Life Cycle Cost Optimization Research Articles

Life cycle cost optimisation in highway concrete bridges management

This study presents a life cycle cost prediction and cost minimisation methodology for a set of highway concrete bridges, during a medium or a long period of time, in order to facilitate the decision process of the structure management. This methodology takes into consideration bridge intervention costs in addition with some Markov matrices degradation model. It applies a genetic algorithm in order to identify the optimised intervention plan, considering the available budget and the desired minimum performance level. Some Portuguese direct and indirect cost parameters, associated with different types of interventions during bridges lifetime, are presented. Finally, a probabilistic sensitivity analysis is carried out using Monte Carlo simulations.

The Maintenance Strategy for Optimizing Distribution Transformer Life Cycle Cost

During the operation, the distribution transformer performance will deteriorate. The maintenance is an essential task in enhancing the safety of distribution transformer. Based on equal deterioration theory, the relationship among distribution transformer failure rate in each period of maintenance was deduced. After analyzing the maintenance costs and the failure costs in detail, the model of optimal life cycle costs for distribution transformer was established. Then the genetic algorithm was used to solve the model for obtaining the optimal maintenance strategy. Finally, the optimization results and the influence factors were analyzed. The results demonstrate the feasibility and validity of the proposed method. DOI: http://dx.doi.org/10.11591/telkomnika.v11i10.3458

Life Cycle Cost Analysis for Ground-Coupled Heat Pump Systems Including Several Types of Heat Exchangers

Ground-Coupled Heat Pump (GCHP) systems are now popular in both residential and commercial applications because of their great advantages as compared to conventional electrical air conditioning systems. One of the most important problems in evaluating the GCHP systems is optimizing the Life Cycle Cost (LCC) of the systems. Yeung firstly proposed LCC optimization model to roughly estimate the LCC of GCHP systems with single U-type heat exchangers. However, in this optimization, only single U-type heat exchanger was considered. Moreover, the optimization did not take into account the eect of pipe sizes on the heat pump and neither considered the capacity of the heat pump. In this paper, a model of LCC optimization with new improvements was proposed to optimize the LCC of GCHP systems in consideration with the eect of pipe sizes and capacity of the heat pump for not only single U-type heat exchanger but also for double, triple U-type, and coil-type heat exchangers.

New Approaches to Through-life Asset Management in the Maritime Industry

European shipbuilders are facing a strong, worldwide competition. Consequently they have to reinvent their market approach and expand their business. In the past, European shipbuilders were focused on cost reduction in the production process to offer new build vessels at a competitive price for decades. Changing the focus from the selling price optimisation to the life cycle cost optimisation could lead to competitive advantages and enable new business opportunities. This new approach of through-life asset management is investigated in the EU- funded project ThroughLife. The minimisation of a vessel’ life cycle costs could be realised by applying new and innovative technologies. However, new technologies are characterised by higher investment costs and uncertainty regarding functionality, reliability and reparability. As a result, the situation can be characterised as a dilemma for the new building yard the ship owner and the repair yard. Therefore the ThroughLife project focuses besides the development of new technologies on the identification, elaboration and application of new business model concepts to overcome this dilemma. One business model concept is the offer of a comprehensive service package against a fixed, time based fee, which would lead to an overall cost reduction due to economies of scale, lower administration costs and a risk reduction for the customer, which would support the market penetration of new technologies. Combining this business model approach with the technology of monitoring sensors increases the potential of this approach. The service provider could use the gathered information to schedule maintenance according to the actual condition of the vessel and identify potential mistreatment by the client. The customer would benefit from reduced, calculable costs and a lower risk level when applying new technologies. Further research contains lifecycle cost model calculations as well as real-life tests of the monitoring hardware in order to proof the concept.

Optimisation of the design of infrastructure components subject to progressive deterioration and extreme loads

The construction of new infrastructure requires solutions that maximise the benefit while meeting acceptable safety levels. The solution to this problem can be obtained through a structural cost-based optimisation. This paper integrates a life-cycle cost optimisation model developed by Rackwitz (2000) with a structural deterioration model that combines the action of progressive degradation (e.g. corrosion, fatigue) and sudden events (e.g. earthquakes). The structural condition at a given time is measured in terms of the system's remaining life, which can be measured in practice through any structural performance indicator (e.g. ductility). It is assumed that sudden events conform to a compound point process with shock sizes and interarrival times that are independent and identically distributed random variables. Deterministic and random progressive deterioration models are also included in the formulation. Randomness in progressive deterioration is modelled as a point process with known arrival times and random shock sizes. Structural reliability is evaluated against prescribed design and operation thresholds that can be used to establish limit states or intervention policies. The entire model is illustrated with an example that compares several life-cycle models showing the importance of taking into account the damage history in evaluating the performance of infrastructure systems.

