【作者】 袁雪霞；

【导师】 金伟良；

【作者基本信息】 浙江大学 ， 结构工程， 2006， 博士

【摘要】 本文以建筑结构施工期模板支撑体系为主要研究对象,系统地分析和总结了国内外研究现状及发展趋势,并在施工现场调研和试验研究的基础上,对模板支撑体系的扣件抗滑承载力和抗扭性能、稳定承载能力、施工过程中的时变体系可靠性、人为错误发生规律和影响程度、人为错误影响下体系可靠性、以及安全风险评估等一系列问题进行了较深入的研究和讨论。并针对传统蒙特卡罗可靠度分析方法的不足,提出了基于LS-SVM的结构可靠度响应面分析方法。本文的主要研究成果的概述为以下几个方面: (1)根据施工现场的调查研究,较系统地分析和总结了模板支撑体系施工过程中人为错误规律。通过现场数据实测、试验研究和统计分析,建立了钢管外径和壁厚、不同部位扣件螺栓拧紧扭力矩、搭设步距和立杆间距等参数的概率模型,得到了各种人为错误的发生率,确定了对不同扣件螺栓拧紧扭力矩情况下,扣件的抗滑承载力的统计模型和抗扭刚度模型。 (2)在分析现有规范存在不足的前提下,对国内常用的模板支撑体系的稳定承载能力进行了理论分析。基于扣件抗扭性能的试验研究成果,提出了考虑扣件半刚性和初始缺陷影响的三维有限元模型。利用该模型进行线性屈曲和非线性屈曲分析,有限元计算结果表明非线性屈曲的分析方法能考虑诸多不利因素应优先采用,具有一定的安全度。因而采用非线性屈曲分析方法,计算了不同搭设参数下模板支撑体系的稳定承载力。为便于施工人员查询,将模板支撑体系的稳定承载力转换为单杆的计算长度系数。分析了不同初始缺陷、扣件半刚性、扣件拧紧力矩和搭设高度对支模架稳定承载力的影响。 (3)以高层现浇钢筋混凝土无梁楼盖结构为对象,进行钢筋混凝土结构和模板支撑体系相结合施工期结构时变可靠性分析。结果表明施工期结构的失效概率远大于使用期间;模板支撑体系的失效主要受模板底部水平杆与立杆连接处的扣件抗滑承载力控制。同时分析了模板支撑方案和施工活荷载对施工期结构体系可靠度的影响。 (4)大量建筑工程事故表明人为错误是导致结构失效的主要原因之一。在实际数据较少的条件下,通过现场调查、试验研究和相关文献,本文采用了HRA法模拟了混凝土结构和模板支撑体系在施工过程中人为错误发生及其对结构参数的影响。 (5)文中采用了蒙特卡罗数值模拟方法进行系统可靠性的计算和人为错误发生及其对结构参数影响的模拟。为确定人为错误的影响程度,比较分析了无人为错误和有人为错误影响下施工期结构体系的可靠性,并且确定了多层建筑结构模板支撑体系施工过程中的检查重点和控制内容。 (6)为了尽可能地避免事故的发生,对模板支撑体系安全风险评估已成为各施工管更多还原

【Abstract】 The reliability of formwork-supporting system during building construction is one of the most important research areas on civil engineering which have a difficulty and challenge. In this paper, the reliability of formwork-supporting system during building construction was studied on the state of the art for formwork-supporting system, The research works included: slip and torsion capability of right-angle coupler, stability bearing capability of formwork-supporting system, system reliability during construction, human error rates and error magnitudes, and human reliability analysis and safety assessment. Aiming at the reliability analysis problems with implicit performance functions, a response surface method based on LS-SLM was presented. The major contents of this work can be summarized as follows.(1) Making full use of site investigation, human errors during construction of formwork-supporting system were summarized. On the basis of the data of site investigation, probabilistic models for geometric parameter and error rate of formwork-supporting system were established. The probabilistic models for slip bearing capability of right-angle couplers with different bolt tightening torque and torsional stiffness model were obtained through experimental study on right-angle coupler.(2) Considering the state of semi-rigid connection, a calculating model by 3D FEM was established to simulate the formwork support on the basis of experimental study on torsional stiffness of right-angle coupler. Linear and nonlinear buckling techniques were applied to analyze the stability of the formwork supports. Initial imperfection, plastic behavior and large deflection response of the formwork supports were taken into account in the nonlinear analytic model. Numerical results indicate that the linear buckling loads are higher than the nonlinear stability and so it is necessary to use the nonlinear stability solution. Nonlinear buckling analysis was used to calculate stability bearing capacity in the case of different design variables. The results of stability bearing capacity were transferred to effective length coefficients that were generally used in practice. The effect of initial imperfection, semi-rigid connection, bolt tightening torque and total height on stability bearing capacity was studied.(3) In view of the significant failure modes of formwork-supporting system and reinforced concrete member, the reliability of time-dependent system during the construction of typical multistory reinforced concrete buildings was developed by Monte Carlo simulation and interpolation technique. The influence of the number of levels of shoring/reshoring and liveload during construction of the building on system reliability was included in the analysis. It is found that the failure probability of structure during construction are far more than service period, and the failure states of formwork-supporting system are mainly caused by the slip failure of the right-angle coupler which connects the horizontal tube below the formwork with the upright tube.(4) According to numerous building failure investigations, failures due to human error are mainly during building construction. Construction processes are so complicated that it is not feasible to model all possible human errors. Naturally, there is a scarcity of statistical data associated with construction errors. It is important that the human reliability analysis (HRA) can consider the interaction of all error types. On the basis of the investigation on site, the experiment research and relative references, HRA method was applied to simulate the error rates and error magnitudes of the reinforced concrete members and the formwork-supporting system during building construction.(5) Probabilistic and human reliability models were developed in this paper to estimate the probability of structural failure during the construction of typical multistory reinforced -concrete buildings in the presence of human error. To measure the influence of the human error on system reliability, two cases for error-free case and error case were considered. Furthermore the check emphasis of formwork-supporting system was pointed during multistory building construction.(6) To study comprehensive evaluation problems in which criteria values and marks were fuzzy numbers, fuzzy numbers were introduced into grey relational comprehensive evaluation field. By combining the grey relational analysis with the fuzzy sets theory, a new multi-level and multi-attribute grey relational comprehensive evaluation method based on fuzzy numbers was proposed. Utilizing the new method, a standard of construction safety appraisal for formwork-supporting system was presented. This study shows the results obtained by the new approach combined with two distances between two fuzzy numbers, plane distance and lattice distance, are approximate to the result computed by traditional grey relational analysis method. This assessment framework was based on the new approach and a survey among project professionals in Zhejiang Province of China. This proposed framework provides a very useful decision support tool for project managers in assessing the construction safety of formwork-supporting system for their projects.(7) A response surface method based on LS-SLM was presented. Because of its high approximate capacity, LS-SVM was employed to approximate the implicit mapping between structural response variables and basic random variables. LS-SLM was learned by samplesgenerated from orthographic design method and the FEA programs, then validated by selected samples according to their probabilistic distributions. The learned LS-SVM was integrated with Monte-Carlo method to calculate the response variables and then failure probability. The new method can be used to solve the reliability problem in large complex structural engineering. The efficiency and accuracy of the proposed method were proved by typical engineering examples of structural reliability analysis.This paper is supported by research project for soft science of National Construction Ministry "Risk Analysis and its Control of Structure during Building Construction"(05-Rl-13) and research project of Construction Department of Zhejiang Province "Risk Analysis and its Application of Tubular Steel Bearing Scaffold with Coupler during Building Construction"([2003]No.226).更多还原