Empirical Markovian-based models for rehabilitated pavement performance used in a life cycle analysis approach

Two empirical Markovian-based models are presented in this paper to predict the transition probabilities associated with rehabilitated pavement. The first model predicts the staged-homogenous transition probabilities as required by the staged-homogenous Markov model. The second model predicts the non-homogenous transition probabilities as applicable to the non-homogenous Markov model. In both the models, the deterioration transition probabilities are predicted as a function of the corresponding values associated with original pavement and two adjustment factors reflecting the impacts of increased traffic load applications and decreased pavement strength. The predicted transition probabilities are used to estimate the future distress ratings required for developing the corresponding life cycle performance curve. The life cycle performance/cost ratio is used to evaluate the cost-effectiveness of potential long-term M&R plans. The life cycle performance is defined as the area falling under the life cycle curve. The life cycle cost is estimated to include initial construction cost, routine maintenance cost, major rehabilitation cost, and added user cost due to work zone. Two proposed cost models are used in the case study for estimating routine maintenance and added user costs. The case study indicates that the proposed empirical Markovian-based models have provided reasonable estimates of the transition probabilities as reflected by the corresponding life cycle performance curves.     

Monte Carlo simulation approach to life cycle cost management

Public private partnerships (PPP) and private financial initiative (PFI) projects face the challenge of meeting unforeseen future risks. Life cycle cost estimate is a crucial part of PFI/PPP procurement. The traditional deterministic cost model can not take into consideration the uncertainty of future events let alone determine the contingency allowance for the projects. The large number of cost items in the life cycle cost model of building projects makes cost control difficult. Monte Carlo simulation method is applied to the Quantitative Risk Assessment of life cycle costing risk management. A PFI school project was chosen as a case study to demonstrate a new simulation approach to life cycle cost management. The lives and replacement cost rates of building elements are the inputs for the simulation model, while the cumulative life cycle cost are the outputs of the analysis. The sensitivity analysis revealed the cost significant items, which provides the most efficient way for cost control. The results of the analysis identify the high risk life cycle assumptions and provide a variation reference for the decision-makers to define risk and contingency allowance in PFI/PPP projects. The approach can also be applied to other types of building PFI projects.     

Estimation of pavement rehabilitation cost using pavement management data

Estimation and scheduling of future pavement maintenance and rehabilitation (M&R) works are one of the primary concerns of highway agencies due to the limited allocations in budget and resources. Two approximate methods for estimation of pavement rehabilitation cost are presented and compared in this study based on highway present condition index (HPCI) and rehabilitation history. The former is based on pavement condition, while the latter is based on historical and statistical trends. Database from a pavement management system (PMS) of various highway sections surveyed in Korea were used in this study to establish a relationship between HPCI and pavement service life and to analyse the trends of rehabilitation periods. The two simple methods presented provide useful information and probable range for the various highway agencies to guide them in the preliminary planning, budgeting, estimating and scheduling of their future pavement M&R works.     

Life cycle cost analysis based on the fundamental cost contributors for asphalt pavements

A life cycle costing system should include the key variables that drive future costs in order to provide a framework for reducing the risk of under- or overestimating the future costs for maintenance and rehabilitation activities. In Sweden, price of oil products is mostly affected by the global economy rather than by the national economy. Whereas the price index of oil products has had a high fluctuation in different time periods, the cost fluctuation related to labour and equipment has been steady and followed the consumer price index (CPI). Contribution of the oil products was shown to be more than 50% of the total costs regarding construction and rehabilitation of asphalt pavements in Sweden. Consequently, it was observed that neither Swedish road construction price index (Vägindex) nor CPI has properly reflected the price trend regarding the asphalt pavement construction at the project level. Therefore, in this study, a framework is suggested in which energy- and time-related costs are treated with different inflation indices in order to perform a better financial risk assessment regarding future costs.     

