【作者】 韩军；

【导师】 李英民；

【作者基本信息】 重庆大学 ， 防灾减灾工程及防护工程， 2009， 博士

【摘要】 建筑结构特别是平面不规则结构的扭转效应会加剧结构在地震中的震害,提出实用合理的设计措施以对其进行控制具有重要的意义。近年来,众多学者对其进行了研究,针对结构扭转设计提出了具体要求及控制措施,相关成果也已在各国抗震规范中体现。然而,以往研究多基于单层弹性简化分析模型或弹塑性层剪切梁模型,尚缺乏系统的多层弹塑性扭转反应规律的研究,宏观剪切梁模型无法揭示结构的真实反应特征;各国规范关于抗扭设计的规定尚有较大差别,一定程度上反映出对这问题的认识还有不小差异;我国现行规范采取的抗扭控制指标在实际工程设计中已经引发了不少困难和争议,这一事实表明尚需对规范指标的合理性和有效性进行校验;现行规范关于抗扭分析与设计的思路和做法仍以少数弹性指标控制为主,尚不够系统。为此,本文通过基于纤维模型的精细弹塑性结构反应分析,研究单层和多层框架和框剪结构的扭转反应规律,研究并校验现行弹性扭转控制指标的合理性和对弹性及弹塑性反应控制的有效性,并对结构抗扭分析与设计方法及措施提出建议。完成的主要工作和取得的主要结论有:①对比并评述了各国抗震规范的结构抗扭控制及设计方法②补充和完善了单层和多层弹性及弹塑性结构的扭转反应规律基于简化模型解析方法研究了单层结构弹性扭转反应规律,着重考察了单向及双向偏心结构受双向地震作用的影响,分析了各弹性扭转控制指标之间的关系;基于有限元数值分析方法研究了均匀、非均匀质量偏心和刚度偏心多层结构的弹性扭转反应规律。基于精细纤维模型分析了单、多层框架结构及高层框剪结构的弹塑性扭转反应规律。结果表明,偏心结构弹塑性扭转反应规律主要影响因素包括能力措施、结构偏心率、地震动强度及强度偏心;现行规范对框架结构的强柱弱梁能力措施、框剪结构的抗弯、抗剪能力措施在大震下并不总是能够达到预期的效果,柱铰为主的质量偏心结构和刚度偏心结构扭转反应规律有所不同;强度偏心会显著影响结构弹塑性扭转反应,给出了控制弹塑性扭转效应的最优强度偏心距。③弹性扭转控制指标的有效性和合理性研究分别按现行规范设计不同周期比和位移比的框架结构,采用精细纤维模型弹塑性时程分析,识别了弹性扭转控制指标对结构弹塑性扭转反应的控制效果。结果表明,扭转周期比尽管在体现加强结构抗扭刚度的概念设计上发挥了不可磨灭的作用,但也不可避免地导致设计中一些不合理现象,且对弹塑性扭转反应未起到有效的控制作用,结合国外规范经验建议取消耦联周期比限值或适当放宽限值;扭转位移比是国际上通用的扭转控制指标,应予以控制;建议以结构平面中点位移计算位移比;由于扭转位移比是相对量,不能有效反映平动位移不同时结构的扭转角大小,当平动位移较小时可根据设防烈度和所采取的加强措施有条件地放宽规范限值要求。④结构抗扭计算分析方法研究考察了偶然偏心、双向输入、填充墙等对结构扭转反应的影响,除规范规定必须考虑的结构外,计算能力和条件允许时也宜考虑其影响;分析了静力非线性分析方法、等效静力法、规范的边榀放大系数的适用性。⑤抗扭加强措施研究考察了边榀加强、强度中心调整、轴压比限制、构件抗扭验算等措施的适用性,并给出相关建议。更多还原

