Efficient strong motion duration of pulse-like records for nonlinear structural analyses     

Constantinos C. Repapis  Petros P. Mimoglou  Vicky V. Dimakopoulou  Ioannis N. Psycharis  Ioannis M. Taflampas 《地震工程与结构动力学》2020,49(5):479-497

The special interest produced by near-field directivity records and their effect on structural response has given a new significance in the velocity time history, its pulse-like content, and relevant parameters and indices. Recent research has shown that directivity pulses inherent in these records govern the linear and the nonlinear response of a wide range of structures. Based on this observation, it is suggested in this paper that a truncated ground motion, limited to the duration of the predominant velocity pulse, can be efficiently used to predict the structural response, instead of the base motion with the total duration, reducing significantly the required runtimes. The proposed methodology is verified for a series of medium to high rise reinforced concrete buildings, for which nonlinear time-history analyses are performed for a vast suite of pulse-like near-field records applied as base excitations with their total duration and the proposed truncated one. Comparison of the results for the response displacements and forces shows very good agreement, permitting the acceptance of the pulse duration as the efficient strong motion time interval of the original record, which determines the response and, thus, it can be used for nonlinear structural analyses.  相似文献   

Multimodal water age distributions and the challenge of complex hydrological landscapes     

Nicolas B. Rodriguez  Paolo Benettin  Julian Klaus 《水文研究》2020,34(12):2707-2724

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Orbital control on cyclical organic matter accumulation in Early Silurian Longmaxi Formation shales     

Siding Jin  Hucheng Deng  Xing Zhu  Yan Liu  Sibing Liu  Meiyan Fu 《地学前缘(英文版)》2020,(2):533-545

High resolution(939 samples)total organic carbon content(TOC)analyses were conducted on the Shuanghe Section of^152.6 m in the Changning area,Sichuan Basin.The sampling section was divided into two units considering the distinct-different deposit environment and sediments accumulation rate.The lower part(Unit 1)and the peer part(Unit 2)with high resolution sample spacing(0.08–0.4 m)enables the identification of the precession cycle in two sedimentary sequences with distinct different sedimentary accumulation rate.MTM Power spectral analyses on untuned TOC series reveals significant peaks exceeding above the 95%confidence level and shows that both Unit 1 and Unit 2 have recorded Milankovitch cycles of 405 kyr long eccentricity,short eccentricity,obliquity and precession.The floating astronomical time scale(ATS)was constructed on the Shuanghe Section in the Early Silurian(~439.673–444.681 Ma),and which was calibrated by 405 kyr long eccentricity cycles.The total duration of the Wufeng and Longmaxi shales is 5.01 Myr.The floating ATS used for estimating the duration of the graptolite zones and each stage in the study interval.Finally,we postulated two models that could verify the linkage between orbital cycle and organic accumulation.To make sure whether productivity or preservation is the main factor that under long eccentricity control,the phase correlation between the obtained filtered signal and the theoretical orbital solution should be made clear in the further research.  相似文献   

相关和频谱分析法在岩溶系统中的应用研究综述     

李建鸿  蒲俊兵  张陶  王赛男 《中国岩溶》2020,39(3):335-344

岩溶含水层由多重含水介质组成，具有高度的非均质性，从系统角度出发，将岩溶系统看作是一个过滤器，将降雨作为输入信号，泉流量、水位、电导率、浊度等物理化学参数作为输出量进行相关和频谱分析是认识岩溶系统内部结构特征的有效方法。文章综述了相关和频谱分析法在岩溶系统研究中的应用，首先介绍了相关和频谱分析法基本理论的形成、发展过程和研究意义，然后总结了如何根据不同的研究目的选择相关和频谱分析法使用的时间序列的长度、周期和类型，最后阐述了该方法应用于岩溶系统分析的局限性。   相似文献   

