Study On Shrink,Creep And Expansion Compensation Of Large Diameter Concrete Filled Steel Tube

Concrete Filled Steel Tube(CFST) is a type of composite structure material that the concrete is filled into thin-wall steel circular steel tube. The fire-resisting limit of CFST components is longer than steel structure and execution of works is easier, together with high bearing capacity, good plasticity and ductility. In recent years, With the construction technology developing and high-performance concrete technology innovating, Concrete filled steel tubular structure was used in great quantities in high-rise buildings. Such as Saiger Plaza in Shenzhen,Diwang building,Beijing world financial center, Jin Yuan building in Fujian,the second-phase extension project of Xianyang international airport, etc. With the development of top,super-tall and bridge structure, the large diameter steel tube concrete work performance study more and more urgent. Along with the increase of steel pipe diameter, if the pipe and the core concrete can work together become a central topic. The concrete shrinkage and creep when the structure under the long-term loads, can make the pipe and concrete cannot woke together. Steel pipe diameter, their impact is more significant. At present, the main method is added Expanding Admixture in the core concrete to counter shrinkage and creep influence and change rapping.Based on extensive reading of references, Introduced the shrinkage,creep concept,the main factors of influence creep and creep analysis theory. Determine the steel tube concrete shrinkage and creep theoretical calculation formula.Introduces the Expanding Admixture applicable range and classification. Contrast Ettringite Expanding Admixture and MgO Expanding Admixture, determine the expansion of the performance Expanding Admixture.Based on the effect of linear regression formula flow theory calculate theory creep values. the method of variable temperature structure analysis is used to simulate the deformation of the Expanding Admixture. Found that as the increasing of the pipe diameter, steel tube concrete creep values decrease. Secondly, with the admixture of Expanding Admixture increasing, limit inflation getting bigger, expansion effect is remarkable. When the admixture is same, along with the diameter of pipe, the reducing range of expansive pipe center's stress is not too much change. For the more than 2000mm pipe diameter, admixture of 12% can enough to compensate for the shrinkage and creep values. Therefore, in actual engineering, the admixture of more than 12% and less than 8% can't experiment. It can greatly reduce experiment time,materials and other fees.