【Abstract】 Torsional response of aseismic structures, especially irregular layout structures, will aggravate structural damage during earthquakes. It is important to take some practical and reasonable design measures to control its effects. Recently, considerable research has been done in this topic, some specific requirements and control measures about torsional design of structures have been proposed, and some corresponding achievements have been presented in seismic codes in many countries which specify requirements and corresponding measures. However, these researches are majorly limited to one-storey simplified-elastic models or elastic-plastic story-shearing-beam models, and a systematic study on the laws of elastic-plastic torsional response of multistory structures is urgently required since the story-shearing-beam models can not reveal the true feature of structural response; a considerable difference exists in the seismic codes of various countries, which implies that we have not got a common review on this issue; the torsion control indices specified in Chinese seismic code has arisen some difficulties and arguments in engineering design, the reasonableness and effectiveness of these indices are to be investigated further; the ideas and practices about torsion analysis and design in present codes are mainly based on several elastic control indices and lack of systematicness. Aiming at the problems mentioned above, the paper firstly studies the laws of torsion response in single- and multi-story frame or frame-shear wall structures based on the fine elastic-plastic dynamic analysis using fiber model, then investigates the effectiveness of the torsion control indices and its effectiveness in controlling elastic-plastic torsional response. Finally, some recommendations for structural torsion analysis and design are suggested.The main research contents finished in this thesis and main conclusions are summarizes as follows:①Methods for structural torsion control and design in seismic codes of various countries are compared and reviewed.②Laws of elastic and elastic-plastic torsion response in single- and multi-story structures are complemented and improved.Elastic torsional response rules for one-storey or multi-storey structures are studied based on simplified dynamic analysis model, the effects of bi-directional seismic action on one-way or two-way eccentric structures are investigated and the relationship between torsional control indices are discussed; based on finite element analysis, the laws of elastic torsional response for multistory structures with uniform eccentricity, nonuniform mass eccentricity and nonuniform stiffness eccentricity are also studied.Based on fine fiber model, the rules of elastic-plastic torsion response for single- and multi-story frame structures and high-rise frame-shear wall structures are analyzed. It is concluded that the elastic-plastic torsion response of eccentric structures are mainly influenced by capacity design measures, eccentric ratio, intensity of ground motion, and strength eccentricity. Capacity design measures such as“strong-column-weak-beam”for frame structures and the bending and shear capability strengthening for frame-shear wall structures specified in current codes, are not always able to achieve the desired effects during strong earthquakes. When column hinges are predominant, rules of torsion response for mass- and stiffness-eccentricity structures are quite different. The optimal strength eccentricity is also purposely proposed to control the elastic-plastic torsion effect, since strength eccentricity has considerable influence on elastic-plastic torsion response.③Reasonableness and effectiveness of elastic torsion control indices are studies. By using elastic-plastic time history analysis based on fine fiber model, effectiveness of elastic torsion control indices to control the elastic-plastic torsion response of frame structures, which are designed according to current seismic code with various torsional period ratios and displacement ratios, are surveyed. It is shown that torsional period ratio may arise some unreasonable phenomena in the structure design and it cannot control the elastic-plastic torsion response in an effective manner, though it is a key step in concept design in the sense of strengthening the torsional stiffness of structures. Also, considering the relative provisions specified in the seismic codes of other countries, it is suggested that the limitation value of coupled torsional period ratio is to be cancelled or relaxed. As for torsional displacement ratio, it is a universal control index which must be controlled in design. Torsional displacement ratio is suggested to be calculated according to the displacement at the midpoint of plane view of structure. When the translation of structure is relatively small, the limitation value of torsional displacement ratio can be properly relaxed according to the seismic fortification intensity and measures, since torsional displacement ratio is a relative quantity which cannot quantitively indicate the real value of torsional angle under various translation of structures.④Various torsion analysis methods are surveyed.The effects of accidental eccentricity, bi-directional input, and infill wall on structural torsional response are investigated. Besides those required in current seismic code, above effects should be considered when it is computationally and conditionally allowed. Applicability of the static nonlinear analysis method, equivalent static method and amplifying factor of fringe frames is analyzed.⑤Torsional strengthening measures are suggested.Applicability of measures such as the strengthening of fringe frames, adjustment of the strength centre, control of axial force ratio, and torsion capacity check of member is explored, and some recommendations are provided.更多还原