This paper concerns the ultimate strength of thin-walled box stub-columns designed to fail by interactive plate buckling between the plate elements rather than by overall column buckling. An experimental study is described, conducted using nine stub-column specimens. The ultimate strength of stub-columns with initial imperfections and residual stresses is investigated using a finite element method (F. E. M.) based on elasto-plastic large deflection theory. Finally, two simplified design methods are proposed for evaluating the ultimate strength of stub-columns.

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The live loads for fatigue design and maintenance of highway bridges are studied based on computer simulations. Simulations of traffic live loads are carried out under various traffic volumes and constitutions of vehicle types. The type of vehicle, the vehicle weight and the array and headway of vehicles are cosidered as random variables. Bending moment responses of simply-supported one-lane girders of various lengths are calculated under usual traffic conditions. Moment ranges are analysed by using the rain flow method. For the evaluation of fatigue damage, the equivalent moment range and the reduced number of L-20 or T-20 live load are presented.

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In order to evalulate the effect of time-dependent material propetrities on the structural behaviour of steel frame structure in fire, a simulative study is carried out by using the experimental functions on the material properties obtained by the high temperature tensile and creep tests. The paper contains the details on the material tests. One-span one-story steel frame in fire environment is analyzed by one-dimensional FEM by assuming both small and finite deformation under the various conditions on the selection of creep property, on the selection of rate-dependent properties of elastic-limit strength, hardening parameter and modulus of elasticity, and on the selection of finite deformation assumption. A suggestion on the adequate level of exactness of the material properties is given based on the numerial results.

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Shearing stress concentration at reentrant corner in built-up box section is studied using an electrical analogy. In the built-up box section, for truss chord members, this corner is made usually by partial penetration groove or fillet weld at outside because of the difficulty of welding on inside corner. Therefore, a sharp reentrant corner is induced and high stress concentration may occur. In the case of partial connection, besides, the tortional rigidity is reduced and angular twist increases. The test results show that the stress concentration at weld root of partial penetration is about 2 times higher than that of the rolled section and the tortional rigidity decreases about 35% in comparison with that of fully penetrated section.

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The web of thin walled curved girder deflects out of surface by bending moment because of it's curvature. This deflection causes the deformation of the cross section of the curved girder, by which the behaviour of curved girders will be complicated.
In this paper, the part of curved girders between vertical stiffeners was analysed, regarded as sectoral plates and cylindrical shell panel structure. The interaction of flanges and web panel was also considered and evaluated.
Several numerical examples show that the deformation of curved I-girders is affected by tosional behaviour of the flange besides shell action of the web.

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The purpose of this study is to present a solution scheme for the problem of out-of-plane instability of thin-walled members. Based on the second order kinematic field, the stiffness equation of linearized finite displacements is formulated for thin-walled members, and given in a concise and explicit form. As a particular case, an important and practical application is made for the lateral-torsional buckling of in-plane beams and frames. Numerical examples are given for straight and curved members, and are compared with existing results. The analysis scheme presented is proved accurate, efficient and versatile.

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An investigation of the effects of cross sectional distortion on the elastic behavior of a thin-walled open section curved beam is presented. In particular, the influence of the distortion on the longitudinal stress and on the transverse bending moment is studied.
The formulation of the problem is derived from the principle of virtual work by assuming the strain field of distortion, and a practical modification of the conventional curved beam theory is established.
The theoretical solutions are compared with the experimental results, and the effects of curvature, longitudinal stringers and transverse stiffening frames are discussed for design purposes.

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This paper presents a frontal-skyline method for reducing unsymmetric matrices which frequently arise in applying the finite element method to boundary value problems. The method makes use of the basic frontal procedure but allows the front to increase in size using compact skyline storage whenever core storage is available.

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In the finite displacement analysis of space frames, a formulation by means of the ordinary direct Lagrangian method makes the governing equations highly nonlinear and complicated largely due to the finite rotations in the space. For this reason, space frames are more often analyzed by the method with the separation of rigid body displacements, compared with plane frames. Nevertheless, its theoretical equivalence to the solutions of the direct Lagrangian method have not been examined so far except that for plane frames.
This paper examines the theoretical convergence and accuracy of the method applied for the analysis of space frames.

