Research And Application Of The Strengthening And Reforming Methods Of Reinforced Concrete Structures

With the development of economy, the focus of buildings is shifting from many new buildings to building and repairing and now to repairing and reforming of existing buildings. According to statistics, reforming saves investment by 40%, cuts construction time by 50%, recoups capital outlay two or three times faster, than building new ones. Moreover, many new buildings are damaged to different extents by numerous natural disasters, and cannot be put into normal use. Besides, modern developments have left many buildings outdated and unfit in function and use. Lastly, the aging of buildings is an irresistible problem. All these have made building strengthening and reforming an increasingly important and urgent. How to take effective strengthening measures to recover the functions of damaged buildings is an urgent project facing all structural engineers, which also serves the starting point for the present research.The paper summarized the characteristics of strengthening, demonstrated the practical significance of strengthening, offered a comprehensive analysis of concrete beams, plates and columns. The paper, through comparison, also pointed the characteristics and application scope of common methods, such as section expansion, surface shape steel wrapping, plate stressing, support point changes, and surface plate bounding The paper also introduced some computing methods of bending shearing of various strengthening plans.Strengthened elements are second-bending members, whose working mechanism caused concrete stress lapping and priority of steel stress, which results in enlargement of deformation and widening cracks of normal beams when the concrete at the top of beams are cracked, and earlier yielding of the steel stress at the bottom of beams than normal beams. The shear stress checking at the superposition is the key to ensuring that the existing and the new structure work concurrently.The paper also made an analysis of finite element methods of surface stress of beams after partly debounding and discussed the effects of surface stress. Our results show the proper thickness of steel is 4~6mm, checking of the steel thickness in design should be done according to the maxim shear stress, and the suggested thickness of adhesives is 2-3mm so that the effects on surface stress can be reducedLastly, the author, based on his own experience of strengthening projects, introduced the procedures, suggested the key points in design and construction. The author hopes that all these will be of some reference value.