An analysis of the cost-effectiveness of rigid pavement rehabilitation treatments

This paper analyses the costs, effectiveness, and cost-effectiveness of three standard rehabilitation treatments of rigid pavements using historical data from the state of Indiana. Treatments investigated are Hot Mix Asphalt (HMA) Overlay, Patching, and Portland Cement Concrete (PCC) Overlay. Performance criteria used are the sudden decrease in surface roughness after treatment, treatment service life, and increase in average pavement condition over the service life. Cost-effectiveness is the ratio of treatment effectiveness to treatment cost. Results suggest that Patching and PCC Overlay treatments are the most effective on the basis of short term and long term effectiveness, respectively. The results also show that at relatively small levels of traffic loading, a change in climatic severity has greater influence on treatment effectiveness than that at higher levels of traffic loading. On the basis of cost-effectiveness, the results suggest that PCC Patching appears to be the best treatment.     

论建设项目全寿命周期管理成本控制

阐述了建设项目全寿命周期的概念,对建设项目全寿命周期各阶段的管理内容进行了分析,从业主的角度探讨了建设项目全寿命周期管理成本控制的几项措施,从而有效降低建设项目全寿命周期成本。     

Simulation-based life cycle cost modeling and maintenance plan for water mains

Life cycle cost (LCC) is an essential approach to decide on alternative rehabilitation strategies for infrastructure systems, such as water mains. The research presented in this article identifies several rehabilitation methods for water mains, which are classified into three main categories: repair, renovation and replacement. A simulation-based LCC (SLCC) model is developed to compare different rehabilitation scenarios/alternatives for various types of water mains (i.e. cast iron, ductile iron, concrete, polyvinyl chloride and asbestos cement). Results show that ‘open trench’ and ‘slip lining’ are the most appropriate methods for the ‘repair’ and ‘renovation’ categories, respectively. However, the most suitable method for the ‘replacement’ category is ‘pipe bursting’ for pipe diameters less than 750 mm (<30″) and ‘open cut’ for pipe diameters greater than 750 mm (>30″). A rehabilitation plan is developed based on the SLCC results. This plan recommends repairing pipes using ‘open trench’ until the breakage rate reaches 0.5 breaks/km/year, then, replace the pipe beyond this threshold. Based on the designed SLCC model, web-based software is developed to determine the optimal rehabilitation scenarios. The developed model and software help academics and practitioners (e.g. municipal engineers) to predict the suitable new installation and/or rehabilitation programs as well as their corresponding costs.     

工程造价中全寿命周期造价管理的应用分析

伴随着市场经济的冲击,建筑企业不断增多,这也间接的强化了建筑市场的竞争。为了更好的提高建筑企业的核心竞争力,许多企业在投标过程中都会尽可能采取低价格,但是这样的低价格也间接降低了企业的经济利润。对此,为了确保企业的经济利润,在建筑造价方面采用合理的控制方式,最大程度降低建筑成本对于推动建筑企业发展而言有着明显的意义和作用。为了更好的降低建筑工程整体成本,本文详细分析工程造价中全寿命周期造价管理的应用。     

Aggregate and disaggregate statistical evaluation of the performance-based effectiveness of long-term pavement performance specific pavement study-5 (LTPP SPS-5) flexible pavement rehabilitation treatments

Engineers continually seek effective techniques for preserving highway infrastructure. Using data from the specific pavement study#5 of the long-term pavement performance (LTPP) programme's western region, this article evaluated the performance of eight flexible pavement rehabilitation treatments. Aggregate and disaggregate post-treatment performance models were developed for each treatment. Effectiveness was measured in the short term (roughness reduction) and long term (estimated treatment service life and area bounded by the performance curve (ABP)). The results showed that compared to 2-inch treatments, 5-inch treatments were on average more effective in terms of the following measures: 47% (estimated service life) and 35% (ABP) depending on the level of surface preparation, mix type and initial pavement condition. Also, relative to minimal surface preparation, intensive surface preparation generally yielded greater effectiveness: 25% (estimated service life) and 49% (ABP) depending on added thickness, mix type and initial pavement condition. Compared to recycled mix treatments, virgin mix was marginally more effective. Finally, compared to pavements treated in poor condition, those treated in good condition were significantly more effective. Treatment effectiveness models were developed for predicting the expected effectiveness of future treatments on the basis of attributes such as treatment type, added layer thickness, level of surface preparation and mix type.     

