| Because of its outstanding property of being light, high strength and extremelygood durability, Fiber-Reinforced polymer (FRP) has been widely used in the field ofstructural strengthening and retrofitting. In order to strengthen or retrofit a RC frameeffectively, the strengthening of the (Reinforced Concrete) RC columns, which are keycomponents in the RC frame, is very important. According to existing researches onFRP confined RC column, being confined by FRP result in highly improvement in itsseismic performance.Real earthquakes always come in random direction. It means that structure in realearthquake actually suffers from multi-dimension earthquake. For square columns,when suffered from a lateral load which is not in principle direction of its section, thedamage in its two principle directions tend to deteriorate each other, and it obviouslyresults in much worse damage in the column. As to the existing researches on seismicperformance of FRP retrofitted RC column, only few of them take account of the actingdirection of lateral load. Furthermore, most of the existing research used low axialcompression ratio and the tested specimens are small scale model. There has not beenany research on seismic performance of FRP confined full scale RC column. Since theexisting of this research gap, experimental research on seismic performance of FRPconfined large scale RC column under lateral load in various direction was performed.Numerical analysis has also been finished based on OpenSees system, the following isthe brief summary of this project:1. The experiment of10RC square columns (7of which were confined by FRPsheet in the plastic hinge region and3others were controls) under combined reversedcyclic displacement excursion and constant axial load was finished, according to the testresult:(1) when the axial compression ratio kept constant, with the increase of theloading angle, which is the angle between the loading direction and the principledirection of section, there are obvious decrease in both the lateral bearing capacity andductility of the column. It should be taken account of seriously in really project.(2) Forthe column tested with axial compression ratio0.75(which correspond to1.3in realproject), compared to which tested with axial compression ratio0.45, it was noticed that the lateral capacity increased about15%, while the ductility decrease seriously; but itsultra-displacement drift was2.44%, which is larger the limit value in the relative code.2. Successfully finished the developing of material module of FRP confined squareRC column by C++programming based on OpenSees system. After modeling andsimulating the experiment in this project with the developed material module, it wasfound that the numerical result and the experimental result were in good agreement,which in turn verified the accuracy and feasibility of the self-developed material modulefor FRP confined RC square column. Based on the self-developed material module,parameter analyses including350load cases were conducted. In the parameter analysis,effect of load angle, axial compression ratio and the length of FRP wrapped region onthe seismic performance of FRP confined RC column were investigated.3. Results of the parameter analysis indicated that:(1) With the axial compressionratio less than0.4, when the loading angle is0degree, the column got its highest lateralbearing capacity; when the loading angle is30degree, the column got its lowest lateralload capacity.(2) With the axial compression ratio larger than0.4, the lateral capacity ofthe column also reached its highest value when the loading angle equaled to0, but thelowest-lateral capacity angle would be45degree.(3) For RC square column of whichthe shear span is larger than3.0, only by retrofitting its plastic hinge region will increaseits seismic performance to a desired level. |
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