场地类别分类方案研究     

陈国兴  丁杰发  方怡  彭艳菊  李小军 《岩土力学》2020,41(11):3509-3522

基于性能的抗震设计，要求工程师设计出具有预期抗震性能的结构，一个关键因素是地震作用的确定，这在很大程度上取决于局部场地条件。通过收集和分析北京、苏州和唐山城区956个钻孔资料，建立地表20 m和30 m深土层走时平均剪切波速VS20和VS30的关系式；现场钻探获取北京城区深105 m的典型钻孔原状土样，试验给出各类土体动剪切模量和阻尼比曲线；建立北京城区170个钻孔的场地反应计算模型，采用Nakamura提出的HVSR法和陈国兴等提出的弱震法估算场地基本周期TS值，结合国内外现行抗震规范的场地分类及一些学者对场地分类的研究成果，提出两种新的场地分类建议方案：基于等效剪切波速VSE和覆盖土层厚度H（地表至剪切波速VS ≥ 500 m/s的基岩深度）的双指标场地分类方案及基于VSE、H和TS的三指标场地分类方案。提出的场地分类方案对我国现行抗震规范场地分类方法的改进有参考价值。  相似文献   

时域反射仪（TDR）测定土壤含水量标定曲线评价与方案推荐     

徐玲玲  高彩虹  王佳铭  金会军  吴青柏  DYCK Miles  何海龙 《冰川冻土》2020,42(1):265-275

时域反射仪（Time Domain Reflectometry）可用于室内和田间快速、 准确、 自动测定土壤含水量， 是目前应用最广泛的土壤含水量测定方法之一。适宜的土壤含水量标定曲线（即土壤表观介电常数和土壤含水量之间的关系）是TDR准确测定土壤含水量的关键。目前文献中存在大量的土壤含水量标定曲线， 但尚未有研究对这些标定曲线进行系统的验证和分析评价。因此， 它们的准确性和适用范围尚不明晰， 严重影响到与土壤含水量测定相关的研究。通过查阅大量国内外文献， 收集整理了一系列土壤含水量标定曲线的经验公式（19个）和半经验半物理模型（5个）， 并利用大量的文献实测数据对其进行综合评价。同时运用均方根差（RMSE）， 平均误差（AD）， 纳什效率系数（NSE）等三个指标对比分析和评价这些标定曲线的准确性和可靠性。研究结果表明： 经验公式中Topp、 Roth（1992）2、 Jacobosen、 Yoshikawa2、 Alharathi模型和半经验模型中Malicki1公式及其修订模型综合性能较好。研究成果可为利用TDR准确测定土壤含水量及土壤含水量标定曲线的选择提供参考和指导。  相似文献   

黔中—渝南铝土矿含矿岩系微量元素区域分布特征及物质来源探讨          下载免费PDF全文

刘平  韩忠华  廖友常  聂坤 《贵州地质》2020,37(1):1-13

黔中—渝南成矿带石炭纪铝土矿含矿岩系,分别形成于修文、息烽—遵义和黔北—渝南三个沉积区,大多数铝土矿属产于碳酸盐岩侵蚀面上的、少数为产于泥页岩侵蚀面上的硬水铝石沉积型铝土矿床。修文沉积区铝土矿中Zr、RE2O3含量最多,息烽—遵义沉积区铝土矿中Ga含量最多,黔北—渝南沉积区Li含量最多,各有特色。修文沉积区铝土矿含矿岩系的母岩,是其下伏寒武系碳酸盐岩与下奥陶统页岩、灰岩、白云岩;息烽—遵义沉积区含矿岩系的母岩为下伏下奥陶统页岩、灰岩及白云岩;黔北—渝南沉积区含矿岩系的母岩,是下伏下志留统泥、页岩和上石炭统石灰岩。碳酸盐岩中Al2O3与稳定的微量元素含量甚少,要演变成大面积铝土矿,必须要配以足够的含Al2O3和微量元素较多的泥、页岩,才可能满足形成大规模铝土矿的物质需求。  相似文献   

