A singular boundary-value problem of an elastic half-space subjected to a force vector at one point of the surface is solved. The force vector has three components which are two tangential and one normal forces to the surface. Solutions to the problem are expressed in orthogonal curvilinear coordinates and are applied to rectangular Cartesian, cylindrical and spherical coordinates, as examples of the orthogonal curvilinear coordinates. The expressions for displacement and stress components are demonstrated in these coordinate systems. They are coincident with the solutions of Cerruti's and Boussinesq's problems when the three components of the force vector are specialized.

View full abstract

An actual discretization is presented for the 3-D tetrahedral element in large displacements. After a decomposition of the total freedom of that element into parameters of position-as-a-rigid-body and those of deformation, the strain-constant interpolation is applied to the defined deformation. The geometrical decompositions and the associated force transformations are developed physically in explicit form. While the material is assumed elastic for finite strains, any geometrically nonlinear effects are taken into account, systematically and rigorously.

View full abstract

A tuning method is formulated to express arbitrary curves with the fuzzy inference rules and the efficiency and the applicability of the method are demonstrated through several numerical calculations. A method to represent the arbitrary curves based on the fuzzy reasoning is applied to a modelling of hysteretic curves on simple plate elements under the repetitive compressive-tensile load. Using this method. so-called Fuzzy Constitutive Relation is applied to the prediction of the cyclic behavior concerned with a section of the thin-walled hollow segments under the constant compressive thrust and the repetitive bending.

View full abstract

Crack closure phenomenon is observed in center-cracked tension (CCT) specimens of structural steel JIS SM520B. The remaining plastic deformation in the wake of an advancing crack causing crack closure is a significant factor of the load interaction effects on fatigue crack growth rates. A prediction model based on crack closure concept is used to compute fatigue crack opening stress and consequently effective stress intensity factor range, ΔK_eff, and correlate it with the measured fatigue crack growth rates. The analytical results are compared with test results under overload conditions. Fatigue crack propagation lives are computed under various load sequences to investigate the load interaction effects.

View full abstract

The behavior of instability of thin-walled, I-shaped plate girders curved in plan subjected to equal end moments is investigated by a nonlinear inelastic analysis. Their inelastic buckling modes are particularly focused. The investigation results show that the curved girders buckle in the three fundamental buckling mode shapes and the possibilities of these instabilities depend on not only the plate-slenderness but also the initial radius of curvature.

View full abstract

This paper proposes a new, unified and efficient method for elastic-plastic hysteresis analysis of truss structures subject to fluctuating loads which is developed on the basis of the principle of minimum complementary energy. For the calculation of complementary energy of each member element due to incremental or decremental leads the origin of stress-strain relationship of nonlinear material in each member element is assumed to coincide with the pre-stressed and pre-strained point resulted by the preceding fluctuating loads. Then member stresses and strains due to incremental or decremental loads are determined by minimizing the total complementary energy of the structure subject to equilibrium conditions at the free nodes. The proposed method is applied to many statically indeterminate trusses with bilinear stress-strain relation material and the reliability, simplicity, efficiency and toughness are compared with those obtained by the finite element method. These results prove that the assumption for the proposed analysis methed is correct and the methed is very powerful and efficient for solving the elastic-plastic hysteresis analysis problems of truss structures subject to fluctuating loads.

View full abstract

In this paper, the secondary buckling phenomena of the elastic rectangular plate subject to the pure bending moment are investigated. The bifurcation points are classified numerically based on the determinant of tangential stiffness matrix and of its diagonal blocks obtained by means of the group-theoretic bifurcation theory. By using the sub-matrices within the whole block-diagonalized one, the informations of the instability points and equilibrium paths after bifurcation are easily obtained. The quantitative influence of the initial imperfections are investigated based on the asymtotic laws and the Monte Carlo simulations.

View full abstract

The moment-curvature relationships for steel box sections subjected to compression combined with uniaxial bending moment are presented in this paper. An analytical model for computing the M-P-Φcurves was proposed. In the analysis, residual stress, initial plate deflection and strain hardening were considered. As a result, an interaction strength formula was proposed for locally buckled steel box columns. The moment-thrust-curvature relationship can be accurately predicted by a set of proposed formulas. Moreover, a set of approximate formulas were proposed to predict the moment-thrust-curvature relationship of steel box column segments without local buckling.

View full abstract

This paper deals with an experimental study carried out to investigate the buckling strength, ultimate stress resultants and their interaction curves of thin-walled stiffened box members due to local buckling. Six specimens of stiffened box members subjected to various combinations of compression, bending and torsion have been tested by using an experimental apparatus.

View full abstract

Pseudo-dynamic tests were performed using six cantilever steel box columns with or without longitudinal stiffeners in order to investigate the behavior of real steel bridge piers under severe earthquakes. Three different artificial earthquake motions of level 2 are used which have been developed by Public Works Research Institute in Japan.
Among the three types of ground motion, the type I ground motion is found to be the severest to the steel bridge piers though the maximum acceleration is the smallest.

