我国大陆及其邻区现代构造滑移线—地震活动格架

我国大陆及其邻区地震活动带的空间展布似乎符合对数螺线的空间图象,而且呈现有规则的空间“网络”结构,可根据弹性力学理论,运用印度板块与欧亚板块相碰撞,在喜马拉雅弧产生强大的板块边界作用力在中国大陆及其邻区的广泛分布来解释。这些对数螺线正是在这种统一应力作用下,形成的构造滑移线,即最大剪应力和剪应变集中区带。可以认为,主要地震活动区、带和现代构造运动的发生、发展都与这些构造滑移线及这些构造滑移线所形成的大大小小的菱形断块相互作用有关。强烈地震不但往往发生在构造滑移线上(或附近),尤其是它们的交汇部位,而且顺滑移线迁移和在不同滑移线之间跳迁和呼应。我国大陆及其邻区地震活动的主要特征以及前兆敏感点似乎都可由上述观点得到解释,并由此观点出发可对潜在震源区、带提出一种新的预测途径和方法。     

中国古木结构建筑基于位移的抗震加固方法研究

提出了古木结构建筑采用基于位移的抗震加固方法,通过限制水平地震作用下结构的最大侧移和最大滑移而防止结构倒塌,其中最大侧移限值由结构的最大水平惯性力及其自身抗倾覆条件确定,最大滑移限值为柱基础半径。根据最大侧移限值并考虑古木结构建筑的特殊性,确定了在罕遇地震作用下的目标位移角及相应的目标刚度。最后分析了构架刚度下对古木结构建筑侧移和滑移的影响,认为适当加大刚度对建筑是有利的。研究结果可为古木建筑的抗震加固提供科学依据。     

汶川MW7.9地震余震序列触发机制研究

余震触发机制的Dieterich解析模型被广泛应用于区域地震活动性的定量分析以及依赖时间的概率地震预测模型的建立等方面. 基于滑移速率和状态相依赖的摩擦定律和弹簧-滑块模型, 从Dieterich断层滑移速率方程出发, 给出了静态应力扰动下触发地震的时钟提前或推后的近似解, 从而明确地阐明了触发地震的产生机制与断层的演化过程密切相关, 并与传统位错模型下库仑应力扰动时间提前或推后量作了比较. 采用对数线性拟合方法求得了汶川M_W7.9主震后余震序列持续时间, 符合Dieterich理论结果. 以汶川余震序列为例, 给出了两种不同的应力扰动模式在该余震序列中的应用. 结果表明, 经典Dieterich扰动解无法给出主震发生后即时余震数量的异常增加, 而考虑主震前后剪应力速率变化的Dieterich分段解则可反映出余震发生率及个数随时间的演化特征.      

汶川Mw7.9地震余震序列触发机制研究

余震触发机制的Dieterich解析模型被广泛应用于区域地震活动性的定量分析以及依赖时间的概率地震预测模型的建立等方面.基于滑移速率和状态相依赖的摩擦定律和弹簧-滑块模型,从Dieterich断层滑移速率方程出发,给出了静态应力扰动下触发地震的时钟提前或推后的近似解,从而明确地阐明了触发地震的产生机制与断层的演化过程密切相关,并与传统位错模型下库仑应力扰动时间提前或推后量作了比较.采用对数线性拟合方法求得了汶川Mw7.9主震后余震序列持续时间,符合Dieterich理论结果.以汶川余震序列为例,给出了两种不同的应力扰动模式在该余震序列中的应用.结果表明,经典Dieterich扰动解无法给出主震发生后即时余震数量的异常增加,而考虑主震前后剪应力速率变化的Dieterich分段解则可反映出余震发生率及个数随时间的演化特征.     

