DAMAGE AND DUCTILITY DEMAND SPECTRA ASSESSMENT OF HYSTERETIC DEGRADING SYSTEMS SUBJECT TO STOCHASTIC SEISMIC LOADS

Damage phenomena observed in structures subject to intense seismic events are the result of stiffness and strength degradation. This paper studies the damage assessment of hysteretic degrading structures described by means of the Bouc-Wen model, modified to represent the mechanical degradation induced by severe earthquakes. In order to consider randomness of seismic action, the analysis is performed by adopting a stochastic approach and the Park and Ang damage functional is also evaluated in stochastic way. A parametric analysis is carried out with the aim to analyse the effect of mechanical characteristics and measure parameters of earthquake intensity on seismic response and damage level. Damage spectra are finally obtained and they are used to develop, on the basis of the Performance Based Seismic Design, ductility demand spectra.     

基于价值转移方法的我国游憩活动价值评价

鉴于目前我国在构建价值转移模型中存在的限制因素,本文采用基于Meta分析的价值转移方法并尝试利用国外游憩活动价值评价的实证研究结果,构建基于Meta分析的国际间价值函数转移模型,估算了我国10种游憩活动的日平均消费者剩余.通过将价值转移模型估算的游憩活动价值“转移值”与国内97个游憩价值评价的“真实值”做比较,对价值转移模型的有效性和可靠性进行统计检验,平均转移误差为18.74％.最后,总结了提高我国Meta回归价值转移模型的具体、可操作性方法及途径.     

Knowledge making and corporate environmentalism from the perspective of the egg tray

ABSTRACT

In the 1990s, there was a change in capitalist thinking on environmental issues in many global settings, which materialised in what has been termed corporate environmentalism. Beginning with a history of the moulded fibre egg tray and one of its primary manufacturers, this is a case study of how corporate environmentalism came about and was enacted as a confluence of corporate priorities, environmental concerns, production processes, materials, and the development of new measuring tools. Unlike the many environmental history studies that emphasise the role of NGOs and policy developments, this study begins in the business world. More specifically, it is based in the making of environmental knowledge in the form of life cycle assessments and environmental accounts and in the environmental reframing of materials like moulded pulp and plastic. In this way it is the story of how it became reasonable for a manufacturer of egg trays to choose the slogan, ‘Choose Fibre. Save Nature’.     

A Risk Assessment for Cultural Heritage in Southern Iraq: Framing Drivers,Threats and Actions Affecting Archaeological Sites

ABSTRACT

This paper proposes a classification of the risks threatening archaeological sites in southern Iraq and suggests some possible remediation to better preserve them. This has been possible thanks to a research methodology that combines remote sensing and ground control on a sample of 558 sites documented by the Iraqi-Italian QADIS survey project. A three-tier typological framework has been created illustrating the risks jeopardising the cultural heritage of the region. This research showed that the most impacting risks are the ones caused by agricultural activity, despite current narratives which mainly focus on looting and violent destruction. To get at the root of the problem, current laws protecting cultural heritage in Iraq are analysed, as well as how the cultural authorities are organised on the ground. Improving the organisation of the SBAH, engaging the local communities towards the issue of sites’ protection and introducing preventive archaeology are among the solutions proposed.     

Restoration Interventions at the Roman Nymphaeum in Amman: Identification and Evaluation

Abstract

Over the last few decades, conservation work has been conducted by the Department of Antiquities of Jordan (DoA) on the Roman Nymphaeum in Amman. This intervention has taken the form of direct and indirect actions. In this article it will be shown that the conservation works concentrated on reinforcing the structure and reconstructing some architectural features of the building, with little consideration of the techniques and materials used. Intervention actions were mostly poor in terms of their scientific approach, and neither proper planning nor a well-defined methodology existed. This study provides a holistic approach for the evaluation of the state of the conservation of the monument in terms of quality and quantity. Thus, the results could be a valuable source for establishing comprehensive risk mitigation for future restoration work and site management. In addition, establishing practical restoration guidelines could help in developing socio-economic benefits for the community through tourism.     

