The 2011 off the Pacific Coast of Tohoku Earthquake that occurred on March 11 brought serious damage to the infrastructure facilities in Tohoku and Kanto districts owing to the strong earthquake motion, tsunami, and nuclear power plant accident. This was referred to as "triple disasters" by a newspaper and was given the name the "Great East Japan Earthquake Disaster" by Cabinet decision. Five years has passed since this disaster occurred. During these five years, restoration works in affected areas have progressed steadily with the aim to make a strong community that is resilient to disaster and restore local life and economic activity. In these activities, civil engineering plays an important role. In particular, the Japan Society of Civil Engineers (JSCE) is considered very important in providing the technical and scientific knowledge necessary for these activities to international societies. In this regard, the JSCE has come out with the second special issue on the Great East Japan Earthquake Disaster. This issue is a valuable collection of papers and reports on various recovery efforts and technological development to achieve the recovery works. Sixteen invited papers and seven general papers are included in this issue. The JSCE takes pride in editing and publishing this second special issue on the Great East Japan Earthquake Disaster. The technical and scientific knowledge and other information on the restoration and recovery works from the natural disaster contained in this issue will be useful for other countries that similarly suffered from earthquake disaster. On behalf of the editorial committee, I wish to sincerely thank the authors, reviewers, and all of the contributors in this special issue.
Special Topic -Division A: Structural Engineering/Earthquake Engineering & Applied Mechanics
This paper deals with the potential of GEONET, GNSS Earth Observation Network as a tool to mitigate earthquake disasters. GEONET presents spatiotemporal information on crustal deformations due to seismic forces, thus it has possible applications to earthquake engineering both in space and time. This paper discusses, as a temporal application, the precursory behaviors of the crust found prior to the 2011 off the Pacific Coast of Tohoku Earthquake to enhance the actual capability of earthquake prediction from engineering viewpoints. The GEONET data also can obtain coseismic crustal deformations closely related with tsunami resulting from a huge interplate earthquake. This paper describes, as a second application, the potential use of GEONET for early warning system against tsunami propagation. The coseismic deformations of the crust also exert another influence on earthquake damage to large-scale structures as a result of spatial differential of displacements, inducing seismic strains within structural bodies. This paper finally discusses, as a third application of the GEONET data, the seismic strain characteristics of ground derived from coseismic crustal deformations, relating them with earthquake damage to civil engineering structures.
This paper presents a design concept of “anti-catastrophe” and proposes a framework of seismic design code for that concept. It proposes that the domain to be considered in the design should be extended in terms of three dimensions: phase, time, and space. We discuss the conditions required for the implementation of “anti-catastrophe”-oriented design. Since concepts of “anti-catastrophe”-oriented design is significantly different from that of conventional design, it is proposed to introduce “Category of Design” (CoD). We then present a design framework which consists of five stages. We also discuss institutional conditions required for this new design codes from the viewpoint of risk governance.
Many bridge bearings suffered severe earthquake loads during the 2011 Great East Japan earthquake; however, no suitable technique exists to evaluate damage to laminated rubber bearings. This paper describes the Acoustic Emission (AE) technique for laminated rubber bearings both for damage assessment after earthquakes and health monitoring of old bridges. First, laboratory tests were conducted using the damaged laminated bearing specimens after the pre-loaded tests. Characteristic AE behavior was observed in the severely damaged specimens during the cyclic loading compression tests. These specimens had many small voids in the rubber, which were found from the microscope observation of the specimens being cut after the loading tests. Then, on-site AE monitoring was carried out at two sites. Many AE hits and large AE energy were observed from the deteriorated rubber bearings; however, few AE activities were observed from the new bearings. These two tests indicated the effectiveness of AE monitoring for early warning and damage assessment of laminated rubber bearings.
