Bifurcation buckling behavior of polygonal-shaped, truss dome structures is studied with the aid of a group theoretic method. This study extends the previous research on simple regular-polygonal truss domes to those with greater number of degree of freedoms and with much more realistic configuration. Unlike the previous research, radial and rotational displacements of the domes are included here in describing their bifurcation modes, in addition to vertical displacements. The method has permitted one to obtain potential bifurcation modes of the domes and hierarchies of bifurcation paths under axisymmetric loadings without performing bifuraction tracing analyses. The applicability of group theoretic method to regular-polygonal domes has been fully assessed through this study.

View full abstract

This papar offers a group theoretic study of symmetry breaking bifurcation points of truss dome structures. A dominant role of symmetry in bifurcation phenomena has been demonstrated through case studies performed on bifurcation points of a series of reticulated regular, polygonal-shaped, truss domes subjected to axisymmetric loadings. Various characteristics of bifurcation points are described in relation with the level of symmetry of main and bifurcation paths. Several rules governing bifurcation points have been derived through these studies with an aim toward the development of a more complete theory in the future.

View full abstract

The discussion, in this paper, is confined to the natural vibration of the fill dam which can be described by the truncated wedge of inhomogeneous rigidity: G=G_m·(z/h)ⁿ where G: modulus of rigidity, z: distance from the top of dam, h: dam height, n: rigidity index, and with rectangular canyon shape. Equilibrium of the bending moment and the shearing force in the vertical direction, together with the shearing force and twisting moment in the transverse direction, leads to the fundamental dynamic equations of the prescribed model of dam.
Finite difference method is used to determine the natural frequencies and natural modes of the dam. The frequencies and the modes are computed for the various rigidity index n, the canyon width and the bottom width, the results are put in order in graphical or tabular forms.

View full abstract

The stiffness equation of linearized finite displacements for straight thin-walled members with inelastic material is derived. An arbitrary orthogonal coordinate system with a single reference point across the section need be introduced in the formulation, which is a clear distinction from the elasticity problem. Also distinct from the elastic analysis is a need to evaluate the magnitude of strains from time to time because of the dependence of the tangent modulus on strain levels. Illustrative examples are given to demonstrate the proposed method for the inelastic finite displacement analysis of spatial thin-walled members, with a simplified consideration on the effect of shear stresses.

View full abstract

The theory of curved, thin-walled, multi-cellular beams and a method of determining the stresses and deformation, including warping, are presented. The equations governing small displacements in the linear elastic range are derived using the principle of virtual work. The solution includes the distortion of the cross-section, the influence of shear deformation, and the variation of longitudinal fibre curvature.

View full abstract

An analysis of fatigue crack growth, using a fracture mechanics concept, and fatigue tests are performed to quantitively estimate the effect of weld defect (blowhole) size and shape on the fatigue strength of partially penetrated longitudinal welded joints. In this analysis, a blowhole is regarded as a ellipsoidal cavity with small initial cracks along its wall. Number, interval, size and shape of initial cracks are determined by closely observed results on the fatigue crack initiation and propagation from the blowhole. The equivalent circular crack size for a blowhole is presented to predict fatigue life by using a simplified approach. The predicted fatigue life is compared with experimental results.

View full abstract

It is well known that closed-form solutions for elastica problems can be expressed by elliptic integrals. However, the problems solved so far are mostly based on inextensional beam theory where the elongation of member axis is ignored.
Herein, general solutions are derived for the extensional theories such as finite displacements with finite strains and those with small strains. In these derivations, special efforts are made to reduce the elliptic integrals to normal forms in order to obtain highly accurate solutions.

View full abstract

A new composite girder with prestressed precast concrete slab has been developed by the authors et. al. In applying this new composite girder to the highway bridges, there are a few unclarified problems for evaluating the fatigue behavior of composite girders. especially the cracking of precast concrete slab under the heavy traffic vehicles. In order to investigate the effects of moving vehicles on the proposed composite girders. five model girders are tested systematically under the repeated loads making use of moving vehicle apparatus. This paper reports and discusses the durability of composite girder with prestressed precast concrete slab panels through the test results.

View full abstract

Minimum weight design method of pedestrian bridges taking vibration serviceability into consideration is studied. To shorten the computatinal time for structural analysis, an approximation method of vibration serviceability analysis is studied and applied successfully. Two-level optimization technique is also studied. In structural level optimization, design variables are reduced to the geometrical moments of inertia from the sectional sizes of primal problem. Member level optimization is formulated as an optimization problem easy to solve and the way to find the optimal design is presented for both continuous and discrete plate thickness. Simple, two-continuous and three-continuous pedestrian bridges are designed by the proposed method and the efficiency and the validity are shown.

