In order to study influential factors, analysis of past relevant information on earthquakeinduced failure of railway embankments was conducted. As a result of computing scores that are empirically assigned to each of the factors, positive correlation with the settlement ratio was obtained. In particular, it was revealed that many of the collapsed embankments were constructed at a site with topography to collect water; they were located at boundaries between different micro-topographies; and they suffered from past damage histories. In addition,detailed case studies were executed on an embankment which exhibited a high value of the above score and suffered from actual extensive collapse, and effects of the strength properties of the fill material and those of the ground water level in the fill were numerically evaluated.
In order to study whether newly-developed geocell can be worked as tensile reinforcement in retaining walls, pull-out tests were performed on geogrid and newly-developed geocell (square shaped) embedded in three different compacted gravelly soils. As a result, different pull-out behaviors were found due to their geometry which can be explained by different pull-out mechanisms. In the case of geogrid, the peak pullout resistance increases slightly with an increase in particle size. On the other hand, in the case of newly-typed geocell, the peak pullout resistance increases significantly with an increase in particle size. Newly-developed geocell can confine larger particles and provide corresponding higher peak pull-out resistance.
A series of undrained monotonic shear tests were conducted on loose toyoura sand using a hollow cylinder torsional shear apparatus. The test result was similar to the trend of critical shear strain based on the cyclic loading test. However, the value of shear strain to cause strain localization due to monotonic loading was smaller than the result of cyclic loading test. In addition, if the relative density was smaller than 23%, the liquefaction of specimen occurs in the monotonic shear test.
Seismic isolation structure is a superior technology to reduce earthquake damage to buildings. There is a "damping material" as one of the main components of seismic isolation, it is required stable energy absorption performance and several hundred millimeter deformation performance. Damping material commonly used is relatively expensive because of special order of strokes, which is a cause of increasing the costs of the seismic isolation. In order to reduce the cost of the seismic isolation structure, development of a simple damper with long stroke using rubber rings, the authors report the experimental results.
Devises using the rolling of viscoelastic materials such as rubber is proposed, then a practical procedure for easy evaluation of the rolling resistance of them is required. This kind of research has been already established in the field of tire technology, and many patents are submitted. In this paper, a new devise using the rolling of O-ring rubber is proposed and the method of simulating the rolling resistance of viscoelastic materials developed in the field of tire technology is applied. Compared with an experiment and a dynamic finite element analysis, the validity of the proposed static and qualitative aspects of method is discussed.
Although structural damage is minor, large earthquake response of structures, especially steel structures, has become to be aware of many researchers. To reduce the response of existing buildings, the authors had proposed a hybrid seismic retrofit system adopted Tuned Mass Damper (TMD) and Soft-first story principle, which has a low cost and easily to be installed. A shaking table test is carried out of a single degree of freedom model, which is seemed as the simplification of building, combined with TMD supported from ground. The result of this test is reported here.
Use of appropriate fragility functions is one the most critical parameters for the accuracy of earthquake risk assessment. This study focuses on computation of fragility functions for brick masonry buildings in Nepal through non-linear analysis using Applied Element Method (AEM). Results obtained from AEM were compared with shaking table experiment and a good agreement was found. Buildings with different configuration, material strength, the number of stories and mortar type were subjected to numerical simulation and probability of damage exceeding a certain level of damage state is calculated for peak ground acceleration (PGA)starting from 0.05g to 1.0g. Fragility functions for low earthquake resistant masonry buildings for different state of damage are plotted based on numerical simulation results.