During the 2011 Off the Pacific Coast of Tohoku Earthquake, a great number of earth structures suffered widespread damage. It took a significantly long time to repair, restore, or reconstruct many of them, and thus the relief operation activities and the rehabilitation works to be conducted at the sites and in the nearby areas were severely obstructed owing to the loss of their function. In this paper, a severe collapse case history of earth-fill dams for an irrigation reservoir is described as a typical and representative case. Based on the lessons learned, a proposal is made for the revision of their design policy, particularly in terms of soil compaction control and issues related to seismic design and construction of earth structures to satisfy the required seismic performance. Its application to the restoration works of the collapsed earth-fill dams is also preliminary reported. It is shown that the old dams collapsed due mainly to their generally poor compacted state and because their top fill consisted of particularly poor compacted sandy soil. The relevant and realistic design should be based on the following procedures: a) use of Level 2 design seismic load relevant to a given earth structure; b) use of realistic soil shear strength, corresponding to the average of actual values of the degree of compaction, which is noticeably higher than the given allowable lower bound; and c) evaluation of the stability by comparing the calculated residual displacement/deformation of a given earth structure with the allowable limit specified in the design. The results of the compaction control at the early stage of the restoration work for the new dams show that the newly proposed method that controls the water content of the backfill to be compacted and the dry density and the degree of saturation of compacted soil works very well.
The 2011 Great East Japan Earthquake caused massive ground damage, including liquefaction of sandy grounds, collapse of river levees and lands developed for housing, etc., particularly in regions across eastern Japan. Not only damage to “currently unqualified” structures that did not conform to existing design standards and codes but also ground damage that could not be explained within the framework of conventional geomechanics and geotechnical engineering was observed. Particularly in the latter case, therefore, it has become necessary to develop new techniques in geomechanics without being restrained by the conventional framework. From the above standpoint, this paper reviews the research that has been carried out in the field of geotechnology after the Great East Japan Earthquake. More specifically, new knowledge relating to the mechanism of liquefaction damage at Urayasu City and other ground deformation caused by the earthquake is introduced, together with the results of research carried out on ground strengthening techniques.
Utilization of soil fractions recovered from disaster debris as geomaterials was highly desirable after the 2011 East Japan earthquake and tsunami because the soil fraction accounted for a third of the approximately 30 million-ton disaster debris and tsunami deposits. Because the quality of recovered soils varied according to treatment systems at each site, as well as the characteristics of original soils, clarification of material properties of recovered soils is important for future catastrophic disaster. In this paper, generation and treatment of disaster debris are briefly summarized. A total of 404 data items, which were obtained in Iwate Prefecture, were analyzed to verify the properties of the recovered soils in relation to the treatment methods. A series of analyses indicated that the soil fractions recovered from disaster debris have quality equivalent to general geomaterials.
A number of infrastructures for Sanriku Railway were seriously damaged by the 2011 East Japan Earthquake. In this paper, the damage by seismic loads and tsunamis are analyzed. In addition to serious damage by seismic loading, embankments, RC viaducts and bridges were washed away by the great tsunami in many places. A number of bridges and embankments could be effectively made highly earthquake- and tsunami-resistant by taking advantage of soil-reinforcing technologies. The design and construction in this restoration work took advantage of technologies that had been developed based on state-of-the-art geotechnical engineering, concrete engineering, and bridge engineering while aiming at cost-effective and fast restoration. At Arakawa Bridge, the PCI girder was washed away and a new PC hollow girder with a small height, pier and geosynthetic-reinforced soil (GRS) embankment was installed. In the Shimanokoshi area, as requested by local people, a collapsed RC viaduct was replaced to a seismic- and tsunami-resistant geosynthetic-reinforced embankment covering slopes with concrete facing connected to geogrid layers reinforcing the embankment to prevent erosion of the backfill and scouring at the slope toes. At three places, in place of the collapsed three simple girder bridges, three GRS integral bridges, which are highly earthquake- and tsunami-resistant due to structural integration of reinforced backfill, full high rigid (FHR) facings and a continuous girder, were constructed and opened to service for the first time. In the existing embankments eroded by tsunami, the roadbed was restored by “reinforced roadbed” and embankment slope was covered with cast-in-place concrete facing or RRS (Reinforced Railroad/Road sloped structures with geocells and reinforcing steel bars) method.