Fatigue Life Assessment and Lifetime Management of Aluminum Ships Using Life-Cycle Optimization

The development of aluminum ship structures has been promoted in the context of the rapid evolution of high-speed and light-weight vessels. Under the repeated and/or fluctuating application of stresses during voyages, fatigue damage of structural ship members is accumulated. For this reason, fatigue reliability analysis has to be conducted for assessing and predicting lifetime performance of aluminum ships. This assessment offers the opportunity to optimally perform the lifetime ship structural management planning. To allocate limited financial resources required to balance the lifetime reliability of ship structural details and the life-cycle cost, single-or multi-objective optimization can be used. The multi-objective optimization problem has several competing objectives such as:(minimizing the life-cycle maintenance cost,maximizing the fatigue reliability of details with welded attachments, andminimizing the fatigue damage. The S-N (stress vs. number of cycles) approach and available sea loading information are used to evaluate the time-dependent fatigue reliability. In this paper, the estimated fatigue reliability is incorporated into a life-cycle cost optimization problem to find the optimal inspection and repair interventions. The proposed approach is illustrated on an aluminum ship detail.

생애주기비용을 이용한 잔교식 안벽의 신뢰도지수 최적화

Optimal reliability indices were found by optimizing life cycle cost(LCC) of pier type quay walls. Failure probability of pier and shore bridge were calculated by response surface method. Then, they were used to obtain recovery cost after damage. Costs for initial construction and maintenance were also considered in finding optimal reliability indices. Target reliability indices which may be used in reliability based design were suggested by numerical examples under seismic load and ship load.

사무소 건물 태양열급탕시스템의 LCC 최적화에 따른 에너지성능 변화 분석

This study examined the energy performance according to the main design parameters of a solar water heating system for an office building using the life cycle cost (LCC) optimization simulations. The LCC optimization simulations of the system were conducted with TRNSYS and GenOpt employing the Hooke-Jeeves algorithm for cases where water temperature was and . The results showed that for water temperature at and the global radiation incident on the collector could be decreased by 16.98% and 28.52%, collector useful energy gain could be decreased by 15.04% and 22.59%, energy to load from storage tank could be decreased by 10.86% and 18.06% and AH energy to load could be increased by 16.86% and 38.50% respectively compared to a non-optimized system. The annual average collection efficiency of the collector was increased by 0.88% for and 2.78% for because of increase of collector slope and decrease of the mass flow rate per collector area. The annual average efficiency of the system was increased by 1.74% and 3.47% compared to the basis system. However, the annual solar fraction of the system was decreased by 6.68% for and 11.26% for due to decrease of collector area and storage tank volume.

Building-Volume Designs with Optimal Life-Cycle Costs

This report provides a detailed overview of the building-volume optimization (BVO) model. It allows for insights into elements that comprise the BVO model, describes its setup as an optimization tool for design and tests its possibilities through exemplary runs. It includes the description of all life-cycle cost (LCC) members involved and explains the implemented optimization process approach. It also provides a perspective regarding the sensitivity and consequences of the BVO model. Serving as decision-support for designers the model qualifies as a practice-oriented application during the early design stage. Test results indicate that LCC considerations can significantly affect building-volume designs during this stage. Therefore, the introduction of cost objectives to the building-volume design represents a valuable approach. Enabling for their inclusion, design issues referring to estimated building performances, are capable of improvement before design finalization. Especially comparisons between initial and operational costs imply that, with increasing life-cycle periods, the impact of operational costs on shaping building-volume design is continuously growing.

Substation Maintenance Strategy Adaptation for Life-Cycle Cost Reduction Using Genetic Algorithm

The choice of the right maintenance strategy is an important but also difficult topic for every energy utility. The difficulty consists in the huge number of interacting cost parameters. The present paper shows how from the biology well known process is adapted as an optimization algorithm in order to handle the parameter diversity. Outgoing from the definition of Life Cycle Cost and a method for substation reliability calculation the main idea of genetic algorithm and its application for Life Cycle Cost optimization is presented. Closing a case study shows the suitability of the algorithm.

Systematic Management of Highway Project Life Cycle Cost

The cost in each stage of construction project has respective characteristics, and has different status in the whole life cycle. The relation between construction cost and maintenance cost is that as one falls, another rises. Systematic management of highway project life cycle cost is achieving the optimal life cycle cost of construction project from the aspects such as material cost control, equipment cost control, human resources cost control, management cost control, new technology cost control and risk control by analyzing the interrelation between the cost in every stage or of every element of projects life cycle.

