Continuous accountability for acceptable building performance

Complexities in building technology when not fully understood, have resulted in a less than favorable aggregate impact on the building's environment. A surprisingly high portion of U.S. non-industrial buildings do not provide satisfactory task environments. Developments in computer technology have infused new thought processes in the way we plan, design, build and operate our buildings. This paper proposes a social and technical use of Knowledge-based-systems (KBS) for continuous accountability to assure healthy buildings. Diagnostics, as an emerging discipline in building design and operation, is also discussed. A proposed framework for such accountability and the resulting ‘chain of custody’, that draws on the medical paradigm and associated diagnostic procedures is presented. It is suggested that KBS also be used for the development and interpretation of criteria for evaluating building performance from initial conception through design, construction and operation. Thus, KBS is expected to aid in the analysis of ‘virtual’ and ‘actual’ buildings that may be ‘sick’ or ‘healthy’. It is proposed that for a building to provide satisfactory performance over its life-time, the ‘life-cycle’ concept must be modified in terms of the roles, responsibilities, and configuration of the building team, and in terms of its costing procedures.     

Finite element analysis of the stability of multilayer elastomeric bearings

The stability of multilayer elastomeric bearings is considered within the framework of two-dimensional finite elasticity. For this purpose, simple constitutive equations which generalize those of a transversally isotropic linear elastic solid are considered. A finite element formulation is discussed which is capable of accounting for very general boundary conditions. For moderate deflections and classical boundary conditions this formulation leads to numerical results in close correspondence with those obtained by Haringx's one-dimensional treatment. It is shown that the presence of boundary conditions in the form of unilateral constraints explains a softening effect which has been experimentally observed during the testing of this type of composite column. Experimental results are also presented which indicate that this softening effect is not produced by a form of material instability. These experimental results provide further justification for the simple constitutive model adopted.     

油砂的蠕变特性与本构模型研究

油砂是一种富含天然沥青的沉积砂。作为一种软化材料,油砂的蠕变性质较松砂和正常固结黏土等硬化材料更为复杂。通过开展油砂三轴蠕变试验,获得了不同应力和应变状态下油砂的蠕变特性;讨论了蠕变势与塑性势之间的关系,提出了等效变形过程的概念,分析等效变形过程的微观机制;讨论了蠕变速率与时间和不可恢复应变之间的关系,提出采用不可恢复应变作为内变量可以描述复杂条件下油砂的蠕变性质,并据此提出了油砂的内变量蠕变模型;应用临界状态理论,分析了硬化型和软化型土的蠕变性质;讨论了剪切带对密砂蠕变性质的影响。     

Problems encountered in detailed design of flexible riser systems

This paper identifies areas of concern within the detailed design of flexible riser systems and presents solutions to a series of problems encountered by the authors involving structural and hydrodynamic nonlinearities. Five critical situations are selected: (1) detailed dynamic analysis of a flexible jumper connected between a floater and a jacket structure with emphasis on the design of bend stiffeners at both ends of the system; (2) dynamic analysis of a multiple flexible riser system with emphasis on the response of a common intermediate subsurface buoyant arch; (3) combined effects of torsional and current loading on a short flexible hose supported at one end on a layover arch; (4) dynamic analysis of a ‘pliant wave’ flexible riser configuration; (5) dynamic analysis of a flexible jumper disconnection procedure and assessment of clashing with the floater at pontoon level.

These solutions are produced using computer programs which use optimized finite difference methods particularly suited to these types of problems. The numerical modelling techniques and results are presented for each condition and the influence of these results on the design of various piping systems is discussed.     

