A life cycle costing approach for discounting in age and interval replacement optimisation models for civil infrastructure assets

Civil infrastructure assets, such as roads, locks, bridges, treatment plants and storm surge barriers, are often characterised by long service lives and corresponding technical life cycles. When life cycles are long, the time value of money plays a role in asset management decision-making on capital investments and operation and maintenance expenditures. In this paper, a new life cycle costing (LCC) approach for discounting in two classes of maintenance optimisation models is developed. These models are the age replacement model and the interval replacement model. Three well-known LCC techniques, which are the present worth, the capital recovery and the capitalised equivalent worth, are combined and used to develop a stepwise methodology. This methodology is validated with the few case-specific mathematical equations that exist in the literature. The advantage of using this alternative LCC approach is its applicability and flexibility for reliability and maintenance engineers. The resulting LCC method builds on well-known LCC formula and enhances the understanding of the inclusion of discounting principles in reliability models. Understanding these principles makes the method flexible. Practitioners can extend or adapt the method to changing circumstances, such as additional cash flows and altering reliability modelling.     

Valuation techniques for infrastructure investment decisions

Public infrastructure owners are increasingly soliciting BOT arrangements to deliver needed infrastructure facilities. Such arrangements potentially preserve a public owner's capital capacity for allocation to projects that cannot support themselves by essentially ‘pulling’ projects from the private sector. Before soliciting these arrangements, however, owners should independently evaluate a project's economic viability to fully appraise the issues and variables involved. Unfortunately, project analysts often apply evaluation methods without regard for their assumptions and limitations. A case study of a toll road project in the USA provides the basis for examining the assumptions behind both traditional and option valuation models. The case demonstrates the use of an option pricing model to augment traditional project evaluation by capturing strategic considerations, in this case the value of project deferment. The presentation illustrates that the selection of a valuation model depends critically upon the characteristics of a project's variables and that informed judgment remains an integral part of the decision‐making process.     

Life-cycle performance,management, and optimisation of structural systems under uncertainty: accomplishments and challenges 1

Our knowledge to model, analyse, design, maintain, monitor, manage, predict and optimise the life-cycle performance of structures and infrastructures under uncertainty is continually growing. However, in many countries, including the United States, the civil infrastructure is no longer within desired levels of performance and safety. Decisions regarding civil infrastructure systems should be supported by an integrated reliability-based life-cycle multi-objective optimisation framework by considering, among other factors, the likelihood of successful performance and the total expected cost accrued over the entire life-cycle. The primary objective of this paper is to highlight recent accomplishments in the life-cycle performance assessment, maintenance, monitoring, management and optimisation of structural systems under uncertainty. Challenges are also identified.     

An integrated method to optimise the infrastructure costs of bus rapid transit systems

A significant effort has been directed in many countries to develop economically feasible transportation solutions which include, in many cases, buses that run on express lanes or that are used as part of a feeder system; these systems are identified as ‘bus rapid transit systems’ (BRT). The purpose of this paper is to present a reliability cost-based optimisation model of these systems. The model couples the transportation requirements and the mechanical performance of asphalt pavement structures. Also it includes critical transportation parameters such as bus sizes, frequency of the routes and passenger demands. Regarding the pavement, the model takes into account the life-cycle of existing or new pavements, which involves a stochastic model of the pavement's mechanical properties and its overall performance. The model is applied to the actual case of Bogota's rapid transportation system, i.e. Transmilenio, showing the importance of this integrated approach to build efficient BRT systems.     

Life cycle assessment of a railway bridge: comparison of two superstructure designs

Railway bridges currently encounter the challenges of increasing the load capacity while the environmental sustainability should be achieved. However, it has been realised that the environmental assessment of railway bridges has not been integrated into the decision-making process, the standard guideline and criterion is still missing in this field. Therefore, the implementation of life cycle assessment (LCA) method is introduced into railway bridges. This article provides a systematic bridge LCA model as a guideline to quantify the environmental burdens for the railway bridge structures. A comparison case study between two alternative designs of Banafjäl Bridge is further carried out through the whole life cycle, with the consideration of several key maintenance and end-of-life scenarios. Six impact categories are investigated by using the LCA CML 2001 method and the known life cycle inventory database. Results show that the fixed-slab bridge option has a better environmental performance than the ballasted design due to the ease of maintenances. The initial material manufacture stage is responsible for the largest environmental burden, while the impacts from the construction machinery and material transportations are ignorable. Sensitivity analysis illustrates the maintenance scenario planning and steel recycling have the significant influence on the final results other than the traffic disturbances.     