In the land reclamation areas of Urayasu City, 8,700 small buildings including residential houses suffered severe damage due to liquefaction during the 2011 Tohoku earthquake. Following this event, Urayasu City adopted grid wall soil improvements as countermeasures to mitigate liquefaction. For the simplified grid wall soil improvement design, the spacing between the grid walls is restricted within L/H = 0.8, where L is the spacing between the grid walls and H is the thickness of the liquefaction layer. However, it is difficult to adopt L/H as a design guideline because the grid wall soil improvement has to be applied underneath existing houses. The construction of grid walls directly underneath houses is impossible. Consequently, the spacing between the grid walls increases. It is suitable to use the settlement of a house as a design guideline for the conditions in Urayasu. Therefore, the following guideline was adopted. For a shock of the same magnitude as that of the main shock in the 2011 Tohoku earthquake in Urayasu no obvious damage must occur to a residential house. To meet this guideline, FL must exceeds 1.0 in all liquefied layers, or the index of settlement Dcy must be within 5 cm and the non-liquefied layer H1 must exceed 5.0 m. The finite element method with a quasi-three-dimensional analysis model can be used to estimate the settlement of houses. However, there are no examples that have adopted the settlement as a design guideline in grid wall soil improvement design. Thus, dynamic centrifuge model tests were conducted to investigate the relationship between the settlement of houses and the grid area. Existing design guidelines for grid wall soil improvement use FL or an excess pore pressure ratio. This study proposes a performance- based design method for grid wall soil improvement and verifies the validity of this approach.
Special Topic -Division D: Infrastructure Planning and Management
Ports are among the most essential infrastructures for international and domestic trades. Since Japan is an island country, its major ports are requested to prepare business continuity plans (BCPs) to facilitate early recovery of port functions in the context of maintaining the local and national economy. Major objectives of the BCPs in ports include maintaining sufficient cargo handling capacity to meet the transportation demands, of which post-disaster forecast is essential to properly secure business continuity in the port. Based on the above consideration, this study discusses the possible development of demand estimation methods for port cargo handling volumes in the aftermath of large-scale disasters. The questionnaire/ interview and inventory analysis are suitable for undertaking the estimation in terms of tramper service cargos such as dry/liquid bulk cargos and complete cars, of which a limited number of cargo owners are involved. The statistical approaches are effective for the estimation of liner service cargos such as container and ferry transport, which involve a large and unspecified number of cargo owners. Theoretical concepts, specific examples and considerations of suggested methods are indicated. The authors deem that these discussions may pave the way to the introduction of further sophisticated methodologies for port-BCP preparation.
This paper reports the detailed process of a residents' workshop for the Reconstruction Land Read-justment Project in Machikata District of Otsuchi Town, Kamihei County, Iwate Prefecture, which suffered devastating tsunami damage caused by the Great East Japan Earthquake (Machikata Machizukuri WS 2013) . It focuses on the community unit to gain a multilateral understanding of the target local community with characteristics, post-disaster changes in lives, residents' sentiments, challenges, and ramifications.
This study aims to define site selection characteristics of shrines affected by tsunamis in the coastal areas of the Sanriku region, to understand the differences between the locations of shrines that did or did not survive the disaster through field surveys and historical reviews. First, through the field survey, this research demonstrates that shrines in the area are generally located on ridge of mountains less likely to be affected by tsunamis and the destroyed shrines tend to be located near the low-lying coastline or on flatlands. Second, through the historical reviews, the characteristics of shrine locations have greatly changed since the middle of the 12th century. This research indicated that shrines were mostly positioned along the ridge line during the time of the ancient belief system and became more diverse during the medieval period from the mid-12th century onwards, when the culture of “kanjo,” the ceremonial transfer of a divided tutelary deity to a new location according to the enshrined deity's character, was introduced to the area. In addition to this general site selection characteristics, the experience from earlier tsunamis affects the re-selection of shrine sites. In conclusion, the site selection system for the shrines consists of global and local mechanisms. Finally, the author suggests the possibility of utilizing the shrine's site selection characteristics as a way to hand down the tsunami experience to the next generations.