滑移隔震结构设置连接摩擦阻尼器的地震反应研究

针对罕遇地震作用下,滑移隔震结构滑移量过大控制力不足的问题,提出了带有连接部件,控制滑移隔震结构过大滑移量的被动控制装置-连接摩擦阻尼器。研究滑移隔震结构附加连接摩擦阻尼器时的地震反应情况,并通过实际算例分析表明:滑移隔震结构附加连接摩擦阻尼器能够在不削弱滑移隔震支撑对中小地震控制效果的基础上,有效地控制大震以及罕遇地震作用时,隔震层的最大滑移量和上部结构的响应加速度。验证了滑移隔震结构附加连接摩擦阻尼器的有效性和适用性。     

中国大陆及邻区地震活动格架及大地震危险性

本文从板块碰撞观点出发,根据理论与实验的结果,强震震中分布,震源机制解,强震地表破裂带以及地质等资料,提出了中国大陆及邻区的地震活动格架。它是两簇近似于对数螺线的构造滑移线,即在统一的区域应力场作用下,最大剪切应力和剪切应变集中的区、带。它们是控制和支配现今地震活动和构造运动的空间分布网络。这种网络结构,为我们研究地震活动时空分布规律,进行地震危险性分析,从而预测未来强震危险区提供了一种新的途径和基本格架。考虑到这些网络具有某种自相似性特点,我们将中国大陆及邻区7级以上大地震沿滑移线的空间分布变换到平面直角坐标网格上。发现它们明显的集中于两条不宽的、相互交叉的条带上,类似于岩石平面 X 破裂图象。这表明未来7级以上,特别是8级大地震危险区,主要位于这两条带上那些在历史上还未发生大地震的地区,尤其是滑移线的交汇部位可能是最危险的地区,这将大大缩小我们寻找大地震危险区的范围。本文还用分维理论研究了地震活动的空间分布规律,计算了中国大陆及邻区地震活动空间分布容量维 D_o 随时间的变化,并提出在本世纪末之前,有发生8级地震的危险性。根据对大地震一些活动规律的分析,认为喜马拉雅弧东段及其邻区可能是未来大地震危险区之一。并在构造滑移线上圈出未来可能发生大地震的危险区。     

叠合柱高墩概率地震易损性分析

为了评估叠合柱高墩的抗震性能,根据结构可靠度理论,推导了概率地震易损性函数解析式。以一座叠合柱高墩连续刚构为研究对象,对叠合柱高墩的合理性能指标进行分析和量化,建立了以轴力为变量的截面概率抗震能力模型。考虑材料强度和地震动的不确定性,采用IDA方法对结构-地震动样本进行地震需求分析,建立了以PGA为变量的控制截面概率地震需求模型并进行概率地震易损性分析。结果表明曲率指标对数均值与对数轴力之间符合三次多项式回归关系,曲率抗震能力随轴力的增大而减小。在纵向地震作用下,曲率需求与PGA之间仍然满足对数线性关系,墩底区域最容易发生损伤,矮墩比高墩更容易发生损伤,在设计地震作用下,叠合柱高墩发生倒塌的概率极小。     

村镇建筑砌体结构滑移隔震性能研究1

村镇建筑多以砖混结构为主,抗震性能相对较弱,砂垫层摩擦滑移隔震技术由于诸多优点较适合广大农村建筑.本文介绍了砂垫层基础滑移隔震的设计原则和分析模型,以常见的两层砖混结构为例,采用Abaqus有限元软件分析不同摩擦系数、不同加速度峰值下隔震层的滑移,并在此基础上确定隔震层在多遇和罕遇地震作用下的摩擦系数及滑移量建议限值;通过验算不同砂浆的抗震受剪承载力,得出不同摩擦力作用下满足抗震受剪承载力的最低砂浆标准,所得结论对农村滑移隔震建筑的选材具有一定参考意义.     

摩擦基底隔震刚性结构滑移反应谱的确定

将地震地面运动模拟成均值为零的两次过滤Ｇａｕｓｓ白噪声过程,使用等效线性化方法获得了摩擦基底隔震刚性结构在地震作用下的均方滑动位移和速度反应。然后,给出了这种结构的最大滑移反应的均值和标准差,并给出了这种结构的滑移反应谱。     