结构生命周期的可靠性管理

结构的抗力性能、使用条件、环境作用等都是随时间变化的过程。结构的运行规律复杂且具有大量的不确定性和不确知性,单纯依靠设计来保证结构的安全性是不够的,而应该综合考虑设计、检测、维护等策略对结构生命周期的可靠性进行管理。首先分析了目前的可靠度设计方法的优点和局限性,对可靠性管理的概念和必要性进行了阐述。继而引入时变可靠度和时点可靠度指标,建立一套考虑安全控制和风险优化的结构生命周期可靠性管理框架,并对其中的若干理论问题进行了讨论。该框架的特点在于,由静态思路转向动态思路,强调信息的更新和充分利用,与现有设计理论和工程实践保持协调。     

Life cycle structural integrity management of offshore structures

An overview of structural integrity management of offshore structures in the oil and gas energy sector is presented in this article. Based on relevant experiences with the hazards, accidents and means to control the associated risks are categorised from a technical and physical as well as human and organisational point of view. Structural risk relates to extreme environmental and accidental events, as well as structural degradation and can be controlled by use of adequate design criteria, inspection, repair and maintenance as well as quality assurance and control of the engineering processes. Such measures are briefly outlined, with an emphasis placed upon a quantitative design approach for dealing with a life cycle approach especially relating to crack degradation phenomena. The current status of risk and reliability methodologies to aid decisions in the safety management of novel and mature offshore structures is briefly reviewed.     

重大基础建设对美国土木工程高等教育的推动作用——以UIUC土木系为例

中国已经经历了近20年的大规模基础建设期,土木工程学科如何抓住国家大建设的机遇,全面提升自己的办学水平,是当前面临的主要问题。而美国历史上也经历了多次基础建设高潮,也随之诞生了一批蜚声世界的土木工程高等教育办学典范。文章以伊利诺伊大学香槟分校土木系为例,介绍了其主要学科方向在不同历史时期介入大型工程项目,积极创新,将基础理论研究和教学水平提升到世界领先地位的经验;分析了中国高校土木工程办学中存在的问题,以及如何依托当前大规模基础建设的机遇全面提升办学水平的策略,以期为中国土木工程高等教育的发展献计献策。     

Time-dependent reliability of ageing structures: an approximate approach

Concrete structures may deteriorate over time due to aggressive service environments, leading to a reduction in their strengths, stiffnesses and reliabilities. In general, the assessment of time-dependent reliability of ageing structures must consider uncertainties in structural deterioration as well as non-stationarities in the structural load processes. This paper develops an approximate method for assessing the impact of structural deterioration and non-stationary live loads on structures, which requires only low-dimensional integration and reduces the cost of assessing time-dependent reliability over a service life extending to 50 years significantly. This approximate method is demonstrated through several examples. The importance of non-stationarities in the resistance and load processes on time-dependent reliability is illustrated and the accuracy of the method is confirmed in several cases utilising Monte Carlo simulation.     

An augmented Lagrangian decomposition approach for infrastructure maintenance and rehabilitation decisions under budget uncertainty

This article addresses a general class of infrastructure management problems raised in maintenance and rehabilitation scheduling. Infrastructure agencies usually face budget uncertainties that eventually lead to suboptimal scheduling planning if maintenance decisions are made without taking the uncertainty into consideration. It is important for decision makers to adopt maintenance and rehabilitation scheduling policies that consider all budget scenarios. The authors propose a multistage, stochastic programming model to address this problem. The authors also develop a solution procedure using the augmented Lagrangian decomposition algorithm. A case study exploring the computational characteristics of the proposed algorithm is conducted and the benefit ofusing the stochastic programming approach is discussed.     

关于高校基建工程造价控制办法的思考

针对高校基建工程造价控制的重要性,通过对高校基建投资的特点和过程进行研究,并与实践工作经验相结合作出论述,旨在为我国高校基建工程造价的控制提供一些理论参考。     

土木工程施工质量与安全管理

建立具有专业管理能力与安全管理的专业队伍,对项目设计、施工程序、施工技术工艺等进行有效的监督,本文结合作者的工作实际,对土建施工中质量与安全方法做了研究,提出了相应的对策与措施,以期降低土木工程施工安全事故率,提高土建施工的质量与安全水平。     

Probabilistic performance prediction model for Austrian torrent control infrastructure

Due to the growing stock of torrent control structures and decreasing investments, the protection level can be reduced in the long term. Therefore, the focus of the future investments has been shifted on efficiency improvement and maintenance of existing structures. The maintenance of the existing structures is necessary to ensure safety from natural hazards, which are increasing as a consequence of the climate change. Due to the increasing number of structures, there is a strong need to develop a good maintenance management for these infrastructure works. This study is based on data from the condition rating programme of the Austrian Service for Torrent and Avalanche Control. For the structures relevant in this work, 75,343 records were available. The data were examined for different construction type and construction materials. The reliability of the structures was determined by means of the Markov chain. The study describes a homogeneous Markov chain model formed by the data of the condition rating. The result of this study is a proposal for a time to failure (TTF) and a time to repair (TTR) for several construction types with different construction materials as well as the time-dependent use of construction materials in the sector of the Austrian torrent control infrastructure.     

