Studies On Experiment And Theory Of Steel Construction Connected With Fasteners

Steel construction system connected with fasteners is a temporary engineering structure, which is assembled with scaffold poles and fasteners and can be installed and dismantled repeatedly. The dissertation takes the fastener-style high-formwork-supports system as the main research object, analyses and summarizes the current domestic and international research situation and development trend, and on the basis of investigation at the construction site and experimental study, it works on the problems of modes of instability and stability capacity of high-formwork-supports system, and carries on comparatively in-depth research and explores the stability theory of the system and designing method of the high-formwork supports, the semi-rigid node, second-order effect and the structure factors that affect stability capacity of the whole frame. The content of the research is mainly the result of a urgently needed project in China, namely, "Construct Technical Research of the Fastener-style High-formwork-supports System", which is taken on by the author. Some of its production has been applied to practical use. The main research production of the dissertation is summarized from the following aspects.(1) According to the investigation at the construction site and the analysis of some typical accidents, it sums up the reasons and characteristics of the accidents in high-formwork-supports system, and proposes effective and feasible countermeasures to prevent such accidents.(2) While lacking the experimental data in high-formwork supports, the author carried on the experimental study of the whole high-formwork supports, and educed the mode of transverse overall instability when high-formwork supports system collapses, and the mode is in good agreement with the numerical results.(3) After analyzing the deficiency of the current criterion , the author carries on theoretical analysis of the stability capacity of the high-formwork supports system which is commonly used in China . The dissertation puts forward the three-dimensional finite element model that takes into consideration the influences of the semi-rigid and initial defect of the fastener on the basis of experimental research results of tensional behaviour of fastener. With this model, the author carries on linear bucking and non-linear bucking analysis, and the result of finite element calculation indicates the method of non-linear bucking analysis should be adopted because it considers a great number of unfavourable factors, and is safe to a certain degree.(4) Since high-formwork-supports system falls into the category of the temporary facility, the material and initial geometry is defect by nature. According to the designing theory of steel structure, the dissertation proposes the designing method of imaginary horizontal force that considers second-order effects, and puts forward the use of generalized imaginary horizontal force to simulate all initial defect of the frame and establishes the finite element model. The comparison between calculation result and experiment result shows the method is feasible and desirable.(5) By establishing the three-dimensional finite element model of high-formwork supports, the author carries on non-linear bucking analysis, and qualitative research on the impact of the stability capacity of factors like vertical pole's span, horizontal pole's step, bridging, a value that is the length of the vertical pole stretching out the top layer of horizontal pole, high-erection of formwork and so on.