Seismic Overstrength of Shear Walls in Parking Structures with Flexible Diaphragms

The objective in current design practice for parking structures is that energy is dissipated through the formation of plastic hinges at the base of shear walls while floor diaphragms remain elastic and are vertically supported by a combination of shear walls and gravity resisting columns. Unfortunately, this objective is not always achieved due to inaccuracies in current methods for calculating demands on shear walls and in calculating the capacity of shear walls (IBC 2003 International Building Code. International Conference of Building Officials. Whittier, CA.  [Google Scholar], ACI code). When demands are overestimated and capacity underestimated, then diaphragm can fail prior to flexural yield of shear walls as was observed in several parking structures in the 1994 Northridge earthquake.

Eigenvalue and inelastic dynamic response analyses were performed in order to investigate the effects of diaphragm flexibility on wall responses and of wall overstrength on diaphragm responses. The elongated periods of parking structures due to diaphragm flexibility were found to significantly decrease seismic force demand on shear walls relative to what is calculated using codes of practice in which diaphragms are assumed to be rigid. This leads to the over design of shear walls, which further compounds the problem by preventing the flexural yielding of these walls and thereby driving inelastic response to diaphragms. Various degrees of diaphragm flexibility, shear wall layout, seismic zone, and the number of stories were considered in these analyses.

Inelastic static pushover analyses were preformed to investigate the design and capacity evaluation of shear walls. The results illustrate that the shear capacity of walls may be close to twice that calculated by codes of practice. The largest overstrengths were observed in shear walls with low height-to-length ratios in which a significant portion of the lateral load was taken by direct strut action to the foundation and without placing demands on the longitudinal tension reinforcement in the shear walls. The article concludes that methods in codes of practice for calculating shear wall demands and capacities need to be improved if good seismic performance of parking structures is to be achieved.     

Performance of Wall to Diaphragm Anchors for Use in Seismic Upgrade of Heritage Masonry Buildings

Performance of wall to diaphragm (WD) anchors in heritage unreinforced masonry (URM) buildings during the recent New Zealand earthquake series is commented on, detailing typical failure modes. Current building code provisions for the design of masonry anchors are discussed and overview of an associated experimental program investigating the effectiveness of a relatively new type of retrofit WD anchors is presented. A total of 40 anchors were tested for pull out capacity (POC), of which 30 were installed in salvaged heritage material assemblages and 10 were tested in-situ at a heritage URM building. The POC of anchors ranged from 13.01 kN to 23.12 kN when installed in a heritage URM wall and between 9.54 kN and 12.16 kN when driven from side into two consecutive floor joists of a heritage timber diaphragm. Investigated also were the effects of embedment length, installation quality, anchor location, condition of masonry, and condition of substrate materials on anchor performance.     

Rocking of Non-symmetric Rigid Blocks in Buildings Considering Effects Associated with Dynamic Soil-Structure Interaction

A dynamic model for the estimation of the rocking and/or overturning response of a free-standing non-symmetric rigid block considering rotational and horizontal excitation is proposed. The block is situated at different levels of a building with flexible base subjected to earthquakes. Base flexibility introduces the rotational component of the excitation due to dynamic soil-structure interaction (DSSI). The model is used to assess the influence of the dynamic soil-structure interaction on the behavior of the block. An illustrative example of the proposed model for non-symmetric rigid blocks in 5-, 10-, and 15-story buildings located in soft soils considering earthquakes from different seismic sources is presented. Results show that it is important to consider kinematic effects as well as inertial effects of DSSI in the dynamic response of contents. The influence of base flexibility depends on the change of spectral intensities associated to the increase of the building structural period and is larger for higher building levels.     

Boundary theory as a means to understanding social space in archaeological sites

Social space in archaeological sites is constructed and produced by differentiation in behavior (habitus) and is characterized by domains or activity areas separated by boundaries. Activity areas vary in their flexibility and permeability to intrusion of other activities. This is reflected in the nature of the boundaries between activity areas. A study of boundaries, archaeologically often represented by transitional space, can provide insight into human behavior, the use and construction of space, and the contemporaneity of activities represented in a site occupation. It is suggested that kill site activities such as primary butchering may have relatively inflexible and impermeable boundaries, that activities such as tool resharpening may be more flexible, and that secondary processing may be more permeable to the intrusion of other activities. A study of a selection of activity areas at Head-Smashed-In Buffalo Jump confirms that these concepts do enhance our understanding of site activity areas and that an examination of boundaries can allow an assessment of activity area contemporaneity.     