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Strength evaluation and optimality of steel compression members are examined focusing on the interactive behavior between overall and local failures. The results of optimization indicate that optimal and efficient design is basically obtained in the region where the local buckling does not occur before yielding of component plates, even if the occurrence of local buckling is allowed for design. This implies that restricting the local buckling by specifying the maximum width thickness ratios may be worth while again to consider to accommodate in design specifications, particularly for ordinary civil engineering structures. The practical importance of allowing the occurrence of local buckling may appear only in the designs of large scale and/or specialty-oriented steel structures and components.

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This paper presents the flexural stress analysis by considering the shear lag phenomenon in the cable-stayed bridges with multi-cellular box girder. For the shear lag phenomenon in the flange plates of such box girders, the parabolic curves with second and fourth oredrs are assumed, then the corresponding variations of the effective width ratio are investigated and discussed by altering the various shear lag parameters. Based upon these parametric analyses, the additional moment due to shear lag is, moreover simplified to apply the flexural stress analysis of the cable-stayed bridges. Finally, this proposed method is demonstrated by the numerical examples of a cable-stayed bridge with flat multi-cellular box girder.

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This paper presents a study on the deformation behavior of thin-walled welded box beams under cyclic bending. The specimens are tested under two-point load bending to have a uniform moment occur in the central segment of the beam. Two different simple models are introduced to predict analytically the cyclic moment-curvature curves of the beams. The numerically obtained stress versus strain curves of plate elements are utilized to calculate the moment-curvature curves.

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The effect of low-temperature stress relieving was examined, using a partially penetrated groove weld with a blowhole. Box section specimens measuring 200mm (W)×250mm (H), made of 15mm thick 600MPa class steel were tested.
The result proved that stress relief could reliably improve fatigue strength. Compared with the as-welded specimen, the 2000 000-cycle strength of the treated weld increased by about 20MPa.

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This paper presents an efficient 3-dimensional sesimic analysis for a soil-foundation-superstructure system. The dynamic substructure method is used to advantage in formulating the whole system as an integral of the far-field, the near field, the foundation and the superstructure. An axisymmetric modeling is taken for the soil and foundation in order to account for its 3-demensional body with use of the Fourier harmonics expansion for response in the circumferential direction. The interface or the interbody partitioning is applied between foundation and surrounding soils, depending on the type of the foundation concerned. The general 3-dimensional analysis is carried out for the superstructure for its complex geometry. The coupled motion between the soil-foundation system and the superstructure is formulated from the component modes method to attain a drastic reduction of the degrees of freedom for frequency response analysis. Case studies are given as numerical examples.

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In order to clarify soil-pile dynamics, a new experimental method using an electromagnetic induction type shock wave source was developed. In the experiment, a ground model was made of water-cured urethane polymer, and a pile of urethane was buried in this gel-like ground. An impulse with duration time of 0.5ms was given to the pile head by the shock wave source. This device consists of an aluminium circular plate and a flat solenoid coil close to this plate. A capacitor discharge through the solenoid serves as the energy source. Using this device makes it possible not only to estimate exact response characteristis of soil-pile systems pretty well but also to follow sharp wave fronts by photoelastic experiments.

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Dynamic Finite Element Method is frequently used in analyzing wave propagation problems. In the case of infinite or infinite half media, the presence of artificial boundaries introduces wave reflections from boundaries. Authors tried to solve the problem applying Smith-Cundall's method and extended the method to three dimensional problem. Smith-Cundall's method is to solve the problem by superposing two types of reflected wave from Dirichlet's and Neumann's boundaries. This method is theoretically complete. Authors made clear the weak point of the method, however, the influence of the weak point on the computed results is small, therefore, the results by this method is reliable. This method treats problems in time domain, so nonlinear problem such as liquefaction can be solved by this method in near future.

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Concerning the dynamic response analysis based on the equivalent linearization of the restoring force characteristics of structures, some examinations taking the mechanism of the analytical procedure into consideration have been conducted with one-degree-of-freedom system. As the results, the extent of difference between the solutions by equivalent linear method and exact ones for both steady and unsteady conditions have been clarified. The causes of difference have been also clarified. With these results the limit of validity in the application of the equivalent linear solutions to the seismic design of structures has been shown clearly. Throughout the process of above consideration some of new knowledge concerning the numerical procedure for non-linear dynamic analysis have been obtained and reported.

