Study On Seismic Performance Of RC Column With High Compressive Ratio Retrofitted By Prestressing Steel Strips

In the practical project, many existing reinforced concrete buildings are seismicallydeficient due to dangerous old buildings to fill strong, changes in code, poor detailingpractice, extend the building use fixed number of year, rezoning of seismic intensity. Inorder to retrofit seismically deficient buildings, the principle, which comes frompackaging engineering, of the pneumatic bundling machine with steel strips strapsobjects through the air pressure tensioning steel strips is applied to seismic retrofit ofthe structure, so the method is proposed to make use of external prestressing steel stripsto retrofit rectangular RC columns. Retrofitted by prestressing steel strips have anumber of advantages, including: superior properties in high tensile strength, lightweight, superior to corrosion, and ease to mechanization, low manpower, virtuallyunnoticeable after installation.Four rectangular RC column specimens (one, which is not retrofitted, as builtspecimen and three retrofitted specimens) have been tested under cyclic loading toinvestigate the seismic performance of columns by retrofitted with prestressing steelstrips. The main variable of this test are axial compressive ratio n, steel strips spacing s.The paper mainly studies through these two parameters:(1) the seismic performance ofthe RC columns retrofitted by prestressing steel strips;(2) the effects of axialcompressive ratio n and steel strips spacing s on the seismic performance of theretrofitted RC columns. According to the experimental phenomena and results, thedevelopment of cracks, failure form, hysteretic curve, skeleton curve, deformationcapacity, energy dissipation capacity and stiffness degradation are comprehensively analyzed, that retrofitted by prestressing steel strips can significantly improve theductility and energy dissipation capacity, and slow down stiffness degradation andstrength degradation of the specimens.Based on the experimental study, a restoring force model of retrofitted columnswith prestressing steel strips is proposed, which is capable of considering the effects ofaxial compression ratio and the constraint of prestressing steel strips on thecharacteristics of retrofitted columns with prestressing steel strips. Based on the sectionanalysis and test date, theoretical formulas and empirical formulas are set up to solvecharacteristic parameters of theoretical skeleton curve. Theoretical skeleton curve of therestoring force model of retrofitted columns with prestressing steel strips has a goodagreement with skeleton curve of experimental results.