Seismic retrofitting of masonry structures has attracted the attention of worldwide researchers and many researchers have come out with different retrofitting materials. Use of Fiber Reinforced Polymer (FRP) as retrofitting material has become very popular in the past few decades. High strength to weight ratio and linear elastic behavior are some of inherent advantages of FRP material. In the past, most of the researchers have evaluated the performance of FRP by performing diagonal compression test or cyclic tests on small-scale or full-scale walls whereas some others used out-of-plane load tests but there were almost no detailed study comprising the dynamic behavior of FRP retrofitted house models using dynamic or shake table testing. Current research work consists of shake table testing of three 1-4 scale house models with wooden truss roof. Out of three house models, one was non-retrofitted (URM) and two were FRP retrofitted house model. In case of two FRP retrofitted house models, one house model was retrofitted with 0.0012 FRP reinforcement ratio whereas other was retrofitted with 0.0006 FRP reinforcement ratio. In both of FRP retrofitted house models, FRP reinforcement was applied only at outer face of the walls. FRP layout and reinforcement ratio was selected based upon previous literature reviews. Response of URM and FRP retrofitted house models was compared in terms of base shear and story displacement hysteresis, story shear and story drift hysteresis, damage levels at different input motions and stiffness degradation. Experimental results have determined that FRP has significantly increased the lateral load resistance of unreinforced masonry structures.
Fiber reinforced polymer (FRP) has become a popular material in the past few decades. It has been extensively used for strengthening and retrofitting of concrete structures. High strength to weight ratio, high initial stiffness, linear elastic behavior and ease in application has made it material of good choice for the seismic retrofitting and strengthening of masonry structure. There are many guidelines proposed by many researchers to determine the amount of FRP based upon the seismic base shear requirements. But, there is no theoretical, numerical and experimental researches to determine the optimum placement and quantity of FRP to reduce the cost of retrofitting. In this research, an attempt has been made in order to find the optimum quantity and placement of FRP for strengthening brick masonry wall system. Required objectives are achieved by performing diagonal compression test on ten masonry wallets. Masonry wallets were carrying different volume and arrangement of FRP strips. Response of masonry wallets with different volume and configuration of FRP strips are recorded using a digital acquisition system.Experimental results are carefully analyzed in order to propose an optimum and efficient retrofitting procedure of masonry wallets with FRP. Experimental results shows that correct retrofitting scheme can not only increase the efficiency but can also reduce the retrofitting cost and effort.
Unreinforced masonry structures are highly vulnerable and have contributed a significant number of causalities during past earthquake disasters. Therefore, improvement of seismic capacity of unreinforced masonry structures is essentially important to reduce causalities due to future earthquakes. In order to improve seismic capacity of unreinforced masonry structures, we have proposed a new composite material which can increase shear strength and deformation capacity of masonry walls. To investigate properties of newly proposed composite materials which are ductile, cost effective and strong enough with large energy dissipation capacity, we have carried out experimental studies. Fiber reinforced polymer (FRP) is a very strong but costly material. It can significantly increase the shear capacity of unreinforced masonry but exhibits catastrophic and brittle failure due to its low ductility. While polypropylene (PP) band is very cheap material but has large deformation capacity. In this study, an attempt has been made to utilize the large deformation capacity of PP-band and an increase in strength with minimal use of FRP. A comparative study has been carried out by in-plane diagonal compression test using different types of masonry wallets, such as non-retrofitted ones, carbon fiber reinforced polymer (CFRP) retrofitted ones, PP-band retrofitted ones and a composite of CFRP and PP-band retrofitted ones.
The present study deals with the earthquake disaster reduction by the development of new composite material to mitigate the collapse of unreinforced masonry structures (URM) in urban and rural areas in developing countries. Collapse of unreinforced masonry walls causes a large number of human causalities due to a strong ground motion. Masonry walls are relatively strong for in-plane shear and much weaker in out of plane direction resulting collapse of masonry structure. Being highly expensive, FRP is a strong material and can significantly increase the out of plane bending strength of masonry walls. Being an expensive material, FRP exhibits a highly catastrophic brittle failure under extreme loading leaving no warning and evacuation time for residents. On the contrary, polypropylene band (PP-band) is a cheap material with much larger ductility and holding capacity to avoid sudden failure, caused by the breaking of wall into small fragments which has been found as a major cause of causalities. In this study, an attempt has been made to find a composite material by using FRP and PP-band to increase the shear capacity and to avoid the catastrophic brittle failure of masonry walls under strong ground shaking. In order to achieve required objectives, out of plane load tests have been carried out using six masonry wallets consisting of three non-retrofitted masonry wallets, PP-band retrofitted masonry wallet, FRP retrofitted masonry wallet and FRP+PP-band retrofitted masonry wallet. Behavior of wallets has been carefully observed in terms of peak strength, deflection and deformation capacity. It has been found that retrofitting of masonry walls using FRP and PP-band is much viable solution as compared to conventional retrofitting techniques because FRP+PP-band reduced the overall cost of retrofitting due to confining and holding effect of PP-band which is a very low cost material.