深时全球海平面变化重建方法的回顾与展望     

许艺炜  胡修棉 《高校地质学报》2020,26(4):395-410

全球海平面变化对古地理、古生物、古气候演化以及能源矿产分布具有重要的控制作用。然而，目前学界对深时海平面变化的驱动机制尚不清楚，部分归因于缺乏高精度全球海平面变化的恢复。文章回顾了全球海平面变化研究的起始与发展过程，归纳出五种类型的深时海平面变化重建方法和技术，即地层学、沉积学、洋盆动力学、同位素地球化学方法和大数据技术。并总结了上述研究方法的原理、优势和不足，并以白垩纪全球海平面重建为实例，讨论了当前深时全球海平面重建的难点和争议点，并对未来深时全球海平面变化重建进行了展望。  相似文献   

Application of open tools and datasets to probabilistic modeling of road traffic disruptions due to earthquake damage     

Catarina Costa  Rui Figueiredo  Vitor Silva  Paolo Bazzurro 《地震工程与结构动力学》2020,49(12):1236-1255

The disruption of a transportation network can have a high social and economic impact on the welfare of a society, as it can significantly affect the daily routines of a community. Although many studies have focused on the estimation of physical risk in the components that compose these networks, only a limited number have analyzed their interconnections and impact in the traffic flow. The present study analyzes how earthquake damage can disrupt the road network in an urban environment, and how this will influence the ability of the population to travel. Traffic due to daily commutes is modeled for different layouts of the network, corresponding to possible disruptions caused by earthquake damage. The duration and length of each trip were calculated both for the undamaged network conditions and for the disrupted network. The increase in the median duration and length of each trip allows estimating the economic loss for each event due to drivers' delay. By combining the probability of a specific road being blocked with its number of users, the average number of affected vehicles was estimated, and the most critical segments identified. The methodology was applied to a case study concerning the road network of the area around the Italian city of Messina in Sicily. The results were calculated for both a repetition of the well-known historical event of 1908 and a set of simulated earthquakes consistent with the national probabilistic seismic hazard model of Italy.  相似文献   

Calibration method affects the measured δ2H and δ18O in soil water by direct H2Oliquid–H2Ovapour equilibration with laser spectroscopy     

Hongxiu Wang  Bingcheng Si  Dyan Pratt  Han Li  Xiaojun Ma 《水文研究》2020,34(2):506-516

The direct H₂O_liquid–H₂O_vapour equilibration method utilizing laser spectroscopy (DVE-LS) is a way to measure soil pore water stable isotopes. Various equilibration times and calibration methods have been used in DVE-LS. Yet little is known about their effects on the accuracy of the obtained isotope values. The objective of this study was to evaluate how equilibration time and calibration methods affect the accuracy of DVE-LS. We did both spiking and field soil experiments. For the spiking experiment, we applied DVE-LS to four soils of different textures, each of which was subjected to five water contents and six equilibration times. For the field soil experiment, we applied three calibration methods for DVE-LS to two field soil profiles, and the results were compared with cryogenic vacuum distillation (CVD)-LS. Results showed that DVE-LS demonstrated higher δ²H and δ¹⁸O as equilibration time increased, but 12 to 24 hr could be used as optimal equilibration time. For field soil samples, DVE-LS with liquid waters as standards led to significantly higher δ²H and δ¹⁸O than CVD-LS, with root mean square error (RMSE) of 8.06‰ for δ²H and 0.98‰ for δ¹⁸O. Calibration with soil texture reduced RMSE to 3.53‰ and 0.72‰ for δ²H and δ¹⁸O, respectively. Further, calibration with both soil texture and water content decreased RMSE to 3.10‰ for δ²H and 0.73‰ for δ¹⁸O. Our findings conclude that the calibration method applied may affect the measured soil water isotope values from DVE-LS.  相似文献