Investigation On Load-carrying Capacity Of RC Beams Strengthened With Externally Wrapped Shaped Steel

With the service life increasing of existing structures, the mechanical behaviour of structural members gradually becomes deterioration, and it will be possible to result in that the structural members can not meet the requirements of original design and additional loads. The strengthening technique of reinforced concrete structures and the load-carrying capacity of strengthened RC members have become a major concern in the present industry. The strengthening methods for RC members mainly include increasing cross-sectional area, replacement of concrete, externally wrapped shaped steel, externally applied prestress, pasting FRP sheet, etc. Among them, the strengthening with externally wrapped shaped steel has been widely used in the practical engineerings, in which the shaped steel or steel plate is externally wrapped over the surface, corners, or both sides of RC member using the lateral batten plate or ferrule for connection, and the gap between concrete surface and steel plate is infused with high-strength cement mortar or epoxy paste to improve the overall mechanical behaviour of strengthened RC member.Based upon the practical renovation engineering of RC framework strctures for denitrification in Zhejiang Zhoushan power plant, a novel strengthening method on RC frame beam and beam-column connection joint encased with angle steel and steel plate is presented through considering the construction conditions on site and the structural characteristics. The load-carrying capacity and failure mode of strengthened RC frame beam are investigated systematically, and the main research works can be summarized as follows:(1) The constitutive models of concrete material are systematically summarized. In particular, the concrete damage plasticity (CDP) model is studied, and the corresponding material parameters are determined. Based on this material model, the mechanical behaviour and failure mode of RC beam can be well predicted using the software ABAQUS.(2) The basic assumptions on the calculation of the load-carrying capacity for strengthened RC beam are supplemented. The calculation method of hysteresis strain in different loading stages for RC beam strengthened with externally wrapped shaped steel is discussed. Based on this, the calculations of flexural and shear loading-carrying capacity of strenghend RC beam are derived.(3) The corresponding numerical models under concentrated load are established using the finite element software ABAQUS. Through the comparisons on ultimate load-carrying capacity and failure mode of reinforced concrete beam before and after strengthening, the causes concerning the improvement of mechanical behaviour, enhancement of stiffness and ductility, and transformation of failure zone for RC beam are illustrated systematicall, then an improved calculation method of shear load-carrying capacity of RC beam strengthened with externally wrapped shaped steel is put forth.The aforementioned study works can offer a solid theoretical foundation for the renovation and strengthening design of RC structures...