Investigation of a Permanent and/or Emergency Seismic Retrofit Technique for RC Columns and Walls

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The development of permanent and/or emergency seismic retrofit technique is a common issue in earthquake hazard field all over the world, and it will be an important topic for the twenty-first century. A large variety of walls, such as, shear walls, spandrel walls and wing walls are often constructed in low-rise or medium height RC frame buildings in Japan. On the other hand, it is well known that transverse confinement of concrete contributes to the enhancement of strength and ductility of concrete. Considering this fact, a seismic retrofit technique of RC columns only or RC columns attached with secondary walls, such as, spandrel or wing walls, by utilizing pre-tensioned high strength steel bars, steel plates and steel angles were proposed in this research. Because of pre-tensioning, the method generates active confinement in addition to conventional shear reinforcement and passive confinement. Furthermore, as an emergency retrofit of the earthquake-damaged RC columns, this method se … More ems to be suitable, because the seismic retrofit can be conveniently and rapidly applied without heavy machinery as a dry construction method. The main research results are summarized as follows :1)By using PC rods and corner pieces through which tensile force was applied, the seismic retrofit of the independent RC column was proposed. This retrofit converts the extreme short column which causes the brittle shear failure into the flexural yielding column which is rich in the ductility.2)In addition to the steel plates or angles, the tensile force applied into PC rod which is directly united firmly around the column surface, the elastoplastic behavior of the retrofitted column under high axial force can be improved drastically.3)The reinforcement which improves not only the ductility but also the both strength and ductility for columns with secondary walls and framed shear walls was proposed.4)The method which reinforces the independent column by applying tensile force into the PC rod, is the dry method. Considering this fact, this reinforcement can also be applied effectively to the emergency retrofit of RC column and remedial work immediately after the earthquake disaster.5)A fiber model analysis including nonlinear shear force-distortion relationship was also tried and analytical examples were presented.6)Axial compression, pure bending and bond behavior of RC columns retrofitted by pre-tensioned PC rods were investigated and the effect of PC rod prestressing was recognized through the loading tests. Less