A PROCEDURE FOR ESTIMATING INPUT ENERGY SPECTRA FOR SEISMIC DESIGN

In this paper, the damage potential of an earthquake ground motion is evaluated in terms of the total power of the acceleration of the ground motion. By assuming an appropriate spectral shape for the input energy spectrum, and using the well-known Parseval theorem for evaluating the total power of a random signal, the peak amplification factor for the equivalent input energy velocity spectrum can be determined. It is shown that the peak amplification factor for the input energy spectrum depends on the peak-ground-acceleration to peak-ground-velocity ratio and duration of the strong motion phase of the ground motion. Values for the equivalent input energy velocity amplification factor vary from about 2 to 10 for most of the recorded ground motions used in this study. Although a considerable scatter of data is observed in this study, the peak amplification factor predicted by the Fourier amplitude spectrum of the ground acceleration provides a fairly good estimate of the mean value of the peak input energy compared to that determined from inelastic dynamic time history analyses, particularly for systems with high damping and low lateral strength. The peak amplification factor derived in this paper provides a more consistent approach for estimation of seismic demand when compared to an earlier empirical expression used for the formulation of duration-dependent inelastic seismic design spectra, even though only a slight difference in the required lateral strength results from the use of the new formula.     

A DAMAGE MODEL FOR THE ANALYSIS OF THE SEISMIC RESPONSE OF MONUMENTAL BUILDINGS

In this paper the Author proposes a damage model for the analysis of masonry plates and shells, which is based on an improvement of a previous constitutive model. The modifications introduced, connected to the head joint damage, allow us to study the influence of masonry texture on the damage modes once the mechanical characteristics of the elements constituting the masonry and the results of tests on simple assemblages are known. Having a nonlinear constitutive model is certainly one of the basic elements for understanding the damage mechanisms in masonry buildings. If, in fact, an elastic-linear constitutive model may be used under normal loading conditions, in critical situations it is necessary to model the damage and the dissipation mechanisms that occur between the elements, stone (brick) and mortar, in correlation with their characteristics and kind of masonry. To validate the model a comparison is made between the numerical and experimental results, in the case of tests available in the literature in masonry panels subjected to out-of plane loading and in a real structure through the observation of the damage in Umbria (Italy) surveyed after the 1997 earthquake.     

EVALUATION OF CONVENTIONAL AND ADAPTIVE PUSHOVER ANALYSIS I: METHODOLOGY

In this paper, a methodology is suggested and tested for evaluating the relative performance of conventional and adaptive pushover methods for seismic response assessment. The basis of the evaluation procedure is a quantitative measure for the difference in response between these methods and inelastic dynamic analysis which is deemed to be the most accurate. Various structural levels of evaluation and different incremental representations for dynamic analysis are also suggested. This method is applied on a set of eight different reinforced concrete structural systems subjected to various strong motion records. Sample results are presented and discussed while the full results are presented alongside conclusions and recommendations, in a companion paper.     

三星堆一号青铜神树的三维数字建模与静力学分析

结构稳定性是评估文物安全的重要方面。三星堆二号坑出土1号青铜树体量庞大、结构复杂,且存在腐蚀、裂纹等危险因素,为了充分记录、评估其保存状况,本研究在原始几何形状和内部构造的基础上,利用三维数字建模技术,建立其几何模型和数值模型,并估算出青铜神树的质量分布和质心位置等无法实地测量的数据,并使用有限元方法,从应力和位移的角度分析青铜树的静置状态下的安全性。经过有限元模拟和材料力学简化计算,发现龙身和树干连接处、树枝根部应力较大,是易受损区域。     

北京市生态城市建设能力的机理与综合评价——基于城市化与生态化视角

基于城市化与生态化两大子系统,从人口与空间城市化、经济城市化、社会城市化、和生态环境水平、生态压力、生态抗逆能力六个层面,构建生态城市建设能力评价的指标体系,运用相关分析、回归分析和主成分分析等方法,对1991-2002年北京市生态城市建设能力机理进行了综合分析与评价。