Numerical Fragility Analysis of Vertical-Pile-Supported Wharves in the Western United States

This study develops seismic fragility curves for vertical-pile-supported wharves commonly found in the western United States. Nonlinear time-history analyses of a two-dimensional numerical model under two ground motion suites are performed. The results show that the jumbo container cranes increase by 10.8% in the wharf deck drift. By using the experiment-based limit states, the proposed fragility curves demonstrate that, at a PGA of 0.50 g, the probabilities of exceeding slight, moderate, extensive, and complete limit states are approximately 23.0%, 7.0%, 4.0%, and 3.0%, respectively, while at a PGA of 1.00 g, the exceeding probabilities increase to 44.0%, 19.0%, 14.0%, and 11.0%, respectively.     

Friction Model for Sliding Bearings under Seismic Excitation

In this article, an experimentally validated model is proposed in order to take into account main sources of performance degradation that could be experienced by friction-based devices during a seismic event. Particular attention is dedicated to the degradation of friction characteristics due to repetition of cycles and consequent temperature rise. This effect can be responsible for overestimate of the dissipation capacity of the device. The proposed model of frictional behavior is suitable for immediate implementation in generalized structural analysis codes and provides an important design tool for realistic assessment of the seismic response of structures equipped with friction-based isolators.     

Bioturbation and the upward movement of sediment particles and archaeological materials: comments on Bueno et al.

The literature on bioturbation, both from the biological and archaeological points of view, is growing steadily. Available data suggests that ants and termites are responsible for the upward movement of soil/sediment particles and archaeological materials. It is argued that this could be the most parsimonious explanation for the stratigraphic data presented by Bueno et al. (2013), given the size range of displaced materials and the environmental setting, composed of a sandy soil in a savannah region.     

VERTICAL EARTHQUAKE GROUND MOTION RECORDS: AN OVERVIEW

Recent research clearly shows the importance of including the vertical component of earthquake ground motion in seismic analysis and design. In addition, pioneering studies [e.g., Elnashai and Papazoglou (1997)] have explored and documented the characteristics of available near-field vertical ground motion records. As a follow-up, this paper complements earlier studies, and investigates additional far-field records and available downhole array vertical motion records. A total of 111 free-field strong motion records (from California) and available downhole array records are employed. Compared to near-field records, far-field records generally contain more energy at longer periods. Based on the available data, response spectra are presented for near-field and far-field records respectively. The currently scarce downhole-array vertical motion records show that significant amplification may occur within the top 10-20 m soil layers. A simple one-dimensional (ID) vertical wave propagation model did not appear adequate for modelling the observed downhole array response. In using such a simplified model, very high viscous damping in the range of 15-25% was needed to match the recorded downhole vertical response, even for small tremors. Additional data and research are required [Beresnev et al., 2002] towards the development of a rational vertical motion site response analysis procedure.     

故宫太和殿二层斗拱竖向加载试验

为了更好地保护古建筑,采取静力试验方法,以故宫太和殿二层平身科、柱头科、角科斗拱为对象,研究了竖向荷载作用下斗拱的受力性能。基于上述3种斗拱构造特征,制作了1∶2比例模型,进行了竖向加载试验,讨论了不同斗拱在荷载作用下的破坏形式、内力及变形特征,归纳了斗拱的竖向刚度计算模型。结果表明:竖向荷载作用下,太和殿二层斗拱的坐斗及与之相交的头翘、正心瓜拱容易产生破坏,且模型倒置时下层构件受力要小于上层构件。对于不同斗拱而言,斗拱极限承载力:平身科角科柱头科;斗拱变形及残余变形量:柱头科角科平身科;斗拱延性:角科柱头科平身科。竖向荷载作用下,太和殿二层斗拱的竖向刚度计算模型可简化为三折线段形式。     

Distribution of Lateral Forces in Base-Isolated Buildings Considering Isolation System Nonlinearity

The ASCE 7 equivalent lateral force method for base-isolated buildings applies a triangular distribution of forces to the superstructure. This distribution attempts to approximately account for the observed effects of isolation system nonlinearity on the superstructure response, but a more rational approximation is needed. Using nonlinear regression analysis of median response data from nonlinear response history analysis of representative systems, improved equations are developed to estimate the lateral force distribution in the superstructure. The ASCE 7 distribution, a revision considered by a SEAONC committee, and the improved distribution developed here are evaluated. Only the improved equations are accurate over many system parameters.     

Effect of Horizontal Component Definition on the Characterization of Vertical Ground Motions: Application to Eastern Canada

In this article, ground motions recorded on rock sites in eastern Canada are studied in order to characterize their vertical acceleration components. Emphasis is placed on the sensitivity of vertical-to-horizontal spectral ratios to: (i) inter-component intensity correlations and (ii) the use of geometric mean horizontal components at each site instead of considering them individually. Four different definitions of horizontal components are investigated. Vertical-to-horizontal spectral ratios are compared with the findings of other researchers. We illustrate how the results can be used to evaluate vertical acceleration demands on rock sites in eastern Canada.     

西安鱼化寨遗址仰韶文化土坑墓发掘简报

一、遗址概况鱼化寨遗址位于西安市雁塔区鱼化寨街道鱼化寨村西北侧,皂河西岸的二级台地上,今西安外事学院北校区西北部。遗址东、北两侧被皂河环绕,地势中心高,周围低(图一)。2002年～     

Subsistence strategies and palaeodiet of Tell al-Husn,northern Jordan: nitrogen and carbon stable isotope evidence and radiocarbon dates

This research examines the diet and subsistence strategies during the Early Bronze Age III (EB III) or/and the beginning of the Early Bronze Age IV (EB IV) and the Middle Bronze Age I–II (MB I–II) periods of Tell al-Husn, northern Jordan. Stable isotope analyses of carbon (δ¹³C) and nitrogen (δ¹⁵N) were carried out on human teeth of known ages. Faunal samples were radiocarbon dated, while their carbon (δ¹³C) and nitrogen (δ¹⁵N) stable isotopes were analyzed for comparative purposes. The results revealed that the diet of the individuals of the MB I is richer in terrestrial animal protein than the individuals of the EB III and/or early EB IV and MB II, a probable indicator for more agricultural activities toward the end of the MB and the LB and during the EB III and/or early EB IV. The results suggested that the individuals of tomb 2 are probably of higher social status or were subjected to different environmental conditions compared to the individuals of chamber 3 of tomb 1. In addition, the results suggested a higher social status for an individual buried contemporaneously with other individuals in chamber 3 of tomb 1.     

The case for extending measures of democracy in the world “Beneath”, “Above”, and “Outside” the national level

This article applies spatial theory, or the view that phenomena are distributed in space, to democracy. This analysis demonstrates that plural (two or more) democratic practices are evident in three spatial categories: (1) vertical stratification (i.e. at different levels of governance), (2) horizontal separation (i.e. among different agents operating at each level of governance), and (3) social association (i.e. in workplaces, families, schools). This finding, that plural democratic practices are demonstrated by agents operating at multiple levels of governance and in various non- or quasi-governmental associations prompts us to argue that measures of democracy in the world should be extended to spaces “beneath”, “above”, and “outside” the national level – presently the dominant locus for regular batteries that test the quality and extent of democratic practices globally. However, global data on the quality and extent of democracy at these other levels needs to be built before such an extension can happen.