Experiment Research And Theory Analysis On Reinforced Concrete Columns Strengthened With Fiber Reinforced Polymer Under Eccentric Loading

In civil engineering, constructions often need to be repaired and strengthened for the reasons such as fault design, improper construct, using function change, design standard improved, building aging, natural calamity and accidents. In recent years, fiber reinforced polymer (FRP) as a new material used in strengthening concrete structure rise in our country gradually. It has drawn common concern in civil engineering area all over the world, and has been considered to be the most prospect method in strengthening, because FRP have many advantage such as low weight, high strength, easy to construct, corrosion resistance, little influence on structure. FRP has been widely applied to civil engineering abroad, the application in our country, however, has been very limited.Based on the destructive tests of 16 columns strengthened with FRP under eccentric loading, the influence on strengthening effect is analyzed with the parameters such as FRP layer, FRP kind, preload, unload, anchor width and anchor space. The results indicate that the bearing capacity of the specimen increased remarkably when strengthened with longitudinal FRP; with the increase of FRP layers, the bearing capacity increased, but it is not in linear relationship; CFRP is superior to GFRP in improving the bearing capacity of the columns, i.e. the higher the tensile strength of the FRP is, the better strengthening effect achieved; the magnitude of lag strain is the key factor to the strengthening effect of structure in secondary load, so it should unload as much as possible before strengthening, but it is unnecessary to spend a large number of manpower and money to unload totally, only unload to 40% can be obtain good result; it is necessary to take reasonable additional anchor to columns strengthened with longitudinal FRP, it can not only improve the strength of the columns, but also improve the ductility of the columns. With the same quantity of anchor, the more the anchor divided, the smaller the width is and the less the space is, the better result can be gain.Finally, based on the test results, the formula of calculating the strength of the reinforced concrete columns strengthened with FRP under eccentric loading is proposed, and good agreement between test and theoretical results is achieved. So, it may supply refers to the designer when strengthening.