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Earthquake is a threat to all kinds of structures including underground structures. Before the 1995 Hyogoken-Nanbu Japan earthquake, however, it was considered that underground structures are at minimum seismic risk in comparison to above-ground structures unless they are crossing the active faults. The collapse of Daikai station in the Kobe subway system during the 1995 Hyogoken-Nanbu earthquake exhibited that underground structures are at high risk of earthquake with shallow overburden. Though researches have been done on this issue, it is still necessary to investigate further the mechanical behavior of underground structure during an earthquake and corresponding efficient seismic enhancement. In this paper, in order to find out an optimum ground-improvement pattern for a rectangular-shaped box culvert constructed in soft ground that does not meet the present seismic requirement, numerical tests with nonlinear 2D/3D dynamic FEM are conducted. Different patterns of the ground improvement for the box curvet constructed with cut-and-cover method are investigated to find out an optimum pattern that can reduce the impact of earthquake in the most effective way. In the 2D/3D dynamic finite element analysis, the ground is Toyoura sand, typical clean sand, and its nonlinear mechanical behavior is described by Cyclic Mobility model. Validity of the proposed numerical method is firstly confirmed with 1 g shaking table test and then numerical tests are conducted to find out the optimum pattern for the ground improvement. Finally, an effective pattern of ground improvement for existing box culvert is proposed by the numerical analysis. [ABSTRACT FROM AUTHOR]

The multi-directional site response of a well-documented downhole array in Japan is numerically investigated with three directional (3-D) dynamic hydro-mechanically (HM) coupled Finite Element (FE) analysis. The paper discusses the challenges that 3-D modelling poses in the calibration of a cyclic nonlinear model, giving particular emphasis on the independent simulation of the shear and volumetric deformation mechanisms. The employed FE model is validated by comparing the predicted site response against the recorded motions obtained from the KiK-net downhole array monitoring system in Japan. The results show that, by employing the appropriate numerical model, a good agreement can be achieved between the numerical results and the monitored acceleration response in all three directions simultaneously. Furthermore, the comparison with the recorded response highlights the significance of the independent modelling of the shear and volumetric deformation mechanisms to the improvement of the numerical predictions of multi-directional site response. [ABSTRACT FROM AUTHOR]

Abstract: JT-60SA is a superconducting tokamak to be assembled and operated at the JAEA laboratories in Naka (Japan). The tokamak is designed, manufactured and operated under the funding of the Broader Approach Agreement (between the government of Japan and the European Commission) and of the Japan Fusion National Programme; JT-60SA aims to prepare, support and complement the ITER experimental programme. The European contribution to the JT-60SA is, for a large fraction, procured by France, Germany, Italy, Spain and Belgium. This paper summarizes the activities carried out at F4E to develop a user-friendly software tool able to assess in real-time if an operational scenario could be structurally withstood by the magnet system of JT-60SA. Such tool is based on a theoretical formulation which is supported by a series of dedicated finite element method (FEM) calculations, and is able to provide a comparative assessment of any candidate scenario with respect to the baseline scenarios, and a quantitative assessment of all electro magnetic (EM) forces acting on the magnet system at any time during the candidate scenario. The tool as it is presented is specifically designed to be used for the JT-60SA tokamak, though it is designed so to that its usage could be extended easily to any other tokamak. [Copyright &y& Elsevier]