View full abstract

A simple analysis method is presented for calculation of forces in sway bracing members of composite-girder bridges. The purpose of development of this method is its application to evaluation of effects of structural types and loading conditions on fatigue crack growth in the region of welds at tops of transverse stiffeners for main girders.
Reinforced concrete floor slabs and main girders are modeled by three-dimensional plate elements, and originally introduced offset beam elements with six degrees of freedom per node, respectively. Sway bracings are considered as plane frames, and stiffness matrices of plane frames are contracted to make sway bracing elements whose nodal points are set only on the planes of floor slabs. Thus, an entire bridge is modeled as a stiffened plate.
Calculated results show that maximum axial forces in sway bracing members coincide well with those obtained by measurements on a bridge in service. The differences between the calculated and measured values are less than 20 percent.

View full abstract

The stress reduction factor to correct for the difference in calculated and measured stresses in bridges is studied. Stress measurements are carried out with control trucks 20 tons in weight and traffic loads on seven bridges on express highways. Values of stress reduction factors are evaluated from both stresses due to control trucks and equivalent stress ranges due to traffic loads during a single day.

View full abstract

The objective of this paper is to discuss analytically the mechanism of dynamic failure of SDOF systems with structural instability. Furthermore, the effects of natural frequency, static load, viscous damping, and magnitude and type of dynamic load on the displacement response and the various energy quantities are also numerically investigated.
As a result, it is revealed that the effective input energy is the most important response parameter which determines the dynamic ultimate state.

View full abstract

In this paper we propose a cyclic plasticity model with high accuracy to predict elasto-plastic behaviors of uniaxial steel members subjected to complicated repetitive loads. The model is based on the multi surface plasticity model and material property parameters introduced are a couple of fundamental surface size functions and weighting functions to describe sizes of state surfaces at arbitrary stress-strain phases. It is revealed that the hysteretic model proposed, by which quasi-static fluctuating stressstrain relations can be predicted, is sufficiently accurate from the engineering point of view.

View full abstract

The fatigue crack growth behavior in the visinity of ΔK_th under computer simulated variable amplitude loads of highway bridge is studied experimentally. Fatigue crack growth under these load fluctuations is evaluated by using the linear damaged rule with paris law and ΔK_th including the influence of stress cycles below ΔK_th with adequate accuracy.

View full abstract

The purpose of this study is to investigate the effect of frequency characteristics and duration of input earthquake motion on the energy responses of structures. In this study, numerical analysis for bi-linear SDOF structures with wide ranging structural parameters was carried out by the use of twelve artificial earthquakes, each varying in duration and frequency characteristics. From the examination of analytical results, it is found that the frequency characteristics of the input earthquake motion has a large effect on the periodical characteristics of all responses of the structures, such as elastic maximum velocity (V_emax), elastic input energy (E_ie), hysteretic energy (E_hp) and so on. It is also found that the duration considerably affects the value of energy responses such as E_ie and E_hp.

View full abstract

Response spectra of strong-motion accelerograms obtained in Japan were dealt with statistically using a multiple regression technique and the spectra at a rock site were scaled in terms of earthquake magnitude. Papageorgiou and Aki's model was considerd as an useful inhomogenous faulting model to explain the spectra. After incorporating the theoretical spectra due to the model with the statistical ones, a scaling law for the paramerers of inhomogeneous fault was derived. It was shown that the localized crack radius of inhomogeneous fault increases with earthquake magnitude M, giving a size of about 1km for M=6 and about 11km for M=8, and the total number of the cracks on the fault is camparatively stable irrespective of M, namely, it ranges from 10 to 20 at most between M=6 and M=8.

View full abstract

A generalized solution of Elliott's solution to transversely isotropic solids is proposed in cylindrical coordinates. The solution consists of five potential functions and includes some new terms corresponding to equal roots of a quadratic equation. When elastic constants of transversely isotropic solids are replaced with those of isotropic solids, the solution is exactly coincident with a general solution to isotropic solids. Expressions for the potential functions are presented in referring to non-axially symmetric problems of finite, hollow cylinders. As an application of the solution, an axially symmetric problem of a finite cylinder subjected to a band load is analyzed.

