【作者】 李明；

【导师】 谢礼立；

【作者基本信息】 中国地震局工程力学研究所 ， 防灾减灾工程及防护工程， 2010， 博士

【摘要】 地震是危害人类生命财产安全最严重的突发式自然灾害之一。尤其是近10年来几次主要大地震,造成的城市基础设施破坏、人员伤亡和财产损失令世人触目惊心。历经50余年的研究,各国学者已达成共识,一致认为近断层(也称近场或近源)地震动呈现了较一般远场地震动更复杂的特征是引起工程结构破坏的一个重要原因,并围绕近断层地震动,开展了大量研究,主要包括近断层地震动的模拟、近断层地震动参数衰减关系、近断层地震动对工程结构的破坏作用分析及针对近断层地震动的隔震与消能减震措施研究等。但迄今也没有形成系统的可供实际工程应用的考虑近断层地震动影响的结构设计或加固理论,尤其是我国。在工程设计或加固时,首先需要判断拟建或已建建筑是否位于近断层区域,其次需要确定采用哪种结构设计方案,最后需要确定采用哪种设计谱和符合哪些条件的输入地震动。为解决这些问题,本研究主要完成了以下几方面工作:划分了近断层区域;提出了我国抗震规范设计谱在考虑近断层地震动时的调整建议;给出了近断层脉冲型地震动的合成方法;分析了近断层脉冲型地震动各要素对结构破坏作用的影响;指出了考虑近断层脉冲地震动影响的结构设计方案,提出了近断层脉冲型地震动作为输入地震动的选择方法。研究的主要内容和结论如下:(1)提出了基于破坏势参数划分近断层区域的方法。在划分近断层区域时,提出了相对断层距的概念,即断层距和矩震级的比值(dr/Mw)。基于PEER数据库中的强震数据,充分分析了以往用于表征近断层地震动潜在破坏势参数随相对断层距的变化,并以其中适合划分近断层区域的破坏势参数划分了近断层区域。以体现方向性效应和上/下盘效应地震记录的分布范围旁证了划分结果的合理性。(2)比较了近断层脉冲型、近断层非脉冲型、远场脉冲型和远场非脉冲型四类地震动的弹性和非弹性反应谱,分析了其对我国抗震规范设计谱和非弹性位移计算的影响,结果表明:近断层脉冲型地震动对我国抗震规范设计谱的影响主要体现于动力系数谱的特征周期,对谱函数形式和最大值取值无明显影响;当考虑近断层脉冲型地震动影响时,我国抗震规范规定的非弹性位移简化计算方法偏于危险。给出了考虑近断层脉冲型地震动影响的动力系数谱调整建议,建议采用时程分析法补充计算我国抗震规范规定的可采用非弹性位移简化计算方法计算的结构。(3)分析了以往等效速度脉冲模型存在的不足之处,提出了新的等效速度脉冲模型;分析了已有脉冲周期和脉冲速度峰值识别方法的局限性,提出了首先采用汉宁窗平滑脉冲型地震记录,再通过平滑后的地震记录,识别脉冲周期和脉冲速度峰值的方法,并验证了识别方法的合理性;改进了近断层脉冲型地震动的合成方法。(4)系统深入的分析了近断层脉冲型地震动各要素对弹性、非弹性反应谱及框架和框架剪力墙结构破坏作用的影响,从本质上分析了前人提出的能量密度(Eρ)、最大增量速度(ΔVmax)、改进的有效峰值加速度(IEPA)、改进的有效峰值速度(IEPV)以及水平峰值速度和峰值加速度比值(PHV/PHA)这些破坏势参数,在表征近断层脉冲型地震破坏作用时的不足之处,指出不能单独以某个破坏势参数衡量近断层脉冲型地震动的破坏作用或作为输入地震动的选择标准,应综合考虑峰值加速度、脉冲速度峰值、脉冲周期与结构周期之间关系的影响。(5)比较了在近断层脉冲型和一般远场地震动作用下,混凝土框架和框架剪力墙结构的响应和破坏机理,依据比较结果提出了考虑近断层脉冲型地震动影响的结构设计方案。提出了在工程背景允许的情况下,应尽量避开受近断层脉冲型地震动影响区域的设计思想,并统计了近断层脉冲型地震动的数量随断层距的分布,为确定这一避让区域提供了依据。(6)分析了考虑近断层地震动影响的基于位移、基于能量和基于力的设计方法的实用性,指出目前在考虑近断层脉冲型地震动影响时,仅能采用基于力的设计方法。依据近断层脉冲型地震动对结构破坏作用的分析结果,给出了时程分析计算时,选择近断层脉冲型地震动的方法。更多还原