This essay is an account from the perspective of a supporting civil engineer and landscape expert on the reconstruction of the Kirikiri district of Otsuchi Town in the Kamihei County of Iwate Prefecture, which was severely damaged by the devastating tsunami triggered by the Great East Japan Earthquake. It also reports and on the process and challenges of the town reconstruction planning and spatial design. One defining characteristic of the process in Otsuchi Town is that the local residents were involved from the conceptualization to the specific planning and design of the reconstruction. This urban renewal method, which can also be called a local residents collaboration style, plays an important role in deciding the spatial design of the whole district and in the negotiations with relevant organizations on the national highway and changing the linear shape of the seawalls. The timeline from after the disaster up to fiscal year 2015 divided into four stages in terms of progress in the town reconstruction planning: 1) decisions on the reconstruction plan objectives and collective housing scope; 2) decisions on the structure of the district; 3) decisions on the spatial image of the reconstruction planning; and 4) a detailed study of the public spaces and facilities. I aim to describe the process of the spatial design in each stage and the resulting and relationships while at the same time show a spatial design that could contribute to urban renewal that may be necessary in the future by describing challenges that arose in the process.
This research focuses on some cities in the areas afflicted by the Great East Japan Earthquake Disaster of March 11, 2011 and by the accident at the Fukushima Daiichi Nuclear Power Station, and demonstrates that some of the post-disaster responses and challenges regarding local public transport stem from the peculiar feature of tsunamis and the nuclear accident, in order to make clear the requirements of local public transport planning taking into consideration the response in cases of wide-scale disaster. Firstly, the responses of bus operators immediately after the disaster were studied through case studies of Hachinohe, Ofunato, and Minamisoma were studied to clarify how the roles of public transport changed with changes in the evacuees' living situations. Secondly, the restoration process of local public transport services after the emergency phase was analyzed through case studies of Ofunato and Minamisoma. Thirdly, a questionnaire survey of residents and evacuees in Minamisoma on the status of their activities and access to grocery stores was analyzed to make clear the impact of the limitation of residents' and evacuees' mobility on their quality of life in the Recovery Phase after the cascading disaster.
Post-Disaster Community Redevelopment is ongoing in Onagawa, Miyagi, for the reconstruction of the town that lost 8% of its population and 2/3 of its infrastructure in the Great East Japan Earthquake and Tsunami on March 11th, 2011. This is a report on the issues surrounding town rebuilding from the perspective of a civil engineer who has been involved in the recovery on-site since the reconstruction plans were formulated in 2011. In a post-disaster redevelopment project, the central government, local government and civil organizations, with their respective intentions, get intensively involved in the reconstruction in a short period of time. It became clear that a coordinator was necessary to keep the public and private sectors on the same page during the hustle and bustle of implementing community development.
In order to examine the economic impact of the damage due to the Great East Japan Earthquake in 2011 and the reconstruction of the disaster-stricken areas and all prefectures, this study aims to develop a dynamic spatial computable general equilibrium model. This model describes the economic dynamics of the damage caused by the earthquake, the resulting reconstructions, and measures the dynamic benefits of reconstruction by using numerical simulations. The findings of this study are as follows: (1) The discounted present value of the dynamic damage cost along with reconstruction from the earthquake was estimated to decrease to about 17.9 trillion yen in total, which was 1.29 times greater than decreases in the direct damage cost of about 13.9 trillion yen in the Tohoku disaster-stricken areas. (2) The damage costs and benefits could be measured more accurately based on the economic theory by introducing the dynamic multiplier of damage costs and benefits into the conventional benefit measurement technique. (3) The forward-looking dynamic model, despite strict constraints and unrealistic assumptions, could show realistic results.
