| The slab-column structure which contains reinforced concrete hollow floor is more and more widely used because of many advantages such as simple architecture, easy to build, increasing the building space utilization, cost-efficient, less form-work, but the forces at the slab-column connections are very complex and the stresses are very concentrated, so it is prone to punching failure, even leading to disastrous consequences. Although domestic and foreign researchers have done a lot of research work on the punching failure problem, no agreements on the understanding of the punching failure mechanism have been reached, and the focus of research are concentrated on the punching capacity,inadequate attention is payed to the punching deformation. In actual project,even if slab-column structure is not as the main anti-lateral force structure, but the slab-column connections must have sufficient deformation capacity to coordinate with the main anti-lateral force structure. Therefore it is necessary to do some in-depth analysis on the punching failure mechanism and deformation capacity of the slab-column connections. The deformation capacity of slab-column connections under vertical loads directly determine its deformation property under horizontal loads, so this paper studies the punching capacity and deformation under vertical loads, the main work and conclusions are as follows:① Based on the existing experimental data this paper has described and compared the three failure modes of the slab-column connections, the essence of these three types of failure has been analyzed from the perspective of punching failure mechanism, which is due to the development of bending cracks leading to reduce the height of compression zone gradually. Finally, the strength of compression-shear area reaches the limit in the case of complex stresses, so the damage happens.② Described six main punching capacity calculation methods, including five kinds of mainstream design specifications: ACI 318-11, GB 50010-2010, BS 8110-97, EN 1992-1-1, DIN 1045-1: 2008, and the widely recognized formulation proposed by DDTheodorakopoulos. Detailed comparative analysis of these six calculation methods has also been done based on a huge number of test data, it shows that due to less factors considered, the results of ACI 318-11 and GB 50010-2010 have a big discrete; Because the factors considered by BS 8110-97, EN 1992-1-1 and DIN 1045-1: 2008 are more comprehensive, from the overall effect in terms of calculation, these three methods are better. With a more substantial basis, the results of the D.D.Theodorakopoulos formulation are good, but lack of consideration for dowel action of the longitudinal reinforcement and size effect of the concrete.③ Collected 203 punching failure experimental data containing the punching deformation of the slab-column connection and established a appropriate database. From the perspective of shear cracks developing mechanisms from bending, layer model theory of compression-shear area and determination of the critical failure surface, this paper constructed a analysis model which can simultaneously calculate the punching capacity and deformation of the slab-column connections.Using the Python language to program the analysis model. Compared the program results with the experimental data, which shows that the analysis model presented in this paper has a good accuracy and can effectively predict the punching capacity and deformation of the slab-column connections. The four major parameters affecting the punching capacity and deformation were analyzed in detail by the model, which can provide some reference value for the improvement of the punching capacity and deformation. |
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