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The ultimate strength of elasto-plastic columns under the condition of parametric resonance is presented in this paper. Special attention is paid to the influence of the initial crookedness, the magnitude of the periodic and static axial force, slenderness ratio and the Bauschinger effect on the dynamic behavior.
The dynamic characteristics are obtained by using a numerical in-plane dynamic analysis which takes both the geometrical and material nonlinearities into account.

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It has been reported that many telecommunication cables of figure-8 section suffered from operating problems and sometimes even failed because of wind-induced large amplitude oscillation, the so-called galloping of cable. In this study, three-dimensional figure-8 cable models are tested at the wind tunnel and aeroelastic behaviour of the cable was observed in detail. It is found that wind-induced significant change of the angle of attack of the cable relative to wind is the fundamental cause of galloping. The critical wind speed that triggered galloping and the initial direction of the self-excited cable motion are explained by the Den Hartog's quasi-steady treatment of the aerodynamic force with some modification.

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As for dynamic shear deformation of an elastic layer of finite length overlying a rigid half-space, such vibrational characteristics as natural frequency and vibration mode shape are well characterized by Love waves in the layer. This fact is demonstrated first by several kinds of laboratory experiments, and next by theoretical discussions. On this basis, impulsive response of the layer is formulated by the mode superposition procedure, giving a well-known statement of Love wave characteristics such as the quarter wave length law and the reciprocal theorem, and indicating a good accordance with the experimental results.

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Shaking table tests of model blocks were conducted to study sliding behavior of a rigid body in the water during earthquakes. The accelerations and hydrodynamic pressures on the model block decreased instantaneously on set of sliding and remained the same levels during sliding. The static and dynamic coefficients of friction obtained from the vibration tests in consideration of the added mass of which inertia force corresponded to the hydrodynamic pressures on the model block were almost the same values as those measured by Euler's method. A method to estimate the displacements of the sliding block during earthquakes was presented. The displacement calculated from the horizontal and vertical base accelerations showed relatively good agreement to the measured value.

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It is necessary to study the behavior of energy response of elasto-plastic multi-mass systems to develop the earthquake resistant design based on the energy concept.
In this paper, for the purpose of getting fundamental information about the behavior of energy response in elasto-plastic multi-mass systems, six mass systems which represent the systems having bi-linear hysteretic restoring force and subjected to sinusoidal excitation are used in the numerical analysis. The response characteristics of elasto-plastic multi-mass systems is examined basically and the linearized estimation of input energy for them is analyzed by the method of modal analysis. The control method of input energy distributed to each story of multi-mass systems is represented.

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The aeroelastic behavior of the overhead telecommunication line of figure-8 section is studied analytically in order to investigate the wind-induced galloping motion of the line. The governing equations of the telecommunication line are firstly derived taking account of its torsional displacement. Numerical analyses are also made on the wind-induced static deformation, the linear free oscillation under wind load and the dynamic response in a steady wind. The results of numerical analyses explain well the experimental fact seen in the wind tunnel test reported in Refs. 1)-4) and it is found that the galloping of the figure-8 telecommunication line can be simulated to some degree using the present analysis.

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Nowadays, steel bridge members are inspected through shop assembly in factory yard at the final process of their fabrication. This investigation proposes an inspection system which excludes the process of shop assembly. To realize this system, however, precise knowledge concerning the accuracy of fablication and assembly is indispensable.
For this reason, main members of a plate girder and a composite girder were measured and data about the accuracy of assembly were gathered. This report studies the relationship between errors of memberes and the accuracy of shop assembly. Such data have never been obtained by conventional inspections. As a result, it was confirmed that members are fabricated precisely enough not to induce any stresses in assembling them. This result will contribute to the development of good inspection systems.

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Fatigue strengths and fracture characteristics of large-size gusset joints are described in this paper. High strength steels of 30 and 45mm thickness are used for specimens. The specimens are fabricated using a similar procedure to that for the actual bridges. In the three types of in-plane and three types of out-of-plane gusset joints, the fatigue strength decreases as stress concentration increases. The results from this study have been used as basis for the revision of the fatigue design code for the Honshu-Shikoku Brideges.