Flexibility in Planning and the Consequences for Public-value Capturing in UK,Spain and the Netherlands

In the 1960s, flexibility was often seen in planning literature as a negative feature, whereas today it is perceived by planners and policy-makers as a positive asset to cope with the challenges of growing complexity, opportunism and diversity in cities. The discussion seems to rest between two approaches. While planning should be flexible to facilitate a non-linear and multi-layered decision-making system, implementation should not be too flexible as the public sector might lose the controlling power and the private sector might gain increasing influence in urban development. This paper uses empirical data from case-based research on British, Spanish and Dutch urban regeneration projects, and provides an analysis of the effects of an important feature of flexibility on public-value capturing. Public-value capturing is the level at which public bodies manage to make developers pay for public infrastructure—infrastructure provision, public roads and space, public facilities and buildings, affordable and social housing—and eventually capture part of the economic value increase. This important aspect of flexibility is the level of certainty about future development possibilities before negotiations between developers and local planning bodies take place.     

Regional Wage Rigidity: The European Union and United States Compared

In recent years it has been pointed out that regional unemployment disparities are much more entrenched across member states of the European Union (E.U.) than they are in the U.S. A 'conventional wisdom' has emerged to the effect that this difference is due in part to the greater degree of wage rigidity in E.U. regions. In this paper we explore this issue by estimating short run and long run real wage (in)flexibility for the regions in five core E.U. countries (Germany, France, Italy, the United Kingdom, and the Netherlands) and for the U.S. states for the period 1976–1994. We find that real wage (in)flexibility varies across regions both in the E.U. and the U.S., but that, on average, regional wages are no less flexible in E.U. core regions than in U.S. states. The paper also examines some of the possible correlates ofregional variations in wage (in)flexibility.     

CODE PROVISIONS AND ANALYTICAL MODELLING FOR THE IN-PLANE FLEXIBILITY OF FLOOR DIAPHRAGMS IN BUILDING STRUCTURES

In this paper a review of the provisions of some modern seismic codes for the analytical modelling of the floor diaphragm action is made and a methodology using simplified 2-D finite elements models for monolithic floors is suggested, taking into consideration the in-plane flexibility of them. The simplified models use the coarsest discretisation mesh possible, simply taking into account all the connection points of the vertical structural elements on the diaphragm of each storey. The efficiency of the proposed simplified F.E. models is tested with comparative response-spectrum dynamic analyses of various building structures with different plan shapes, according to EuroCode 8 [EC8, 1994]. The simplified models provided excellent results for the dynamic characteristics of the entire building and the stress state of the framing substructure and a fair estimation for the in-plane stresses of the floor diaphragms.     

Geosystems and Geostructures

An attempt is made to distinguish geosystems and geostructures as the two basic objects of study in geography. Geosystems and geostructures are interdependent but different spatial formations. Geosystems are defined by direct, reverse, and transformed relationships among such relatively autonomous components as natural environment, population, and economy. Geosystems tend to be superimposed on one another and are relatively flexible and stochastic. Geostructures, on the other hand, are distinguished by a unity of heterogeneous components, by comparatively clearly defined boundaries, and by considerable rigidity of construction. (One of the authors, A. M. Smirnov, died in July, 1969.)     

