Analysis of the Influence of Creep on the Clamping Stress of Concrete Filled Steel Tubular Columns under Axial Compression WANG Yuanfeng, HAN Bing (School of Civil Engineering and Architecture, Northern Jiaotong University, Beijing 100044, China) The method of calculating the tightening stress of members during the creep process, the method was first applied The variation trend of the hoop stress of the member during the creep process is compared with the test results to prove that the method is correct and effective.
The internal working load is about 70% of the ultimate load. For most practical projects, the used load is generally 50% to 60% of the ultimate load. Therefore, only the creep behavior of the CFST in the elastic working range is analyzed.
As a composite component, the steel pipe and the concrete participate in the force, and the steel pipe produces a hoop effect on the concrete. It is precisely because of the existence of the ferrule that the concrete performance of the concrete-filled steel tube has significant characteristics: the elastic range of the core concrete is significantly large, the plasticity is obviously improved, and the strength of the member is greatly improved. However, when the concrete-filled steel tube member is subjected to creep deformation, The tightness of the steel tube to the concrete makes the creep of the concrete filled steel tube very complicated. The creep of the CFST axial compression members is analyzed below.
1 Considering the compressive hoop stress, the creeping concrete-filled steel tubular members of the CFST axial compression members are subjected to long-term load, and the cross-section stress is redistributed according to the creep of the CFST.
Since there is no new external force, this redistribution is only a redistribution of the internal stress of the system, and does not affect the external load, so there is an amount of the upper axial internal force.
Pp=the amount of the tightening force after the axial deformation coordination condition; T is the steel content of the concrete filled steel tube; Es is the elastic modulus of the steel; *s is the Poisson's ratio of the steel, taking 0 283 in the stress Under the action, the core concrete is transformed into the theory and the c is the creep degree of the concrete. According to the theory of the secondary effect flow, the specific value can be considered considering the influence of the lateral deformation of the concrete filled with concrete, which is *cp,2 For the radial effective creeping Poisson's ratio of concrete, the formula is the initial stress of the creep calculation formula of the concrete-filled steel tubular axial compression members considering the tightening effect.
The result is in good agreement with 5.
Table 1 The following calculations are used for the following calculations: the inner diameter of the steel pipe is 108 mm, the steel core of the C4Q steel pipe is 16Mn, and the elastic modulus E=206K1tfMPa yield strength / y = 315 MPa.
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