断层演化过程中的周期和非周期地震滑移及非地震滑移一维断层模型分析

本文首先根据Dieterich和Ruina提出的含速率和状态的摩擦定律(Dieterich-Ruina定律), 基于一维弹簧-滑块模型推导了地震复发周期的解析表达式, 然后将该近似解与数值模拟结果以及Barbot等的相关研究进行了对比分析． 此外, 本文还利用数值模拟与理论分析研究了断层周期和非周期演化的力学成因机制以及非地震滑移形成的另类力学机制, 并讨论了一维弹簧-滑块模型的优点及其局限性． 结果表明: ① 震后滑移和自加速/成核阶段的持续时间在整个演化过程中不能被忽略; ② 在修正后的复发周期模型中, 复发周期的长短除了与断层特征尺度、 作用于断层面上的有效正应力和远场加载速率相关外, 还受Dieterich-Ruina定律中摩擦参数的取值以及临界滑移距离的影响; ③ 当给定各个物理参数和几何参数时, 目前所得到的解析近似解可以很好地估计地震的复发周期, 其相对误差可小于5%; ④ 在断层演化过程中, 施加剪切应力加载会产生非周期的地震滑移, 而在自加速/成核阶段后期或震后滑移阶段早期, 施加较大的剪切应力加载, 则会出现非地震滑移．      

Tall building performance‐based seismic design using SCEC broadband platform site‐specific ground motion simulations

The scarcity of strong ground motion records presents a challenge for making reliable performance assessments of tall buildings whose seismic design is controlled by large‐magnitude and close‐distance earthquakes. This challenge can be addressed using broadband ground‐motion simulation methods to generate records with site‐specific characteristics of large‐magnitude events. In this paper, simulated site‐specific earthquake seismograms, developed through a related project that was organized through the Southern California Earthquake Center (SCEC) Ground Motion Simulation Validation (GMSV) Technical Activity Group, are used for nonlinear response history analyses of two archetype tall buildings for sites in San Francisco, Los Angeles, and San Bernardino. The SCEC GMSV team created the seismograms using the Broadband Platform (BBP) simulations for five site‐specific earthquake scenarios. The two buildings are evaluated using nonlinear dynamic analyses under comparable record suites selected from the simulated BBP catalog and recorded motions from the NGA‐West database. The collapse risks and structural response demands (maximum story drift ratio, peak floor acceleration, and maximum story shear) under the BBP and NGA suites are compared. In general, this study finds that use of the BBP simulations resolves concerns about estimation biases in structural response analysis which are caused by ground motion scaling, unrealistic spectral shapes, and overconservative spectral variations. While there are remaining concerns that strong coherence in some kinematic fault rupture models may lead to an overestimation of velocity pulse effects in the BBP simulations, the simulations are shown to generally yield realistic pulse‐like features of near‐fault ground motion records.     

Seismic response of sliding equipment and contents in base‐isolated buildings subjected to broadband ground motions

Base isolation has been established as the seismic design approach of choice when it comes to protecting nonstructural contents. However, while this protection technology has been widely shown to reduce seismic demands on attached oscillatory equipment and contents (EC), its effectiveness in controlling the response of freestanding EC that are prone to sliding has not been investigated. This study examines the seismic behavior of sliding EC inside base‐isolated buildings subjected to broadband ground motions. The effect of isolation system properties on the response of sliding EC with various friction coefficients is examined. Two widely used isolation models are considered: viscously damped linear elastic and bilinear. The study finds isolation to be generally effective in reducing seismic demands on sliding EC, but it also exposes certain situations where isolation in fact increases demands on EC, most notably for low friction coefficients and high earthquake intensities. Damping at the isolation level is effective in controlling the EC sliding displacements, although damping over about 20% is found to be superfluous. The study identifies a physically motivated dimensionless intensity measure and engineering demand parameter for sliding equipment in base‐isolated buildings subjected to broadband ground motions. Finally, the paper presents easy‐to‐use design fragility curves and an example that illustrates how to use them. Copyright © 2014 John Wiley & Sons, Ltd.     