Special Topic -Division E: Materials, Concrete Structures and Pavements
This paper deals with how tsunami force acted on bridge girders when the Great East Japan Earthquake broke out on March 11, 2011. First of all, almost all data of bridge girders in the inundation area were collected. Satellite images in internet websites were introduced to make a quick survey on how many bridges were in the inundation area and how many of them were damaged. Detailed data on the bridges, such as dimensions and types, were obtained from authorities that have maintained those bridges. For damage analysis of bridge girders, Prof. Kosa's method was introduced to see whether bridges were washed away or not by tsunami. Motion pictures of the tsunami taken by residents when it happened were examined to evaluate the velocity and height of the tsunami. In order to examine how bridge girders were washed away, an experimental investigation was conducted using a big water channel. Hydrodynamic analysis was conducted to evaluate the test results. In addition, a new numerical simulation technique was developed to follow the movement of a bridge girder during the tsunami.
The 2011 Tohoku Region Pacific Coast Earthquake struck off Tohoku and Kanto regions of Japan on 11 March 2011. We conducted investigations of structural and surface damage to pavement in the runway, taxiway and apron at Sendai Airport for the purpose of re-opening the airport for commercial flights. Many cracks were confirmed in the asphalt pavement in the runway and taxiway. However, it was clarified that these cracks except the one in the taxiway were not fatal structural damage that would hinder the provisional use of the airport. Large settlement was confirmed in a part of the asphalt pavement in the taxiway and concrete pavement in the apron due to liquefaction. It was confirmed that these settlement areas needed to be reconstructed for the re-opening of the airport. Furthermore, the effect of the void underneath the cement concrete slab on FWD deflection was clarified.
“Reconstruction Roads” are the highways constructed to accelerate recovery from the Great East Japan earthquake that occurred in 2011. The total distance of Reconstruction Roads is approximately 360 km, which includes more than 250 bridges. Because Reconstruction Roads are located in a cold zone, durability against frost attack is necessary for their concrete structures. In addition to freezing and thawing effects, bridges also suffer from alkali silica reaction (ASR) and chloride attack from the use of deicing salt. During the construction of a reinforced concrete (RC) slab of the “Mukai sada-nai Bridge,” we designed the concrete and reinforcing materials to be durable. A multiple defense strategy is a key phrase in our durability design. To prevent possible deterioration, at least two countermeasures were applied. The use of fly ash is a core countermeasure because it is effective against both ASR and chloride attack. Air content was designed at 6% to achieve antifrost performance. An expansive agent was also used to reduce the risk of shrinkage cracks. Epoxy-coated reinforcing bars were used to resist corrosion. An RC slab was carefully constructed at the Mukai sada-nai Bridge. Wet curing continued for three months to obtain a pozzolanic reaction. The quality of the hardened concrete was checked by element tests and nondestructive tests. Additional costs to enhance durability were acceptable with regard to risk control. Success at the Mukai sada-nai Bridge was followed by the construction of other durable RC bridge decks on Reconstruction Roads.
Special Topic - Division F: Construction Engineering and Management
Evaluating the benefits of disaster mitigation action quantitatively and sharing these results with the society are extremely useful in promoting mitigation action. Many studies, however, have focused on the investigation of the damage but not on the mitigation effects of preparedness. Hence, this study analyzed the mitigation effect of the Business Continuity Plan (BCP) on financial damage to non-manufacturing industries in the Great East Japan Earthquake. Our analysis showed the following: 1) In many companies, there is no difference in the direct damage to the company group with BCP and to the group without BCP. 2) The sales of the damaged group without BCP decreased about 5% compared to those of the damaged group with BCP for more than two years. In other words, the effect of mitigating financial damage by BCP is more than 10% of annual sales on the average. 3) The relationship between BCP and sales was analyzed under limited variables, and the coefficient of BCP showed positive effect on sales with significance at a 5% level. Although our result is only an indication, it could be said that this finding, which shows cost-benefit information on BCP, is useful to promote BCP.