On the prediction of the interaction effect caused by continuous ballast on filler beam railway bridges by experimentally supported numerical studies

To estimate mechanical properties to be used for numerical analyses of railway bridges, experimental tests on railway ballast have been performed within the framework of the European research project DETAILS (Design for optimal life cycle costs of high-speed railway bridges by enhanced monitoring systems), supported by the European RFCS-Fund. German two-track railway bridges often provide two separated bridge decks. However, interaction effects between the two bridge decks take place due to a continuous ballast layer. Not only in view of numerical modelling, the mechanical behaviour of the ballast in the contact area between the separated bridge decks is of great interest, as SLS and even ULS issues are affected by the so far neglected interaction. After a short introduction, experimental tests are described in the first part of the paper. As a first approximation, it is shown that linear elastic springs can be used for taking into account the load transfer between ballast-connected structures. Thus, the springs represent a kind of shear stiffness of the ballast layer. Considering the test results, such an approach is applied for numerical analysis of a filler beam bridge with two separated decks and a continuous ballast layer. The modelling approach and related numerical results are presented in the second part of the paper. As conclusion both experimental and numerical results are discussed with regard to the dynamic design of simply supported and ballasted railway bridges.

Legal Environment for Warranty Contracting

Due to the public expectation of better road performance accompanied by economic development and population growth over the past decades, state highway agencies have been under intense pressure for continuous improvement in the quality and cost efficiency of transportation projects. To meet these challenges, state highway agencies must seek innovative approaches to deliver highway projects, including outsourcing some of the agency’s functions and shifting maintenance responsibilities to contractors. Many states have implemented alternative contracting methods in project programming and execution to provide lasting and functional roadways at the optimum life-cycle cost to the public. The performance warranty is one of the innovative practices that has been declared operational by the Federal Highway Administration since 1996. Use of warranties in some states has required changes to state legislation and agency regulations. This paper discusses the laws and regulations needed to successfully incorporate per...

Life-Cycle-Management of CV Cables based on Degradation Diagnosis -Usability Assessment in Small-scale Application Considering Variation of Evaluated Cost-

Life-cycle management (LCM) based on degradation diagnosis, which is called condi- tion-based maintenance (CBM) can be useful for preventing an unexpected failure and extending service life of electric power apparatuses, resulting in reduced life-cycle cost (LCC). In our previous study, we formulated numerical model of CBM and applied the model to calculate the LCC of 6.6 kV XLPE cables, for which relatively rich data on degradation are available. Assuming that cables with longer water-tree length as a nondestructively measurable replacement criterion are replaced after the diagnosis in CBM, we evaluated the economic advantage of CBM against time-based maintenance (TBM) where all the ca- bles are replaced with a certain fixed interval. To carry out reliable CBM, accurate data are necessary as well as a well-established diagnostic method. However, power apparatuses are used under various condi- tions and furthermore failure probability would be different even with the same condition, and the data available for CBM are limited. Therefore, it is important to carry out robust CBM even with the insuffi- cient and/or inaccurate data. In this study, by using the data which is intentionally formulated to be dif- ferent from the master data, we examined the influence of accuracy of the data on CBM and evaluated its reliability and robustness. The main results are as follows. In TBM, if the replacement of 6.6 kV XLPE cables is carried out with the apparent optimal interval which is calculated by using the incorrect or in- complete data, the LCC can be much larger than the optimum LCC with the accurate date. On the other hand in CBM, the LCC is smaller than that of the optimum TBM, and does not change so much with the diagnosis parameters, i.e. replacement criterion and diagnosis interval. The results suggest that CBM can contribute to reliable life-cycle management even if the correct and complete data are not available to de- termine the diagnosis parameters.

Optimizing product support (spare parts procurement) strategy by considering system operating environment – A case study

Existing industrial system / machinery availability depends highly on the form and the level of product support. Product support, which is also referred to as after sale service to the product, is important for the customer as well, because it assures the expected function of the product in its operational phase. Product support is affected by different factors, such as reliability and maintainability characteristics and the operating environment of the product. The forecasting of required product support and spare parts based on these factors is one approach for product life cycle cost optimization along with system availability maximization. This paper describes a method to estimate the spare part requirements based on an estimation of reliability of the existing product under the influence of the product-operating environment. Subsequently, in a case study, the management of the spare parts inventory based on the geographical location and required performance of the product will be addressed.