Non‐structure‐specific intensity measure parameters and characteristic period of near‐fault ground motions

This paper focuses on the effects of long‐period pulse of near‐fault ground motions on the structural damage potential. Two sets of near‐fault ground motion records from Chi‐Chi, Taiwan earthquake and Northridge earthquake with and without distinct pulse are selected as the input, and the correlation analysis between 30 non‐structure‐specific intensity measure parameters and maximum inelastic displacements and energy responses (input energy and hysteretic energy) of bilinear single degree of freedom systems are conducted. Based on the frequency characteristic of near‐fault ground motions with remarkable long‐period components, two intensity indices are proposed, namely, the improved effective peak acceleration (IEPA) and improved effective peak velocity (IEPV). In addition a new characteristic period of these ground motions is defined based on IEPA and IEPV. Numerical results illustrate that the intensity measure parameters related to ground acceleration present the best correlation with the seismic responses for rigid systems; the velocity‐related and displacement‐related parameters are better for medium‐frequency systems and flexible systems, respectively. The correlation curves of near‐fault ground motions with velocity pulse differ from those of ground motions without pulse. Moreover, the improved parameters IEPA and IEPV of near‐fault impulsive ground motions enhance the performance of intensity measure of corresponding conventional parameters, i.e. EPA and EPV. The new characteristic period based on IEPA and IEPV can better reflect the frequency content of near‐fault ground motions. Copyright © 2009 John Wiley & Sons, Ltd.     

钢筋混凝土高层建筑抗震时程分析选波方法比较研究

针对钢筋混凝土高层建筑抗震时程分析输入地震波选择问题,以《建筑抗震设计规范》（GB 50011-2016）设计谱为目标谱,将满足谱匹配原则的加权调幅选波方法与国内学者建议的其它输入地震波选择方法进行了对比研究。以3栋钢筋混凝土高层建筑（15层、30层和44层）为实例,针对8度罕遇地震作用和Ⅱ类场地条件,将上述方法建议的各7条地震波输入结构进行弹塑性时程分析。以结构最大层间位移角均值沿楼层分布为比较参数。结果表明:加权调幅法可用于钢筋混凝土高层建筑抗震时程分析,可以较好地降低结构地震反应均值的离散性。在8度罕遇地震作用条件下,以不同学者建议选择的地震波为输入,高层建筑时程分析结果仍呈现出较大的不同。     

云南漾濞6.4级地震公共建筑的震害特征

2021年5月21日云南漾濞发生6.4级地震,成为继2014年6.5级鲁甸地震和6.6级景谷地震之后云南省内时隔7年的又一次震级大于6级的破坏性地震。漾濞地震虽然与鲁甸地震在震级、震源深度和震源机制等方面均较相似,但漾濞地震震中附近的地面运动强度远不及鲁甸地震,且漾濞县的抗震设防烈度远高于鲁甸;相应地,漾濞地震对抗震设防建筑造成的破坏也远轻于后者。本文首先通过比较这三次地震震中附近的强震记录的反应谱,并结合公共建筑的震后应急评估结果,说明漾濞地震和鲁甸地震中公共建筑破坏程度的显著差异。进而以位于漾濞县城的两栋钢筋混凝土公共建筑为例,介绍此次地震中砌体填充墙和吊顶等典型非结构构件的震害。     

长周期地震动强度指标与SDOF体系残余变形相关性分析

为分析两类长周期地震动作用下如何选取合理的强度指标作为结构抗震设计的输入,从2011年东日本9.0级地震、2003年十胜冲8.0级地震和2016年熊本7.3级地震数据库中选取90条可靠的远场长周期地震动。从1994年美国北岭6.7级地震和1999年台湾集集7.6级地震数据库中选取60条近场长周期地震动,以SDOF体系为研究对象,讨论了阻尼比、屈服刚度折减系数和强度折减系数对残余变形与18个地震动强度指标的相关系数的影响,对比分析了两类长周期地震作用下相关系数之间的异同。研究结果表明:在考虑近场长周期地震动作用时,建议应根据结构周期的大小来选择合适的强度指标作为地震动的输入。远场长周期地震动作用下,以PGA、PGV和PGD为代表的强度指标与残余变形的相关程度均较高,PGV稳定性略好于PGA和PGD,建议PGV作为地震动输入的控制指标。残余变形相关系数受阻尼比、屈服刚度折减系数以及强度折减系数影响不大。     

