Comparative life-cycle analysis of steel-concrete composite bridges

Competitiveness of steel construction and, in particular, steel and composite bridges, requires a broader view that encompasses the concepts of sustainability and life-cycle assessment in parallel with the classical structural and geotechnical issues. Also, from the economical viewpoint, the progressive transfer of operational duties from the National Road Authorities to private companies in the context of design, build and operate contracts, reinforces the need for an integrated approach.It is the purpose of the present paper: (i) to present an integrated methodology for a life-cycle and sustainability analysis (LCA and LCCA); and (ii) to apply such an integrated approach to a case study of a composite bridge. The proposed approach, besides structural considerations, contemplates environmental aspects (energy consumption, raw materials, and environmental impacts), economical aspects and a brief discussion of degradation and maintenance aspects. The case study consists of a three-span continuous bridge with spans of 27.2 m + 35.0 m + 27.2 m, thus totalling 89.40 m. Finally, some comparisons are presented between alternative solutions.     

Sustainability assessment and rating of buildings: Developing the methodology SBTool–H

Although sustainable building is a multidimensional concept, attention to the issue often focuses solely on environmental indicators, ignoring the substantial importance of social, economic and cultural indicators. Building sustainability involves various relations between built, natural and social systems and therefore comprises a complex of different priorities that require consideration at each stage of a building’s life-cycle. To cope with this complexity and to support sustainability systematic, holistic and practical approaches to building design need to be developed. The main objective of a systematic methodology is to support the development of a building design that achieves the most appropriate balance between the different sustainability dimensions, and is, at the same time, practical, transparent and flexible enough to be easily adapted to different types of buildings and technology.     

Investment priorities for the management of hydraulic structures

Maintenance management of the hydraulic structures requires the selection of the most necessary maintenance intervention to ensure their proper operation and structural safety. Given the characteristics of these structures, many types of damage may appear, so it is not easy to take a decision. The purpose of this paper is to present the Prioritisation Index for the Management of Hydraulic Structures (PIMHS), a multi-criteria decision-making system based on the three axioms of sustainability (social, environmental and economic), which orders and prioritises non-similar maintenance investments in hydraulic structures. The results obtained show that PIMHS can be used by decision-makers to prioritise, in hydraulic structures, all kinds of maintenance interventions where the damages cannot lead to dam break.     

Risk-chasing behaviour in on-site construction decisions

Risk-chasing behaviour in on-site construction decision-making can result in illogical decisions and, thus, significant project losses. Accordingly, the authors conducted a set of experiments in order to detect the existence of such behaviour under a range of typical project conditions within a set of common situations. Fifty-three project leaders participated in the experiments by making choices framed by a set of 24 questions. Each question related to a known behavioural tendency, included the influence of an external parameter, and contained information from which expected values could be derived. Participants were well distributed by geography, age and experience. Contrary to the common perception that construction decision-makers are relentlessly risk-averse, they demonstrated risk-chasing behaviour when the decision occurred in over-budget project conditions. Younger participants were even more risk chasing in such conditions. Understanding and identifying where such behaviour occurs could ultimately lead to the development of means of avoiding the resulting losses.     

城市地下综合管廊PPP模式融资风险管理研究

在我国城市地下综合管廊发展探索阶段引入PPP模式融资,能够有效激发综合管廊快速发展的内在动力和外在市场。通过系统总结分析国内外综合管廊和PPP模式的发展经验和研究动态,指出风险管理是制约综合管廊PPP模式发展的关键因素,为进行有效的风险管理,文中采用HHM法识别出综合管廊PPP模式融资的八大主要风险因素,并利用RFRM法结合改进层析分析法、熵权法和贝叶斯决策对风险因素进行初步过滤、多视角过滤和量化过滤。根据风险因素的定性和定量过滤的结果,提出了有关完善法律政策体系、规范合同条款、重视运营管理和构建风险分担机制的风险防范和风险规避的相关建议,以期为综合管廊PPP模式的风险管理提供有益的参考。     

Time and cost securing in complex large-scale projects

Meeting time and cost objectives in complex projects involves specific problems and risks. An attempt is made to analyse the components of total cost increase of a project caused by time delay. An outline is given as to how these considerations can be used to estimate cost increases in investors' decision situations as well as to ascertain fair contractual penalties and claims for compensation and for the evaluation of justified project acceleration costs.     

A holistic approach to asset management in the Netherlands

The objective of the national agency for road and water infrastructure in the Netherlands is to deliver best service to the public at lowest life cycle cost, given public acceptable risk. This requires a sound and well-structured system of management and maintenance. Such a system consists of elements such as reliable asset data, long-term performance based maintenance programmes, clear steering objectives and transparent procurement strategies. Asset management will make it possible to show what network performance can be achieved, at which costs and with which associated risks. A model defining an asset owner role, an asset manager role and a service provider role was chosen as a governing principle for the design of the asset management process. The design of the process described in the paper sets the boundary conditions to carry out projects with the minimum amount of hindrance for the user while involving the market in the best possible way.     

论旧桥加固方案设计

针对现有公路桥梁中相当一部分已不能满足使用要求的现状,介绍了多种旧桥加固方案,以恢复和提高这些桥梁的承载能力,使其继续为现代交通运输服务,给国家带来巨大的经济效益。     

Computational platform for the integrated life-cycle management of highway bridges

Throughout their service life, highway bridges are subject to progressive deterioration in performance; an issue that may render the use of these facilities unsafe at some point in time. Over the last few decades, there has been successful research towards developing procedures for establishing the various vital elements required in the life-cycle management of civil infrastructure. It is noted, however, that frameworks for integrating these elements together are lacking. The objective of this paper is to present an integrated framework for the life-cycle management of highway bridges in the form of a detailed computational platform. The elements integrated into the framework include the advanced assessment of life-cycle performance, analysis of system and component performance interaction, advanced maintenance optimization, and updating the life-cycle performance by information obtained from structural health monitoring and controlled testing.     

