Experimental Research And Finite Element Analysis On The Flexural Property Of Reinforced Concrete Corners-Hole Slab

Reconstruction of old city building has become a hot issue in local governments in our country. Reinforced concrete frame structure composed of wide column and double beams is a new concept in renovating of old buildings. It can be widely used in masonry structure and concrete structure reform of the residential, hotel, hospital, etc, especially can meet the transformation requirements for small space into a large space. Although the structure of system has already widely used in practical engineering, the systematic theoretical research at home and abroad is almost a blank.In the frame structure composed of wide column and double beams underpinning and rebuilding process, based on the consideration of convenient construction, opening holes in four corners of the foor in order to pour concrete of the column and then forming reinforced concrete slab with four corners-hole. Corners-hole slab often appears, but all kinds of literature show that research reports related with the corners-hole slab have not been seen before at home or abroad. Therefore, it is necessary to do some experimental study and finite element analysis on the plastic limit analysis of corners-hole slab. The formation and the position of plastic hinge line with the corners-hole slab under load and its ultimate bearing capacity can contribute to the reasonable assessment of carrying capacity of existing building panel, perfect its design theory and have an important significance for reinforcement and reconstruction of old buildings.Based on the national natural science fund project Research on Flame Structure System of Double Reinforced Concrete Beam and Wide Column in the Old Masonry Underpinning Reconstruction,7 different perforation coefficients of slabs were designed and producted. According to the influence of the size of the hole on flexural properties, the related experimental study and theoretical analysis were carried out. Experimental study of static load was conducted to observe the experiment process and the destructive pattern and study on the cracking load of the specimens, the morphology and development regularity of cracks, the ultimate load, yield line pattern and so on. Based on finite element software ABAQUS, simulation of nonlinear finite element was done and the finite element analysis results were compared with the experimental results. The research results show that for the corners-hole slab simply supported on four sides, steel of the span centre area is yielded first, steel around the holes afterwards and then the yielded range of the span centre area expands to the corners and plastic hinge line is formatted, in the end the top of the corner slab concrete is crushed at approximately 45 degrees along with the plate edge direction. The opening coefficient K has a certain effect on the force performance and failure characteristics of the corners-hole slabs. The cracking load, yield load and ultimate load gained based on finite element analysis method fit relatively well with the test results, which shows that enough accuracy simulation on the static mechanical properties of the corners-hole slabs is conducted based on ABAQUS and the accuracy of the test is also verified at the same time. Using the plastic hinge line method, different yield line patterns are proposed aiming at corners-hole slabs of the different opening coefficient K and the calculation formula of ultimate bearing capacity is established according to the principle of virtual work method, which shows that the proposed yield line patterns are reasonable and feasible, the established calculation formula of ultimate bearing capacity is applicable, and in the end a linear regression equation is obtained by introducting a coefficient related to the opening coefficient K and the plastic hinge line patterns are simplified.