【作者】 魏巍；

【导师】 白绍良；

【作者基本信息】 重庆大学 ， 结构工程， 2004， 博士

【摘要】 钢筋混凝土结构考虑二阶效应的非线弹性强度性能和非线弹性稳定性能的理论认识对工程设计具有重要的指导意义。虽然各国学术界近年来在一般意义结构的二阶效应强度及稳定研究方面已取得诸多关键性进展，但针对钢筋混凝土结构的特点，在这一领域仍有一系列重要问题有待澄清，以便进一步改进目前从理论上尚不完全确切的设计概念和经验性过强的设计方法。本论文在我国国家设计标准《混凝土结构设计规范》本轮重要修订需要的推动下，对这一领域若干有待解决的问题进行了分析和试验研究，取得了以下有一定学术进展和创新性的研究成果： ① 在利用计算机模拟分析对不同偏心距钢筋混凝土压杆考虑二阶效应影响的强度和稳定性能基本规律作了较全面模拟分析的基础上，明确指出了考虑二阶效应的细长偏心压杆应以其能够发挥出最大轴向承载力的曲率状态作为主导承载能力极限状态，从而有必要新增细长杆件的轴向最大承载力验算条件。本论文在识别了细长钢筋混凝土偏心压杆从强度失效到稳定失效的过渡规律后，以经过试验验证的非线性模拟分析结果为依据，给出了细长偏心压杆同时适用于强度失效和稳定失效的连续过渡的极限承载力验算公式。 ② 在对框架柱非线弹性稳定失效规律进行分析的基础上，首次给出了由上述极限承载力表达式、杆件的等效长度l₀和杆件偏心距调整系数C_n三者组成的“有侧移”和“无侧移”框架细长柱稳定失效承载能力验算体系，并根据稳定验算中承载力等效的原则给出了偏心距调整系数C_n的明确定义。这一实用方法的有效性已经通过系列非线性有限元分析结果进行了检验。 ③ 在对“有侧移”和“无侧移”框架二阶效应规律进行了较充分、较全面分析的基础上，首先明确指出了欧共体国家和我国混凝土结构设计多年来使用的柱偏心距曲率表达法在“有侧移”框架情况下存在的最大问题是所采用的“极限曲率”与实际形成P-△效应的引起框架侧移的截面弯矩不相呼应。针对此问题本论文提出了对采用η曲率表达式的η-l₀设计法的全面调整建议。经考虑非线性的结构二阶分析验证，所提方案能有效纠正原方法存在的偏差，明显改进了设计质量。另外，还首次查明了由弹性失稳临界状态杆件挠曲特征经分离杆件法确定的“等效长度”l₀在“无侧移”框架中与实际二阶效应规律在某些特定情况下的严重不协调性和在“有侧移”框架中导致不准确性的主要来源，并建议了有关调整措施。 ④ 对本学科点原自编的基于刚度法的杆系结构非线性有限元分析程序NLACF作了进一步改进和优化。通过不同情况下使之在平面弧长法、柱面弧长法和简单重庆大学博士学位论文位移控制法之间进行切换的手法，使之能有效模拟细长钢筋混凝土单杆和杆系结构的考虑二阶效应的强度失效特征和稳定失效特征。本论文还利用自已完成的受力较复杂的门式框架试验结果和本学科点完成的特细长柱失稳试验结果和各种弯矩分布的偏压单柱试验结果对该程序的模拟效果作了多方位检验，检验结果令人满意。 ⑤在利用非线性模拟程序对各个工程实例中框架梁、柱实际非弹性受力状态相对应的“当量弹性刚度”逐一进行计算的基础上，通过对比分析给出了用于我国《混凝土结构设计规范》考虑折减刚度的弹性二阶分析法中的梁、柱统一刚度折减系数的合理取值建议。该建议方案已为规范采纳。更多还原

【Abstract】 The guidance of theoretic recognition to second-order effect about nonlinear strength and stability characteristics becomes more important for RC members in structural design. Although research on second-order effect for ordinary structural strength and stability problems has been made progress recently, there remains a series of important problems needed to clarify, in order to improve the design methods which are now ambiguous in conception and reply heavily on empirical experience. The research in this paper was driven by the revision of China Standard "Code for Design of Concrete Structure". From the analytical and testing results, this paper made some academic progress as follows.(1)Computer simulation of RC compressed members with different eccentricity was carried out, with strength and stability rules considering second-order effect taken into account. On this basis, the ultimate curvature corresponding to the maximal axial loading force as the main bearing capacity state is proposed. So it is necessary to add the check condition of axial loading force capacity for slender members. After identifying the rule from strength to stability failure of slender RC eccentricity compressed member, the ultimate bearing capacity check formula from strength to stability failure of such members is proposed, based on the nonlinear simulation results which were verified by testing results.(2) On the basis of analysis of nonlinear stability failure rule, the check system consisting of ultimate bearing capacity formula, the member’s equivalent length, and the eccentricity modification factor Cn, is established for sway and no-sway frame’s slender columns. According to the criteria of equivalent bearing capacity, the definite definitions of eccentricity modification factor Cn is proposed. The effectiveness of this method has been evaluated by a series of nonlinear finite element simulation analysis.(3)Based on the comprehensive analysis of second-order effect of sway and no-sway frame, the ultimate curvature adopted in the column’s eccentricity curvature formula is not corresponding to the frame sway moment caused by the P effect in Europe and our country’s RC structure code, In allusion to these problems, an improved suggestion of method adopting 77 curvature formula is presented. Verified by the nonlinear second-order structural analysis, the suggested method agrees well. In addition, it is also found for the first time that the equivalent length derived frommember isolation method is not in accordance with its actual second-order effect rule in some cases. Reasons of the discrepancy leading to inaccuracy of sway frames were identified and the improved methods were proposed.(4)Based on the member-by-member finite element analysis program formulated by our research group, the method that switches from arc-length methods to simple displacement control method was added to the program, so that the member’s strength and stability failure characteristics can be simulated well. Comparison of the simulation results with both testing results of port frames under complex loading, and other eccentricity compressed column test results, shows that the simulation agrees well.(5)Equivalent elastic stiffness of the beams and columns corresponding to their nonlinear loading states was calculated one by one by using the nonlinear analysis program. And the rational uniform stiffness reduction factor used in elastic second-order analysis for China Standard "Code for Design of Concrete Structure" were proposed. These suggestions were adopted by the national code.更多还原