in the floor,the load-deflection curve decreases slightly,and the growth rate of deflection begins to accelerate.The load-deflection curve grows slowly along the long span direction,and the prestressed composite slabs of cast-in-place layer have good deformation coordination performance.Compared with concrete composite slabs,the cracking load of cast-in-place prestressed composite slabs is greatly increased and the crack width is smaller.The crack development law of cast-in-place prestressed composite slabs shows a certain bidirectional mechanical performance.(3)Under the influence of joint joints,the stress concentration of concrete composite slabs at joint joints and the strain value of reinforcement is much greater than that of concrete in cast-in-place layer,and the influence of prestressed composite slabs in cast-in-place layer is less.(4)On the basis of the static load test,the prestressed composite plate of cast-in-place layer under vertical load is analyzed based on the ABAQUS finite element analysis software.The simulation values are in good agreement with the test values.It is verified that the new composite plate has the characteristics of high initial stiffness,high bearing capacity,crack resistance,coordinated deformation and good mechanical performance.(5)According to the deflection,crack control grade and bearing capacity control requirements of the prestressed composite slabs applied in cast-in situ,and according to the secondary stress characteristics of the composite slabs,the function and safety of the composite slabs when there is no support in the installation stage are analyzed,and the temporary support scheme in the installation stage is proposed,considering the safety checking calculation in the normal use stage of prestressed loss.The security checking calculation of each stage in the construction process of prestressed composite slab must be obtained.