Geographies of relatedness

This paper explores the analytic purchase and substantive concerns of what I am calling geographies of relatedness . Drawing on recent work in feminist anthropology which has reconsidered kinship as classificatory system and practice, and highlighting the attentiveness to sites, scales and contexts within this work, I suggest ways in which a focus on relatedness may shape approaches to established and emerging matters of concern in human geography. I consider first the foundational status but flexible meaning of 'blood' in kinship thinking, and the ways the flexibility of kinship can be curtailed and its foundational status reinstated in relation to the nation and the state. Second, I consider the geographies of relatedness that are constituted through and practised in the process of establishing degrees of biological connection, delimiting difference, mapping human 'diversity' and defining personal, collective and human origins at different scales and with different effects. A focus on geographies of relatedness, I argue, highlights the ways blood ties or similarly naturalized connections move between and connect categories of relatedness with different sizes, extents and configurations across space, as well as different temporalities. It suggests an alertness to new global mappings of human relatedness and difference and combines a critical attention to ideas of the 'nature' of human reproduction as foundational, original or primal in the natural order of the social, to ideas of 'place of origin': personal, national, ethnic, racialized, universal in their familiar and emergent forms.     

High-Performance Organizations and Employment Flexibility: a Case Study of in situ Change at the Powell River Paper Mill, 1980–1994

Throughout virtually all mass production industries in North America, including the Canadian newsprint industry, a significant theme of restructuring involves a transition from 'Fordist' to more 'flexible' methods of production and employment. In this paper, shifts towards smaller, more flexible employment conditions are assessed from the perspective of a model of 'high-performance organizations'. In this model, employment flexibility is defined in terms of the blurring of the boundaries between management and workers and by continual investment in skill promotion in the pursuit of a polyvalent workforce. In practice, such issues are subject to labour-management bargaining, the outcomes of which are uncertain. Empirically, this paper provides a case study of bargaining over employment flexibility, specifically at the Powell River paper mill, to assess the extent to which the standards of the high-performance model are being achieved.     

The Effect of Stiffened Floor and Roof Diaphragms on the Experimental Seismic Response of a Full-Scale Unreinforced Stone Masonry Building

An extensive experimental program was carried out at EUCENTRE, within a research project on the evaluation and reduction of the seismic vulnerability of stone masonry structures. The main part of the experimental program has been devoted to the shaking table tests on three full-scale, two-story, single-room prototype buildings made of undressed double-leaf stone masonry. The first building tested was representative of existing unreinforced stone masonry structures with flexible wooden diaphragms, without any specific anti-seismic design nor detailing. In the second and third buildings, strengthening interventions were simulated on structures theoretically identical to the first one, improving wall-to-floor and wall-to-roof connections and increasing diaphragm stiffness. In particular, in the third specimen, steel and r.c. ring beams were used to improve the diaphragm connection to the walls and collaborating r.c. slab and multi-layer plywood panels were used to stiffen floor and roof diaphragms, respectively. This article describes the strengthening interventions applied to the third building prototype and presents the experimental results obtained during the shaking table tests. The results obtained permitted the calibration of a macroelement model representative of the nonlinear behavior of the structure.     

事有定数:明人对科举功名的认识

自隋、唐以降,伴随着科举制的创立、发展与完善,科举入仕成为社会普遍追求的理想人生模式, 以科举制度、科举人物、科举故事为核心内容的科举文化是中国传统文化的一个独特的构成部分。观照明人关于科举人物、科举故事的诸多记载和议论,基本上可以认为,命定、风水、报应等传统思想,因其理论上的包容性和阐释中的灵活性,是明人解释科举功名现象的主要理论依据。这种现象的生成,既是科场激烈竞争所引发的焦虑与无奈的结果,也是明人对社会、自然整体认知局限的自白。     

SIMULATION OF NONLINEAR SOIL-STRUCTURE INTERACTION ON A SHAKING TABLE

A new method to simulate soil-structure interaction effects in shaking table tests has recently been presented by the authors. In this method, analog circuits or digital signal processors are used to produce soil-foundation interaction motions in real time. Their expressions of soil-structure interaction motions are based on published rigorous formulations of impulse response functions or flexibility functions of foundations resting on or embedded in homogeneous or layered soils of semi-infinite extent. In this paper the method is further extended to take the “far field” soil non-linearity into account. An example of non-linear soil-structure interaction simulation using the present method is also described.     

The Welfare Economics of Rural-To-Urban Migration: The Harris-Todaro Model Revisited

In this paper we extend the Harris-Todaro model of rural-to-urban migration to include urban agglomeration effects, some urban real wage flexibility, and a government budget constraint. Without employment subsidies laissez-faire migration is excessive unless real wage flexibility and agglomeration effects are high. Laissez-faire migration is too low compared with the first-best outcome supported by a subsidy, if its financing involves no costs. Simulations suggest that such a program would imply a substantial increase in taxation. If, as seems likely, an increase of this magnitude involves economic costs then the optimal outcome falls well short of first-best.     

