Presented is a review of shape optimal design and shape design sensitivity analysis with an emphasis on techniques dealing with shape of the boundaries of two- and three-dimensional bodies. Attention is focused on the continuum structural shape optimization based on numerical models by either finite elements or boundary elements. This requires sophisticated design sensitivity analysis techniques and a careful choice of design variables.

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The Distinct Element Method (DEM), in which soil is represented as an assembly of numerous discrete particles, does not account for the continuity of the medium. The extended method has another physical structure which represents the effect of the internal material between the particles as mortar of concrete. We simulated the two-dimensional dynamic fracture process of the Cypress Double-Deck Bridge on Interstate 880-Line suffered by the 1989 Loma Prieta earthquake using this method. Results agree well with the real damage qualitatively and confirmed that this method can simulate the collapse of structures involving discontinuous behavior.

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This paper deals with strong-motion peaks in terms of seismic source, propagation path and local site conditions. Especially emphasis is placed on the effect of local site conditions. Peak acceleration, peak velocity and peak displacement are analyzed in a similar fashion because they are interrelated. A semi-empirical model is first derived with the aid of seismic source theories and then applied to strong-motion records obtained in Japan. The resulting semi-empirical expressions for the peak acceleration, velocity and displacement are compared with strong-motion data observed during the 1989 Loma Prieta, the 1985 Michoacan and the 1971 San Fernando earthquakes. The semi-empirical expressions explain well the observed strong-motion data in other countries even though they were obtained based solely on Japanese data.

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The subject of this paper is to analyze the stress functions near the circular interface crack between dissimilar elastic media. These problems are researched many laboratories, but the results are to have accumurate singular point and no practical use. The proposed method is to perform weight integral calculus and to construct process zones at crack tips along the interface. It is shown that in the process zone both finite stress and opening displacement exist but no oscillation appears.

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This paper presents a computational approach for the impact response of the sand cushion under a falling rock by using distinct element method (DEM). At first, the static loading test and falling weight test for the sand cushion are performed by using a small size model. It is found that the impact load of a sand cushion can be estimated by using the spring constant of sand obtained in the static loading test. Secondly, the relation between the spring constant of sand and the fictitionus elastic modulus of a sand element in DEM is found and the impact response analysis is performed by combining the DEM with Rigid Body Spring Model (RBSM). It has been confirmed that this computational approach can estimate the impact response of a sand cushion by comparing with the experimental results. Finally, the actual size impact tests have been simulated by this approach. It has been found the weight impact load is about 2 times smaller than the transmission impact load and the transmission energy factor is about 6-13% in the case of the span length of H type beam 8-12m and sand cushion 90cm.

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Methodology of probabilistic back analysis is discussed based on the maximum likelihood estimation. The probabilistic back analysis solved by Gauss-Newton method is found to have the same algorithm as that of Extended Kalman Filter method, and the only difference between the probabilistic approach and the deterministic approach is due to how the weighting matrix of the objective function is determined for the back analysis. Three types of objective functions for the back analysis are proposed depending on the quality and quantity of given observed data. The mathematical interpretation of solutions by the EK-WGI method is also discussed and made clear. A back analysis with a simple model is numerically performed in order to demonstrate the proposed probabilistic back analysis method.

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Shield tunnel is being increasingly adopted in recent years for constructing tunnels for traffic, water supply and sewerage. Because they are extremely important as lifeline facilities, development of a rational seismic design method suitable for shield tunnels is very important.
Shield tunnels deform in accordance with the deformation of subsurface ground during an earthquake.Although axial deformation is predominant, flexural deformation becomes important when soil condition varies along the tunnel axis, and when the tunnel is rigidly connected to other structures.
Because shield tunnels are of segments, bolts and secondary (inner) linings, evaluation of equivalent stiffness requires accurate estimation of deformation characteristics. Failure mechanism is also important for estimating nonlinear hysteretic behavior of shield tunnels subjected to a significant earthquake. There are however few studies on the deformation and failure mechanism of shield tunnels subjected to flexural deformation. Therefore, a series of loading tests of shield tunnel specimens subjected to alternative bending moment was conducted. Presented in this paper are failure mechanism and deformation characteristics of shield tunnels with and without secondary lining, and importance of the secondary lining for increasing ductility of shield tunnels.

