This paper provides rigorous derivation of a Hamiltonian from a given Lagrangian of solid continuum, for a possible improvement of dynamic analysis. The derived Hamiltonian, unlike an ordinary one, has momentum and strain as argument, and the associated canonical equation includes spatial derivative in it. Characteristics of the Hamiltonian of this form are studied. The appearance of strain rate in the canonical equation, which has been overlooked in the past researches, is pointed out. For numerical computation, a Hamiltonian for discretized functions is derived. It is shown that discretized strain rate appears in the canonical equation when suitable discretization scheme is applied.
This paper seeks to reformulate moving particle semi-implicit method (MPS) in order to provide a mathematical interpretation of the method. It is shown that gradient and Laplace operators are evaluated by using volume integral of the Taylor series expansion of a target function and that the form of the volume integral evaluation of the differential operators is similar to MPS, suggesting that the volume integral evaluation is a mathematical interpretation of MPS. Numerical experiments using one-dimensional setting indicate a possibility of improving the accuracy of computing the differential operators when the reformulated MPS is used. Remarks on directions towards improving the accuracy of MPS are made.
Recently, damage to steel truss bridges due to corrosion has become a serious problem worldwide. In particular, severe damage due to corrosion at gusset plate connection is being widely reported. Corroded gusset plates that have reduced load-carrying capacity can lead to the collapse of the entire bridge. Attachment of stiffening plate and member replacement are among the conventional methods often applied to repair corroded structures. However, these repair works lack efficacy because of the heavy machinery and welding facilities required. In this study, two carbon fiber-reinforced polymers (CFRP) bonding methods, outside bonding and both-sides bonding, are proposed to improve the strength of the corroded gusset plate connection and decrease stress on the corroded section of the gusset plate. CFRP is used as the repair material for the corroded gusset plate connection in the proposed methods because of its light weight, high strength, and superior durability. Loading tests were conducted with a model approximately 50% the size of a real bridge and degrees of corrosion assumed to be approximately 50% and 75% of the gusset plate thickness.
Recently, numerous instances of severe corrosion damage to the gusset plate connections of steel truss bridges have been widely reported across the world. The corrosion of gusset plate connections has been confirmed to decrease load-carrying capacity, and it can lead to the collapse of the entire bridge. In this study, the remaining load-carrying capacity of a corroded gusset plate connection was evaluated using load testing and finite element method (FEM) analysis. Two different types of gusset plate corrosion were investigated: the corrosion loss of the lower chord flange-to-gusset weld and the corrosion loss of the gusset plate thickness. The loading tests and FEM analyses were conducted on an approximately half-scale model of a real bridge. Corrosion effects were evaluated for an assumed disconnection of 50% of the weld length, and for the loss of 50% and 75% of the gusset plate thickness in a selected region. This study then implemented parametric FEM analyses of the effect of the degree of corrosion on the remaining load-carrying capacity of the gusset plate connection. Finally, based on the results of the parametric FEM analysis in cases with corrosion loss of the gusset plate thickness, a method for evaluating the local buckling strength of the corroded section was proposed.
In the downstream tidal basin of the Kiso River, large-scale groins about 200 m long were constructed and a different river environment with pools and creeks was created by scouring, sedimentation, and foresting in intermediate areas of the groins. The scouring zone downstream of the large-scale groins played an important role in creating and maintaining an embayment water zone. In this study, we examined the scours that formed behind the large-scale groins in the Kiso River by field observations using acoustic Doppler current profiler (ADCP) and other observation equipment set downstream of the groins. The mechanism of creating downstream scour was then investigated by 2-D and 3-D numerical analyses in considering the effects of groins' lengths on the scouring. As a result, we found that offshore-heading streams occurred behind the groins during ebb tide and flood event, which may have caused the scouring downstream of the groins.
The effect of artificial flood on river channel disturbance is clarified quantitatively using the results of field observations and numerical simulations. Based on the prediction of positive impacts expected in the maintenance of ancient watercourses, channel changes were analyzed using river bed calculations during the flood of August 2016, which was the largest available scale. Results showed that the vegetative area lost owing to the flood tended to be larger along the old watercourse than they were in the current channel, and was also noticeable in the section where the old watercourse was actively maintained by excavation. This research has demonstrated that the maintenance of the old watercourse has positive impact on the restoration of gravel bars by promoting channel changes during floods.
In this study, freeze-thaw experiments were conducted on saturated fine-grained soils using different pre-consolidation pressures and overburden loads in order to predict the permeability of freeze-thawed soil. Two types of freeze-thawed experiments were carried out with the artificial ground freezing on-site construction condition considered: (1) one-dimensional freeze-thaw test, and (2) a horizontal displacement restrained freeze-thaw and vertical permeability test, which enables horizontal freezing under restricted horizontal displacement. The results show that the permeability of freeze-thawed soil is obviously influenced by overburden pressure rather than pre-consolidation pressure, overconsolidation ratio, and frost heave ratio. The results also suggest that the permeability of freeze-thawed soil can be predicted by the freeze-thaw test in which the effective overburden pressure is considered, rather than strength or over consolidation ratio of the ground materials and other freezing conditions.
The New Waste Disposal Area is the final disposal site in Tokyo Port to dispose of the wastes such as municipal/industrial wastes, construction waste soil and dredged soil. Therefore, to utilize this area for a long time, measures for expanding its capacity or reducing the volume of wastes have been taken. The work for volume reduction of disposed clayey soils was carried out with the vacuum consolidation method at block C of the area to prolong its service life. In this project, the prefabricated vertical drains (PVDs) with a width of 150 mm and a thickness of 3.9 mm were used. The PVDs were installed in the clay layer at the average elevations of +1.5 to -33.8 m with a square spacing of 1.8 m with the negative pressure of 65kN/m2, which is equal to the consolidation pressure increment, was applied for 310 days. The trial period began in 2005 and the main project period started in 2007 and was completed in 2015. During this period, work was performed on 383,000 m2; the mean settlement volume was 5.13 m and the volume obtained through settlement consolidation was 2,167,000 m3. This means that the service life of this disposal area was extended for 2.3 years. This paper provides the general overview of this project with a focus on geotechnical engineering.