• Ground response mechanism under different geometrical configurations of jacked rectangular pipe was investigated. • Higher jacking force is needed with increasing aspect ratio of the jacked rectangular pipe. • Square shaped cross-section design is conductive for deep and long-distance jacking construction. For rectangular pipe-jacking construction, the primary priorities of smooth construction include minimizing the ground response and designating the appropriate jacking force to achieve the best results in environmental protection and energy conservation. The geometric cross-section design of the jacking rectangular pipe and its engineering performances such as the ground surface displacement, the jacking force consumption, and the stress-bearing state are easy to be ignored in the field construction. In this paper, the ground response characteristics under four kinds of rectangular pipe aspect ratio (H/W) with the same utilization cross-section area were investigated by using the calibrated finite element method (FEM) based on a case study conducted in Japan. The theoretical jacking force of each pipe section design was calculated and compared to provide a reference for long-distance or large-section jacking conditions. The stress-bearing state of each pipe was considered under different buried depths. The results show that the ground surface response decreases while the jacking force increases with increasing the aspect ratios. Thus, a reasonable design of the rectangular pipe section should comprehensively consider the influence of geometric effects on the ground and its stress-bearing state during the jacking construction. The findings of this study provide a practical reference for the safe and economic design of the jacking rectangular pipe and engineering management. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents the results of the study on thin walled steel portal frames, which are used in Japan as basic structural frames for motorway viaducts. A serious problem found in many such frames is the development of fatigue cracks at the beam to column connection. To act as a measure against the fatigue failure, in some cases a hole is provided at the beam-column connection of the frames. In this study, dynamic analysis using real earthquake data from 3 different earthquakes were carried out to examine the influence of such a hole on the global behavior of the frame and also on the local out of plane displacement around the location of the hole. Non-linear, large displacement analysis was performed using the FEM program MSC. Marc. The hole radius was varied and used as a parameter of study. The hole had significant effect on local out of plane displacement and global behavior, specifically when the radius of the hole was larger than 100mm. [Copyright &y& Elsevier]

Abstract: Urushi is a complex natural polymer that has been used to protect and decorate objects for many hundreds of years. It is an important material as decorated objects can obtain great value and historical worth. These objects are often exposed to environments that are detrimental to both their aesthetic appeal and structural performance and restoration and conservation procedures are needed to preserve these objects over long periods of time. The conservation work requires a detailed understanding of the material properties of the Urushi lacquer film. However, Urushi exhibits complex viscoelastic behaviour under load that has not been fully characterised to date. This paper presents the sample preparation technique and experimental data from a comprehensive mechanical testing programme for Urushi film. The viscoelastic response was investigated by tests at various loading speeds and creep and recovery tests. A number of constitutive models were fitted to the creep and recovery data and a good fit was seen with a number of these, most notably a modified generalized Kelvin fluid (MGKF) model. Some samples of Urushi were artificially aged by laboratory exposure to ultraviolet (UV) irradiation before mechanical testing. The ageing increased strength and reduced the ductility of the Urushi and it was shown that the MGKF model was capable of modelling the ageing behaviour by using ageing-time dependent material parameters. The models were implemented in the commercial FEA software ABAQUS, offering the potential to accurately model the Urushi behaviour in a complex structure. [Copyright &y& Elsevier]

Abstract: In this paper, natural rock slope deformation across fractures predominantly in a chert rock mass was monitored using six surface fracture displacement sensors, and the deformations arising from thermal stresses were predicted using (5m×5m) two-dimensional (2D) finite element (FE) plane strain analysis coupled with a model for rock mass expansion due to freezing of pore water. A new and simple method to minimize displacement proportional to temperature (due to thermal response of chert rock mass and sensor) was proposed. By applying the method, the corrected displacement, u′, can be well recognized. Under u′, clear rock mass movement, which could be related to fracture growth, was observed. In addition, progressive fracture opening and closure were noted. Results from this study indicate insignificant influences of weather conditions on fracture/rock mass movement. Furthermore, under numerical analysis (FE), in the rock mass model (with 1-m deep fracture), tensile stresses that were large enough to induce fracture growth appeared at the fracture tip when temperature lowered. And in the rock slope model (with 1-m deep fracture), small tensile stresses, which were sufficient to cause fracture growth along the planes of weakness, were observed. This research suggests that freezing effects on deformation of chert rock mass are insignificant, and we tentatively suggest that thermal fatigue predominantly caused the permanent fracture deformations. [Copyright &y& Elsevier]