【Abstract】 Earthquake is one of the most serious natural disasters to human lives and properties in sudden burst mode. Especially, in the past decade several large earthquakes caused infrastructure damage, casualty and property loss, which shocked all the people around the world. After nearly 60 years of study, scholars of different countries come to a common understanding that the complicated and special feature of the near-fault (near-field/source) ground motion is an important factor that causes the structure damage. Subsequently, many studies related to the near-fault ground motion arose, mainly including simulation of near-fault ground motion, setting up attenuation relationship of near-fault ground motion, analyzing the damaging effect of near-fault ground motion on structures and finding reasonable methods of vibration isolation or energy dissipation under near-fault ground motion. However, till now no systematical method and theory are proposed for structure design and structure reinforcement to consider the influence of near-fault ground motion, especially in China.During the process of designing or reinforcing structures, firstly, it is necessary to judge whether the building is located in the near-fault region, and then we need to decide which structure design scheme is to be used, the last step is to choose a computational method, that is to decide the design spectrum and input ground motion. To solve the previous problems, this paper proposes the definition of near-fault region and analyzes the effect of near-fault pulse-like ground motion on the design spectra of China Seismic Code, and then puts forward a synthetic method to simulate the near-fault pulse-like ground motion. The effect of the parameters of near-fault ground motion on structure damage is analyzed. It is given that structure design scheme considering the effect of near-fault pulse-like ground motion and how to select this type of ground motion for time history analysis. The main objectives and results of this study are shown as following:(1)Based on damage potential parameters, a method for near-fault region zoning is proposed. When defining the near-fault region, a concept of Normalized Rupture Distance (NRD) is established, and this distance is defined as the ratio of rupture distance to moment magnitude (dr/Mw). Depending on the PEER strong ground motion database, the variation of damage potential parameters with NRD is analyzed, and then the near-fault region is defined according to some appropriate parameters. The rationality of zoning result is proved to some extend by the distribution range of ground motions, which embodies directivity and hanging/ foot wall effect.(2)The features of elastic, inelastic response spectra of near-fault pulse-like ground motion, near-fault non-pulse-like ground motion, far-field pulse-like ground motion and far-field non-pulse-like ground motion are compared, and their effects on design spectrum of China Seismic Code and inelastic displacement of structures are analyzed. It shows that the near-fault pulse-like ground motion mainly affects the design characteristic period of ground motion, and has no special influence on the spectral function and the maximum value. A suggestion for modifying the design spectrum is also provided, which takes the near-fault pulse-like ground motion into account. Additionally, the result shows that the method adopted in China Seismic Code for inelastic displacement calculation tends to be unsafe when the near-fault pulse-like ground motion is considered, and therefore the time history analysis is needed as a complement.(3)The insufficiency of the previous equivalent velocity model is analyzed, and a new model of equivalent velocity pulse is put forward. The limitation of existing methods for identifying pulse period and pulse amplitude is given. A new criterion is provided, which firstly uses the Hanning Window to smooth the pulse-like ground motion, and then identifies the pulse period and pulse amplitude parameters. And the rationality of the identification method is proved. The previous method used for synthesizing near-fault ground motion is improved as well.(4)The effects of every element of near-fault ground motion on elastic and inelastic spectra, reinforced concrete frame structure and reinforced concrete frame-shear wall structure are deeply analyzed. The deficiency of different parameters used to represent damage potential of near-fault ground motion is pointed out, including energy density (Eρ), maximum increment velocity (ΔVmax), improved effective peak acceleration (IEPA), improved effective peak velocity (IEPV) and ratio of peak horizontal velocity to peak horizontal acceleration (PHV/PHA). The results show that the damage potential of near-fault ground motion can not be represented by a single parameter, while it should be described by peak acceleration, peak pulse velocity and the relationship between pulse period and the natural vibration period of the structure synthetically. (5)Dynamic response and damage mechanism of reinforced concrete frame structure and reinforced frame-shear wall structure under near-fault pulse-like ground motion and far-field ground motion are compared. According to the results, structure design scheme considering the effect of near-fault ground motion is put forward. It is proposed that the near-fault pulse-like ground motion influence area should be evaded with the permission of the engineering background as possible, and the distribution of the number of near-fault ground motion along the rupture distance is counted as well, which can be used as the reference for deciding the preventing area.(6)The practicability of different seismic design methods considering the effect of near-fault pulse-like ground motion is discussed, including force based seismic design method, energy based seismic design method, and displacement based seismic design method. It is showed that only the force based seismic design method is practicable for current seismic design method. Based on the analysis results of the damage potential parameters, the method of selecting near-fault pulse-like ground motion is given for time history analysis.更多还原