A Research On Affecting Factors To The Bearing Capacity Of Concrete Column Under The Confine Of Two Layers Of Stirrups

RC column confined using two layers of stirrups is a new type of confined concrete, which can make the core concrete constraints divide into three parts, namely unconfined concrete cover, singly-confined and doubly-confined concrete core. As these features listed above, it undoubtedly for the ductility of the test specimen not only will have been improve significantly, but also can effectively reduce the cross-sectional area of pillars, improve space utilization and have higher project practical value.In order to study the mechanical properties of Restraint Square Concrete column confined using two layers of stirrups under axial pressure, conduct a test with 18 Restraint Square Concrete column confined using two layers of stirrups and describe the state of the specimens in detail, we find that the ductility and strength of the specimens are affected by stirrup characteristic value. The test results show that the ductility of specimens will raise with the increase of stirrup characteristic value, and the intensity of specimens has little relationship. Through studying fiber reinforced concrete specimen with different content of fiber under the same strength, the study find that the fiber content has obvious effect on ductility and strength of the specimens. By introducing the concept of the average effective constraint confining pressure, we set up double stirrup stress-strain of confined concrete formula,compared with the experimental curve, and proved that the formula can satisfy the required precision of test.