关于太平天国史研究的几个问题

太平天国史的研究,有几个问题需要重新认识。洪秀全早期的宗教宣传和活动并非“纯粹的宗教宣传”,而是具有政治意义和策略价值;农民领袖平均、公有思想作为一种鼓舞农民斗志的理想无可厚非,洪秀全等所实施的现行政策与公有制理想是有距离的,他们已注意到切合实际问题,所采取的实际政策是灵活的;由平均、公有思想转到仿行资本主义思想是一种进步,这种转变不是“脱离实际”的,而是有客观因素,具有现实性;拜上帝信仰与太平天国相始终,它使太平天国兴,又使太平天国亡;太平天国起义具有革命性质,是一场具有资产阶级民主革命的某些特点或色彩的农民革命,并起了重要的历史作用。     

WORKING WITH 'WILD ROSE I': LEAN PRODUCTION IN A GREENFIELD MILL

The Alberta Newsprint Company mill in Whitecourt, Alberta, with its state-of-the-art paper machine dubbed Wild Rose I' is one of the most efficient newsprint mills in North America. This paper documents the systematic drive by the Alberta Newsprint Company to achieve lean production by the use of flexible work practices in a greenfield mill, which began production in 1990. The analysis begins by examining the way in which the workforce for the new mill was recruited as the first step to creating a flexible workplace. Information from questionnaires completed by 96 employees, who represent approximately half the total labour force, and semi-structured interviews with managers and employees, is used to describe the extent to which the anc mill has achieved various forms of labour flexibility. The nature and extent of these new work arrangements are compared among departments within the mill. Finally, we explore the recent restructuring of wages in the mill. These events illustrate some of the unanticipated consequences arising from the implementation of lean production in a remote geographical setting.     

Slanted Newspaper Coverage of Immigration: The Importance of Economics and Geography

When compared to studies of media effects, relatively few studies of the media focus on factors that influence the behavior of media organizations. Specifically, there are few empirical studies of the attributes and incentives of news organizations that might lead to slanted coverage of particular policy issues. In this study, we identify factors that lead to negatively slanted coverage of a specific policy issue: immigration. Using content analysis, geographic information systems (GIS) data, and contextual data, we find that newspaper ownership and proximity to the U.S.–Mexico border are related to slant in news articles and opinion pieces regarding immigration.     

Definition of Seismic Input for Out-of-Plane Response of Masonry Walls: I. Parametric Study

Response of masonry walls to out-of-plane excitation is a complex, yet inadequately addressed theme in seismic analysis. The seismic input expected on an out-of-plane wall (or a generic “secondary system”) in a masonry building is the ground excitation filtered by the in-plane response of the walls and the floor diaphragm response. More generally, the dynamic response of the primary structure, which can be nonlinear, contributes to the filtering phenomenon. The current article delves into the details and results of several nonlinear dynamic time-history analyses executed within a parametric framework. The study addresses masonry structures with rigid diaphragm response to lateral loads. The scope of the parametric study is to demonstrate the influence of inelastic structural response on the seismic response of secondary systems and eventually develop an expression to estimate the seismic input on secondary systems that explicitly accounts for the level of inelasticity in the primary structure in terms of the displacement ductility demand. The proposed formulation is discussed in the companion article.     

Integrated IT-based Geography Teaching and Learning: A Macquarie University case study

Use of information technology (IT) is increasingly common in geography teaching and learning. This paper outlines a still relatively unusual initiative involving the integrated use of a variety of IT-based components across all aspects of a large course unit. Multiple evaluations reveal strongly positive reactions to the IT-based approach and the time and place flexibility offered; there are few technical impediments to, and no detectable gender differences in, students' use of the system. Most aspects of the integrated approach work well, although it has not yet succeeded in facilitating a genuinely participative online dialogue. Many aspects of the initiative can be transferred cost-effectively to other contexts.