Abstract: The probabilistic safety assessment (PSA) is important for nuclear power buildings in Japan because the risk of the occurrence of seismic ground motions beyond the design assumption cannot be denied. In this paper, the building fragility of the seismic PSA was evaluated using a high accuracy analysis model (three-dimensional nonlinear FEM building model considering soil–structure interaction and basemat uplift behavior). First, the response analyses were conducted increasing the input acceleration up to 3500Gal, until the damage of the building reached the ultimate condition. The damage of the building was estimated from the shear strain, the axial stress, and the consumed strain energy of the shear walls. Then, the influence on the response given by the vertical ground motion and the basemat uplift was evaluated. In addition, considering the shear destruction of the web wall and compressive crash of the flange wall as the fracture modes, the building fragility was evaluated. As a result, it was shown that the investigated method is efficient for more accurate seismic PSA estimation. [Copyright &y& Elsevier]

Abstract: During a severe earthquake, most moment-resisting steel framed structures are designed and detailed to resist the earthquake through a combination of strength and damage, where the damage occurs in specific, controlled locations in the beams. Contrary to prior opinion and practice, the Northridge and Kobe earthquakes of the mid 1990s showed that the ability of steel structures to deliver this behaviour is not a given, but is dependant on careful design and detailing, and on how the material behaves under the accumulation of damage. This paper focuses on the latter topic and develops a simple and powerful damage parameter to predict failure in the flange of a beam undergoing inelastic action under any loading history. This can be used to illustrate the influence of different loading regimes and to determine element failure in a finite element model. [Copyright &y& Elsevier]

Abstract: The purpose of this paper is to investigate estimation of velocity, water elevation and contaminant concentration in a river current using the Kalman filter finite element method (KE-FEM), which is an improvement of the Kalman filter finite element method previously presented by the authors group. The state variables, velocity, water elevation and contaminant concentration, in the whole domain can be obtained by the finite element method. Combining the Kalman filter and the finite element method, a practically useful method can be obtained. The Kalman filter is an estimation method based on the system and observation equations. The non-liner shallow water equation is utilized for the state equation. The explicit Euler method is used for the temporal discretization. The finite element method based on the linear interpolation is employed for the spatial discretization. The long computational time is required for the computation by the previous method. To reduce the computational time, the computational domain is divided into two parts, the main and subsidiary domains. In the main domain, filtering procedures are carried out, whereas only a deterministic process is taken for the variables in the subsidiary domain. Eliminating the state variables in the subsidiary domain, the drastically efficient computation is carried out. The flow in the Teganuma river in Japan is computed as practical applications. Close agreement between observed and computed results was obtained. [Copyright &y& Elsevier]

Abstract: Reduced beam section (RBS) moment resisting connections are among the most economical and practical rigid steel connections developed in the aftermath of the 1994 Northridge and the 1995 Kobe earthquakes. Although the RBS connection effectiveness was widely investigated using US design and construction practices, only limited data exist from European research. In the present paper the results of an experimental study of RBS moment connection with radius cut subjected to cyclic loading and using the HEA profiles, widely used as beam members in Europe, is presented. A theoretical model is also created with the finite element method and the results are compared with those obtained from the experimental study. The analyses confirm the need for readjustment of the geometrical characteristics of the RBS in order to apply to the European profiles. [Copyright &y& Elsevier]

Abstract: The nonlinear behavior of basemat uplift, which is an important point in seismic designs of nuclear power plants in Japan, has been investigated by arranging joint elements between the reactor building basemat and the soil on a three-dimensional (hereafter referred to as 3D) FEM model of the soil. However, the nonlinearity of the basemat uplift has been investigated separately from the nonlinearity of reactor buildings. These nonlinearities have yet to be taken into account simultaneously in past studies. In this paper, models of the building and the soil using 3D FEM elements with consideration to the nonlinearity of building materials as well as the nonlinearity of the basemat uplift were subjected. The behavior of the building''s elements were investigated by carrying out seismic response analyses for horizontal ground motions only, as well as for simultaneous horizontal and vertical ground motions using these models. As a result, it was found that there was little difference in the horizontal response of the building between the horizontal input motions only and the simultaneous horizontal and vertical input motions. The effects of the vertical ground motions on the basemat uplift behavior which is represented by the ground contact ratio were also slight. [Copyright &y& Elsevier]