Specification of the design wind load—A critical review of code concepts

In a simplified approach, the design wind load can be specified based on an appropriate small target value of the exceedance probability. For the ultimate limit state, the reasonable reference period is the projected design working life of the structure; for the serviceability limit state a suitable reference period is one year. Basically, at least the extreme wind speeds and the extremes of the aerodynamic coefficients have to be understood as random variables. Further random variables are the duration of a single storm and the relative intensity over the length of the storm. Neglecting these two parameters may lead to underestimations of the design wind load. The design values of the wind speeds are specified in codes with mainly two different concepts: either in terms of a product of the characteristic wind speed and a partial factor or directly as design value. The variable wind speed is represented in codes by gust wind speeds, by 10-min mean wind speeds or by hourly mean wind speeds. For the design value of the aerodynamic coefficient, mainly two concepts are used in codes: the mean value of the extremes or the 78%-fractile value, the latter known as ‘Cook–Mayne’ coefficient. The paper tries to sort out the differences between these approaches and tries to comment on one or the other shortcoming. Additionally, the complexity of the codification task is discussed when different wind climates have to be covered.     

Why projects fail? How contingency theory can provide new insights – A comparative analysis of NASA’s Mars Climate Orbiter loss

When important projects fail, the investigation is often focused on the engineering and technical reasons for the failure. That was the case in NASA’s Mars Climate Orbiter (MCO) that was lost in space after completing its nine-month journey to Mars. Yet, in many cases the root cause of the failure is not technical, but managerial. Often the problem is rooted in management’s failure to select the right approach to the specific project. The objective of this paper is to enrich our understanding of project failure due to managerial reasons by utilizing different contingency theory frameworks for a retrospective look at unsuccessful projects and perhaps more important, potential prevention of future failures. The evolving field of project management contingency theory provides an opportunity at this time to re-examine the concept of fit between project characteristics and project management, and offer deeper insights on why projects fail. After outlining several existing contingency studies, we use three distinct frameworks for analyzing the MCO project. These frameworks include Henderson and Clark’s categorization of change and innovation, Shenhar and Dvir’s NTCP diamond framework, and Pich, Loch, and De Meyer’s strategies for managing uncertainty. While each framework provides a different perspective, collectively, they demonstrate that in the MCO program, the choices made by managers, or more accurately, the constraints imposed on them under the policy of ‘better, faster, cheaper’, led the program to its inevitable failure. This paper shows that project management contingency theory can indeed provide new insights for a deeper understanding of project failure. Furthermore, it suggests implications for a richer upfront analysis of a project’s unique characteristics of uncertainty and risk, as well as additional directions of research. Such research may help establish new and different conceptions on project success and failure beyond the traditional success factors, and subsequently develop more refined contingency frameworks. The results of such research may enable future project managers to rely less on heuristics and possibly lead to a new application of “project management design.”     

Equivalent constant rates for post-quake seismic decision making

The objective of this paper is to develop a methodology to quantify the time-varying post-quake aftershock threat in a manner consistent with the development of conventional design ground motion levels, which are typically based on a constant probability of exceedance of a given ground motion intensity. We use the frequency of collapse of a mainshock-damaged building in the aftershock environment as a proxy for the life-safety risk faced by an arbitrary building occupant. We demonstrate that the time-varying aftershock threat can be transformed to an equivalent constant collapse rate for a mainshock-damaged building by considering the total expected number of aftershock collapse events in the time interval of interest and a ‘social discount factor’, typically taken to be from 3% to 5%. The ability to quantify the time-varying life-safety risk in the aftershock environment in a manner compatible with existing building code provisions will allow informed building evacuation and re-occupancy decisions to be made. While this concept has been introduced for the aftershock environment, it may also be a potential solution to a wider class of safety problems involving transient life threats.     

New ‘rural lifestyle estates’ in The Netherlands

Recent studies tend to indicate that no longer all presently agricultural land in The Netherlands is required for sustainable agricultural production. Apart from various urban uses and some projects turning agricultural land into nature reserves or giving it a secondary function, like national landscape parks or drinking water supply area, it is not easy to find alternative users for the land presently managed by farmers. At the same time, many urban companies or families are vainly looking for building lots away from our ‘compact urban areas’. This paper explores a way to bring this supply and demand together in a landscape-wise more than acceptable manner: the planning concept and experiment of ‘new rural lifestyle estates’.     