Being common attraction for the people as economic viable solution for housing, unreinforced masonry (URM) construction has been economical and locally available in every part of the world with different types and form. Performance of URM masonry structures during different earthquake is still big question mark and has posed serious threats to human life in the past and future seismic disasters. The highest fatality rates during any earthquakes were always associated with masonry housing. Enhancing the performance of brick masonry in particular during the earthquake with material which will be cheap and having better performance during the earthquake have been dream of researcher and practicing engineer. The Polypropylene band (PP-band) retrofitting has been used for the retrofitting of masonry structures in many under developing countries. PP-band has been used as mesh on the walls with plaster coating. In the past behavior of PP-band is investigated during dynamic testing on small and full scale masonry houses. The PP-band applied on the masonry wall are connected at every intersection of the mesh. In the current research work an attempt was made by reducing the PP-band mesh connectivity for reaching the optimization in manner of time and cost for retrofitting of URM masonry structure. By varying these parameters we can propose a solution of PP-band retrofitting with less work force, price and duration by testing them in ¼ scale model on shake table test. Comparison of PP-band mesh performance having its connectivity at all points and with zero points has been made in damaged assessment of the structure.
This paper analyzes actual conditions and methodologies of building damage assessments which carry out damaged area suffered from The 2011 off the Pacific coast of Tohoku Earthquake. Authors conducted questionnaire survey for local governments which suffered from earthquake and Tsunami disaster. As a result of questionnaire survey, it become clear that duration of building damage assessment survey, number of supporting staffs, survey tools and so on are difference among the local governments which has some type of damages. And, many local governments have some opinion to carry out the building damage assessment which needs to keep fairness,quickness and accuracy. Furthermore, many big earthquakes will expect to occur in near future,and then we need to develop the efficiency, fairness and quickness methodologies to carry out the building damage assessment.
This article describes the “past”and “future”research activities on “Gradual progress on semisolid metal forming process”mainly in The University of Tokyo. That means, the “past”research activities include the history of semisolid forming process as well as highlighting their and advantages and drawbacks. The “future”portion explains the prospects of the following three themes that are being researched in our laboratory now. They are, (1) the semisolid metal forming process by using a servo press, (2) recycling and refining of scrap metals by using semisolid metal forming process, and (3) a micro structure control of metal matrix by using the semisolid metal forming technique.
This report describes a new microscopy technique, which probes spontaneous emission from samples with nanoscale spatial resolution. We have developed a passive THz near-field microscope by introducing an ultrahighly sensitive THz detector (CSIP) and a scattering-type scanning near-field optical microscope. Here we show a result, which probes THz evanescent waves with 60 nm resolution with our microscope. Finally we also show nano-thermometory as an application.
As represented by Miura-ori, origami has inspired various types of deployable structures. Usually, these Origami structures are designed under the assumption of "rigid folding", which means each plane is undeformable and connected with ideal joints. In this study, a new strategy for designing deployable structures are proposed by using partially elastic origami models. These new origami structures take into account the elastic deformation. It enables us to estimate the elastic energy through folding and unfolding process and to design self deploying origami structures.