Water mains renewal planning framework for small to medium sized water utilities: a life cycle cost analysis approach

For the last few decades, concerns have repeatedly been raised about deteriorating water mains in Canada. Small to medium sized water utilities are generally impacted more due to lack of technical and financial resources. This paper presents a user-friendly life cycle cost (LCC) analysis-based decision support tool to help these utility managers to prioritize water mains rehabilitation or replacement (R/R) strategies. The deterioration curves for water mains of different materials and sizes have been developed based on their likelihood of failure. The proposed model is implemented for the water supply network of City of Kelowna (Canada). It compares the costs of various R/R scenarios for each pipe over its life cycle and suggests the most cost-effective decision to the managers to efficiently allocate their limited resources.     

A comprehensive life cycle water analysis framework for residential buildings

Most studies on the environmental performance of buildings focus on energy demand and associated greenhouse gas emissions. They often neglect to consider the range of other resource demands and environmental impacts associated with buildings, including water. Studies that assess water use in buildings typically consider only operational water, which excludes the embodied water in building materials or the water associated with the mobility of building occupants. A new framework is presented that quantifies water requirements at the building scale (i.e. the embodied and operational water of the building as well as its maintenance and refurbishment) and at the city scale (i.e. the embodied water of nearby infrastructures such as roads, gas distribution and others) and the transport-related indirect water use of building occupants. A case study house located in Melbourne, Australia, is analysed using the new framework. The results show that each of the embodied, operational and transport requirements is nearly equally important. By integrating these three water requirements, the developed framework provides architects, building designers, planners and decision-makers with a powerful means to understand and effectively reduce the overall water use and associated environmental impacts of residential buildings.     

Life cycle cost assessment of masonry structures

The objective of this study is to propose a life cycle cost (LCC) model able to assess the structural performance of masonry structures. For this purpose the proposed LCC model is used for assessing the structural behaviour of one unreinforced and three retrofitted masonry structures derived following three retrofit scenarios that are suitable for strengthening this type of structures. According to the proposed LCC model the exceedance probabilities required, are calculated by means of fragility analysis (FA). In particular, FA is applied to the unreinforced and retrofitted masonry structures and the limit-states' exceedance frequencies are obtained by convolving fragilities with hazard curve. Life-cycle cost analysis models are recognised as suitable for assessing the structural performance, especially when the structure is expected to be functional for a long period of time. For the needs of the study, linear time history analyses are performed over a large database of natural records.     

A life cycle assessment of in-place recycling and conventional pavement construction and maintenance practices

The application of in-place recycling techniques has emerged as a practical and effective way to enhance the sustainability of agency pavement management decisions for asphalt-surfaced pavements. However, the potential environmental benefits resulting from applying in-place recycling techniques have not been fully documented in the literature. This paper presents a comprehensive pavement life cycle assessment (LCA) model that extends the typical pavement LCA's system boundaries to include the environmental impacts resulting from the usage phase and the production of the energy sources. The results of the application of the pavement LCA model to a specific highway rehabilitation project in the state of Virginia showed that in-place recycling practices and an effective control of the pavement roughness can improve significantly the life cycle environmental performance of a pavement system.     

Strategic policy analysis for infrastructure rehabilitation using system dynamics

Recent requirements for sustainable development and increasing trend for public–private partnerships (PPPs) have added additional complexities to the policy-making process in the infrastructure management domain. To support policy analysis, this paper presents a system dynamics (SD) model to analyse the impact of different strategic policies (e.g. budgeting, PPP involvement) on infrastructure serviceability, backlog accumulation and sustainability. The proposed model has been implemented on a network of school buildings from the Toronto District School Board asset inventory. Four sets of experiments with different policy scenarios over a 50-year strategic planning horizon have been conducted to investigate policies related to rehabilitation, budget distribution, government investment and PPP involvement. The proposed model was implemented on a commercial SD software incorporating all the dynamic interactions among the strategic parameters. The experiment results show that the model works as a practical decision support tool that enables asset managers to test the effectiveness of various strategic policy scenarios on long-term infrastructure performance.     

