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The calculation of expected-losses-reduction, adopted in practices of cost-benefit analysis of disaster mitigation investment, fails to capture the catastrophic features of disaster, most typically characterized by large magnitudes of collective damage. The risk management methods to cope with disaster can be classified into two categories: risk control through disaster mitigation and risk finance to allocate catastrophe risks through market transactions. The paper claims that the cost-benefit evaluation of mitigation investment should reflect social applicability of risk finance technology to take into account the catastrophic aspects of natural disaster. The paper presents an extended framework of economic valuation of catastrophe risk mitigation and summarizes remaining issues to be concurred in future research.

This study presents a methodology for determining the stability of sheet-pile structures in the construction of sea-port system, and thus proposes a priority plan for maintenance and rehabilitation (M&R) of sheet-pile structures. In details, we formulate a mechanical model to evaluate the stability of sheet-pile structures, which are measured by means of ground stability or shrinkage in account of risks associated with seismic forces. Based on the formulation of mechanical model, we develop a hybrid simulation model for determining a set of priority rule in M&R activities. This hybrid model enables managers of sea-port system to minimize the M&R expenditure in their expected management term. The usefulness and practicability of our model are proved through the implementation of an empirical study using monitoring data on sea-port structures in Osaka city.

On the pavement in snowy cold region, water spray is often carried out as snow thawing and removing activities in winter. Therefore in most cases, pavement surface is in wet condition, and it causes the generation of a lot of potholes. Usually, for the potholes, emergency repair is immediately conducted using patching mixtures. However under these circumstances, the patching mixture falls away soon due to the constraint in the repairing work. Consequently, as for the maintenance in snowy cold region, it is important to develop the optimal repair method or patching mixture material for such region. In order to provide the fundamental discussion of this issue, this study statistically evaluates the durability of the patching mixtures of potholes. Concretely, the generation process of potholes are modeled by the Weibull hazard model, and the durability performance of the patching mixtures is verified by estimating the hazard model based on the inspection data of actual potholes on the national road in snowy cold region and monitoring data after repairing them.

In recent years, a technique of asset management is being applied to maintenance and renewal of infrastructure facilities in consideration of a better fiscal management. Asset management of infrastructures focuses on the reduction and equalization of annual maintenance costs over the lifetime. In the field of river management, researches on the potential of maintenance cost reduction have been done for machinery and equipment, such as flood gates and sluiceway facilities. In such researches, however, social benefit and cost of the introduction of asset management, which are crucial in assuring the effectiveness, do not seem to be properly assessed. In this study, a social cost of losing the function of river management facilities is evaluated, taking sluiceway facilities for flood control as examples of such facilities. The social cost is assumed to consist of (i) maintenance and renewal cost of sluiceway facilities, and (ii) potential economic loss due to inundation resulting from the sluiceway facilities lost their functions. In the first step, the maintenance and renewal cost of sluiceway facilities for a particular year was calculated by aggregating cost items in maintenance schedule for the year, and future costs were also calculated by accumulating the annual costs. The result of this calculation revealed that the maintenance cost varies significantly from year to year. It also showed that the equalization of the costs over the lifetime is important, which implies the necessity of prioritization of facility maintenance. In the next step, to assess the importance of each facility and to prioritize the facilities, potential economic losses due to inundation supposing that these facilities lose their function were calculated by inundation simulations and flood damage impact studies. As a result of this study, a scheme of evaluating the facilities in terms of social cost reduction is presented. The scheme enables a quantitative assessment of the importance of each

Hanshin Expressway is an urban expressway network in Osaka-Kobe area accommodating more than 900,000 vehicles per day. Since it is one of the most important transportation infrastructures in the area, the highest level of Rehabilitation and Maintenance (R&M) quality is always required and we have met the need by developing many efficient maintenance methods. However, due to the lacks of the sufficient budget for highway R&M, the highway administration bodies are requested to reduce the expenditures for R&M activities. Hanshin Expressway has accelerated to develop a new approach for efficient Road R&M after its privatization. In this paper, the logic model for R&M (named HELM; Hanshin Expressway Logic Model), which was developed by the Hanshin Expressway Corporation, is presented to administrate the whole system of R&M activities in an efficient way. This paper presents the risk management diagrams for the highway patrol, by which the administrative bodies can efficiently design the optimal patrol frequency given the predetermined risk levels based on HELM. The paper is concluded by summarizing the ongoing research agenda to improve the HELM throughout the PDCA cycles of the real R&M activities.