View full abstract

During the recent few years, a total of 59 steel box column specimens modeling steel bridge piers have been tested under a constant axial load and cyclic laterl loads in NAGOYA university. Also same type of experiments conducted by other reserchers have been studied.
The influences of the parameters such as width-thickness ratio, slenderness ratio and number of cycles of loading on the strngth and deformation capacity of the tested columns are investigated.
In order to estimate the strength and ductility capacity of columns, simple and effective formulas are proposed which can be used for seismic resistant design.

View full abstract

Local stress properties and fatigue strength of the joint between longitudinal and transverse ribs in orthotropic steel deck plate were investigated experimentally. In order to induce the out-of-plane deformation to the web of transverse rib, loading system which can simulate the passing load was built using three loading jacks. The results of stress measurements and fatigue tests showed that the crossing detail without scallops on the deck plate side had lower local stress and longer fatigue life than that with scallops.

View full abstract

Based on the dynamic substructure technique, the author proposes a static seismic analysis method, the Ground Response Method, for underground structures modeled by a structure and surrounding soil which is represented in finite elements. Through the comparative study of the Ground Response Method with existing static seismic analysis methods, it is verified that the GRAMBS provides the almost equivalent results to those obtained using the Ground Response Method, but the FEM Seismic Deformation Method gives uncertain results. The author proposes a new seismic load which is equivalent to seismic ground strains and modifies the FEM Seismic Deformation Method. Consequently, it is found that both of the proposed methods can be used more widely for various types of underground structures, especially for large-scaled structures and deeply constructed structures.

View full abstract

Impulsive response in an elastic layer overlying an elastic half space is formulated using Love wave modes and leaking modes. These modes are integrated with respect to frequency. From a viewpoint of the ray theory, it can be explained that the leaking modes are generated by the constructive interference of the plane wave propagating in the layer. Effect of the leaking modes are predominantly large near the source point. At a large distance from the source point, on the other hand. effect of Love wave modes only remain, because the leaking modes attenuate rapidly.

View full abstract

A new method for calculating spectrum with respect to horizontal earthquake motion as vector is intruduced. The spectrum is named herein as “Vector spectrum”. Furthermore, a new method for calculating the frequency response function based on the vector spectrum is proposed. These methods were applied to the observed earthquake motion and were compared with the results calculated by the usual method. As a result of these, it is found that vector spectrum is useful to evaluate the frequency characteristics of horizontal earthquake motion quantitatively and that the proposed frequency response function is also useful as the index to represent the amplification characteristics of earthquqke motion because it has the high equivalency and stability in comparison with the usual method.

View full abstract

The vibration, buckling and dynamic stability of a non-uniform rectangular plate on a Pasternak foundation under the action of a pulsating in-plane load is studied. The small deflection theory of the thin plate is used. This problem is solved by using the Hamilton principle to drive time variables. The dynamic stability is solved by the harmonic balance method.
Natural frequencies and buckling properties are shown at first. Then, regions of instability which contain simple parametric resonances and combination resonances are discussed for various boundary conditions and parameters of Pasternak foundation, non-uniform cross-section and thermal gradient.

View full abstract

The spatial correlation of earthquake ground motion is examined in terms of the coherence function based on twelve earthquake events observed at the Chiba array. Considering a preliminary analysis and previous works about the coherence function, a Gaussian coherence function model is suggested for space-time earthquake ground motion assuming its limited portion to be homogeneous and stationary. A nonlinear regression analysis is conducted for estimating parameters of the coherence function model, and the average and variance are evaluated for the regression coefficients obtained from each event. The frequency-dependent correlation scale derived from the model is discussed. Finally, application of the coherence function model to the records observed at the site in Lotung, Taiwan, is also carried out.

View full abstract

Dynamic response of a dam interacted with foundation and reservoir is evaluated by an FE-BE method in time domain. Interaction effects and radiation damping are expressed in terms of reduction rate of V_s, internal damping ratio and added mass for several impedance ratios. The evaluated results applied to conventional FE analysis is presented. Interaction effects on incident seismic wave are also discussed. Both the FE-BE method and the FE one are applied to earthquake response analysis of an actual dam. The simulated responses are almost similar to each other, showing a good agreement with the observation.

View full abstract

Earthquake observation is conducted at the site of a reinforced-concrete retaining wall with expanded polystyrol (EPS) backfill. The EPS was adopted since the bearing capacity of the site is not large enough for an ordinary soil embankment. The records show that the EPS backfill vibrates almost in the same mode with the ground and that the tensile force of anchor is negligibly small. A finite element analysis is also conducted and the results of the analysis agree well with the observation. Stability analysis of the retaining wall reveals that if the current stability analysis method for the ordinary gravity-type retaining walls is applied to the EPS retaining walls, the safety factors for sliding and overturning become unreasonably small.

View full abstract

In most system optimization approaches, continuous optimization techniques have often used. However, in generally, structural system parameters consist of both discrete and continuous elements. Hence, an efficient algorithm which is relevant to a discrete system is desirable.
In this study, an algorithm is proposed to estimate the discrete parameters, based on an importance sampling procedure of a Monte Calro method. In this method, discrete system parameters which are ramdomly sampled from an importance sampling, are updated with objective function, and numerical examples are worked out to demonstrate the discrete parameters optimization of the proposed algorithm.

View full abstract