浅谈建筑物加层中的抗震问题

叙述了建筑物增层的现实情况，提出建筑物尤其是处于地震重点监视防御区的建筑物增层时，必须考虑建筑物的场地、结构、材料等抗震因素。     

基于汶川地震建筑物破坏的抗震设防要求分析

汶川8.0级地震给川西地区造成了严重的建筑物破坏与人员伤亡。通过大量对汶川地震灾区的建筑物破坏情况实地调查,并根据现行建筑物抗震设防要求与建筑抗震设计规范,从建筑物选址、抗震设计及建筑施工等多个环节,对汶川地震中的典型建筑物破坏案例进行讨论分析,探讨破坏原因,并提出相应的解决措施,为今后建筑物的抗震设防工作提供参考经验与科学依据。     

钦州市建筑物抗震性能普查及震害预测分析

通过对钦州市主城区建筑物开展抗震性能普查,摸清了钦州市主城区重要建筑、民用群体建筑和普通民居的抗震性能状况,对建筑物抗震性能进行了分级评定,找出了城市建筑抗震薄弱区.采用PKPM有限元结构分析软件对重要建筑中的砖混结构建筑进行了震害预测分析,最后总结了钦州市主城区建筑物抗震性能存在问题并给出了建议.     

震后居民点建筑物的工程状态预测

对近20年来破坏性地震后果的工程分析和地震时考察建筑物的经验得出，同一类型的抗震建筑物和普通建筑物的震害性质相似、定量指标不同；地震时抗震建筑物震害程度低于普通建筑物；抗震建筑物震害程度的数值分布符合高斯规律。大量资料分析认为，抗震建筑物震害程度取决于地震烈度，具有线性特征。提出了承重砖石墙建筑物、框架和大板房屋建筑物在地震烈度Ⅶ～Ⅸ度时建筑物震害程度的计算公式，并绘制了曲线图。抗震建筑物震害程度均方差较少，与普通建筑物大约相当。提出的有抗震措施建筑物震害程度与地震烈度呈线性关系具有近似性，但可用于评定震后居民点建筑物的期望工程状态。     

农村民用建筑工程抗震设防初探

本文在统计分析大量资料的基础上，发现农村民用建筑物在抗震设防方面存在诸如：①缺乏震灾意识，防震观念淡薄；②房屋结构简单，抗震性能低；③有女儿墙、高门脸、高屋脊等不利抗震的建筑形式；④省投资，省材料，无技术，房屋工程质量差；⑤建筑材料质量差，影响工程抗震性能；⑥缺乏管理，施工质量低等薄弱环节。鉴此，提出下述一些对策及措施：①加强地震知识宣传，提高防震减灾意识；②加强对农村民用建筑的抗震研究，探索设计推出防震抗震示范建筑物；③加强农村建材市场和施工队伍的管理；④加强农村建筑施工队的业务技术培训，提高质量意识；⑤加强农村震害预测和防震减灾规划编制工作；⑥在抓好在建、新建工程抗震设防的同时，要重视原有建筑物的抗震鉴定；⑦研究制定农村民用建筑抗震设防法规；⑧建立健全各级防灾机构，强化各级政府减灾职能。     

地震动参数在建筑物抗震设计中的应用

传统考虑后期使用年限的地震动参数研究,在建筑物抗震设计中的应用,缺乏地震危险性分析和建筑物损伤指数分析,应用性差。提出新的地震动参数在建筑物抗震设计中的应用方法,以地震危险性分析为基础,通过水平地震动加速度衰减关系方程,求得建筑场地水平向基岩峰值加速度和反应谱,以此得到地震动加速度反应谱方程,利用该方程获得地震动反应谱参数,采用变形和线性组合构建损伤指数模型,获取地震波作用下地震动参数对建筑物损伤程度。实验结果表明,利用所提方法得到的地震动反应谱最小误差为0.563,小于允许误差4.0;在50年超越概率63%的条件下地震动参数值分别为0.26、0.095,所提方法可在规定误差范围内得到地震动反应谱参数值,其进行建筑物抗震设计精度和应用性高。     

建筑物偏心结构对其抗震性能的影响

偏心对建筑物的抗震效果有很大的影响。在对三种常见建筑物框架结构在偏心扭矩作用下的受震反应进行数值模拟时,采用6层建筑物模型,通过三维非线性模拟偏心结构对建筑物抗震性能影响的分析,采用最大层间位移作为衡量标准,绘制易损曲线来进行结果分析。结果显示:若忽略意外扭矩的影响,可能会高估钢结构体系的抗震性能,而影响安全评估结果;如果采用全层5%质量偏心来考虑意外偏心扭矩的话,会低估钢结构建筑物的抗震性能。     

