Study On Concentrated Mechanical Behavior Of GFRP Grid Stiffened Concrete Slab

In engineering,it is common for concrete slab components to be constrained on four sides and bear concentrated forces.This type of structure has complex force characteristics and is easy to crack during use.The durability of reinforced concrete structures is poor.Once damaged,it is not easy to replace and repair.In recent years,due to the characteristics of high-strength lightweight FRP,various forms of FRP structural applications to the field of civil engineering,it provides a new way to solve these problems.This paper presents a novel 3D molded FRP grating stiffened concrete slab,FRP structure can provide a stronger tensile strength of the bottom plate when the slab cracking,3D molded grid can provide restraint for the development of internal cracks in concrete,so as to ensure the integrity of the structure to improve the bearing capacity.In this paper,the mechanical performance of the grid-stiffened concrete slab is studied through experimental research,acoustic emission signal analysis and numerical simulation.The main work and conclusions are as follows:1.A comparative static loading test was carried out on different types of grid-stiffened concrete slabs under different working conditions.The results show that the cracks of the plain concrete slab are in the shape of "Y",and the cracks of the grid-stiffened concrete slab are radial from the loading position to the surroundings.The existence of the grid can effectively inhibit the development of cracks and make the strain transition on the section smoothly.The angular lift of the grid-stiffened concrete slab is greater than that of the plain concrete slab,and with the increase of the height of the grid,the total lift is reduced.2.Acoustic emission technology was used for damage monitoring,and the phase space reconstruction of the collected acoustic emission energy time series was carried out.Combined with fractal theory,the acoustic emission signal was processed by C-C method and G-P algorithm,and the correlation dimension of the composite plate was obtained.The characteristic analysis of correlation dimension of different types of plates was carried out.The change of correlation dimension can reflect the failure process of the specimen.The results show that the average value of the minimum value of each channel of the plain concrete slab is between 0.2-0.3,and the average value of the maximum value is between 1.3-2;The minimum average value of each channel of the grid-stiffened concrete slab is between 0.02-0.07,and the maximum average value is between 0.5-1.1;The brittle failure of plain concrete slab is more sudden,and its correlation dimension value is too large.The correlation dimension feature can provide a certain reference for the different failure modes of two different structures.3.The crack propagation model of the grid-stiffened concrete slab was established by ANSYS/LS-DYNA.The development mechanism of cracks in the concrete slab stiffened by the grid was studied.The results show that the internal force is symmetrically distributed before cracking,the maximum value of the internal force is not in the geometric center of the plate,and the stress in the long side is slightly larger than the stress in the short side.In the case of a thin plate,it will cause cracks to penetrate and cause tensile stress on the top of the plate;a grid with a larger height can effectively inhibit the cracks from developing along the thickness of the plate.4.Analyzed the relevant parameters of concrete strength,plate thickness,grid height,aperture,thickness of protective layer,etc.outside the test conditions,and clarified its influence on the mechanical performance of components,and provided a certain reference for the design and application of related components.