Ultrasonic tip echo is scattered wave which radiates all direction from the sharp tip of reflection source such as fatigue cracks. Tip echo has been utilized for sizing defects as so-called “tip echo method” and also may apply to identify fatigue cracks from other defects. In this study, radiation characteristics of the tip echo were experimentally examined. A linear phased array ultrasonic testing system was applied to send and receive ultrasonic waves in various directions. The experimental results demonstrated the relationship between incident wave directions and directivity of the tip echo. Besides, the tip echo method was applied to a fatigue crack in a welded steel plate, and damping of echoes due to fatigue crack closure was indicated.

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  To demonstrate the sealing performance of a metal cask subjected to impact load due to a commercial aircraft crash against a spent fuel storage facility, a horizontal impact test was carried out. In the test, an aircraft engine missile with a speed of 57.3 m/s attacked the reduced scale metal cask standing vertically containing helium gas. In the test, the leak rate of the helium gas and sliding displacement of the cask lid were measured. At the impact, the leak rate increased rapidly and reached to 4.0×10^-6 Pa·m³/s. After that, the leak rate decreased slowly and converged to 1.0×10^-6 Pa·m³/s after 20 hours from the impact test. The leak rate of a full scale cask was evaluated using that of the reduced scale cask obtained by the test taking account of the reduction factor. As the result, the leak rate of the full scale cask was less than 1×10^-4 Pa·m³/s.
 This result showed that the sealing performance of the full scale metal cask would not be affected immediately by the horizontal impact of the aircraft engine with a speed of 57.3 m/s.
 In addition, to simulate the cask behavior in the impact test, an impact analysis using dynamic analysis code LS-DYNA has been executed. The numerical results agree well with test results. The following were necessary to obtain good results by the analysis.
  1)Experimental material data for input to the analysis contition
  2)Exact analytical model of the cask lid
  3)Initial conditions around the cask lid simulating the test for the analysis.

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  Fabric reinforced rubber shows an anisotropy and viscosity in wide strain range. In this paper, an anisotropic visco-elastic model based on Mooney-Rivlin model is developed for fabric reinforced rubber. Anisotropy is introduced, in this constitutive model, by using a structure tensor that shows direction of reinforced fiber. A new strain energy density function for anisotropic elasticity is proposed to improve accuracy associated with shear behaviors. After developing an elastic model, an anisotropic viscosity is modeled by a kind of Maxwell viscosity model at large strains. In addition to the development of constitutive model, a simple fracture prediction method, which refers to the finite element solution incorpolated with our proposed constitutive model, is proposed. Finally, our proposed constitutive model and fracture prediction method are validated with comparisons of uni-axial tension tests with fabric reinforced rubber.

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  It is required to develop a method for earthquake response analysis for ultimate limit state in the context of performance based design. Focusing on Moving Particle Semi-implicit (MPS) method as a prospective method for that purpose, we perform basic study. Formulations for elastic shear and compressional wave propagation are shown and their accuray depending on descretization level is examined by numerical simulations. Formulations for element-based Rayleigh damping, which is often used with Finite Element Method (FEM), viscous boundary condition and 2E input (specify only upward wave), are proposed for MPS method and verified through numerical simulations. Responses calculated by FEM and MPS method are compared with a two dimensional multi-layer slope model which considers Rayleigh damping and 2E input. The agreement of both results are very good, therefore it can be concluded that practical lelvel of earthquake response analysis can be performed by MPS method.

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  This research proposes a novel approach for the displacement reconstruction using one of distributed optical fiber strain sensors, PPP-BOTDA. The remarkable point is that, not only using raw strain data, but using the non-uniformity index of strain distribution profiles, which is normalized Laplacian value (NLV), the algorithm can detect boundary condition changes of structures. In the verification, the algorithm was applied to the deflection identification of a composite laminate specimen with an embedded optical fiber network. From the NLV distribution, the change of the fixed end condition of the specimen was evaluated, and using the updated FE model, the deflection was able to be reconstructed with high accuracy.

