A PRACTICAL MODEL FOR SEISMIC ANALYSIS OF REINFORCED CONCRETE SHEAR WALL BUILDINGS

A simple macro-model for reinforced concrete shear walls is proposed, which consists of spring elements representing flexure and shear behaviour. The model for flexural behaviour is based on section analysis, while the model for shear behaviour is based on key parameters of the flexural behaviour. Four wall test specimens are selected to evaluate the reliability of the model. Modelling parameters for the backbone curves and the hysteretic rules are examined by conducting static and time history analyses, with the hysteretic response of a test specimen compared to that calculated using the proposed model. Results show some differences between measured and calculated shear force versus shear distortion relationships, but the model is acceptable because the differences do not significantly affect calculated global response. Parametric studies are also conducted to examine the influence of modelling parameters on seismic demand and capacity, which are the major design parameters for structural performance evaluation. Differences due to variation in modelling parameters are not significant, further indicating that the proposed model is reasonable.     

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.     

Skeletal evidence for hyperparathyroidism in a 19th century child with rickets

The skeletal remains of a child aged 2.5–3.5 years, recovered during archaeological excavations at the churchyard of St Martin's Church, Birmingham, UK, were examined using gross observation, radiography and scanning electron microscopy. Lesions suggestive of the presence of rickets and of secondary hyperparathyroidism were found. This appears to be a first report of secondary hyperparathyroidism in response to rickets in a palaeopathological specimen. The potential of microscopic examination of bone for interpreting disease processes is emphasised. Copyright © 2006 John Wiley & Sons, Ltd.     

现代测绘技术在古建烫样数字化项目中的应用

烫样是研究清代皇家建筑的珍贵文物,为配合文物信息数字化工作的开展,针对烫样数据的采集和处理方法进行了深入研究。在综合考虑多种数据采集方法的特点及烫样数字化记录的难点后,选择使用手持式三维扫描仪与多视角三维重建技术相结合的方式来进行烫样的基础数据采集,并通过实践总结出了一套完整的数据采集和处理工作流程。与此同时,针对成果可能的应用方式做了些许尝试,且为数据的后期维护与进一步利用拟定了数据管理系统的建设方案。     

我国旅游业研发总体水平、区域分布与政策建议

本文利用文献法和定量分析等方法,深入分析了我国旅游业技术和研发现状。针对我国旅游业研发总体水平低,研发能力集中于发达地区等问题,从观念、政府、机构、人才等方面提出了具体政策建议。     

Securing the Return: How Enhanced US Border Enforcement Fuels Cycles of Debt Migration

Expanded border enforcement has made unauthorised migration to the US more risky, costly, and prone to failure. Research on the material consequences of border enforcement for migrant‐sending households in Central America reveals that the economic hardships enforcement exacts on migrants at times diminishes enforcement's desired deterrent power. Heightened risks have driven up the cost of migration and pushed many to fund their trips through loans. Consequently, migrant detention, deportation, or death can result in poverty and privation for indebted households and the seizure of loan collateral, typically homes and land, in turn prompting crises in household reproduction. With a US wage the most viable means to ameliorate economic hardships, enforcement outcomes push some to return migration. Our findings suggest that US border enforcement efforts at times perpetuate the very unauthorised migration they seek to impede, while also helping to reproduce the border itself by deepening the marginalisation that drives migration decisions.     

Potemkin Revolution: Utopian Jungle Cities of 21st Century Socialism

This paper explores the entanglement of ideology and materiality in the production of the spaces of 21^st century socialism. “Millennium Cities” are currently being constructed for indigenous communities throughout the Ecuadorian Amazon, with revenues derived from petroleum extracted within their territories. As iconic spatial symbols of the “Citizens’ Revolution”, the Millennium Cities would appear to embody “the original accumulation of 21^st century socialism”—a utopian state ideology promising the collective appropriation of natural resources without the dispossession of the peasantry. Drawing on extensive field research, we argue that they are better understood as a simulation of urban modernity that is symptomatic of the predominance of ground rent in South American capitalism, and which conceals the violent repression of an autonomous indigenous project of petroleum‐based modernization. The original accumulation of 21^st century socialism can therefore be interpreted as a “fantasy of origins”, which functions to reproduce the primitive accumulation of capital.     

Displacement Ductility Limits for Pile Foundations in Cohesionless Soils

The displacement ductility limit for seismic design of concrete piles is determined for the range of cohesionless soils expected in practice. The curvature ductility capacity associated with specified performance limit states, namely, the “serviceability” and “damage-control” limits, is determined based on the current provisions for confining steel. An analytical model is applied to assess the displacement ductility factor at the specified curvature ductility level. The investigated parameters include the soil stiffness, pile diameter, longitudinal reinforcement ratio, axial force level, and pile above-ground height. A set of design displacement ductility factors is recommended and verified to ensure the satisfactory seismic performance.     

Effects of Geometrical Features on the Seismic Response of Historical Masonry Towers

ABSTRACT

Historical masonry structures are often located in earthquake-prone regions and the majority of them are considered to be seismically vulnerable and unsafe. Historical masonry towers are slender structures that exhibit unique architectural features and may present many inadequacies in terms of seismic performance. The seismic protection of such typologies of structures and the design of effective retrofitting interventions require a deep understanding of their behavior under horizontal loads. This paper presents the results of the seismic performance evaluation of historical masonry towers located in Northern Italy. A large set of case studies is considered, comprising a significant number of towers with high slenderness and marked inclination. First, a preliminary assessment of the dynamic behavior of the different towers is carried out through eigenfrequency analyses. Then, non-linear dynamic simulations are performed using a real accelerogram with different peak ground accelerations. A damage plasticity material model, exhibiting softening in both tension and compression, is adopted for masonry. The huge amount of results obtained from the non-linear dynamic simulations allows a comparative analysis of the towers to be performed in order to assess their seismic vulnerability and to show the dependence of their structural behavior on some geometrical characteristics, such as slenderness, inclination, and presence of openings and belfry. The evaluation of different response parameters and the examination of tensile damage distributions show the high vulnerability of historical masonry towers under horizontal loads, mainly in the presence of marked inclination and high slenderness. Some general trends of the seismic behavior of the towers are deduced as a function of the main typological features.