View full abstract

The modal damping of flexural oscillation of suspended cable models was measured and is reported in this paper. Numerical analyses of free oscillation of the cables were also made to calculate natural frequencies, normal modes and additional dynamic strains. It is found that the additional dynamic strain of each normal mode is the primary cause of modal damping and that the damping of the first in-plane symmetric mode is much larger than that of other modes around the ‘crossover’ point of the first and second natural frequencies. The effects of the span length, the tensile rigidity and the chord inclination are also investigated.

View full abstract

The influences of the transition radius of fillet, and the width of flange on the fatigue strength of flange gusset joints are examined by using the fracture mechanics concept. The results of this study have been used as basis for revision of fatigue design code for the Honshu-Shikoku Bridges.

View full abstract

A method is presented for the transient flexural vibration analysis of clamped thin Voigt-viscoelastic rectangular plates. The analysis is done by making use of a series of characteristic beam-functions which identically satisfy the boundary conditions and the Stokes method to solve the governing differential system having viscous damping. An approximate expansion formula is developed and applied to the transient flexural vibration problem of the clamped Voigt-viscoelastic rectangular plate subjected to a concentrated transverse arbitrary exciting load.

View full abstract

In this paper, a strut model is developed to evaluate the ultimate strength of the compression members in truss plane. The struts are restrained by the rotational springs at both ends concerning the restraining effect of the adjecent members, and are compressed by the axial load with eccentricity concerning the end moment. The accuracy of the ultimate strength analysis using the strut model is examined by the comparative calculations of the full truss models. The relations between the ultimate strength of the struts and the restraint, eccentricity and slenderness parameters are clarified by a number of parametrical calculations. And a design formula on the strength of truss compression members is proposed as a function of these mechanical parameters.

View full abstract

Elasto-plastic shear buckling of square plates containing centrally located circular holes is investigated analytically. Critical loads are obtained by the Rayleigh-Ritz method in combination with the finite element method used only to evaluate in-plane stresses. The plates are subjected to uniform shear stresses or uniform shear deformations. Ratios of the hole diameter to the plate length are 0.15, 0.3, 0.5, 0.7 and 0.85. The influence of the circular hole and in-plane loading condition on buckling strength is considered on various sized holes. The results suggest that the buckling strength in the uniform shear deformations is higher than the uniform shear stresses in the elastic and elasto-plastic ranges. These phenomena are more remarkable for the clamped plates than the simply supported plates in the elastic range and for the simply supported plates than the clamped plates in the elasto-plastic range.

View full abstract

When the structural reliability analyses are performed using stochastic finite element method, the spatial variations of material properties are so significant that they must be treated as random functions of the spatial coordinates. Spatial variation of material properties for each element is considered by locally averaging the quantity over the element. Displacements are considered in terms of the integration of each element's strain. This paper evaluates the relation between element discretization and random functions of the spatial coordinates with respect to the accuracy using Monte Carlo simulation. This paper includes a brief discussion on the applicability of stochastic finite element method using first-order gaussian approximation, comparing that of Monte Carlo simulation.

View full abstract

Since urban freeway bridges were opened for traffic more than ten years ago, there have been so many reports on the necessity of reparing cracks and deformations. For an example, the cracks at the connection plate between girder and lateral load-distribution cross beam are reported, and also the cracks at the connection plate between girder and sway bracings for composite plate girders. The investigation for the cracks, the establishment of repair and reinforcement method, and the feedback to the design standard specifications are now urged and many arguments are in progress in many places. In this research, we would like to find out one of the effective solutions by fabricating the test girders with the previous design and with present design, investigating the effects of the rigidity of the cross beam upon the fatigue crack and comparing and discussing the proposed structual details.

View full abstract

There are a large number of inequality constraints in a structural optimum design problem, however, an optimum design point is usually located on active constraint surfaces that are equivalent to equality constraint. If we select such equality constraints among the inequality constraints, the inequality constrained problem can be transformed into an equality constrained problem. An optimum point of the new problem that is subjected to the selected equality constraints is obtained by using the Lagrange multiplier technique. In this paper an optimization method in which selection techniques are used is proposed, and a simple example on optimum solutions of composite plate girders is shown.

View full abstract

In this paper, for the lateral-torsional instability of beams between cross members, the following investigations are carried out;
(1) The basic strength curves of rolled and welded laterally unsupported beams with initial clockedness and residual stresses are obtained by using the FEM analysis.
(2) A formula on the ultimate strength of elastically restrained beams at both ends is developed with concerning the basic strength of beams.
(3) The strength of the isolated beam models restrained by intermediate descrete supports are parametrically analized.
(4) The restraining effects of the adjecent members and bracing systems on the lateral buckling strength are investigated more precisely by the FEM analysis. And the practical formulae obtained by modifying Nethercot-Trahair method based on the elastic buckling theory are proposed.

