Experimental Study On Seismic Performance Of Reinforced Concrete Frame Columns With Welding Stirrups

The make of weld stirrups is finished by special resistance welding spot welding machine,whose size is in accordance with the design one. It can reduce the steel consumption by usingthe weld stirrups as a result of no steel hook of the stirrup end. Furthermore, it is convenientto pour concrete in construction, especially at the beam-column joints and the steel-intensivezone. Since the weld stirrups have a good performance of, it would not exhibit the decouplingphenomenon like the normal assembling reinforcement. Thus, the core concrete is confinedeffectively, so that the seismic behavior of columns is improved. In this paper an experimentalinvestigation of the behavior of reinforced concrete columns with weld stirrups under lowcyclic lateral reversed loading and a constant axial loading is presented. And effects of thedesign parameters on the seismic behavior of columns are analyzed, such as stirrup mode andaxial compression ratio.A total of nine reinforcement concrete column specimens were designed and tested under lowcyclic lateral reversed loading and a constant axial loading, which included five with weldstirrups and four with normal lashing stirrups．The developing regularity of crack and failurecharacteristics of specimens were observed in the process of loading. By comparing columnswith weld stirrups and the ones with normal lashing stirrups, effects of stirrup mode and axialcompression ratio on load-displacement curves, maximum bearing load, ultimate drift ratio,energy dissipation capacity, displacement ductility, stiffness degradation and strengthdegradation of columns were analyzed. The test results indicate that: it is clear that the failuremode of all specimens is classified as a flexural failure. Compared with the columns withnormal lashing stirrups, the hysteresis curve of weld reinforcement concrete columns is fuller,and the displacement ductility is better, indicating that columns with weld stirrups haveexcellent seismic behavior. Ultimate drift ratio of columns with weld stirrups is a little bigger than those with lashing stirrups. But the stiffness degration and strength degration of the twokind columns are similar.As far as the columns with weld stirrups, energy dissipation of the column specimens, whichare with the same axial compression ratio, is improved with the increase of stirrup ratio, aswell as the displacement ductility. Energy dissipation of the column specimens, which arewith the same stirrup ratio, is slightly improved with the reduction of axial compression ratio,as well as the displacement ductility. On the basis of experiment research, a restoring forcemodel of reinforcement concrete columns with weld stirrups is proposed, which takes axialcompression ratio and stirrup ratio into account. After the computation, the calculate resultsbased on the proposed model have good agreement with the test results.