Assessment of the dynamic stability of the portals of the Dorukhan tunnel using numerical analysis

Instability problems may arise during the construction and operation of tunnels depending on the quality of the rock mass. In particular, determining instability problems at the portals of a tunnel is of utmost importance during excavation and operation of the tunnel. Slope instability and rockfalls are the most frequent instability problems that may be encountered at tunnel portals. Such instability problems can be triggered by dynamic effects such as earthquakes, blasting, etc. This study investigates the stability of the portals of the Dorukhan Tunnel connecting the provinces of Zonguldak and Bolu in the close vicinity of the North Anatolian Fault Zone (NAFZ), which is a well-known strike-slip 1500 km long fault. The effect of an earthquake that may occur in the NAFZ on the extent of failure has also been studied by numerical analyses. In the analyses, a three-dimensional dynamic analysis computer code, based on the finite difference method, has been used. According to results of the dynamic numerical analyses, the Devrek portal was found to be more stable than the Mengen portal. Moreover, it was found that, for acceleration values of dynamic wave higher than 0.5g, tunnel portal slopes and the areas as far as 20–50 m from the tunnel entrance may suffer serious damage. Wave propagation perpendicular to the tunnel axis was established to cause more damage around the openings and in the portal slopes as wave compared to propagation parallel to the tunnel axis.     

“Rio+10”, sustainability science and Landscape Ecology

The ‘sustainability debate’ has had a profound influence on contemporary Landscape Ecology. This paper explores the implications of the second global summit for the research agendas that developed after the Rio Summit (1992), and argues that although the Declaration from Johannesburg 2002 restates the earlier summit concerns, the messages it sends to the research community are subtly different to those a decade earlier. The growing body of literature, which identifies the need for a new kind of sustainability science, is reviewed, and its relevance to Landscape Ecology is discussed. Although recent commentators have argued for a more transdisciplinary approach to Landscape Ecology that appears to meet the requirements of this new science we still lack ways of taking this forward. The paper concludes by proposing a new paradigm for Landscape Ecology based on the concept of ecosystem goods and services, or natural capital. It is argued that in the decade since the Rio Summit, a key focus of the future research agenda for the discipline should be an exploration of the ‘sustainability choice space’ defined by the interaction of biophysical limits and social and economic values at the landscape-scale. The paper provides a conceptual model (the tongue model) that describes how biophysical and socio-economic constraints can be combined in sustainability planning.     

European 3G auctions: Using a comparative event study to search for a winner's curse

This paper seeks to identify any possible winner's curse in the European 3G licence administration processes. The existence of a winner's curse has been suggested as a reason to relax the licensing conditions and the regulatory environment. The winner's curse will be tested by comparing event studies across countries which differ in terms of licence administration procedures. If a winner's curse occurred in some auctions, we may expect a ‘winner's bounty’ for those companies obtaining licences through non-auction methods. The study finds that there is at least short-term evidence of a winner's curse.     

Green’s functions for the bending of thin plates under various boundary conditions and applications: a review

Green’s functions of a point dislocation for the bending problem of an infinite thin plate containing an arbitrarily shaped hole under displacement, stress, and mixed boundary conditions and for a bimaterial problem are stated and the review of the related works is given. The point dislocation is defined by the discontinuity of the plate deflection angle. The original formulation for these problems consists of two parts: a principal part containing singular and multi-valued terms, and a complementary part containing only holomorphic terms. The Green’s functions were obtained in closed forms by using the complex stress function method in junction with the rational mapping function. The applications of the Green’s functions are demonstrated in studying the interaction of a hole or inclusion with a line crack in an infinite plate subjected to bending. The Green’s functions can also be used as the kernels for boundary integral representations in boundary element method analysis, where they can notably simplify the procedure of the standard boundary integral equations.     

Defining resilience for the US building industry

ABSTRACT

Initiatives to operationalize the concept of resilience in the building industry are rapidly emerging. The concept of resilience has introduced a way to explore solutions to some important problems in the building industry. However, much of the work that has taken place to date represents activities generally assigned to risk management, which is discussed as being inherently insufficient for sustaining the functions of the built environment under stresses. This commentary considers the opportunities and limitations for mainstreaming resilience into building industry processes and actors. Barriers include indeterminate analytical meaning, event and performance uncertainty, immature regulatory standards setting, and untested enterprise economics. Further, the multiple outcomes of recovery and the relationship between building recovery and adaptation are discussed and, along with economics of resilience investments, a research need highlighted. A simple heuristic is presented to illustrate the complement of resilience to risk management and advance the integration of resilience into existing industry workflows.     