The estimation of ground subsidence processes is an important subject for the asset management of airport facilities. In the planning and design stage, there exist many uncertainties in geotechnical conditions, it is impossible to estimate the ground subsidence process by deterministic methods. In this paper, the sets of sample paths designating ground subsidence processes are generated by use of a one dimensional consolidation model incorporating inhomogeneous ground subsidence. Given the sample paths, the mixed subsidence model is presented to describe the probabilistic structure behind the sample paths. The mixed model can be updated by the Bayesian methods based upon the newly obtained monitoring data. Concretely speaking, in order to estimate the updating models, Markov Chain Monte Calro method, which is the frontier technique in Bayesian statistics, is applied. Through a case study, this paper verified the validity of the proposed method and illustrated its possible application and future works.

In asset management of infrastructures, predicting deterioration of structures is one of an essential technique to make a decision on the optimal maintenance policy. However, as for large-scaled infrastructures that consist of a huge number of structural components, in order to estimate their deterioration process with high accuracy, the heterogeneity of individual components has to be considered because each component possesses different material characteristics and designs and is in unique service under various environmental conditions. This paper focuses on especially educational facilities from among infrastructures, and constructs its asset management system considering the heterogeneity in deterioration process of individual components. This system mainly consists of 3 functions as: 1. database, 2. deterioration prediction and 3. life-cycle cost evaluation. The database stores the basic structural and component’s information and visual inspection data. Based on these information and data, the deterioration prediction is statistically carried out. Specifically, the deterioration process can be basically expressed by random proportional hazard model, and the heterogeneity can be modeled as probability fluctuation in the hazard rate. Furthermore, the time-dependent hazard rate is formulated by the Weibull hazard model. The heterogeneity of the hazard rates across the individual characteristics of components is explained by the random proportional Weibull hazard model in which the hazard rates are subject to Gamma distribution. In the 3rd function, through the comparisons of the life-cycle costs between the multiple repair/renew strategies, the optimum one is decided. Here, as the deterioration process of individual components can be formulated by the Markov transition probabilities defined by the estimated hazard rates, the proposed life-cycle cost evaluation method organically links to deterioration prediction results via Markov decision process. In addition, an

Road pavements are often designed to accommodate two important functions. The first function is to make suitable surface characteristics, which provide safety and comfortable driving for road users. The second function is to ensure a certain level of structural durability for its performance over a long period of time. These two functions need to be considered carefully in view of maintenance and management. Without a proper maintenance and management plan or strategy, the functionality of road pavements will not be assured. In view of maintenance and repair (M&R), temporary M&Rs are often implemented in practices, only to restore its condition states and satisfy the immediate performance. Current M&R methods are not significantly improve the durability of pavement structures. This practice can be regarded as a limitation in the field. This paper is developed with aim to give an answer to this limitation. In a glance, the paper proposes an innovative approach by combination of Markov hazard model and Mixture Hazard Model to trigger an optimal M&R strategy in a long-term planning view. The deterioration speeds of road sections are comparatively evaluated. Based on the results of obtained deterioration speeds, a further investigation on structural performance can be tested. We conduct an empirical study on a set of monitoring data for 71.140 km national roads in Japan to verify the usefulness of the proposed methodology.

It is necessary to identify infrastructures relatively deteriorating fast, and to monitor, repair andrenew the infrastructures. However, regarding methods to extract the infrastructures from inspection dataobtained through ordinary inspections, there is actually no systematized methodology. In this paper, theauthors propose the multi-stage mixed Markov deterioration hazard model and its multi-hierarchicalBayesian estimation. Furthermore, the benchmarking analysis towards stratified deterioration speedscorresponding to decision making levels and the methodology to extract intensively monitoredinfrastructures on each level are proposed. In order to verify the effectiveness of the proposed methodology,empirical analysis is carried out using the visual inspection data of 10,689 expansion joints in 21 lines ofactual highway. The authors first mentioned that the deterioration process significantly depends on (1) kindof expansion joint, (2) kind of surface layer pavement and (3) traffic volume, and clarified that the expectedlife span of the expansion joints is about 18 years and it varies about 5 years due to the above mentionedfactors. Then, it was found that the expected life span of the expansion joints varies from about 9 years toabout 55 years by considering the heterogeneity of each line. Furthermore, the authors clarified that theexpect life span varies from about 5 years to more than 100 years in the fastest deteriorating line byconsidering the heterogeneity of each expansion joint. Finally, by using the estimated result, the authorscarried out the relative evaluation of hazard rate and extract the intensively monitored expansion joints.