扣件式高大模板支架初始缺陷计算方法研究

发布时间：2018-04-20 16:08

本文选题：扣件式高大模板支架 + 初始缺陷　；参考：《重庆大学》2014年硕士论文

【摘要】：扣件式钢管是目前我国建筑业大跨度、高空间模板施工中通用的支架结构，虽然针对扣件节点刚度、搭设参数对架体极限承载力的影响进行了深入研究，但近年仍发生了大量的模板坍塌事故，表明当前的研究还不能满足实际工程的需要。本文选取模板支撑架体初始缺陷对架体承载能力的影响为研究对象，对架体中存在的各种缺陷进行详细分类，采用有限元模拟计算手段分析各种初始缺陷对架体极限承载力的影响程度，并对现有的三种初始几何缺陷计算方法进行对比分析，最后利用ANSYS和MATLAB GUI功能编制初始几何缺陷的计算软件，，为施工现场考虑初始缺陷对扣件式钢管支架结构的影响提供技术手段。论文的主要研究内容和研究结论包括： ①将扣件式模板支撑体系中存在的初始缺陷按力学缺陷、材料缺陷、搭设参数偏差和初始几何缺陷进行分类。建立了典型模板支撑架体有限元模型，通过ANSYS分析的结果表明，力学缺陷中半刚性节点由铰接变化为完全刚性连接时，架体极限承载力值提高了约5.68倍；材料缺陷中钢管壁厚由3.96mm降低至3.24mm时，架体极限承载力值降低6.66%左右；初始几何缺陷值由5mm增加至20mm时，架体极限承载力值将降低15.32%；因此，架体的极限承载力值对力学缺陷、材料缺陷和几何初始缺陷均较为敏感。 ②因扣件式节点半刚性力学性能及其在整体架体中的作用已进行了较为深入的理论和试验研究，故采用在有限元模型中直接纳入半刚性节点的方法来考虑实际模板架体的力学缺陷，并给出了相应的有限元建模方法和参数取值。 ③通过材料缺陷和几何参数偏差对架体极限承载力值的概率分析表明，在钢管壁厚、外半径等材料缺陷以及立杆步距等搭设参数偏差中，钢管壁厚的影响最为显著，所以采用对规范中承载力验算公式加入修正参数的方式考虑其不利影响，修正参数的取值按施工现场壁厚的实测数据确定； ④针对直接缺陷分析法、一致缺陷（特征）模态法和假想水平力法这三种初始几何缺陷计算方法，对比其在不同因素（节点半刚性值、立杆步距等）作用下模板支撑体系极限承载能力的差别及变化规律，^w以规范规定的最大允许偏差为标准，确定了三种计算方法中的等效初始缺陷参数的设置。将三种计算方法得到的结果进行了对比分析，表明三种计算方法考虑初始几何缺陷后得到的架体极限承载力值比较一致，差别不大，能满足工程精度要求。 ⑤基于ANSYS的参数化建模技术和MATLAB GUI功能编制了考虑扣件式高大模板支架初始缺陷的计算软件，为施工现场管理人员准确计算其极限承载能力提供了技术手段。
[Abstract]:Fastened steel pipe is a common support structure in the construction of large span and high space formwork in our country at present. Although the influence of fastener joint stiffness and setting up parameters on the ultimate bearing capacity of frame is deeply studied. However, a large number of formwork collapses still occur in recent years, which indicates that the current research can not meet the needs of practical engineering. In this paper, the influence of the initial defects of the formwork supporting frame on the bearing capacity of the frame is selected as the research object, and the various defects in the frame are classified in detail. The influence of various initial defects on the ultimate bearing capacity of the frame is analyzed by means of finite element simulation, and the three existing calculation methods of initial geometric defects are compared and analyzed. Finally, the calculation software of initial geometric defects is compiled by using ANSYS and MATLAB GUI functions, which provides a technical means for considering the effect of initial defects on fastener steel pipe support structure in construction site. The main contents and conclusions of this paper are as follows: The main contents are as follows: 1. The initial defects in the fastener formwork bracing system are classified according to mechanical defects, material defects, setting parameter deviations and initial geometric defects. The finite element model of the typical formwork bracing frame is established. The results of ANSYS analysis show that the ultimate bearing capacity of the frame is increased by about 5.68 times when the semi-rigid joints are changed from hinged joints to complete rigid connections. When the wall thickness of steel tube decreases from 3.96mm to 3.24mm, the ultimate bearing capacity of frame decreases by about 6.66%, and when the initial geometric defect value increases from 5mm to 20mm, the ultimate bearing capacity of frame decreases 15.32. Therefore, the ultimate bearing capacity of frame is related to mechanical defects. Both material defects and geometric initial defects are sensitive. (2) the mechanical properties of fastener joints and their role in the integral frame have been studied theoretically and experimentally. Therefore, the semi-rigid joints are directly incorporated into the finite element model to consider the mechanical defects of the actual formwork frame, and the corresponding finite element modeling method and parameter selection are given. Through the probability analysis of material defect and geometric parameter deviation to the ultimate bearing capacity value of frame body, it is shown that the influence of steel tube wall thickness is the most significant among the material defects such as steel tube wall thickness, outer radius and the setting up parameter deviation such as step distance of vertical pole. So the unfavorable effect is considered by adding the modified parameters to the calculation formula of bearing capacity in the code, and the value of the revised parameters is determined according to the measured data of the wall thickness in the construction site. (4) for the three initial geometric defect calculation methods, the direct defect analysis method, the uniform defect (characteristic) modal method and the imaginary horizontal force method, the different factors (node semi-rigid value) are compared. According to the maximum allowable deviation stipulated in the code, the setting of equivalent initial defect parameters in the three calculation methods is determined according to the difference and variation law of ultimate load-bearing capacity of formwork bracing system under the action of standing bar walking distance etc. The results obtained by the three calculation methods are compared and analyzed. It is shown that the ultimate bearing capacity of the frame obtained by the three calculation methods after considering the initial geometric defects is consistent and has little difference, and can meet the requirements of engineering precision. 5. Based on the parameterized modeling technology of ANSYS and the function of MATLAB GUI, the calculation software considering the initial defects of fastener type high formwork support is developed, which provides a technical means for the construction site managers to accurately calculate their ultimate bearing capacity.
【学位授予单位】：重庆大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TU755.2

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