The authors propose a fixed-abrasive tool with spiral groove on its surface, to eliminate or decrease the loading of swarf. The spiral groove, which is produced by a spiral wire wound around the tool, allows continuous evacuation of swarf and elongate the tool life. Through grinding experiments, it was confirmed that our spiral groove tool makes almost no loading of swarf while conventional fixed-abrasive tools easily make it. It was also shown that the spiral groove tool realizes a mirror finish even with ultra fine abrasive grains.
The tool life experiments were conducted and deep discussion was made for clarifying the main factors of low machinability of sintered steel Fe-2%Cu-0.8%C. Cutting tools used were cemented carbide P10, cermet P10 and coated carbide with superlattice of TiAlN/AlCrN. The tool life of the cemented carbide was shorter in wet turning than in dry turning. The cermet had a much longer tool life than the cemented carbide in wet machining. The coated carbide showed excellent cutting performance. As a result, it may be concluded that copper added to the sintered steel has a negative effect on the machinability and that a thick coating with CrN is effective for increasing the machinability.
The present report describes a reliable fabrication method of metal micro-electrodes embedded in polydimethylsiloxane (PDMS) using a dry peel-off process which is one of transfer techniques of metal layers to polymers. Two different surface modifications with self-assembled monolayers were carried out for easy and reliable transfer of Au micro-patterns to the PDMS;(1) perfluorodecyltrichlorosilane (FDTS) on silicon substrate for easy release of the Au patterns from the Si substrate, (2) (3-mercaptopropyl)trimethoxysilane (MPTMS) on the Au patterns to promote the adhesion between the Au patterns and PDMS. Moreover, we showed two different applications of Au micro-patterns in flexible PDMS, such as 1) the flat stamp for micro contact printing and 2) micro-heaters for local heating.
To date, very few studies have been done to quantitatively evaluate in-mold flow behavior and fiber breakage phenomenon in injection molding using long carbon fiber reinforced material. This study therefore aimed to clarify the correlation between resin flow behavior and fiber breakage behavior by focusing on fiber breakage phenomenon inside the mold. The length of fibers remaining in the long carbon fiber reinforced material which had passed through the flow channels inside the mold was evaluated. And fiber orientation was observed using an X ray CT device especially for channels with progressing breakage. The results clarified that at the entrance of the sprue, fiber breakage progresses the most when fibers orientating in a corrugated pattern are crushed due to the velocity gradient inside the sprue.
MID （Molded Interconnect devices）had been developed as three dimensional circuit boards, and currently are in use as multiband antennas in mobile phones as a functional device. Aiming at application of MID to mechatronic devices such as actuators and sensors, the authors research on novel production technologies required for the purpose. This paper introduces a novel production method using sacrificial material that allows circuit structuring on various shaped surfaces, especially shadowed surface, which was not possible with conventional methods. The method has realized a peeling strength of 0.99N/mm, of a fine copper quality obtained by excluding oxygen while eluting the sacrificial material.
A truss structure can change its shape and mechanical property by using shape memory alloy (SMA) in parts of the structure. It enables bidirectional drive by using a plurality of SMA wire. From Brinson’s constitutive equation for the SMA, we have formulated the incremental form of the finite element analysis under the assumption of finite deformation and have developed the simulation tool of the adaptive truss structure with SMA wires. We have compared the calculation results with the experimental results and have verified the validity of the proposed computational procedure.
Today, many Asian and Pacific (AP) countries are accelerating deployment of transportation infrastructure. On the other hand, not only developing counties but also developed countries are suffering from urban traffic problems such as traffic congestion, accidents and environmental damage caused by heavy traffic due to dense population and rapid economic growth. In this situation, several countries are trying to solve these traffic problems by applying Intelligent Transport Systems (ITS) and achieving positive results. In order to facilitate the development and deployment of ITS in the entire Asian Pacific region, it is important to share the common understanding how to use ITS effectively to solve urban traffic problems, how to integrate information technology and transportation infrastructure and how to deploy a platform for ITS. This paper discusses about how to develop ITS as solution for urban traffic problems in AP countries.