The neglect of aesthetics in landscape planning in Switzerland

In this paper, landscape is defined as any part of the Earth’s surface in which various aspects, such as terrestrial, aquatic, natural and cultural interact with differing dominance. Within landscapes, energy and material flows over time are major driving forces of landscape dynamics. Such a comprehensive approach to landscape should also be applied in landscape planning, however this is rarely the case in Switzerland. The concept of landscape aesthetics in particular is neglected, therefore, four theses are formulated and discussed in this paper.The tourist industry promotes Switzerland with pictures showing beautiful scenery. Some of the landscape elements shown, e.g. ecclesiastical buildings and historical profane buildings, are widely recognised for their aesthetic values, and scientifically examined by art historians and other disciplines. Strangely enough, this is not the case for cultural landscapes, despite the fact that they also reflect the history of human culture. This paradox evolves from the dichotomy between natural sciences and humanities. There is a lack of multi-, inter-, and trans-disciplinary approaches to studying cultural landscapes. The long-term genesis of the elements of the cultural landscape is illustrated by the typical structure of traditional cultural landscapes, i.e. “the hides of land” (i.e. strip-shaped forest clearings) (Hufenfluren).Between 1750 and 1850, many painters depicted the beauty of the traditional cultural landscape. Their paintings are acknowledged as a part of culture and treated accordingly, but this is not the case for the remains of the cultural landscape they painted. Comparing maps from different points in time reveal the loss of elements of cultural landscapes. Results show how traditional systems of land use led to highly structured landscapes, whereas today’s land-use levels out the scenery. Lack of public support significantly reduces the success of the legal tools to limit this process.     

Urban growth and environmental degradation: The case of Cairo, Egypt

The immense growth of cities, especially in developing countries, is resulting in the urbanization of both poverty and environmental degradation to a greater degree than ever before. This paper examines the processes of growth and degradation in the Greater Cairo Metropolitan Region (GCMR), currently the world’s tenth largest mega-city. It reviews the region’s growth and selected environmental issues as well as impacts of current efforts on managing the region. The assertion of this paper is that current management policies and bodies lack a comprehensive view of urban governance for the region, which does not bode well for the future environmental and economic sustainability of the region.     

Particle size distribution dynamics during precipitative softening: declining solution composition

Particle removal is a critical step in the treatment of surface water for potable use, and the majority of drinking water treatment plants employ precipitative coagulation processes such as alum and iron “sweep-floc” coagulation or lime softening for particle pre-treatment. Unfortunately, little is quantitatively known about how particle size distributions are shaped by simultaneous precipitation and flocculation. In an earlier paper, we demonstrated the effects of the saturation ratio, the mixing intensity and the seed concentration on the rates of homogeneous nucleation, precipitative growth and flocculation during precipitation of calcium carbonate at constant solution composition using electronic particle counting techniques. In this work, we extend those findings to systems more closely emulating the conditions in actual softening processes (i.e., declining solution composition). Key findings include the strong dependence of the rate of flocculation on the initial saturation ratio and demonstration of the benefits of seeding precipitative softening from the perspective of optimizing the effluent particle size distribution. The mixing intensity during precipitation was also shown to strongly influence the final particle size distribution. Implications of the findings with respect to softening practice are discussed.     