提高抗震强度

苏联塔吉克加盟共和国科学院抗震工程与地震学研究所建成了一个综合试验基地,在那里可以模拟任何强度的地震。建立这个综合试验基地的目的是:要以与实际建筑物相同的尺度检测建筑物的结构、材料以及各个砌块的抗震强度。该综合试验基地采用连续方式进行试验,这种试验方式为把在地震活动频繁区域内建设的建筑物和构筑物的最合理的工程措施,以及最经济而又坚固的方案加速推广到建设实践中去开辟了一条途径。除了正在使用的用爆破地震法进行住宅抗震试验的工程试验场之外,这个新建的综合试验基地已成为苏联较大的地震学家的科学实验基地。     

基于复杂网络的建筑物强震下抗毁性估计模型

城市所处的地震危险性环境和城市建筑物的易损性是影响复杂网络建筑物强震环境下抗毁能力的关键因素。由于现阶段对建筑物抗震抗毁能力的评定仍存在一定困难,对建筑物震害程度测评只能通过强震之后建筑物受破坏的程度进行评估,且评估结果不够精准,因此提出基于复杂网络的建筑物抗震能力的评估方法。考虑到地震中的危险性因素,以地面峰值加速度为参数对强震环境下复杂网络建筑物抗毁性进行测评和分析,在此基础上提出对复杂网络下建筑物的防震抗毁能力进行评估的相对建筑物抗震性能指数,并结合建筑物抗震能力评估标准确定其抗震能力水平;再进行仿真实验加以测量,并结合震害经验,证实该方法的有效性。     

基于目标-能力差距分析的建筑物抗震韧性评估方法

传统建筑物地震易损性分析忽略了不同种类建筑物在城市抗震防灾全周期中所发挥的作用,缺乏对灾后功能恢复能力的分析。针对该问题,从规划视角入手,提出基于目标-能力差距分析的建筑抗震韧性评估方法。首先,确定不同防灾功能建筑物的重要度分级,提出用功能损失和恢复时间两个指标量化表征多水准下建筑物的抗震韧性目标;其次,基于结构易损性分析估算建筑物的功能损失值,采用指数型和直线型两种恢复模型评估建筑物的恢复时间值;然后,基于功能损失值、恢复时间值与目标值之间的差距,确定建筑物的抗震韧性等级,从而根据建筑物重要度等级确定震前保障和震后救援的优先次序和韧性提升策略,为抗震防灾规划的编制提供支撑。     

A new seismic isolation system and its feasibility study

<正>This paper introduces a new seismic isolation system called a periodic foundation(PF),where inclusions are periodically arranged.The PF is different from traditional base isolation in that it causes a fundamental frequency shift in the structure,thus reducing its response and generating a frequency gap.If the frequency contents of a seismic wave fall into the gap,it can not propagate in the foundation.Thus,it will exert no influence on the structure above.A systematic study of the band of frequency gap for a 2D PF is conducted.The influence of physical and geometrical parameters such as density and elastic modulus as well as filling fraction of the PF and its materials on the band of frequency gap are investigated, and a design with a frequency gap as low as 2.49-3.72 Hz is achieved.This band of frequency gap corresponds well to the design spectra in earthquake engineering.Numerical simulations of a six-story frame structure with different foundations demonstrate that a proposed PF can greatly reduce the seismic response of an isolated structure.This investigation shows that PFs have great potential in future applications of seismic isolation technology.     

Seismic dispersion and attenuation in layered porous rocks with fractures of varying orientations