Special Topic -Division G: Environmental Systems and Engineering
This is a review of the restoration and rehabilitation of sewer systems damaged by the Great East Japan Earthquake and Tsunami. The disaster caused serious damage to sewer systems, amounting to approximately 470 billion JPY. The damage was mainly caused by the tsunami, but the damage due to liquefaction was also serious. The tectonic activity caused additional discharge loads to municipalities in coastal areas. The nuclear accident at Fukushima Daiichi Nuclear Power Plant also affected sewer systems in such forms as radio-contamination of sewage sludge and reduction of power supplies. In addition, migration of users of sewer systems took place. In the restoration activities, sewage treatment plants (STPs) were restored step-by-step, and guidelines were developed to strengthen STPs against tsunamis. The effectiveness of different countermeasures against earthquakes and liquefaction were examined, and new countermeasures were proposed. Software measures such as the introduction of business continuity plans and information technologies are recognized as effective measures for overcoming disasters. In particular, the sewer systems in Sendai City have been successfully restored and rehabilitated after the disaster, with different hardware and software measures. In contrast, sewer systems in small municipalities seriously damaged by the tsunami are still taking time to rehabilitate.
Minami-Gamo Wastewater Treatment Plant (MGWTTP) is the most important facility for the Sendai City sewerage system. The plant treats about 70 percent of the municipal wastewater from Sendai City. On March 11th, 2011, the plant was devastated by the Great East Japan Earthquake and the ensuing tsunami. Its foundation was heavily damaged. Sedimentation and aeration tanks were bent. Most of the mechanical and electrical equipment became flooded by seawater and were washed away. MGWTTP completely lost its wastewater treatment function. Due to this damage, the Sendai City Government decided that MGWTTP could not be repaired and instead should be rebuilt as a brand-new wastewater treatment plant (WTTP). In order to maintain a sanitary environment in Sendai during the construction of the new WTTP, a temporary municipal wastewater treatment was required to meet the effluent standard BOD of 60 mg/l as proposed by the National Sewerage Disaster Countermeasures Committee of the Ministry of Land, Infrastructure, Transport and Tourism. Therefore, the government implemented a mid-level treatment employing a contact oxidation with string media. MGWTTP became the largest WTTP that adopted this method in Japan. Operating the mid-level treatment facility, the new MGWTTP was completed five years after the Great East Japan Earthquake. In this paper, the process until the completion of the new MGWTTP is outlined. The Sendai Declaration of Sewerage Works Disaster Risk Reduction, which was adopted at the 2015 Sendai Symposium, is also introduced.
This paper describes an experimental study on video image-based analysis by using digital image correlation (DIC) to acquire the dynamic behaviors of concrete structures. We used video images recorded by a high-frame-rate camera in laboratory and field tests and then calculated the time series of the in-plane displacement fields of the images to measure the behaviors of concrete structures, such as changes in deflection and cracking. The results obtained from a cyclic loading test on a damaged T-shaped concrete beam successfully proved that our method provided reasonable dynamic deflection and crack-opening displacement. A concrete bridge slab was measured from the ground in a field traffic loading test. It was found that the in-plane displacement of images was affected by deflection due to live loading; thus, we estimated deflection by using video images recorded under the slab. The estimated deflection was satisfactorily found to correspond to measurements obtained from a laser displacement sensor. Moreover, we demonstrated the extraction of the displacement in maximum crack opening by subtracting the estimated deflection.