Progress has been made in the diversification and repeated reuse of reclaimed asphalt pavement (RAP) in recent years. However, evaluating the quality of RAP containing polymer-modified asphalt (RAPm) has been difficult, and no method has been established for its reuse as hot mix asphalt. We have been developing recycling technology to restore RAP to the original condition of each material by separating it into aggregate and asphalt using hot water, and have succeeded in restoring aggregate from RAP containing straight (nonmodified) asphalt (RAPs). In this paper, we examine the recovery of aggregate from RAPm using hot water and the restoration of asphalt quality using high-temperature, high-pressure water. This technology can be applied to RAPm to rejuvenate asphalt.
The Suez Canal Bridge was constructed through a grant aid from Japan and completed in September 2001. Stone Mastic Asphalt pavement (SMA) was adopted over the orthotropic steel deck of this bridge because SMA was utilized for the orthotropic steel deck in Japan and SMA did not need any special machines, which were indispensable for the Gussasphalt Pavement ((nonporous) mastic asphalt pavement) and were unavailable in Egypt. After the bridge opening, however, hair cracks on pavement began to appear from June 2002 due to overloading of vehicles whose axle weights sometimes exceeded 25t. Upon advice from Japan, the General Authority for Roads, Bridges and Land Transport (GARBLT) limited the axle weight of vehicles to 13t. In September 2003, after inspection of the bridge, the bridge was handed over to Egypt. In 2011, a study team from Japan International Cooperation Agency (JICA) was dispatched to investigate the condition of the pavement and the steel deck. Although the pavements were heavily cracked, no fatigue cracks on the orthotropic steel deck were found. The steel deck surfaces were investigated and rusts were confirmed. The thickness reduction was measured. The average largest thickness reduction was 0.5mm. As seepage water was confirmed on the steel deck, 20 water monitors were embedded. The team recommended the repavement using the Gussasphalt Method as it was practically the only one method applicable at present in Japan. In 2016, GARBLT decided to repave the bridge using its own method and actually repaved the bridge. JICA experts could not give any advice because there were no related experiences in Japan. However, this pavement was deemed viable. Before the repavement, the water monitors were checked and seepage water was confirmed. After the removal of the pavement, all of the steel deck surfaces were investigated.
Human inspection of defects of concrete tunnel lining is usually slow, laborious, and disruptive to traffic. This necessitates automated alternatives using sensors and computer-aided processing. The conventional image-matching methods only use the cost value of the pixel being processed based on similarity metric to estimate an image-matching location. To improve the image-matching efficiency, this paper proposes an image-matching method that relies on the curvatures of the cost curve at candidate matching points. This is followed by applying a median filter to mitigate the matching errors. Moreover, experimental results for an actual tunnel demonstrate that the curvature measurement can select the matching points accurately. The authors have developed an image-stitching software to create a high-resolution panorama of the tunnel lining surface for assisting in defect inspection.
Today, gasoline and diesel fuel with high sulfur content are widely used in Mongolia. According to the analysis results of fuel sample, the sulfur content in gasoline and diesel meet the Mongolian National Standard requirements, but the sulfur content in gasoline is two to eight times higher than that of the Euro 4 standard, and the sulfur content of diesel is also 22 to 23 times higher than that of the Euro 4 standard. We tested Lubricon A-112M, which is an enzyme-based additive used in bunker fuel. In this study, we conducted an emission factor measurement by using two vehicles with gasoline and diesel engines under three conditions; using ordinary fuel, using fuel additive once, and using fuel additive for six months. Then, vehicle emission was predicted by comparing EF measurement results. The results show that for the vehicle with a gasoline engine, when using Lubricon A-112M, the emission level of NOx decreased by 1.69 to 1.87 times (26%–37%). For the vehicle with a diesel engine, when using Lubricon A-112M, the emission level of NOx decreased by 1.04 to 1.51 times (4%–30%), and the emission level of particulate matter (PM) decreased by 1.52 to 2.06 times (20%–26%). We compared the results obtained in real situation with those obtained in the scenario in which the fuel additive was added and the new gas exhaust standard was applied. In this scenario, the fuel additive was used in 30% of all vehicles from 2016, and the Euro 4 standard was applied to all vehicles except those over 10 years old from 2020. The results of the scenario show that the emission level of NOx and PM reduced by approximately 8% and 13% in real situation until 2020. After that, NOx and PM reduced by 6–22% and 16–30%, respectively.
In recent years, rooftop greening has been actively carried out across Japan as a measure to reduce the effects of global warming and urban heat islands and to create a comfortable environment. In this experiment, we focused on bamboo, otherwise perceived to be a nuisance and in need of effective use. We examined its practicality as a base material for rooftop greening when mixed with composted sewage sludge. The results confirmed stable vegetation in a base material with a mixture of composted sewage sludge and bamboo powder at a 1:1 ratio. The experiment also showed high microorganism activity and an increase in nitrogen content, which confirmed the practicality of bamboo in the base material. The rainfall test indicated good drainability and water retentivity and showed that the base material sufficiently satisfied the criteria for live load and drainage water quality. Therefore, we conclude that the base material with the above mixture ratio has high practicality.