In recent years, under the policy of i-Construction, the adaptation of information technology to construction sites has been progressing, and improvement in productivity is expected. Information obtained from construction sites is being utilized not only for construction management but also for as-build inspection. However, the process of on-site inspection conducted by a inspector to ensure immutability has not been streamlined yet. In this research, a new as-build inspection system using blockchain is proposed through the design of a system that guarantees the immutability of construction management information, the development of a prototype, and the proof of concept test.
For the construction of infrastructure in developing countries, technical standards of design, construction and maintenance are important to secure the quality of their infrastructure. It is expected that the transfer of Japanese technical standards to developing countries could promote exports of Japanese infrastructure system. Aiming to promote Japanese technical standards for port facilities overseas especially developing countries, this study summarizes the overseas promotion strategies of major international technical standards, and discusses the overseas promotion strategy of Japanese technical standards for port facilities. It is effective to customize the technical standards based on Japanese ones to conform with natural and construction conditions of the partner country. In Vietnam, a series of new design, construction and maintenance standards for port facilities has been developed to conform with Vietnamese local conditions based on Japanese technical standards. In addition, this study presents the basic concept of customization of technical standards for port facilities in Japan to conform with local conditions, the generalized customization methodology to apply to other developing countries, and the summary of important notices on the customization.
Initiation and propagation of a large number of fatigue cracks on a steel slab of an expressway viaduct would reduce its fatigue durability considerably. For such failures and damages which cannot be repaired radically with usual repair methods, it is necessary to establish management plans considering large scale repair methods based on the initiation status and the propagation process of failures and damages. In this study, a method is proposed to estimate initiation and propagation processes of fatigue cracks on steel slabs with high accuracy, considering initiation timings, which cannot be directly observed by visual inspections, as latent variables. Then a methodology is proposed to select between normal repair and large scale repair for each repair unit based on life cycle costs calculated with the estimated initiation and propagation processes of fatigue cracks. Lastly, the proposed methodology is demonstrated with actual steel slabs of expressway viaducts.
A new seismic retrofitting method which is called the side retrofitting method was developed. The side retrofitting method is the method reinforcing flexurally the termination zone of the longitudinal bars of RC bridge pier which reinforcing members were placed only two-sides of the pier and enables to retrofit without removing such as machine room under the viaduct which is difficult to remove. In this paper, the concept of the side retrofitting method was described and the design methods were determined using the test results. Additional beam tests to examine anchor bar volume to ensure the flexural reinforcing effect were carried out using RC beam specimens which two-sides of the existing beam member were retrofitted by fixing RC reinforcing beam members with anchor bars. Construction methods of the side retrofitting method were also described in this paper. Finally, two practical applications to RC bridge pier structures of the Shinkan-sen which under viaduct are used for machine rooms were presented, and the effects of side retrofitting method applied to such piers with machine room under viaduct were examined in terms of seismic capacity, work period and construction cost.
For the preventive maintenance management of expressway slopes, it is indispensable to accurately, efficiently and economically select high-risk slopes for failure, landslide sites, and dangerous mountain streams due to debris flow, distributed over wide area. The authors have introduced an airborne electromagnetic prospecting which is suitable to shortly detect the resistivity of belt-like ground in a wide area.
In this paper, an overview of the airborne electromagnetic prospecting for the preventive maintenance management was described, together with describing such resistivity presentation methods as the absolute value one, the enhanced value one, and the logarithmic enhanced value one which was newly developed. To select some kinds of hazardous slopes, a chart combining both resistivity presentation methods of the absolute value (high accuracy) and the logarithmic enhanced value (threshold) ones was proposed to classify the ground characteristics, together with verifying the validity and effectiveness. Finally, it was concluded that the proposed technique can be applied to understand the ground characteristics and to select hazardous slopes for the preventive maintenance management of highway slopes.
A bridge is a composite structural system consisting of various members hierarchically. Therefore, to determine the timing of inspection and repair, it is necessary to consider the relationship between members in which the deterioration of one member can affect the deterioration process of another member. In this study, the authors focus on the corrosion process at the end of steel girders caused by water leakage from the expansion joint. Speciﬁcally, two state modes are deﬁned according to the state of water leakage from the expansion joint, and the corrosion process of the end of steel girders is expressed as a regime switching Markov deterioration hazard model with hazard functions set to each state mode. The model is estimated using actual inspection data to verify the difference in the rate of corrosion propagation of the ends of steel girders depending on the state mode of water leakage of the expansion joints, and the effect of preventive maintenance of the water-stopping device is analyzed to restrain the corrosion of the ends of steel girders and to reduce the life cycle cost of the entire bridge.
As deteriorated sewerage pipes are increasing, the efficient renewal of pipes is considered important. Since sewerage pipes are buried and form a complex underground network, it is effective to integrate a certain number of renewal projects and conduct them all at once. Accordingly, in this study, the authors estimate a mixed Markov deterioration hazard model by using the visual inspection data on concrete pipes, and evaluate the deterioration heterogeneity of individual pipes. Furthermore, the authors evaluate the spatial heterogeneity distribution obtained from heterogeneity parameters and the data on pipe locations with the dual Kernel density estimation, carry out the screening of intensive management districts, and propose a methodology for examining policies for renewing pipes. Lastly, the effectiveness of the proposed method is empirically discussed with reference to the cases of application to sewerage pipes managed by Osaka City.