Wave‐induced fluid flow plays an important role in affecting the seismic dispersion and attenuation of fractured porous rocks. While numerous theoretical models have been proposed for the seismic dispersion and attenuation in fractured porous rocks, most of them neglect the wave‐induced fluid flow resulting from the background anisotropy (e.g. the interlayer fluid flow between different layers) that can be normal in real reservoirs. Here, according to the theories of poroelasticity, we present an approach to study the frequency‐dependent seismic properties of more realistic and complicated rocks, i.e. horizontally and periodically layered porous rock with horizontal and randomly orienting fractures, respectively, distributed in one of the two periodical layers. The approach accounts for the dual effects of the wave‐induced fluid flow between the fractures and the background pores and between different layers (the interlayer fluid flow). Because C₃₃ (i.e., the modulus of the normally incident P‐wave) is directly related to the P‐wave velocity widely measured in the seismic exploration, and its comprehensive dispersion and attenuation are found to be most significant, we study mainly the effects of fracture properties and the stiffness contrast between the different layers on the seismic dispersion and attenuation of C₃₃. The results show that the increasing stiffness contrast enhances the interlayer fluid flow of the layered porous rocks with both horizontal and randomly orienting fractures and weakens the wave‐induced fluid flow between the fractures and the background pores, especially for the layered porous rock with horizontal fractures. The modelling results also demonstrate that for the considered rock construction, the increasing fracture density reduces the interlayer fluid flow while improves the dispersion and attenuation in the fracture‐relevant frequency band. Increasing fracture aspect ratio is found to reduce the dispersion and attenuation in the fracture‐relevant frequency band only, especially for the layered porous rock with horizontal fractures.     

Characteristics and method of synthesis seismic wave based on wavelet reconstruction

A novel method of synthesizing seismic wave using wavelet reconstruction is proposed and compared with the traditional method of using theory of Fourier transform. By adjusting the frequency band energy and taking it as criterion, the formula of synthesizing seismic wave is deduced. Using the design parameters specified in Chinese Seismic Design Code for buildings, seismic waves are synthesized. Moreover, the method of selecting wavelet bases in synthesizing seismic wave and the influence of the damping ratio on synthesizing results are analyzed. The results show that the synthesis seismic waves using wavelet bases can represent the characteristics of the seismic wave as well as the ground characteristic period, and have good time-frequency non-stationary.     

利用小波重构合成地震波方法及特性研究

针对傅里叶变换合成地震波理论的不足，提出一种利用小波重构合成地震波的方法. 以控制频带能量为标准，推导了合成地震波的公式. 运用抗震设计规范中的相关设计参数合成了地震波，并分析研究了在合成地震波时小波函数基的选取方法和阻尼比对合成结果的影响. 结果表明，用小波重构合成的地震波能够反应地震波基本特性和场地特征周期，并具有很好的时频非平稳性.      

Interaction of multiple courses of wave‐induced fluid flow in layered porous media

Different theoretical and laboratory studies on the propagation of elastic waves in layered hydrocarbon reservoir have shown characteristic velocity dispersion and attenuation of seismic waves. The wave‐induced fluid flow between mesoscopic‐scale heterogeneities (larger than the pore size but smaller than the predominant wavelengths) is the most important cause of attenuation for frequencies below 1 kHz. Most studies on mesoscopic wave‐induced fluid flow in the seismic frequency band are based on the representative elementary volume, which does not consider interaction of fluid flow due to the symmetrical structure of representative elementary volume. However, in strongly heterogeneous media with unsymmetrical structures, different courses of wave‐induced fluid flow may lead to the interaction of the fluid flux in the seismic band; this has not yet been explored. This paper analyses the interaction of different courses of wave‐induced fluid flow in layered porous media. We apply a one‐dimensional finite‐element numerical creep test based on Biot's theory of consolidation to obtain the fluid flux in the frequency domain. The characteristic frequency of the fluid flux and the strain rate tensor are introduced to characterise the interaction of different courses of fluid flux. We also compare the behaviours of characteristic frequencies and the strain rate tensor on two scales: the local scale and the global scale. It is shown that, at the local scale, the interaction between different courses of fluid flux is a dynamic process, and the weak fluid flux and corresponding characteristic frequencies contain detailed information about the interaction of the fluid flux. At the global scale, the averaged strain rate tensor can facilitate the identification of the interaction degree of the fluid flux for the porous medium with a random distribution of mesoscopic heterogeneities, and the characteristic frequency of the fluid flux is potentially related to that of the peak attenuation. The results are helpful for the prediction of the distribution of oil–gas patches based on the statistical properties of phase velocities and attenuation in layered porous media with random disorder.     

