| 摘要 |
A large number of existing reinforced concrete structures, such as buildings and bridges, if subjected to abnormal loads, such as those expected during earthquakes or bomb blast, may experience significant inelasticity in their critical regions. It is economically not feasible to replace the entire existing infrastructure with new and improved structures; retrofitting provides the only solution to the problem of seismically and otherwise structurally deficient existing structures. A new retrofitting process has been developed to improve strength and deformability of existing reinforced concrete columns. The process involves determining column critical regions, identifying critical stresses that may lead to brittle shear and/or compression failures, determining external prestressing to overcome some of these stresses and to provide lateral confining pressure to improve the ductility of compression concrete. External prestressing is provided by placing prestressing hoops around the column at predetermined locations. Each loop includes a strand that encircles the column with its ends fixed under tension to an anchor. The invention is applicable to concrete columns of any geometric cross-section. For circular columns prestressing may be applied directly on the surface of the column by the strands. For columns with rectilinear geometry such as square, rectangular and other polygonal cross-sectional shapes, additional hardware is necessary between the strand and the flat surfaces to distribute the prestressing force as evenly as possible on the surfaces of the column. External protection of hardware against corrosion, fire and vandalism may be carried out by means of fiber reinforced or plain concrete jackets, shotcreeting or similar sprayed applications of cement based materials, and different types of paints.
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