Division B: Hydraulic, Coastal and Environmental Engineering
Measurements of flood flow have been conducted intensively at major control sections in Japan for storing reliable hydrological data for use in a long-term river planning. However, such a measurement pays attention only to flow passing through one cross-section; thus, spatial flow features are not available, while river channel changes its feature at every flood event. In this research, we performed concurrent measurements of a snowmelt flood of the Uono River using an image analysis and radio-controlled acoustic Doppler current profiler (ADCP). In the image analysis with STIV (Space-time Image Velocimetry), three video cameras were used to cover a river reach of about 300m by changing their view angles at every location. On the other hand, the boat-mounted ADCP was remotely controlled to form a zigzag trajectory to cover the same reach. The accuracy and limitation of STIV was made clear through a comparison with ADCP data and a spatial distribution of correction factor from surface to depth-averaged velocity was found to have a weak correlation with a large-scale bed slope.
Some level of settlement is allowed in the design of oil tanks if uneven settlement is controlled within allowable values. Considering the critical condition of piled raft foundation (PRF), that is, secure contact of raft base to the ground surface, PRF is considered one of the rational foundations for the oil tanks. However, PRF has a complex interaction with soil under horizontal seismic loading, especially if the tank rests on a liquefiable soil. On the other hand, the pile installation method can affect the pile bearing capacity and the liquefaction resistance of sand as well. In this study, a series of centrifuge tests was performed to investigate the mechanical behavior of oil tanks supported by PRF on liquefiable sand. In the tests, slab and piled-raft foundations were modeled. In the case of PRF, two different methods of pile installation (Driven and Non-Driven) were modeled and the Driven PRF models were made with two different pile numbers. Using the observed results, such as accelerations of the tank and ground, displacements of the foundation and excess pore water pressures of the ground, advantages, and limitations of PRF for oil tanks on liquefiable sand are discussed.
Division D: Infrastructure Planning and Management
This study was conducted to verify the effects of some geometric factors, such as the angular direction change, the available visual information amount, the width variation of streets, and the axis deviation on street space on the continuity of the street network, to have a good legibility along the street. The main purpose of this research is to provide a classification of route types considering the legibility of street space. The experiment was conducted around the Minami Urawa Station in Saitama Prefecture. The street network in the study area was analyzed using two types of parameters, such as visibility parameters and spatial parameters. The visibility parameters were obtained through statistical calculations using visibility attributes defined through a field survey, while spatial parameters were hypothetically defined using the knowledge about the street network of the study area and referring to the literature. Both parameters were analyzed using PCA (Principal Component Analysis) and Cluster analysis to define route types. The results of the research clearly illustrated that there was a significant relationship between the visual characteristics of the street network and the street space legibility. Seven types of routes were classified and their attributes were clarified. These attributes affected the wayfinding behavior of the pedestrians in the study area.
Division E: Materials, Concrete Structures and Pavements
This study aims to clarify the shear resistance mechanism of reinforced concrete and prestressed concrete tapered beams without stirrups. Three series of seven beams with different parameters (a/d ratios and prestress levels) were tested. The results showed that there is no effect of the taper on the short beam due to the arch action. The slender RC tapered beam (2.5<a/d<4.5) had the higher shear capacity, while the RC tapered beam in large a/d ratio (a/d equals to 5.0) had the smaller shear capacity. When the prestressing force was introduced, the tapered beam again had the larger shear capacity. In addition, nonlinear FEM analyses were conducted to complement the experiments and verify the results, which showed a good agreement including load-deflection curves, load capacities, and crack patterns. A new evaluation method for the shear capacity of tapered beams without stirrups was finally proposed, by determining the location of the critical section through the nonlinear FEM analyses.