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  In order to seismically strengthen existing bridge piers, it is commonly required to improve only their ductility while suppressing any excessive strengthening of load bearing capacity. In the present study, we proposed and verified a new method, which is, unlike the conventional method of providing longitudinal stiffeners, the same stiffeners are provided to existing cylindrical steel piers while elaborately allowing a slight gap in between the bottom of a stiffener and bottom plate of a pier. The estimated seismic effect has been verified by an experiment and the numerical analysis. Our studies showed that only the ductility has been effectively increased by being contacted the bottom of stiffeners and the bottom plate of piers after seismic force has reached a maximum level.

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  Thick steel plate, which is often used as flange of plate girder bridges recently, may have yield stresses and residual stresses changing in thickness direction, caused by cooling process etc. in manufacturing process. In this paper, the distributions of material properties and residual stresses in thickness direction are investigated experimentally by using SM570 steel thick plate with 98mm thickness, and their effects on the ultimate strength of plate or plate girder are also clarified analytically. Following conclusions are obtained as results; 1) yield stress and tensile strength are parabolic distributions with the maximum at the surfaces and the minimum at the center. Oppositely, for elongation, with the minimum at the surfaces and the maximum at the center. 2) the residual stress is parabolic distribution with compressive stresses near the surfaces and tensile stresses near the center. Moreover, from analytical results, 3) these distributions of yield stress and residual stresses do not influence plate strength so much.

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  Numerous fatigue cracks have been found in steel bridges. To maintain steel bridges, repair and retrofit methods of such fatigue cracks have been developed. One technique we developed was to produce plastic deformation of the steel surface near the crack in order to close crack opening by using air tool. This method is called Impact Crack Closure Retrofit treatment (ICR treatment). We carried out plate bending fatigue tests of out-of-plane gusset specimens. Fatigue cracks at turn-around welds and those which propagated 10mm were ICR-treated. Fatigue test results of specimens after ICR treatment showed significant improvement of the remaining fatigue life.

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  Many fatigue cracks are found at vertical stiffeners and rib cross points of steel deck structures. Fatigue improvement of these details by the application of Ultrasonic Impact Treatment was planned. Residual stress measurement by X-ray and stress range measurement by a test truck were conducted at a bridge under traffic. Based on these measured data, local stress based fatigue tests by joint specimens were conducted. In this test, the absolute value of local stress gives dominant effect to fatigue performance. Through the fatigue test and field measurement, it is confirmed that applying UIT to objective details can improve fatigue performance.

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  Fatigue cracking from an incomplete penetration of the intersection of three welding lines is a serious problem. Those structural details can be seen in many places such as beam-column joints of bridge piers. This study examined the applicability of ultrasonic testing with phased array transducers for the quality evaluation of the three dimensional incomplete penetration. Prior to the detection of three dimensional defect, images of two dimensional incomplete penetrasion of corner weld and cruciform welded joints were obtained precisely by the use of synthetic aperture focusing technique (SAFT). Those two dimensional incomplete penetrations form surfaces of three dimensional incomplete penetration. Detection of a prism shaped three dimensional incomplete penetration was attempted. Some small echoes from the tip or surface of the incomplete penetration could be obtained. The size of incomplete penetration was estimated successfully.

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  The bridges by weathering steel which can abbreviate painting were widely adopted in Japan to reduce LCC (Life Cycle Cost). But it is reported that some part of bridge cross-section is severely rusted by the effects of various environment factors although most part of bridge cross-section is mildly rusted. This paper discussed the effect of environment factors to the rust distribution of bridge section by using observed data for one year in Naebiki-Bridge in Niigata prefecture such as the distribution of airborne salt and its washdown by rainfall. Furthermore, a new approach method to evaluate partial corrosion level is proposed in this paper.

