Experimental Investigation Of The RC Famed Joints Strengthened With RC Jackets Under Cyclic Loadings

For RC frame structure, with the increase of strengthening and renovation for existingbuildings, the original joints cannot achieve the aim of current standard for earthquake-resistance,which has more rigid requirement. Storey increase and renovation also need seismic strengtheningof joints. In addition, for new buildings, it often happens that there are not enough or even notransverse steels. In a word, research for seismic strengthening of joints is a study subject that hasan important theoretical significance. Strengthening with outer closed RC is a method frequently used in civil engineering. Due to itsreasonable stress, flexible layout and definite load transfer, it is widely applied in thereinforcement of RC structures. Although experts worldwide have done a great deal of work onresistance to bending, shear and earthquake of RC beams or columns strengthened by enlargingtheir sections, joints strengthened with outer closed RC have almost not been studied. The results of a comprehensive experimental program, aimed at providing a fundamentalunderstanding of the behavior of RC joints strengthened with outer closed RC. Three testspecimens were constructed, one of which had no outer closed RC and the other two had differentouter closed RC. The failure process and mode has been observed, and load-displacement curves,cracking and ultimate load, and the strain of longitudinal and transverse steels have been recorded.The results demonstrate that the outer closed RC is an effective method for seismic capacity of RCframe joints. Moreover, space length of transverse steels; length and thickness of outer closed RChave some influence on the effectiveness. The mechanism of RC joint strengthened with outer closed RC is theoretically analyzedaccording to the results of this experiment and reinforced concrete theory; in the same time thesimplified shear strength formula has been proposed by the author, based on which the calculatedvalues agree with the experimental data. In general, it can meet the need of engineering designin practice.