This study proposes an innovative idea of shear reinforcement in concrete beam by replacing the conventional steel stirrups with CFRP grids at the shear span inside concrete cover. The compatibility between the internal grids and the surrounded concrete was investigated first in the elementary test. Flexural performances of two concrete elements reinforced by different spacing of internal grids were compared and discussed. After that, a concrete beam test was conducted with a total of eight RC beams varied in the number of grid strips in the shear span and the spacing of reinforcing grids. The experimental results showed that the shear capacity and the shear carried by internal CFRP grids significantly improved with a higher amount of grid strips; however, the increasing ratio of shear capacity was not proportional to the shear reinforcement ratio. Moreover, the location of internal grid in the shear span was an important part of the shear-resisting effectiveness in this study since the more number of grid strips located near the center of the shear span was much more effective to resist the propagation of diagonal shear crack than the grids at the edge. Finally, a model for evaluating shear carried by internal CFRP grids was introduced. Validity of the proposed model was explained by comparing with the experimental results and also other sets of experimental results.
Division F: Construction Engineering and Management
Many cities in Japan are located in alluvial plains, and the vulnerability of urbanized areas to flood disaster is highlighted by frequent flooding due to heavy rainfall or typhoon. Underground spaces are also flood-prone areas because those are below the ground, and water intrusion into underground space inflicts severe damages on human beings and urban functions and infrastructures. In order to reduce human suffering due to flood inundation in underground spaces and low-lying areas, needless to say, early evacuation is one of the most important countermeasures. This paper shows some experimental results of evacuation tests from underground spaces under inundated situations. The difficulties of evacuation from underground space was investigated by using three real-scale models (door, staircase, and car), and the limits for safety evacuation is discussed. From the results, it is found that water depth of 0.3–0.4m would be a critical condition for safety evacuation through staircase and door while 0.7–0.8m deep on the ground would be a critical situation for safety evacuation through the doors of the car. The relationship between the critical depth condition for the safety evacuation and the age of male subjects was also investigated by using the experimental results of real-scale door model tests and the Physical Fitness Survey results. A multiple regression model presented here properly reproduces the characteristics of the experimental results, such as the critical depth condition and its age-associated difference for safety evacuation. The same model is applied to the female's experimental results of real-scale door model tests and shows the overall distribution of the experimental results although the regression output still has considerable variation, especially in the young generation.
Although the importance of understanding the diverse values of participants in global infrastructure projects has been increasingly recognized, research on methods to assess moral values in such contexts is still lacking. This article proposes a method for extracting context-specific moral values in three steps: (1) vignette development, (2) interviews, and (3) data analysis. The article illustrates how the method can be applied to understand the way project members make and rationalize their decisions when faced with moral trade-offs in the management of infrastructure projects.
A study to characterize municipal solid waste was carried out at various sources in Hoi An, a famous World Heritage City of Vietnam. The purpose of the research was to identify the generation rate and compositions of household waste from different types of areas of the city (rural, urban, and tourist quarters) as well as waste from tourism sources. The result will contribute to harmonized solid waste management for the city. Wastes from household, hotels, restaurants, and streets were collected daily in two weeks for generation and composition sampling. A stratified random sampling method was applied, and several statistical tools were carried out to analyze obtained data. As a result, the mean of household waste generation was 0.223 kg capita-1 day-1. The average waste generation per capita in the urban region, which included the city center — ST1 (0.203 kg capita-1 day-1) and the urban areas - ST2 (0.264 kg capita-1 day-1), was almost double that of the countryside - ST3 (0.12 kg capita-1 day-1). The difference was statistically significant. Waste from tourism sources may have a great contribution in the total amount of waste generation since tourist services are important and active activities in the city. The results of the study showed that hotels generated about 0.6 kg room-1 day-1, one restaurant produced an average of 26.18 kg day-1, and the mean of daily waste generation from tourist streets was 6.99 kg per 100 m per day. Degradable waste counted for more than half of municipal waste, and combustible waste (textile, leather, wood, diapers, etc.) had higher portions, which meant that biological and thermal treatment technologies could be potential options for the purpose of decreasing the amount of waste to landfill for the city.