Public works for infrastructure are classiﬁed into three kinds of works: government-led, directly managed, and labor-divided works. In all kinds of works, construction requires construction management and element technologies. Since the rapid economic growth period, public works have changed from directly managed ones to labor-divided ones, through subcontracting agreements between prime contractors and subcontractors. In this process, the construction element technologies owned by prime contractors were transferred to subcontractors, developing a labor-divided system in which prime contractors have construction management technologies, while subcontractors have construction element technologies. This study clariﬁes the actual situations and timings of the degradation (hollowing-out) of construction element technologies of prime contractors and the transfer of the technologies to subcontractors, and the fact that the hollowing-out is still progressing, through analyses, including questionnaire surveys.
In construction projects, there may occur delay in project completion, which is driven by unforeseen risk events. In such a situation, it is necessary to allocate the delay liability among those who are involved in the construction contract. This paper formalizes delay in a construction schedule by use of PERT, and utilizes cooperative game theory to investigate the impacts of respective risk events, which occurs in network activities of a construction schedule, upon completion delay of the project. The concept of nucleolus, a solution of cooperative games, plays an important role in liability allocation. And the practical applicability of the proposed model is investigated for a delay liability allocation issue, which is appeared in the construction project in the real world.
It is effective of road administration in local government to introduce comprehensive outsourcing system for efficient road maintenance works. However, there are some cases that decision-making of local government officers to introduce the new system becomes negative even though there is a good chance that the cost reduction effect is obtained. This study focused on the prospect theory which is the decision-making theory under uncertainty. Then, this study established a model to calculate a utility for introducing the comprehensive outsourcing system taking a behavioral property of local government officers into account. Besides, this study specified the behavioral property by using a method based on behavioral economy and analyzed their decision-making behavior. As a result, it is showed that some powers are necessary to change the situation that introduction is not taken for granted to a situation that it is taken for granted to promote local government officers to introduce the new system. In addition, this study proposed some specific methods to achieve this change by utilizing nudges.
In the 1990s, academic experts pointed out that the effect of competition limitation played a role in reducing the risk of dumping and suppressing the negative impact on contractors. After the construction industry’s declaration to put a stop to cartels, the bidding and contracts system was reformed by orderers, including countermeasures against dumping. However, this has been causing issues because the price determination structure reliant on the estimation standard remains in place. In this research, the authors conducted hearings and literature surveys from the perspective of compliance with working conditions with regard to the public procurement system in Europe and the Americas, conducted a comparison with the Japanese system, and examined the information. The results showed that working hours and payment of wages are appropriately implemented and managed through a system in which the orderer requires the contractor to comply with working conditions, which is intended to ensure a level playing field. As a result of examination, this research made clear the importance of grasping payment of wages and the actual situation of working hours by the orderer.
Aiming for the slim and simple design and construction of in-ground LNG storage tanks, we solicited performance-specified technical proposals. Regarding the wall thickness of the skeleton, the bottom slabside wall connection method, and the amount of reinforcing bars in the skeleton, which have a great influence on the construction cost, the design concept was clarified so as not to cause cost increases due to excessive design while ensuring safety. This allowed a high benchmark to be achieved. In particular, it was clarified in the application guidelines to have a structure that enhances both performance required for the skeleton and economic efficiency by adopting a design method in which the amount of reinforcing bars on the side walls depends on the toughness of the skeleton.
As a result, the amount of side wall reinforcing bars can be reduced by 40% compared to the existing tanks. In addition, the construction cost was significantly reduced not only by reducing the amount of reinforcing bars but also by developing various technologies. (In addition to reducing the amount of reinforcing bars, various technological developments were carried out to achieve a significant cost reduction.)
Many cases of errors related to the design deliverables of construction consultants have been reported. The Ministry of Land, Infrastructure, Transport and Tourism (MLIT) has made red-yellow checking (verification for consistency) mandatory in detailed design, and the Japan Civil engineering Consultants Association (JCCA) has strengthened verification and checklists, but these measures have not yet eliminated all errors. In addition, human verification according to the verification guidelines has become a great burden. In this paper, a prototype of a road design check system utilizing 3D models is developed in order to improve productivity by reliably eliminating design errors and improving verification efficiency. Prior to the development of the system, 185 cases of errors in road design deliverables were analyzed, and it was confirmed that almost all errors could be eliminated by using 3D models.
The Eddie Current Test (ETC) is capable of detecting cracks from the surface of paint film and has excellent efficiency and economical advantage to Magnetic Particle Testing. But when it is applied to a round weld part where the shape and direction of weld bead changes frequently, it is said that ETC likely fails to detect small crack or miss judge as crack exist where it doesn’t. The newly developed eddy current flaw detection imaging system performs C-Scope imaging by displaying the estimated crack shape at the scan position. We attempted to improve the accuracy of fatigue crack detection of the crack in the early stage of propagation by removing signal noise, which shows spatial distribution around a round weld. Furthermore, accuracy of the C-Scope images were evaluated using real fatigue crack specimens produced in the beachmark loading fatigue test.
The purpose of this study is to propose a way of risk management for infrastructure projects by ODA in developing countries based on case analysis of highway projects in India. The results of analysis revealed the importance of partnership with local contractor and participation using technology of Japanese contractors. For ODA construction projects, more positive involvement in additional survey for risk reduction and quality improvement by using technology and experience of Japanese government, consultants and contractors are required from the early stage of the projects.