罕遇地震下高层RC框架结构双地震动强度参数易损性分析

为研究高层RC框架结构罕遇地震下的易损性,设计了一个7度区典型11层RC框架结构。采用IDA方法进行时程分析,以地震动峰值地面加速度和结构第一自振周期对应的谱加速度为地震动强度指标,最大层间位移角为结构损伤指标,分别得到了单一地震动强度和双地震动强度参数下的IDA曲线和失效概率,绘制了双地震动强度参数下易损性曲面,并对单一地震动强度和双地震动强度参数下的易损性分析结果进行了对比。结果表明:罕遇地震下,采用双地震动强度参数结构失效概率明显低于采用单一地震动强度参数结构失效概率;对高层RC框架结构,采用双地震动强度参数进行易损性分析反映的地震动信息更全面;采用双地震动强度参数得到的结构失效概率公式更能真实量化不同强度地震作用下结构的失效概率。     

Dynamics of a sliding-rocking block considering impact with an adjacent wall

A freestanding rigid block subjected to base excitation can exhibit complicated motion described by five response modes: rest, pure rocking, pure sliding, combined sliding-rocking, and free flight. Previous studies on the dynamics of a rocking block have assumed that the block does not interact with neighboring objects. However, there are many applications in which the block may start or come in contact with an adjacent boundary during its motion, for example, a bookcase or cabinet colliding with a partition wall in an earthquake. This paper investigates the dynamics of a sliding-rocking block considering impact with an adjacent wall. A model is developed in which the base and wall are assumed rigid, and impact is treated using the classical impulse and momentum principle. The model is verified by comparing its predictions in numerical simulations against those of an existing general-purpose rigid-body model in which impact is treated using a viscoelastic impact model. The developed model is used to investigate the effects of different parameters on the stability of a block subjected to analytical pulse excitations. It is found that wall placement (left or right) has a dominant effect on the shape of the overturning acceleration spectra for pulse excitations. In general, decreasing the gap distance, base friction coefficient, and wall coefficient of restitution enhance the stability of the block. Similar observations are made when evaluating the overturning probability of a block using earthquake floor motions.     

复杂退台高位转换高层建筑振动台试验与分析

对一幢具有转换层的复杂退台式框架剪力墙高层建筑的1/35缩尺模型进行了模拟地震振动台试验,深入研究该结构的动力特性和地震反应特征.试验及理论分析表明:该结构的抗震性能基本满足现行规范要求;由于结构上部逐渐退台,因而结构顶部有较明显的鞭端效应;结构首层和结构转换层及其相邻层的剪力墙、转换层上下层柱是受力较大的区域,应当局...     

Duration effect of near-fault pulse-like ground motions and identification of most suitable duration measure

The duration effect of near-fault pulse-like ground motions on structural demands and the identification of most suitable duration measure are systematically addressed in this paper. Firstly, the duration effect of the Mavroeidis & Papageorgiou (M&P) pulse on the normalized maximum displacement and normalized hysteretic energy of elastic-perfectly-plastic, bilinear and rigid-plastic (i.e., Newmark sliding block) single-degree-of-freedom (SDOF) systems is analyzed by using dimensional analysis. Particularly, an intrinsic length scale is proposed to present well the normalized responses. It is shown that the duration effect of M&P pulses on the normalized responses is affected by the frequency ratio and normalized yield displacement. Generally, the duration effect is significant on the normalized hysteretic energy, whereas it is not remarkable on the normalized maximum displacement of ordinary inelastic SDOF systems, except for the normalized sliding displacement of Newmark sliding blocks. Then, a set of 65 spectrally equivalent strongest near-fault ground motions is input to the aforementioned SDOF systems, and the correlation analysis between seismic responses and duration measures is conducted. It is shown that the associated results are consistent with those obtained by dimensional analysis. Moreover, the uniform duration generally presents the best correlation with seismic demands, and thus is identified as the most suitable duration measure. Finally, the correlation statements are further validated on three 5-, 10-, and 20-story shear frame buildings with strength and stiffness degradation under spectrally equivalent ground motions.