Wireless networking in tunnelling projects

Emerging collaborative technologies and working methods often require tremendous engineering and organisational efforts for successful implementation of information and communication technologies (ICTs). According to a research conducted in Turkish construction industry, most of the problems that occur during the construction phase are due to lack of co-operation and communication between designers and contractors and lack of prompt expert decisions during on-site engineering. Similar to any major construction project, tunnelling project’s success is highly dependent on collaborative team work where communication and information exchange take place between project members. Distributed collaborative teamwork, as the case in most of the large scale construction projects as well as tunnelling projects, empowered by state of the art information and communication technology, promises more efficient work processes, reduced travelling needs, and increased opportunities for project communication. Following the fast development of mobile computing in recent years, many sectors have adopted mobile devices and wireless technologies enabling real-time information transfer thereby improving business processes. For some years, the feasibility of implementing wireless solutions to construction sites has been researched. Potentially, mobile and wireless technologies enable construction staff to be more flexible in terms of location and time. For better use of mobile collaboration in construction projects, mobile technologies and construction sector have to be examined in some detail to implant the most suitable technology for real-time information access and improved collaboration of distributed teams in construction. However, case studies in construction are very limited in number and scope. This paper discusses and proposes an implementation scenario of wireless networking in Marmaray; a multi-site tunnelling project in Istanbul. Benefits, possible problems and cost assessments are discussed.     

The “Change” and the “Constancy” of Landscapes

Scientifically recognizing and wisely intervening the evolution of landscape is an important topic in Landscape Architecture, since evolution (change) is absolute. For human, landscape changes, however, can be measured in a relative sense. Upon such an understanding, the concept “persistent landscape” highlights the landscape’s continuity and stability over time, as well as the stable variety of physical environment. The key to understand this concept lies in landscape architects’ observation of not only the stability of natural ecosystems but also the harmony of cultural-social contexts. However, the rapid urbanization has caused many pressing problems such as the loss of characteristics in urban and rural area, environmental pollution, ecological fragmentation, and cultural fracture, which calls for landscape architects who can re-recognize the man-land relationship and formulate scientific strategies for sustainable development. In this issue, LA Frontiers hopes to offer landscape architects with insights to meet contemporary needs by embracing new landscape forms and implications, so as to create healthier and more poetic-quality living environments with cultural and spatial characteristics.     

软岩与水相互作用的非线性动力学过程分析

软岩与水相互作用的非线性动力学过程的研究不仅对软岩软化的研究方法具有探索价值,而且对于合理确定软化的参数及其应用具有重要的实践意义。结合东深供水改造工程中灰白色泥质粉砂岩不同饱水时间后的试验数据分析,发现该类软岩的软化具有非线性特点。将时间序列的分维分析方法应用于软岩与水相互作用系统中,通过重建相空间,确定了描述该系统所需的最少变量数。试验中发现,软岩的微观结构、力学参数是反映软岩软化的控制性因素,因而取微结构孔隙分布分维值Ds、粘聚力c和内摩擦角?值作为描述该系统的3个变量。在此基础上,应用反演分析理论,确定了软岩软化的非线性动力学模型,再将以上3个变量的时间序列值通过求残差平方和极小值的方法与模型进行逼近,得到模型中各个未确定的参数,从而对软岩与水相互作用过程进行非线性动力学分析。结果表明:所给出的非线性动力学模型计算得到的微结构孔隙分布分维值Ds、粘聚力c和内摩擦角?值与试验获得的相应参数值的分布曲线非常接近,说明软岩与水相互作用具有显著的非线性动力学特点;同时,利用所建立的模型可较好地预测软岩在饱水条件下,一定时间后的微观结构参数和力学性质变化规律。     

Fluid-structure interaction in Morison's equation for the design of offshore structures

A simplified model of a steel jacket structure is used in a nonlinear time history dynamic analysis with a view to examining the influence of interaction damping. It is found that, for certain combinations of wave and structural parameters, the response amplitudes are significantly dependent on the inclusion of relative velocity and acceleration terms in Morison's equation. Thus, it is possible to estimate, from the mathematical model, values of hydrodynamic damping which are required for the dynamic analysis of an offshore structure by methods which ignore fluid-structure interaction.After a brief literature review, the theory of Morison's equation is discussed. A computer program, PLATDYN, is then described which computes the dynamic response of a structure in various sea states. The method of representing the full structure by a reduced number of members is explained before the results of the analysis are presented. Finally, a procedure is proposed which provides an economic method of including the effects of interaction damping in the design of offshore structures.