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  On August 1, 2007 at 6:05 PM, I-35W steel deck truss bridge over Mississippi River in Minneapolis catastrophically failed into the river resulting in the 13 people dead and more than 100 people injured. Determining the cause of the collapse is required to prevent bridge failures from similar causes. This paper attempted to reveal the cause of the I-35W bridge collapse using a finite element model. Firstly, an analysis of the bridge collapse mechanism specified that the failure of U10 gusset plate initially occurred and led to the collapse of entire span. Secondly, the result of calculating the stress in U10 gusset plate indicated that the gusset plate was likely to fracture under the loading and the structural conditions at the time of accident. Finally, an example of the method of preventing the bridge collapse was proposed.

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  This paper presents a 3D shake table experiment on a 7.5 m tall 2 m diameter circular reinforced concrete column which was designed in accordance with 2002 Japan Road Association design code. Failure mechanism was clarified based on a series of excitations and fiber element analyses. It was found that the column behaved satisfactorily under a near-field ground motion recorded during the 1995 Kobe, Japan earthquake. The scale effect on the ultimate displacement due to pull-out of crashed core concrete from steel cage and the lateral confinement by hoops are presented.

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  A seismic damage rate for segmented pipelines is formulated based on the failure mechanism of mechanical joint system. Current damage rates per unit pipe length were obtained on the basis of observation data which were collected in damaged pipelines suffered by major earthquakes. Newly developed segmented pipe having mechanical stops in Japan are seismically strong enough not to be observed in recent earthquakes. A theoretical approach is adopted to obtain a simple formula of damage rate for this segmented pipe. A new seismic design method is also developed which will be useful for performance-based design of segmented pipelines under seismic risk.

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  It has been shown in various past studies including the author’s ones that the most efficient way to upgrade the seismic performances of bridge structures will be to install a kind of energy absorption devices, such as buckling restrained braces (BRB) and shear panel dampers (SPD). In this paper, performance tests and analysis of BRBs made of an aluminum alloy (A5083P-O) are studied. The target performances of the so-called high performance seismic dampers that are supposed to withstand level 2 earthquakes three times are first clarified, and a series of performance tests have been carried out for BRBs. Moreover an numerical study using the modified two surface model developed by the authors for A5083P-O aluminum alloy is also presented and discussed from various view points including the overall buckling.

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  The load when CFRP strips peel off from steel plates, namely debonding load is known to become higher by stepping the CFRP strips. In the previous research, the conditions to maximize the debonding load were provided for the CFRP strips with one step. In this study, they are given for the case of multiple steps by applying the properties that the stress in the middle of the steel plate and the debonding shear stress at the end of the adhesive each converge into a certain value as the length of the CFRP strips are large, to each of the steps of CFRP strips.

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  The objective of this study is to develop a new stress analysis method for a steel plate with multilayered CFRPs under uni-axial loading. In the method, strains in each layer are considered to be state variables in first order simultaneous differential equations deriving from force equilibriums in infinitesimal regions. A general solution for strain is numerically calculated from eigenvalue analysis for a system matrix making from the differential equations. Unknown coefficients in the general solution are determined from continuous and boundary conditions for strains in each layer. In order to verify the validity of the proposed method, comparisons with analytical solutions, laboratory experiment and finite element analaysis were carried out. As a result, it was confirmed that the proposed method involved conventional analytical solutions, and made possible to analyze stress distributions of a steel plate with multilayered CFRPs.

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  In Japan, Allowable Stress Design (ASD) method has been used for more than 30 years. However, Limit State Design (LSD) method is now global standard design procedure. Since the ultimate flexure strength of composite girder can attain to the plastic moment, which is considerably higher than the yield moment, benefit from introducing LSD is apparent. On developing LSD, correct evaluation of ultimate strength is one of the important issues. In this paper, experimental results on ultimate coupled flexure and shear strength are given. Furthermore, citing our previous analytical results on the ultimate flexure strength, we proposed a method for evaluating flexure, shear and coupled strength of composite girders.

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