Modification of Dynamic Foundation Response Due to Soil-Structure Interaction

This paper presents the results from extensive parametric dynamic analyses of soil-structure systems that focus on the clear modification (increase or decrease) of the acceleration amplitude at the foundation with respect to the free-field, especially for squatty structures. Properties of the systems are selected such as to cover a wide range of meaningful geometries and materials for engineering practice. The results are presented in terms of weighted modification factors of the maximum foundation acceleration amplitude with reference to the corresponding maximum acceleration amplitude at free-field, for squatty and more slender structures. For the large majority of the studied systems, foundation acceleration decreases from the free-field by 10–15% on average. Nevertheless, acceleration demand at the foundation increases compared to the free-field, for 30% of squatty and for 15% of the more slender structures. Modification of the foundation acceleration amplitude is also correlated with the ratio of the predominant period of the input motion to the flexible-base system period. Finally, the findings of this study are compared with sparse available recorded data from the Seismic Hazard Harmonization in Europe database.     

关于中日钓鱼岛争端中"美国因素"的历史考察

文章对中日钓鱼岛争端中的“美国因素”进行了系统考察。二战后美国的日本政策与钓鱼岛问题的产生、发展及变化有着密切联系。在冷战的国际背景下,美国政府通过托管琉球与“第27号令”将中国钓鱼岛纳入其托管之下。20世纪70年代初美国又将钓鱼岛的“施政权”作为冲绳的一部分“归还”给日本,为中日钓鱼岛争端打下“楔子”。冷战结束以来,美国政府在钓鱼岛主权归属上由“模糊中立”到当今小布什政府的“小心介入”,反映了美国政府在钓鱼岛问题立场上的变化。     

从“■”同“苟”说起

“苟”与“苟”本是两个形、音、义皆不同的字。由于隶定之后,字形相近,而“苟”字又在传世典籍中鲜有用例,故二字混而不别。“”本是“苟”的古文异体,亦被误认为是“苟”的异体,并因此由不同角度讹变出不同的字形。本文力图阐明“苟”、“苟”混而不别及相关异体产生的原因由来。     

Cumulative Ductility Spectra for Seismic Design of Ductile Structures Subjected to Long Duration Motions: Concept and Theoretical Background

A seismic design procedure that does not take into account the maximum and cumulative plastic deformation demands that a structure will likely undergo during severe ground motion could lead to unreliable performance. Damage models that quantify the severity of repeated plastic cycling through plastic energy are simple tools that can be used for practical seismic design. The concept of constant cumulative ductility strength spectra, developed from one such model, is a useful tool for performance-based seismic design. Particularly, constant cumulative ductility strength spectra can be used to identify cases in which low-cycle fatigue may become a design issue, and provides quantitative means to estimate the design lateral strength that should be provided to a structure to adequately control its cumulative plastic deformation demands during seismic response. Design expressions can be offered to estimate the strength reduction factors associated to the practical use of constant cumulative ductility strength spectra.     

An Analytical Study on the Seismic Vulnerability of Masonry Buildings in India

Two analytical models for unreinforced masonry (URM) buildings are proposed with the aim to simulate their seismic response and to estimate corresponding vulnerability functions. The proposed models are implemented in SAP 2000 nonlinear software to obtain capacity curve parameters for representative Indian URM buildings, based on a field survey and statistical analysis. Vulnerability functions are estimated using the obtained capacity curves. Damage Probability Matrices (DPMs) are obtained using the approximate PGA-intensity correlation relationship as per Indian seismic building code and are compared with the commonly used intensity scales and empirical damage data observed after the 2001 Bhuj earthquake.     

Behavior Factor for Performance-Based Seismic Design of Plane Steel Moment Resisting Frames

Simplified expressions to estimate the behavior factor of plane steel moment resisting frames are proposed, based on statistical analysis of the results of thousands of nonlinear dynamic analyses. The influence on this factor of specific structural parameters, such as the number of stories, the number of bays, and the capacity design factor of a steel frame, is studied in detail. The proposed factor describes the seismic strength requirements in order to restrict maximum storey ductility to a predefined value. Interrelation studies between maximum storey ductility and the Park-Ang damage index are also provided for the damage-based interpretation of the performance levels under consideration. Realistic design examples serve to demonstrate the ability of the proposed factor to convert conventional force-based design to a direct performance-based seismic design procedure.     

景观生态系统及其要素的理论分析

景观生态学是个新兴且发展迅速的学科领域。对其基本概念、原理和理论的研究探索与规范是目前该学科的重要方向。本文即是在前人工作基础上并结合论文作者的理解,比较系统地讨论了景观生态系统及其要素、要素结构等问题。以期对正在形成的学科"范式"提供一定参考。     

Impact of Modification on Ground Motion Characteristics and Geotechnical Seismic Analyses for a California Site

The impact of different modification techniques on ground motion characteristics and results of seismic geotechnical analyses is investigated for a site in California. Twenty-eight motions were selected and scaled and also modified using both time domain (TD) and frequency domain (FD) techniques. PGV and PGD of the TD-modified motions are found to be larger than their FD-modified counterparts, but slightly less than the scaled ground motion characteristics. Cyclic stress ratios and amplification factors are similar for all sets of motions. Newmark-type slope displacements caused by the scaled and modified ground motions are similar (within 25%) for a variety of sliding masses.     

从"圣·迭戈"号沉船考古看海上的社会生活

对古代航海船只上社会群体生活状况的研究是社会史研究的重要课题,也是人类航海史研究不可或缺的内涵构成。但由于资料的缺乏,海上社会生活研究一直没有得到足够的关注。近些年来,由于考古工作者对沉船的科学发掘及对生活遗迹与遗物的详细纪录,使得古代海上社会生活的研究获得越来越丰富的资料。本文以"圣·迭哥"号沉船考古发现为基础,并结合文献资料、航海日记以及其他古代沉船的相关信息,对古代海上社会群体的生活状况以及社会关系进行了复原与探讨,以期能为海上社会生活史的深入研究做基础性的工作。     

Experimental Study on Seismic Performance of Mechanical/Electrical Equipment with Vibration Isolation Systems

A prototype diesel generator equipped with a vibration isolation system consisting of restrained isolators (denoted as I/system) is quasi-statically and dynamically tested. Sequentially, the seismic simulation tests are conducted to further investigate the effectiveness of additional snubbers incorporated into the vibration isolation system (denoted as I/R system). Comparing the test results to the static design demands specified in ASCE 7-10, the recommended component amplification factor could represent the horizontal acceleration amplification phenomenon of the generator equipped with I/R system; however, the seismic force demands for static design of I/R system might not be appropriate and conservative enough.