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The torsional rigidity of H-beam with transverse stiffeners will increase due to its stiffeners, and the average angle of rotation per unit length will be smaller than that of H-beam without stiffener.
In this study, torsional experiments of H-beams with transverse stiffeners were performed. From these results, the torsional rigidity of the H-beam with stiffeners was evaluated as the imperfectly restricted warping torsion caused by transverse stiffeners, and the torsional strength was discussed.

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In this paper, it is investigated that how axial load and buried length of pile-head into footing under lateral load effect on the stress distribution of footing concrete on pile-footing interface. For the evaluation of the effects, the connection between pile-head and footing is treated as an axisymmetric body subjected to non-axisymmetric loading. and the evaluation is performed by Finite Element Analysis. For the analysis, it is assumed that debonding or slip never occur on the interface.
The results suggest that axial load and buried pile-head length have significant effects on the stress distribution, and the cohesion on the interface is very significant factor on the stress distribution.

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An analytical model for two-dimensional finite element method is developed to clarify the behavior of piled foundation subjected to lateral load. The formulation of this procedure is presented and numerical simulations are carried out for two different models of a piled foundation with twenty-five piles. It is found from these simulations that the proposed procedure is useful to evaluate the three-dimensional behavior of piled foundation.

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The present paper proposes the general higher-order theory of plates by using of Legendre polynomial expansion along the plate thickness. This theory has some simpler form than the other approximate theories such as expansions by Power series, Fourier series and Chebyshev polynomials along the thickness. Particularly, the components of dynamic inertia terms have no coupling with each other for the case of homogeneous plates of the present theory. The other theories cited above can not separate from the components of dynamic terms.
In the paper, lower-order theories due to these approximations are summarized for the cases of bending behaviours as well as stretching ones. At last, some numerical examples for dynamic loading with step time function are shown for the case of simply supported, isotropic plate.

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The earthquake observation was carried out on an actual tank, which is annular and cylindrical, made of a prestressed concrete and is on a pile foundation. The accelerations, hydrodynamic pressures and strains of reinforcing bars were recorded for 16 earthquakes. The observed data were processed using A-D conversion and spectrum analysis. The observed results were checked by the numerical analysis which is based on two kinds of method, one is an analytical solution by potential theory and another is a finite element method using a coupled fluid-structure model. It was concluded that the stresses of the side wall were induced mainly by the dynamic water pressure acting on the side wall and that the dynamic water pressure was magnified due to the coupled fluid-structure motion.

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The purpose of this paper is to present a plastic design method of two-span continuous beams with variable cross section which is satisfied the requirements of deflection and stress constraints at service loads. This design is also intended to minimize the structural weight of the beams, and is shown a procedure to determine the modified stepped moment distributions correspond to the required plastic moment distributions in order to perform the practical design. Design loads are of any combinations of moving single and distributed live loads and dead load which are usually considered as bridge loadings.

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Egg-shaped sludge digester tank model with the scale of 1/30 was made of acryloid plastic. Horizontal and rocking vibration tests of the tank model were carried out on the shaking table with rather high frequency (10-25Hz) and the impulsive water pressures on the tank wall in various water depth were measured. Theoretical solutions to analyze the impulsive water pressure in an axisymmetric rigid tank were deduced by using the transfer matrix method. It was proved that the theoretical values agreed well with the measured ones obtained from the model tests. The calculating diagrams were drawn to be able to obtain easily the equivalent mass of water in tank, its center of action and the equivalent moment of inertia of water.

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A simple dynamic response analysis method by employing an equivalent linearization model for liquefaction was previously developed by the present authors (No. 340, Proc. of JSCE, 1983-12). However, the study using this method remained within discussion only for undrained saturated sandy soil which was modelded as a single degree of freedom system. This paper has extended the method into one which can be applied to multi-layered soil deposits, where for the verification of effectiveness of this extended method, analyzed numerically are a one-layered deposit which is modelded as a four degree of freedom system and the site profile of KAWAGISHI-CHO of NIIGATA city which is modelded as an eleven degree of freedom system. From comparison of analytical results of pore-water pressures by this method and by Finn's effective stress method, it can be concluded that this method is also effective as a simple tool of response analysis for liquefaction of multi-layered sandy deposits.