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Fatigue strengths of scallop details in welded structural members were investigated by experiment and FEM analysis. Fatigue strength of this detail based on nominal stress was extremely low because high stress concentration occurred in the gap of scallop. Fatigue strength based on hot spot stress are plotted on narrow band above the JSSC's E class design curve (80MPa for 2×10⁶ Cycles), which shows that fatigue assessment method based on the hot spot stress is valid for estimating fatigue strength of scallop details.

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In case of structures under compressive loading, it is often observed experimentally that the ductility of structures is considerably lost due to the localization of plastic buckling patterns. This implies that the phenomena of this kind has an unfavorable effect on the earthquake resistance. Herein, we present a versatile theoretical method to analyze the localization of buckling patterns including that under cyclic loading. As numerical examples, two types of structures, i. e. a multiply supported column and a truss tower under compressive force, are analyzed in order to show the validity of the proposed method. In these examples the cyclic localization phenomena is also discussed in terms of the influence on deformation capacity.

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To establish a simple and rational method for dynamic response analysis of RC rock-shed structure under rock-falling, applicability of Finite Strip Method (F. S. M.) and 2-dimensional frame method on the impact behavior of RC rock-shed structure is considered. The experimental results obtained from the full scale impact test of RC rock-shed structure are used to confirm the applicability of those analytical methods.
Finally, it is shown that the main part of dynamic response of RC rock-shed structure will be predicted by using F. S. M.

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This paper describes reduction effects on seismic stresses in the cross section of shield tunnels with the backfilling area filled with flexible materials. First of all, a tunnel and ground model were produced and then reduction effects on stresses by backfilling were confirmed as the result of pure shear loading test. From the result of simulation by FEM of small strain stage, it was clear that calculated values were in good agreement with experimental values. In case the flexible back-filling materials are applied to actual structures, sufficient reduction effects by cutting off tangential forces are verified.

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This paper deals with the problem of nonlinear dynamic responses of a large-scale off-shore structure that is surrounded by thick ice. In modeling the system, a modified joint element is employed to simulate sliding phenomena at the interface between the soil and the structural base, frequency independent semi-infinite elements are used to model the parts of the water system away from the structure. The anisotropy of the ice and material nonlinearity of the soil are considered as well.

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Some investigations are applied to the surface waves in the three dimensional elastic medium. At first, after formulating a thin-layered element and discrete wave number method, the validity of the method is examined from an analytical point of view. It is found that the present method, which represent the solution for the elastic wave motion in terms of normal modes, is equivalent to the analytical solution, when the elastic medium exists on the rigid basement. The present solution and the analytical solution complement each other for the undestandings of these solutions. Next, the characteristics of the surface wave modes of the negative group velocity are investigated using the present method. Impulsive responses, which only have the negative group velocity modes, are synthesized, and compared with the complete solutions. It is found that the effect of the negative group velocity modes on the complete solutions is very small.

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A series of loading tests was made for studying nonlinear behavior of reinforced concrete bridge columns subjected to a significant earthquake. Three types of loading schemes were adopted for six specimens. It was found that the specimens subjected to ground motion in the shaking table tests show considerable different response and failure mechanism with the loading test with the step-wise displacement control. The loading scheme especially the number of loading for each loading step is extremely important. Accuracy of the equal energy assumption and the equal displacement assumption which are often adopted in evaluating nonlinear displacement from elastic response was clarified based on the shaking table test results.

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This paper is concerned with the time domain Green function of fullspace subjected to uniformly distributed loads of impulsive/sudden application. The procedure is based on the integral transform method: the Laplace transform with respect to time and the Fourier transform with respect to space variable along the direction of load distribution. The inverse transform is first carried out on the Laplace parameter numerically along the contour integration path. The inverse Fourier transform is conducted analytically by use of the related integral formulea. Based on thus obtained Green function, the indirect BEM is formulated for elastodynaic initial boundary value problems. Example computations include the response of a halfspace soil (plane strain assumption) subjected to suddenstrip surface loads in order to investigate the effect of the Rayleigh wave propagation. Another example is carried out for a uniform layer on rigid base in order to clarify the effect of the eignemode for the wave propagation.

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This paper describes the simple and practical approximate calculation method of bending moment considering geometric nonlinearity in arch bridges. In this method, the diagrams of the increasing ratio of bending moment obtained by analytical method simplified as possible within the scope of practical design are used. This method can be applied to most types of arch bridges, including sitiffened arch, that should be disigned considering geometric nonlineality.

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