Study On The Structural Performance Of Fastener Formwork Support System With Initial Imperfection

With the rapid development of the modernization of cities in China, fastener formwork support system has been widely used in the project, and its safety and stability strongly guarantee that construction goes well. However, it is often ignored since it is used temporarily and collapse accidents take place frequently. Therefore, its safety is increasingly valued in the project.Fastener formwork support system which has imperfections such as initial bending and abradant wall thickness in the process of being repeatedly used for a long time has great impact on structural properties. However, detailed index of formwork support system's imperfections which result from being used repeatedly is not mentioned in the specification. This paper explores the state of steel pipe's outer diameter, wall thickness and initial bending and examines distributions of measured data by statistically analyzing the measured data of formwork support system. And besides, it also analyzes the impact of formwork support system with rigid connection and semi-rigid connection on the structure and discusses the impact of initial imperfection(outer diameter, wall thickness and initial bending of steel pipe) on the ultimate bearing capacity and other performance of scaffold by using finite element software. And the conclusions are as follows:(1) The ultimate bearing capacity of formwork support system will go down with the decrease of connection's rigidity; and the ultimate bearing capacity of formwork support system with semi-rigid connection is 45.41% lower than that of scaffold structure system with rigid connection. Therefore, the design's reliability will improve by calculating ultimate bearing capacity of semi-rigid connection.(2) Study on the nonlinear analysis of scaffold structure reveals that X-bracing near the corner evolves into yielding phase at the forefront and loses bearing capacity first, therefore, pole setting in the corner and neighboring X-bracing should be the key reinforced parts.(3) On the premise of scaffold with semi-rigid connection, the ultimate bearing capacity of formwork support system grows up with the increase of outer diameter in the simulation experiment; similarly, it also ascends with the increase of wall thickness. Therefore, the stability of formwork support system will be greatly improved by controlling the size of outer diameter and wall thickness of steel pipe.(4) The ultimate bearing capacity of formwork support system will drop off significantly if imaginary horizontal force is exerted on the structure; the ultimate bearing capacity of formwork support system will be 24.14% lower if 1% ultimate load is exerted on the structure; and designer can get the initial imperfection by exerting 1%~2% ultimate load on the structure when designing construction.