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Dynamic shakedown tests have been done using rectangular steel beams under traveling loads. Test beams are simply supported at one end and cramped at another. The moving load with a constant horizontal speed is applied to the test beams. The tests have been made and compared for a static ultimate strength test, a fixed point static shakedown test, and four series dynamic shakedown tests with different traveling speeds.
Also, the test results for two series with different speeds are compared with the numerical analysis using a lumped mass and flexibility model. From these results the dynamic shakedown is confirmed. It is found that the converged deflection becomes larger but the dynamic shakedown load smaller as increase of the traveling speed of moving load and the dynamic shakedown load analytically obtained is in good agreement with the experimental results.

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Mechanical behavior and failure properties of plane models composed of aggregates and mortar are studied experimentally and theoretically using an elasto-plastic finite element method. The plane models idealized concrete, the shape and arrangement of its aggregates being varied. In theoretical analysis, the interface between mortar and aggregate is represented by joint element. The constitutive equations of the mortar and interface between mortar and aggregate are based on the plastic flow theory to present the influence of dilatancy. The aggregate is assumed a linear-elastic material. Using these analytical model, it is found that the theoretical analysis and the actual behavior of biaxial loading tests coincide with each other. From the results of this successful analysis, it may be concluded that the shape of aggregates relates with the hydrostatic pressure and the arrangement with the deviatric stress, respectively.

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Recently underground pipelines have been constructed in the places where large ground settlement could occur. And many underground pipelines were destroyed by the ground settlement due to liquefaction and so on in the past earthquakes. In designing underground pipelines, ground settlement is considered to be one of the most important problems.
In view of these facts, ground settlement which has influence on underground pipelines was classified into 3 patterns. And for the most critical pattern both analytical and experimental investigations were executed. As the result were confirmed the effectiveness of not only the proposed basic countermeasure for the critical ground settlement pattern but the adaptation of the linear analytical solution to the nonlinear region of ground spring.

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The effects produced in the relative displacement and average strain, whose exact estimation is indispensable for earthquake-resistant design of pipeline structures, are investigated, when the distortion of seismic waves is also taken into consideration as well as their propagation. As one reason for wave distortion a dispersive wave such as Love wave is considered. This wave is assumed as a stationary wave with respect to both time and place having the same power spectral density function at every location. The spectra of the relative displacement and average strain are formulated, and their characteristics (predominant frequency and r. m. s. value) are examined. Then, by means of simulation technique of propagating dispersive waves, the analytical results are proved.

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A dynamic analysis method of continuous girder bridge is proposed to evaluate its natural frequencies and mode shapes, which is applicable for any conditions of imperfect rigid connections of beam and elastic supports. These conditions of nodal imperfections and support restrictions can be approximately modeled by four kinds of elastic springs independent of each other, i. e. momental and shearing ones for connections and rotational and vertical ones for supports respectively. In this analysis method, the basic unknowns of equilibrium equations are the integral constants in general solution of mode shape function, neither deformations nor forces of beam, which are used in current methods, e. g. eigen-stiffeness method or dynamic four-moments method, etc. Then, the characteristic equation can be obtained from equilibrium equations constructed by substitution of all deformations and forces represented by these unknowns for equilibrium relationships at all nodal points. Because the transformations between deformations and forces of beam need not be induced, the procedure of analysis can be simple, and moreover it is possible to use properly and advantageously each relationships between deformations and forces in accordance with scale of spring constants, which are varied from zero to infinite in magnitude.

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In this paper, the ultimate strength of steel plate elements in the concrete filled square steel tubular columns is analyzed by using the F. E. M. based on the elastoplastic and large displacement theory. It is found through numerous parametric analyses that the influence of restrictions due to the concrete core upon the boundary conditions concerning the in-plane displacement of the steel plate element along the unloaded edges is tought to be negligible in an ordinary composite column. Furthermore, it is difficult to prevent the local buckling of steel plate elements by the shear connectors, even when they are sufficiently welded on the plate elements and anchored into the concrete core. A tentative design method is proposed by adopting a simplified ultimate strength curve and a column model approach using an effective stiffener which consists of a plate element and a longitudinal stiffener for unstiffend and stiffened steel plate elements, respectively.

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The cable stayed bridge can be designed economically by introducing the cable prestresses. It is the most important and difficult problem to determine the optimum cable prestresses in the design of cable stayed bridges. However, there are few studies on the optimum cable prestresses. In this study, an attempt is made to determine the optimum cable prestresses based on the strain energy criterion. The validity of the strain energy criterion on the optimum cable prestresses is proved by simple models. This proposed method is applied to some actual cable stayed bridges. The results show that the proposed strain energy criterion is very useful to determine the optimum cable prestresses even in the case of multi-cable types.