View full abstract

There are few studies on ultimate strength of steel plates under in-plane combined loading. Therefore, their basic strength curves of specifications in many countries cannot help being based on the elastic buckling theory. Evaluation of the ultimate strength is essential to promotion of the limit-state design method.
This paper presents characteristics of ultimate strength of steel plates under in-plane bending and compression, on the basis of the elasto-plastic finite displacement theory. The interaction curves also presented, to evaluate the ultimate strength which has been computed making use of FEM.

View full abstract

In this paper, an attempt is made to develop an expert system for evaluating the structural durability of bridges. The damage assessment of reinforced concrete decks is considered, because their failures have been occasionally reported. Similar to the usual expert systems, this system consists of interpreter, data-base and rule-base. All rules are represented by means of production rules with certainty factors. Both data-base and rule-base are divided into several groups to reduce the execution time and make the modification of rules easier. An application example is presented to illustrate and demonstrate the expert system developed herein.

View full abstract

Coupled vibrations, in which horizontal and rocking components coexist, of circular disk on elastic half space are analyzed rigorously by means of the direct integral equation method. The conventional methods for the dynamic compliance theory of circular disk have depended exclusively upon the relaxed condition of contact. In the circumstances, the horizontal and the rocking modes were artificially separated; consequently, they could solve the coupled vibrations only approximately, and there was noticeable difference among the results obtained. One can solve this problem rigorously by means of the direct integral equation method which was established recently. In this paper the direct integral equation for the coupled vibrations is presented. It is solved numerically, and the stress of contact as well as the dynamic compliance are determined highly accurately.

View full abstract

A rational procedure for determining design load combination and safety format is proposed, in which reliability-based structural design is developed on the basis of limit state probabilities. Load factors or safety factors associated with each design load combination in a safety format are optimized numerically through the objective function so that uniform level of structural reliabilities evaluated by limit state probability can be realized to the target, regardless of structural types and dimensions. Conceptual diagram of limit state probabilities is introduced to interpret the structural reliability, and the methodology to estimate the factors is showed with numerical examples using structural models and load combinations.

View full abstract

The method with the separation of rigid body displacements is most commonly used in the finite displacement analysis of structures. This method introduces local moving coordinates in order to remove the rigid body rotations of respective finite elements. The local coordinates utilized in the analysis of plane frames are classified into two kinds and the choice of the local coordinates is known to have an effect on the accuracy and the convergence of the solutions.
This paper precicely examines the theoretical effect of local coordinates on the accuracy of the finite displacement analysis for plane frames.

View full abstract

This paper presents the both experimental and analytical approaches to evaluate the energy absorption capacity of cantilever steel pipe for the development of the impact resistant design of the A-type slit Sabo dam. Initially, the static and impact experiments are performed in order to measure the relationship between load and deformation. The energy absorption capacity is obtained by integrating the area of the load-ultimate deformation curve. Secondary, the impact response analysis is performed by modelling the cantilever pipe into the simple two degrees of freedom system accounting for the local deformation of pipe. It is confirmed that the impact energy calculated by the impact response analysis is relatively good agreement with the one measured by the impact test. Therefore, it is found that these results will provide the useful data for the impact resistant design from the viewpoint of energy design.

View full abstract

The crack detection ability was compared and investigated using various non-destructive testing methods on the fatigue cracks generated on the fillet welded joint. As a result, for the detection of cracks, the magnaflux examination and the eddy cullent examination were found effective. However, in the case of dye penetrant examination, even wide cracks on plate surface could not be detected. On the other hand, for the estimation of the crack depth, the peak echo method using the ultrasonic examination was found excellent, allowing the detection of cracks with depth larger than 2.5mm, with an accuracy of better than 1mm.

View full abstract

The finite strip analysis was performed for flange local buckling of curved I-girders with warping stress as well as bending stress, using the total flange model supported simply along the flange-web connection.
It was shown that the correct buckling load cannot be obtained from the half flange model separated along flange-web connection, because of curvature and warping normal stress. The formulae were obtained for width-thickness ratio of curved girder flange, by a slight change of the current specification for straight girders of highway bridge. introducing the parameters considered the effect of warping normal stress.

