• Journal of the Korean Society of Safety
• /
• v.24 no.2
• /
• pp.62-68
• /
• 2009

Life Cycle Cost(LCC) is adopted to decide the target of safety level in designing suspension bridges. The LCC are evaluated considering two types of uncertainty; aleatory and epistemic. The nine alternative designs of suspension bridge are simulated to decide the safety level which can minimize the LCC. The LCC is calculated through the probability of failure and safety index including the uncertainty. This method results in the useful tool deciding the optimum safety level with minimal LCC as the main design factor.

• Proceedings of the Korean Operations and Management Science Society Conference
• /
• 1991.10a
• /
• pp.405-421
• /
• 1991

In this paper, faults existing in a software system is classified into three types; simple, degenerative and regenerative faults. The reliability functions and failure rates of both a software module and system which have a mixture of such faults are obtained and the expected number of failures in the system after time T is also derived. Using the formulas obtained, a cost-reliability model and an efficient algorithm for optimal software release time are proposed via nonlinear programming formulation ; minimizing the total test cost with constraints on the failure rates of each module. Application of this model to several cases are presented and it appears to be more realistic.

• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 2000.10a
• /
• pp.109-114
• /
• 2000

In this paper, an optimum design model for minimizing the life-cycle cost (LCC) of high-speed railway steel bridges is proposed The point is that it takes into account service life process as a whole, and thus the life-cycle costs include initial (design, testing, and construction) costs, maintenance costs, expected strength failure costs and expected serviceability failure costs. The problem is formulated as that of minimization of expected total life-cycle cost with respect to the design variables. By processing the optimum LCC design the effective and rational basis is proposed for calculating the total LCC and the sensitivity analysis of LCC is peformed. Based on a numerical example, it may be positively stated that the optimum LCC design of high-speed railway steel bridges proposed in this study provides a lot more rational and economical design, and thus the proposed approach will expedite the development of new concepts and design methodologies that may have important implications in the next generation performance-based design codes and standards.

• Journal of Korean Society of Industrial and Systems Engineering
• /
• v.20 no.43
• /
• pp.357-364
• /
• 1997

After the buyer purchases the product, the seller's role does not end. If the product fails to function properly before the end of the warranty period, the seller is responsible for its repair or replacement under the seller's warranty policy. There are two common types of warranty policies: the free replacement warranty and the rebate warranty. Under the free replacement warranty policy, replacement or repairs during the warranty period are provided by the seller free of charge to the buyer. Under the rebate warranty policy, a failed item is replaced by a new one or is repaired at a cost to the age of the failed item. The rebate warranty is most often used for items such as a battery or an automobile tire which wear out and must be replaced at failure. This paper proposes a easy way of estimating the warranty cost under the free replacement warranty policy assuming an exponential product failure function on repairable products.

• Current Photovoltaic Research
• /
• v.2 no.3
• /
• pp.140-145
• /
• 2014

The globally used PV qualification tests and reports the pass/fail only. Therefore, the reliability of new PV materials and parts can't be compared quantitatively with the reliability of the PV parts and materials in the market. Global PV materials and parts companies test and compare their materials, parts, and modules using the failure-to-test (FTT). However, it takes a long accelerated stress test (AST) until failure. It also needs to test the new and existing materials and parts. Therefore, it requires excessive equipment time and cost. In order to reduce the time and cost, a new reliability enhancement methodology has been developed. It tests the PV materials, parts, and modules in the global market and stores them in the PV reliability database. It reduces the time and cost of the comparison and enhancement of PV reliability. An example of the reliability enhancement of the PV encapsulant, EVA is presented.

• Journal of Korean Society of Industrial and Systems Engineering
• /
• v.24 no.62
• /
• pp.1-10
• /
• 2001

The electronics industry is fast growing segment of manufacturing and service industries. It is important that the manufacturer develops a product with adequate life cycle, high quality, and low failure rate in the specified time period. Environmental Stress Screening(ESS) and burn-in are widely used in the electronic industry to assist in the elimination of early failure. In this research, we construct optimal cost model of combined ESS and burn-in under various warranty policy and establish optimal testing times for given environments. Also we conduct sensitivity analysis on various parameter. The results of this study are summarized as follows. Comparing free warranty policy to rebate warranty policy, optimal ESS time is longer under free warranty policy, and optimal burn-in time is longer under rebate warranty policy. Free warranty policy higher than rebate warranty policy in total cost.

• Journal of Korean Society for Quality Management
• /
• v.20 no.1
• /
• pp.39-47
• /
• 1992

This paper is concerned with cost analysis and determination of warranty period in a stepdown warranty policy. Manufacturer's warranty cost is analyzed for nonrepairable item, where the warranty is assumed to be renewed at any failure within the warranty period. It is shown that from this result in free replacement policy, pro-rata policy and hybrid policy can be easily calculated. The method of determining optimal warranty period is also explored.

• Proceedings of the Korean Society for Quality Management Conference
• /
• 1998.11a
• /
• pp.269-276
• /
• 1998

This paper proposes an opportunistic age replacement policy. The system has two types of failures. Type I failures (minor failures) are removed by minimal repairs, whereas type II failures are removed by replacements. Type I and type II failures are age-dependent. A system is replaced at type II failure (catastrophic failure) or at the opportunity after age T, whichever occurs first. The cost of the minimal repair of the system at age z depends on the random part C(z) and the deterministic part c(z). The opportunity arises according to a Poisson process, independent of failures of the component. The expected cost rate is obtained. The optimal $T^{\ast}$ which would minimize the cost rate is discussed. Various special cases are considered. Finally, a numerical example is given.

• Journal of Korean Society of Industrial and Systems Engineering
• /
• v.16 no.27
• /
• pp.21-25
• /
• 1993

This article is concerned with cost analysis in stepdown warranty policy. The repair of item is divided into two policies. First, perfect repair can be considered that the failurerate is the same as new item. Second, minimal repair is shown that the failurerate is the same as just before the item failure In this paper, the minimal repair model is introduced. And it is assumed that manufacturers repair the item failure within the warranty periodn. But warranty period is not renewed at all. At this point the warranty cost is analyzed in manufacturer's and customer's point of view.

• Proceedings of the Earthquake Engineering Society of Korea Conference
• /
• 2001.04a
• /
• pp.387-393
• /
• 2001

Installing vibration control devices in the structure rises as a solution instead of increasing structural strength considering construction cost. Especially, viscoelastic dampers show excellent vibration control performance at low cost and are easy to install in existing structures compared with other control devices. Therefore, cost-effectiveness of structure with viscoelastic dampers needs to be evaluated. Previous cost-effectiveness evaluation method for the seismically isolated structure(Koh et al., 1999;2000)is applied on the building structure with viscoelastic dampers, which combines optimal design and cost-effectiveness evaluation for seismically isolated structures based on minimum life-cycle cost concept. Input ground motion is modeled in the form of spectral density function to take into account acceleration and site coefficients. Damping of the viscoelastic damper is considered by modal strain energy method. Stiffness of shear building and shear area of viscoelastic damper are adopted as design variables for optimization. For the estimation of failure probability, transfer function of the structure with viscoelastic damper for spectral analysis is derived from the equation of motion. Results reveal that cost-effectiveness of the structure with viscoelastic dampers is relatively high in how seismic region and stiff soil condition.