大震前地震活动图像演变及中期向短期过渡的地震活动性标志

通过多震例分析，表明大震前地震活动图像具有类似的演变形式，即空段－背景空区－增强活动－条带－平静，地震平静可以看作是中期短期过渡的地震活动性标志，从图像演变角有助于识别异常平静，并有可能把震前平静的时间尺度缩短至几个月量级。     

基于高灵敏度检波器数据的分频匹配滤波方法及其应用(英文)

具有较高自然频率的高灵敏度检波器在采集数据时可以通过压制低频信号来相对提高高频能量,但这也造成了其低频响应差的问题,如果将高灵敏度数据与常规数据进行优势组合,就可以达到拓宽频带的目的。为此,本文提出分频段匹配滤波的方法,即在保持常规数据低频优势的前提下,对其高频端进行匹配滤波,实现不同频带范围内的优势互补,从而改善地震记录。通过引入不同主频的雷克子波模拟得到具有常规数据和高灵敏度数据特点的理论模型,论证了分频匹配滤波方法的可行性。在对野外单炮地震记录处理中发现,分频匹配滤波方法拓宽了地震记录的有效频带宽度,提高了地震记录的分辨率。     

Resilience-based retrofitting of existing urban RC-frame buildings using seismic isolation

The improvement of the seismic resilience of existing reinforced-concrete (RC) frame buildings, which is essential for the seismic resilience of a city, has become a critical issue. Although seismic isolation is an effective method for improving the resilient performance of such buildings, target-oriented quantitative improvements of the resilient performance of these buildings have been reported rarely. To address this gap, the seismic resilience of two existing RC frame buildings located in a high seismic intensity region of China were assessed based on the Chinese Standard for Seismic Resilience Assessment of Buildings. The critical engineering demand parameters (EDPs) affecting the seismic resilience of such buildings were identified. Subsequently, the seismic resilience of buildings retrofitted with different isolation schemes (i.e., yield ratios) were evaluated and compared, with emphasis on the relationships among yield ratios, EDPs, and levels of seismic resilience. Accordingly, to achieve the highest level of seismic resilience with respect to the Chinese standard, a yield ratio of 3% was recommended and successfully applied to the target-oriented design for the seismic-resilience improvement of an existing RC frame building. The research outcome can provide an important reference for the resilience-based retrofitting of existing RC frame buildings using seismic isolation in urban cities.

     

Earthquake Probability of the “Seismic Gap” on the Longmenshan Fault

Using the layered viscoelastic medium model, this paper calculated the coulomb stress loading effect on the Lushan epicenter generated by the Wenchuan earthquake. Then combined with the rate-state friction law proposed by Dieterich J. (1994), we obtain the probability of an M_W ≥ 6.0 earthquake occurring in the vicinity of Lushan. The results show that the probability of M_W ≥ 6.0 earthquake of the Lushan region in 2013 is up to 18%, indicating that the stress disturbance caused by the Wenchuan earthquake accelerated the Lushan earthquake. This paper also calculates the coulomb stress accumulation on the "seismic gap" generated by the two earthquakes of Wenchuan and Lushan, and combined with the background seismicity, gives the M_W>6.0 earthquake probability of the "seismic gap". Although there may be a certain error in the results because of the Dayi earthquake, selection of the medium model parameters and background seismicity, the seismic probability of the "seismic gap" is increasing. Thus, we think destructive earthquakes are still likely to occur in the "seismic gap".     

汶川和芦山地震之间地震空区综合研究进展

为了探索汶川与芦山地震之间的地震空区的深部结构,探讨该地区的物质运移方式及动力学模式,评价区域断层的地震活动性,本研究小组于2015年5月至今共开展了2期共约3年的地震观测.前期得到的主要结论包括：（1）地震空区两端应力状态差异显著,且存在沿断裂带的横向应力差;（2）接收函数分析发现一个平行于马尔康断裂的Moho面上隆,泊松比较高的条带状结构从地震空区延伸到龙日坝断裂,可能是下地壳撕裂和部分熔融的结果;（3）地震空区以下,上地壳速度相对偏低,在下地壳存在明显的部分熔融体,这可能是地震能量不能积累的原因之一;（4）地震空区完整性震级M_c=0.2以上的地震的活动性仍然很低;基于密集的监测台阵（约70台地震计）的走时定位也初步显示了龙门山断裂带的地震空区段仍然很平静,但是其东边的断裂带（包括大邑断裂等以及一些隐伏断裂）上地震活动比较活跃.判断这些断裂可能是该区域应力积累的主要断裂,值得进一步关注;（5）提出了地震空区产生的机制：空区北东-南西两端水平应力差导致空区地壳的撕裂,地幔物质上涌,产生部分熔融,空区地壳抬升以塑性形变为主,穿过空区段的龙门山断裂带地震活动性低,地表地形较平滑.