View full abstract

Bannosu Viaduct, one of the Honshu Shikoku Bridges, neighboring to the Bisanseto Bridge, is planned to carry 4 lane roadways and 4 railway lines. This viaduct has such high piers as 40 to 70 meters height and its supporting layer is 30 to 70 meters deep from ground surface.
This viaduct is therefore essentially liable to oscillate, and the earthquake resistant design is important in structural design.
The pier is adopted the type of I section with earthquake resistant wall to secure the rigidity perpendicular to the bridge axis. In this type. it is feared the shear rigidity of wall is reduced with crack of concrete by drying shrinkage or earthquake.
In this paper, the earthquake resistant design of I section pier considering the reduction of shear rigidity of wall is mentioned.

View full abstract

An input model properly representing mutually correlated earthquake ground motions is inevitably required in dynamic analysis of large scale line-like or network-like structures such as suspension bridges and buried pipelines. In this context, this paper investigated a simulation method of spatially as well as temporally variative earthquake ground motions by utilizing an autoregressive model where the properties of the actual propagating ground motions were taken into consideration in the model representation. The simulation method was justified by showing the consistency of the properties of simulated waves to the prescribed ones.

View full abstract

This paper deals with the harmonic response of the ground surface around a rigid structure with rectangular base resting on an elastic ground and being excited by the traveling wave from an adjacent source. The contour diagrams of the amplitude ratio defined as the ratio of displacement in the wave field with the structure to the one in the free wave field are examined. Though the screening effect of waves by the structure is similar to that by trenches in the range of high frequencies, this effect is caused by the interference of the wave in the free field and the one in the scattered field excited by vibrations of the structure.

View full abstract

In order to consider the effects of viscoelastic properties of horizontal multilayers for frequency response functions to incident P or SV plane harmonic waves at an arbitrary angles, loss factor Q^-1 as attenuation factor and generalized Snell's law which were applied to inhomogeneous wave propagation, were introduced into well-known Haskell type matrix.
In the present paper, the formulation is exact in that no low-loss approximations are made. Quantitative estimates for the characteristics of frequency response functions of both directions of horizontal and vertical motion for inhomogeneous waves to practical subsoil layers were derived, and compared with those of elastic layers and those of some special case of viscoelastic layers.

View full abstract

In order to investigate disaster restoration and system performance recovery of lifelines, a model is required which can forecast quantitatively time sequential changes in the restoration process. For this purpose, a functional evaluation model which treats the mechanism of disaster's influence, was described, and then a quantitative and realistic functional evaluation model which takes into consideration inter-chain between lifelines was derived. Utilizing a method of system dynamics (S. D.), the whole functional evaluation of electric power and water supply systems which play the most important role in lifeline systems was investigated.

View full abstract

A method was developed to identify parameters on a hysteretic restoring system of non-degrading type by appling the Extended Kalman filter incorporated with a weighted global iteration. The method is based on a simplified versatile hysteretic model by Bouc and Wen. By this method a nonlinear model of non-degrading type equivalent to any hysteretic system may be identified in terms of the model's parameters at the stage of their stable convergency to optimal ones. Numerically simulated data were used for the verification of the method.

View full abstract

The seismic behavior of repaired/strengthened RC structures is defficult to analyze theoretically. However, this paper will show that analysis can be effectively done by using the so-called HYLSER (HYbrid Loading System of Earthquake Response) system. Three repairing/strengthening methods were considered: (i) the epoxy resin grouting method; (ii) the reinforcing bars welding method; and (iii) the steel plate covering method. Obtained stiffness deteriorating processes were verified to be almost the same as those of the original ones if adequate repairing methods were performed.

View full abstract

In this paper, considering that valuable information concerning the aseismic design of structures are hidden in saturated records, a more resonable method to mend the Japan Meteorological Agency's (JMA) low-magnification seismograms is proposed through a shaking table test. This method is able to mend a saturated seismogram with an error lower than 10% for engineering purpose. Seven JMA's records with saturations obtained during the 1968 Tokachi-oki earthquake, the 1978 Miyagiken-oki earthquake and the 1983 Nihonkai-chubu earthquake are mended by the proposed method. Consequently, some mended displacement seismograms are found to give much higher response spectra than design values for long-period (5 to 15 seconds) structures.

View full abstract

This study reviews the non-destructive testing methods and evaluates their reliability and adaptability for the detection of fatigue cracks which develop from a blowhole at the root of the corner weld. X-ray, ultrasonic, magnetic particle, liquid penetrant, and eddy current testing methods are provided. For the internal crack, ultrasonic testing appears to be desirable. Minimum crack sizes detectable are about 8mm∅ with a high accuracy. For the crack opened to the surface, eddy current and magnetic particle testing give a fair estimation. But it must be understood that fatigue cracks will be missed by liquid penetrant testing.

View full abstract