A multi-criteria analysis for bridge sustainability assessment: a case study of Penang Second Bridge,Malaysia

Bridges are a critical part of our nation's economic prosperity and local community well-being. One of the latest trends in bridge engineering is sustainable design, which is designing so that resources are available for many generations to come. Sustainable design considers the ecological, economic and socio-cultural environments and works to balance all three. There are some sustainable infrastructure rating systems (RSs) available, such as Envision that can be applied to bridges. However, no system has been developed that would specifically apply to bridge sustainability assessment. The objectives of this study are first, to investigate bridge sustainability issues from three main aspects: environmental, economical and social; and second, to apply multi-criteria analysis to assess the sustainability of the Penang Second Bridge in Malaysia. A hierarchy structure of the sustainable bridge attributes was developed for each RS, and an analytical hierarchy process method was then applied for the appraisal of the sustainability of a bridge pertaining to the relative attributes. The research involved a committee of Malaysian bridge professionals to support the rational decision-making. The results reveal that the case study has achieved most of the criteria of the sustainability assessments.     

Fragility analysis of track-on steel-plate-girder railway bridges in Korea

More than 40% of the bridges in conventional Korean railway lines are track-on steel-plate-girder (TOSPG) bridges. They are characterized by a superstructure consisting of railway tracks sitting directly on steel plate girders without any ballast system. Most of these bridges have been designed with little or no consideration given to seismic loading. In this paper, seismic fragility curves of TOSPG bridges in Korea are developed. Fragility curves are developed first for the components, by using the probabilistic seismic demand model. The developed component fragility curves show that the bearings are the most vulnerable components of the TOSPG bridges against seismic loading. On the other hand, the piers are much less vulnerable, although they contain no reinforcing bars. This is because the superstructure mass is very light, and therefore horizontal loading transferred from the superstructure to the piers is minimal. A generic damage measure is introduced for measuring the system-level damage of structures out of the component-level damages. The system fragility curves are then developed, using the generic damage measure. Finally, representation of seismic risk in terms of expected seismic losses is demonstrated. This demonstration shows how the fragility analysis is utilized for risk assessment and support in decision-making.     

可持续性与城市:一种景观规划的方法

介绍了2项城市规划设计的国际性实践操作案例.通过2项案例探讨了景观规划、景观都市主义以及可持续性和可具弹性方面之新举措,对这些内容背后存在的理论体系进行了回顾和揭示.在此基础上,针对实现具有可持续性和弹性的社会城市化过程所面临的巨大挑战,提出了规划和设计上新的理论方法以及新的实践操作范式.     

‘Resilience thinking’ in transport planning

Resilience has been discussed in ecology for over 40 years. While some aspects of resilience have received attention in transport planning, there is no unified definition of resilience in transportation. To define resilience in transportation, I trace back to the origin of resilience in ecology with a view of revealing the essence of resilience thinking and its relevance to transport planning. Based on the fundamental concepts of engineering resilience and ecological resilience, I define ‘comprehensive resilience in transportation’ as the quality that leads to recovery, reliability and sustainability. Observing that previous work in resilience analysis in transportation has focussed on addressing engineering resilience rather than ecological resilience, I conclude that transformability has been generally overlooked and needs to be incorporated in the analysis framework for comprehensive resilience in transportation.     

Financially sustainable management strategies for urban wastewater collection infrastructure – development of a system dynamics model

Causal loop diagrams are developed for wastewater collection networks to identify complex interactions and feedback loops among physical, financial, and social sectors. Causal loop diagrams are then incorporated into a novel system dynamics based decision support tool that can be used for financially sustainable management of wastewater collection networks. Data requirements to develop the decision support tool are discussed along with how can the decision support tool be used to manage a utility.The presented causal loop diagram is the first known attempt to lay out the interrelationships among system components using a formal technique. The causal loop diagram establishes the existence of several interacting feedback loops and demonstrates that the management of wastewater collection networks constitutes a complex dynamic system for which traditional management tools are deemed inadequate. The use of causal loop diagrams can be useful to mitigate effects of the silo-based organizational culture prevalent in many water utilities.The system dynamics model is the first known decision support tool to quantitatively simulate the influence of interrelationships and feedback loops in wastewater collection network management. The model is a mathematical representation of the causal loop diagram to capture cost drivers and revenues sources in the system. It also includes a set of policy levers which allows formulation of various financing and rehabilitation strategies. The model can be used to develop short- and long-term management plans. The impact of financing and rehabilitation strategies on system performance can be simulated and evaluated in terms of financial and service level metrics. The decision support tool can also be used by utilities to ensure essential data is collected and flows within organizational units.     

基于遗传算法的建设工程风险决策多目标优化研究

在建设工程风险决策过程中,只考虑单个目标因素的决策并不能满足实际工程的要求。为了使决策更加科学、合理,在风险识别和风险评价的基础上,综合考虑包括风险管理成本在内的多个目标因素对决策结果的影响,建立了工程风险多目标决策优化模型,通过多目标遗传算法NSGA-Ⅱ,实现了工程风险决策方案的优化。最后,对优化结果的分析和评价,证明了所建立的模型在解决工程风险决策问题上的有效性和实用性。