Abstract: This paper presents the results of a benchmark on thermal fatigue crack growth evaluation for a thick-wall cylinder subjected to cyclic thermal transients. The simplified crack growth evaluation methods of both JNC in JAPAN and A16 procedures proposed by CEA in France are presented. The predictions obtained using both methods are compared with the experimental data. The JNC method, which accounts for the non-linear stress component provides predictions of crack advance in a good agreement with the experimental data. In contrast, significant differences are observed between the A16 predictions and the experimental data. The discrepancies are mainly due to the non-linear stress component which is not accounted for in the A16 method. When using the JNC stress intensity factor solution determined by finite element analysis to account for the non-linear stress component, the A16 method well predicts the thermal fatigue crack growth behavior. [Copyright &y& Elsevier]

Currently, an increasing number of single-box multi-cell composite box-girders with corrugated steel webs (SBMC-CBGCSWs) have been built in China and Japan. However, the torsional stiffness of SBMC-CBGCSW is dramatically decreased due to the employment of thin corrugated steel webs (CSWs). Investigations of SBMC-CBGCSW under pure torsion are relatively limited, therefore, additional research is needed to investigated to guarantee the safety of such bridges. In this paper, an experimental study on four scaled specimens subjected to pure torsion is conducted to understand the effect of the number of cells and spacing of CSWs on the full torsional response of SBMC-CBGCSW. The failure mode, cracking patterns, and buckling patterns of specimens are presented, and a new shear strain relationship between CSWs obtained from experimental results is proposed to evaluate the contribution of inner CSWs to the torsional behavior of SBMC-CBGCSW. Then, finite element analysis (FEA) models are created to compare with experimental results, such as torque-twist curves, shear strains of CSWs and shear strains of concrete slabs. Finally, a parametric study is performed to examine the effect of geometric factors, such as the ratio of width to height, ratio of width to span length, ratio of width to thickness of slab, number of cells and spacing of CSWs, on such bridges under torsion. • Cracking and buckling patterns and failure modes of 4 scaled SBMC-CBGCSWs under pure torsion are presented. • Effects of number of cells and spacing of CSWs on full torsional response are examined. • Torque-twist curves and shear strains obtained from FEA agree well with that of test. • A new shear strain relationship between CSWs is proposed. • Parametric study is performed to clarify the effect of geometric factors and find optimum positions of CSWs. [ABSTRACT FROM AUTHOR]

This paper presents the absorption performance of honeycomb-backed microperforated panel (MPP) absorbers, which are needed to improve the acoustics of an existing 91 m3 small meeting room where the reverberation time is over two seconds from 250 Hz to 2 kHz, for comfortable speech communication. In Japan, MPPs are difficult to use combustible materials, particularly, panels with holes for interior walls owing to fire regulations. Therefore, we implemented the MPP absorber as an additional attachment that can be hung on walls and ceilings. First, the absorption characteristics of the MPP absorber were designed to reduce reverberation times at mid-frequency using an electroacoustical equivalent theory. Then, a wave-based finite element method simulation was used to determine the absorber placement. Absorption coefficients of the honeycomb-backed MPP absorber were also measured in an irregularly shaped reverberation chamber. Finally, the effect of the installed MPP absorbers was checked by acoustic parameter measurements. As a result, we observed that the reverberation time was reduced under 1.5 s in all frequencies, the equivalent absorption area doubled, the early decay time values were also reduced from 2.7 s to 1.0 s at 1 kHz, the clarity ( C 50 , mid ) increased by more than 5 dB, and the speech transmission index (STI) value increased from 0.55 to 0.67 by one rank up. [ABSTRACT FROM AUTHOR]