Integration of durability with structural design: An optimal life cycle cost based design procedure for reinforced concrete structures

The durability design of concrete structures is traditionally based on implicit and prescriptive requirements for materials, material constituents and structural dimensions. With the use of such rules, it is however not possible to visualize an explicit relationship for durability over the lifetime of a structure and determine what constitutes acceptable durability at an optimum cost. An explicit durability design procedure for the design of reinforced concrete structural elements is presented in this paper. The procedure attempts to directly integrate considerations of durability into the structural design process while ensuring lifetime cost optimization. The evaluation of durability is made on the basis of service life which is determined based on the principle of exceedance of defined limit states – a concept commonly used in structural design. Two limit states for corrosion of reinforcement induced by chloride ingress from sea water are used. The service life decides the magnitude and timing of future costs incurred during the design life of the structure. Tradeoffs between initial costs and future costs are examined to determine the optimum design alternative from a life cycle cost perspective. Further the influence of various design and environment variables on the life cycle cost and hence durability of the structure is also evaluated.

Multiobjective Optimization Applied to Maintenance Policy for Electrical Networks

A major goal for managers of electric power networks is maximum asset performance. Minimal life cycle cost and maintenance optimization becomes crucial in reaching this goal, while meeting demands from customers and regulators. This necessitates the determination of the optimal balance between preventive and corrective maintenance in order to obtain the lowest total cost. The approach of this paper is to study the problem of balance between preventive and corrective maintenance as a multiobjective optimization problem, with customer interruptions on one hand and the maintenance budget of the network operator on the other. The problem is solved with meta-heuristics developed for the specific problem, in conjunction with an evolutionary particle swarm optimization algorithm. The maintenance optimization is applied in a case study to an urban distribution system in Stockholm, Sweden. Despite a general decreased level of maintenance (lower total maintenance cost), better network performance can be offered to the customers. This is achieved by focusing the preventive maintenance on components with a high potential for improvements. Besides this, this paper displays the value of introducing more maintenance alternatives for every component and choosing the right level of maintenance for the components with respect to network performance.

Life-cycle cost assessment model for fiber reinforced polymer bridge deck panels

To enhance the application of fiber reinforced polymer (FRP) bridge deck panels in the infrastructure area, a practical method is required that would allow probable assessment of the life-cycle cost of advanced composite applications in construction compared with that of conventional materials, at various discount rates, while integrating the available reference data. The overall objective of this research is to develop a performance-based probable life-cycle cost assessment model for FRP bridge deck panels. The life-cycle cost assessment model for FRP bridge deck panels comprises a life-cycle performance module (module-1) and a life-cycle cost optimization module (module-2). The model thus developed in this paper can then be used for other applications of composites in construction. The objective of module-1 is to develop an analytical model that is capable of predicting the structural deterioration over time to assess the deterioration rating per year of FRP bridge deck panels. The objective of module-2 is to develop an analytical model that is capable of assessing the optimal life-cycle cost of FRP bridge deck panels. Three case studies were conducted to validate the logic and results of the process algorithm for the life-cycle cost assessment. The model will be very helpful for the construction industry in evaluating various material options and to justify or deny the feasibility of using composite materials on specific construction projects. Since the life-cycle cost assessment of composite materials in construction has not been dealt with as proposed, it is anticipated that many of the procedures and systems mentioned would include fundamental research and possible innovations.Key words: fiber reinforced materials, Monte Carlo method, life-cycle cost, performance valuation.

Pump Systems Matter — part 1

In an effort to encourage US pump system specifiers to move away from purchasing decisions based on lowest initial cost towards one based on optimum life cycle costs, the Hydraulic Institute introduced the Pump Systems Matter™ initiative. In the first of a two-part article, Robert Asdal, Vestal Tutterow and Aimee T. McKane explain the background and the need to focus on the pumping system and not just the pump.

Simulation-based determination of optimal life-cycle cost for FRP bridge deck panels

Fiber-reinforced polymer (FRP) composites are increasingly being used in civil infrastructure applications. FRP composites, however, are still relatively unknown to the practicing civil engineer and infrastructure systems planner. There are several unresolved issues to be considered in order to increase their application in construction of infrastructure. Recently, life-cycle cost analysis (LCCA) has been shown to identify how cost-effective FRP composites are compared with conventional materials [Hastak, Makarand and Daniel W. Halpin (2000). Assessment of life-cycle benefit–cost of composites in construction. Journal of Composites for Construction, ASCE, 4 (3) 103–111]. Although many models for estimation of life-cycle cost in FRP composites have been proposed, it remains difficult to predict the end of service life for new advanced materials. It is, therefore, important to assess the life-cycle costs of replacing conventional construction materials with advanced composites. This paper introduces an analytical model to determine optimal life-cycle cost under different discount factors (i.e., interest rates) and inflation rates. It presents a method to estimate the service life for FRP bridge deck panels. Monte Carlo simulation is used to account for uncertainty in those two parameters.