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Slip displacement of a friction controlled mass excited by an earthquake ground motion is predicted both analytically and numerically. A set of linear differential equations each representing one continuous slip is solved with a stationary Gaussian excitation. and an analytical relation between accumulated slip and maximum velocity of ground motion is obtained. With 172 records of strong motion observed in Japan, 43000 time histories of slip displacement are calculated numerically for various friction coefficients. A two D. O. F. regression equation of maximum slip displacement on friction coefficient and characteristic displacement of ground motion is found to explain 76% of total variance of 36249 D. O. F. The regression equation has also a good agreement with the analytical solution.

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In order to reduce serious traffic vibration of the urban viaducts caused by running cars, an active control method is investigated using an actuater device. THe principle of reducing the vibration is based on the counteractive energy of vibration provided from the actuater, which corresponds to bridge vibration characteristics. First, a series of experimental tests on a scale model was carried out, and on the basis of the results, a system of active control by the use of an actuater was developed. Second, appling the system on an actual viaduct on the Metropolitan Expressway, it was attained that the amplitude of responses was reduced to the half of the previous responses. The vibration of a building in the vicinity also became about two-thirds of the previous vibration.

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This paper reports the test results of twelve curved model girders subjected to the combined loads of bending and shear by changing radii of curvature, aspect ratio and slenderness ratio of web plates as well as stiffness of longitudinal stiffeners. Through the collapse tests. buckling and ultimate strength of curved girders are investigated as the interaction curves of bending and shear. For the ultimate strength. two interaction curves are proposed, i. e. one is a theoretical curve taking accounts of the reduction of ultimate strength for bending due to warping stresses on the curved flange plates and the other is experimental one based upon our past test researches on pure bending and pure shear.

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A method of numerical analysis for the nonlinear dynamic response of a marine cable structure subject to hydrodynamic forces due to wave motion is presented. An isoparametric trinodal curved finite element, which was previously developed for static large deformation analysis of cable structures, is applied to the discretization of the equations of motion. In the numerical computation hydrodynamic forces due to wave and current acting on a cable member are strictly evaluated in an automatic process by taking into consideration the interaction of motion between water particles and structural members. Brief explanation is given as to the computational program developed on the basis of the present theory for analyzing a deep-water offshore structure comprising skeleton and buoyant members. Numerical examples shown suggest the applicability of the program to practical problems.

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By using the three-dimensional theory of elasticity, analytical solutions were deduced to obtain load sharing ratios and coefficient of group effects of piles supporting the caisson foundation. The results by the numerical calculations are as follows. The coefficients of group effects of piles in the horizontal direction are generally smaller than those in the vertical direction. In ordinary circumstances, the latter is two to three times as large as the former. The ratios (R_s) of the maximum load sharing ratio of the pile to the average one in the horizontal direction are R_s=1.2-2. On the other hand, ratios (R_s) in the vertical direction are R_s=1.02-1.1. In rational design of the caisson foundation supported by pile-group, the results mentioned above should be taken into consideration.

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This paper describes an analytical theory and method to compute the nonlinear surface ground motion by using a real restoring force. A surface ground motion is mathematically expressed in a wave propagation equation or vibration equation. A restoring force function of soil is given in mathematical model. The most important point of the analytical method suggested in this paper is to use real restoring force for a shearing stress necessary for calculation. The authors don't use a mathematical model but a physical model to represent a restoring force characteristics of soil. The analytical apparatus is a micro-computer connected a dynamic triaxial soil testing machine. We have got the nonlinear response characteristics of surface ground motion in liquefaction process.

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In the Galerkin formulation. the trial function is required Cm-1 continuity on element boundaries. To avoid this requirement, the differential equation is integrated by parts. This integration changes the initial differential equation form and the physical meaning of the equation vanishes. The formulation presented here is led by the least squares criterion and intermediary functions. The residuals on element boundaries are formulated by the Gauss' theorem. The formulation belongs to the mixed method in the method of weighted residual. Therefore, the formulation may be available for problems whose functionals have not been found and does not require the Cm-1 continuity. This makes it easy to understand the physical meaning of the formulation.

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