Seismic Rehabilitation of Non-ductile Concrete Columns Using Advanced Composite Jacketing

在美国的许多地区，存在着一些建于20世纪50年代和96年代的钢筋混凝土框架结构，这些结构主要是为重力荷载作用而设计的。在地震荷载作用下，这些结构中使用的结构细节可能导致结构的非延性破坏。因此，这些结构的性能被认为是可疑的中等到严重的地震载荷。本研究的重点是这些框架柱的抗震改造，这是它们的非延性行为的主要原因。这些柱在弯曲铰区没有足够的搭接，以及沿构件长度缺乏横向钢筋，使它们容易发生搭接、剪切和轴向弯曲压缩失效。先进的纤维环氧复合材料护套将用于提高这些柱的强度和延性：(1)在搭接区，在接头上产生围压；(2)沿着构件，通过桁架机制提高抗剪能力；(3)在塑性铰区，通过在压缩和增加抗剪能力中限制混凝土来提供延性。将进行实验测试，以评估先进的纤维-环氧复合材料护套改造设计，考虑材料类型、纤维取向、护套刚度、主动与被动护套压力系统以及循环单轴横向载荷与轴向载荷相结合的参数。将夹套改造后的性能与相应的已建非延性柱在循环荷载作用下的性能进行比较。该研究计划将开发实用的方法，成功改造柱使用纤维环氧树脂包覆复合材料，并将制定指南，改造非延性柱，可应用于实践工程师。＊＊＊

9422245 Ricles In many regions of the United States there exists several reinforced concrete frame structures constructed in the 1950's and 1096's which were designed primarily for gravity load effects. The construction details used in these structures can cause non-ductile structural failure under seismic loading. As a result, the performance of these structures is considered suspect for moderate to severe seismic loadings. This study focuses on seismic retrofit of the columns of these frames, which are the major reason for their non-ductile behavior. These column have insufficient lap splices in the flexural hinge zone as well as a lack of transverse steel reinforcement along the length of the member, making them prone to lap-splice, shear, and axial-flexural compression failures. Advanced fiber-epoxy composite jackets will be used to enhance the strength and ductility of these columns: (l) in the laps- splice zone to create a confining pressure on the splice, (2) along the member to enhance the shear capacity through a truss mechanism, and (3) in plastic hinge zones to provide ductility by confining concrete in compression and increasing shear capacity. Experimental testing will be conducted to assess adtanced fiber- epoxy composite jacket retrofit designs considering the parameters of material type, fiber orientation, jacket stiffness, active vs. passive jacket pressure systems, and cyclic uniaxial lateral loading combined with axial load. The performance of the jacket retrofit will be compared with that of corresponding as-built non-ductile columns under cyclic loading. The research program will develop practical methods for successfully retrofitting columns using the fiber-epoxy wrap composite material, and will develop guidelines for retrofitting non-ductile columns that can be applied by practicing engineers. ***