A probabilistic approach for economic analysis of a shopping center in seismic zone

The occurrence of an earthquake causes direct and indirect losses in economy. Performance of the built environment can determine both the magnitude of the losses and the speed of recovery from earthquakes. Earthquake losses can be minimized by the use of planning techniques. This paper presents a probabilistic approach for economic evaluation of a shopping center constructed in a seismic zone. Decision-makers can benefit from this approach, before and after an earthquake occurrence, by considering the probability distribution and variability. Life cycle cost concept is taken into account in the formulation of future worth estimation. Therefore, the approach simulates all the benefits and costs, which are prone to variation within Monte Carlo framework. The probabilistic approach can be used to assess the effects of recovery periods.     

A multi-objective optimisation approach for sustainable pavement management

Addressing the multidimensional challenges involved in advancing the sustainability of pavement systems requires the development of optimisation-based decision support system (DSS) for pavement management with the capability to identify optimally sustainable pavement maintenance and rehabilitations (M&R) strategies. The main objective of this research work is to develop a multi-objective optimisation framework that hosts a comprehensive and integrated pavement life cycle costs–life cycle assessment model that covers the pavement’s whole life cycle, from the extraction and production of materials to construction and maintenance, transportation of materials, work-zone traffic management, usage and end-of-life. The capability of the proposed DSS is analysed in a case study aiming at investigating, from a full life cycle perspective, the extent to which a number of pavement engineering solutions are efficient in improving the environmental and economic aspects of pavement sustainability, when applied in the management of a road pavement section. Multiple bi-objective optimisation analyses considering accordingly agency costs, user costs and greenhouse gas emissions were conducted based on a multi-objective genetic algorithm. Pareto fronts were obtained for each analysis, originating a set of non-dominated maintenance and rehabilitation solutions. Posteriorly, a multi-criteria decision analysis method was used to find the best compromise solution for pavement management.     

钢筋混凝土桥面板全寿命成本影响因素敏感性分析

钢筋混凝土桥面板维护的全寿命成本受多种因素的影响,为有效降低全寿命成本,对各个因素的敏感性进行分析是十分必要的。通过对一实际在役钢筋混凝土桥梁的桥面板维护的全寿命成本进行分析,调整各个参数在一定范围内变化,观察全寿命成本随之的变化情况,以此来分析各个参数的敏感性。结果表明:各参数的敏感程度依次为折现率、日均车流量、车辆行驶成本、绕路时间、铺设LSDC成本、去除破损混凝土成本。该结果为降低钢筋混凝土桥面板维护的全寿命成本提供一定的指导依据。     

The probabilistic time and cost risk analysis of a challenging part of an urban tunneling project

A predominant characteristic of geotechnical works and more particularly tunneling projects, is the uncertainty that surrounds the geologic medium in which the construction is to be performed. This paper is dealing with the risk analysis of both the construction time and cost of a challenging part of Tehran Metro Line 7, an urban tunneling project which is currently being under development. The Decision Aids for Tunneling (DAT) has been utilized for this assessment, concerning the risk analysis by taking into account different scenarios relating to the measures implemented to prevent surface subsidence problems. The results have shown that selection of different sorts of methods will help control the risk of escalating the project’s total construction cost and time to completion. This research delivers useful information to concurrently help the owner, the contractor as well as the designer of the project in making the most appropriate decisions under such a highly uncertain and challenging geological environment.     

Condition-based maintenance decision support system for oil and gas pipelines

The 2013 report card of America's infrastructure has scored the condition of oil and gas pipelines as D+ which means that such pipelines are in a relatively poor condition. More than 10,000 failures have been recorded in the US. These failures have resulted in environmental, health and property damages. Therefore, there is a definite need to give more attention to the maintenance of oil and gas pipelines. This paper develops a comprehensive model for the maintenance planning of oil and gas pipelines. The model selects rehabilitation/repair alternatives for oil and gas pipelines based on their condition during their service life. These alternatives are then used to calculate the cash flow throughout the service life of these infrastructures. The model, which uses Monte Carlo simulation and fuzzy approach to address the uncertainties in the estimation of the maintenance operation costs and the economic parameters, calculates the Equivalent Uniform Annual Worth of the identified alternatives. The optimum maintenance programmes consist of the alternatives that have the lowest life cycle cost of oil and gas pipelines. The model is expected to support pipeline operators in the maintenance decision-making process of oil and gas pipelines.