Reliability,availability and maintainability analyses for railway infrastructure management

Abstract

Reliable, available, maintainable and safe operation in railway transportation is significant for passenger and freight transportation. For these reasons, European Union put into practice a standard in 1999 known as EN 50126 to prevent railway accidents and to ensure a high level of safety in railway operations. The EN 50126 standard consists of these following concepts: Reliability, Availability, Maintainability and Safety (RAMS). These concepts are also recognised as RAMS analyses, which enable to do risk analyses to minimise the risks to the acceptable levels. In this study, a model framework including some stages was developed and the Reliability, Availability and Maintainability (RAM) analyses were applied to the railway infrastructure management. In addition, a case study was analysed for Uzbekistan high-speed railways between Tashkent and Sirdaryo train stations. The RAM analysis techniques were used during the analysis stages. The analyses were performed for the track geometry and the each type of railway track components to achieve a reliable, available and maintainable railway infrastructure management.     

土木工程专业生产实习教学方法改革的研究与探索

生产实习是土木工程专业教学过程中的重要环节,对于应用型院校的学生而言,这一教学过程尤为关键。本文分析了现阶段生产实习的现状和存在的问题,阐述了生产实习教学方法改革的意义,并针对存在的问题提出了提高土木工程专业生产实习教学效果的具体措施。     

The blue garden: coastal infrastructure as ecologically enhanced wave-scapes

Hard coastal infrastructure such as breakwaters and seawalls are built according to engineering parameters of structural performance and cost efficiency. Especially in urban settings, they conflict with the diverse needs and values of other users and stakeholders, such as sustaining coastal ecosystem biodiversity and providing the public with open, accessible spaces for socialisation and recreation. The presented research explores how the discipline of landscape design can contribute to their evolution. Building on recent precedents in developing multi-functional, ecologically enhanced seawalls, it proposes the concept of the blue garden, and explores two of its key features: bio-engineering the form and materiality of seawalls to enhance their performance as ecosystem service providers; and utilising computational fluid dynamics to poetically shape sea waves as a visual, aural and tactile landscape material to enhance its social and experiential value. It concludes with a pilot study that implements these principles for a specific urban site.     

土木工程大类专业结构力学教学探讨

结构力学是土木工程大类专业的一门重要专业基础课程,在培养土木工程大类专业复合型人才教学计划体系中起着承上启下的重要作用。在＂大土木＂背景下,从结构力学的学科体系出发,对教学内容、教学方法及政策导向等方面进行分析探讨,以促进教学方法的改革。     

Risk-informed condition assessment of civil infrastructure: state of practice and research issues

Civil infrastructure in the United States is at risk from aging, leading to structural deterioration of bridges, buildings, and other facilities from aggressive chemical attack, corrosion, and other physical mechanisms. Decisions regarding maintenance, rehabilitation and other requirements for continued utilization of a facility should be supported by quantitative evidence that aging has not caused structural strength or stiffness to deteriorate to the point where the capacity of the system to withstand or mitigate future extreme events is impaired. Current codes of practice provide little guidance for the proper evaluation of existing facilities for continued service, since their focus is on new construction. Rehabilitation investments should be aimed at maximizing the likelihood of successful future performance at minimum costs. Probabilistic risk analysis methods can provide quantitative tools for the management of uncertainty in condition assessment and are an essential ingredient of risk-informed management decisions. Such tools are data-intensive and require improved physical models of deterioration processes to realize their full potential in facility risk management.     

土木工程专业实验教学改革与创新

文章以提高学生实际操作能力、培养专业兴趣、发展创新能力为目的,阐述了实践教学与理论教学的关系。以钢筋混凝土简支梁实验为例,分析了实验教学改革的目标和方向,介绍了学生参与试件制作到应变片粘贴直至实验全过程的实验教学模式,从而提高教学质量、创新人才培养模式。     

Life-cycle of structural systems: recent achievements and future directions

Structural systems are under deterioration due to ageing, mechanical stressors, and harsh environment, among other threats. Corrosion and fatigue can cause gradual structural deterioration. Moreover, natural and man-made hazards may lead to a sudden drop in the structural performance. Inspection and maintenance actions are performed to monitor the structural safety and maintain the performance over certain thresholds. However, these actions must be effectively planned throughout the life-cycle of a system to ensure the optimum budget allocation and maximum possible service life without adverse effects on the structural system safety. Life-cycle engineering provides rational means to optimise life-cycle aspects, starting from the initial design and construction to dismantling and replacing the system at the end of its service life. This paper presents a brief overview of the recent research achievements in the field of life-cycle engineering for civil and marine structural systems and indicates future directions in this research field. Several aspects of life-cycle engineering are presented, including the performance prediction under uncertainty and optimisation of life-cycle cost and intervention activities, as well as the role of structural health monitoring and non-destructive testing techniques in supporting the life-cycle management decisions. Risk, resilience, sustainability, and their integration into the life-cycle management are also discussed.