Global Stress Analysis Of High Formwork Support System Of Fastener-Style Steel Pipe For Cast-In-Place Concrete Structure

With the highly development of the city construction , high formwork support system has been more and more extensively applied to the cast-in-piace concrete structure. While high formwork support system of fastener-style steel pipe, a style of frame system, is mostly widely used in China recently. However, because of the uncertain and unsafe factors during designing calculation and practical building of this frame, collapses of high formwork support system frequently take place, and meanwhile seriously affect the safety of construction and the performance of building.While the present calculation methods only takes the stability of one step in a single pole of the support system into consideration, but presents no specific calculation requests of high supporting pole, and fails to think over the mechanism of interaction between each pole of the formworksupport system. Research in this paper is about the alternative rule of the axial force of supporting pole with different support height during the period of casting concrete through field detection. Combining with theoretic analysis, this paper studies the interaction between high formwork support system and concrete structure of main building. Also, it analyzes the entire stability of high supporting system, and presents a theoretical analytic model which can be gradually agree well with the working properties of high formwork support system. Meanwhile, this paper establishes an entire numerical analytic model of high formwork support system. It systemically studies the alternative rule of axial force among vertical struts, horizontal struts and crossing struts, and the interaction between high formwork support system and the main building of cast-in-place concrete structure. Also, the affection of factors including different casting routs of concrete and horizontal loading and the changing of constraint of main structures on the internal force of the high formwork support system has been simulated.The uneven force distribution of high vertical strut and its basically alternative rule are discovered for the first time. The influent rule of horizontal poles and crossing struts affecting on the stability of vertical strut and the properties of casting routs affecting on support system have also been discovered. An improvement of the design calculation of high formwork support system and engineer controlling methods is presentedaccording to the analysis results, and it provides a scientific basis to the safety, high efficiency and economic work of high formwork support system with fastener-style steel pipe. It also provides an available reference to the safety of construction of structure engineer.