Fatigue crack growth rates of structural steels (JIS SS 41, SM 50, SM 58 and HT 80) were measured under constant amplitude and variable amplitude block loadings. The measurement was carried out using Compact-type specimens according to the ASTM E 647-78T. The fatigue crack growth rates were measured in the range of ΔK between 10MPa√m and 35MPa√m. Within the test data, the crack growth rates of all four steels were in good agreement. The variable amplitude block loading was represented by an equivalent stress range computed by the root-mean-cube method, and crack growth rates under variable amplitude block loading were in good agreement with that under constant amplitude loading.

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This paper provides a simplified approach to the strength of compressed steel stiffened plates from a knowledge of the catastrophe theory. The strength prediction for both global and local buckling modes is presented.
The elasto-plastic buckling stress is firstly obtained with consideration of the elasto-plastic behavior of the material and the residual stresses of both stiffeners and plate panels. Then, the reduction of the ultimate strength due to the initial out-of-flatness can be explicitly determined by the imperfection sensitivity curve based on the concept of the bifurcation set in the catastrophe theory.

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A method to determine fractile values from statistical data is proposed: the fractile value for an exceedance probability about 0.5 is first determined from the data and next, the correction factor which is also calculated from the data is multiplied to that fractile, yielding the fractile value of a required exceedance probability. By means of Monte Carlo simulation, its accuracy and those of commonly used methods are compared. The result shows that proposed method is the most stable to various distribution models and coefficients of variation.

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A design method based on the column approach is proposed for evaluating the ultimate strength of orthogonally stiffened wide plates with some heavy longitudinal stiffeners (stringers) in steel box girder bridges including the main box girders of cable stayed bridges. The method is verified by the elasto-plastic and large deflexion analysis (F. E. M.). It is shown that the dimensions of transverse stiffeners in orthogonally stiffened wide plates with small aspect ratio can be greatly reduced without significant variation of the ultimate strength either by increasing the size of the longitudinal stiffeners or by replacing some longitudinal stiffeners with stringers so proportioned that the elastic buckling strength remains constant. The required stiffness of the flange plate of the stringer to avoid lateral-torsional buckling is also investigated by the F. E. M.

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A theoretical study on the ultimate strength of thin-walled box stub-columns subjected to compression and bending is performed by using a finite element method (F. E. M.) on the basis of the elasto-plastic large deflection theory in order to develop an interaction curve at the ultimate state. A modified column method to calculate the ultimate strength of thin-walled box columns considering the local bucking of Plate elements is proposed by using the interaction curve of stub-column. Through numerous calculations by the modified column method, an approximate formula for predicting the ultimate strength of thin-walled box columns is given in this paper.

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A linearized finite displacement theory of the Timoshenko beam is formulated as the counterpart to so-called beam-column theory of the Bernoulli-Euler beam. The corresponding stiffness equation is derived in a useful form for practical applications. Both theory and stiffness equation result in the same buckling load as the Engesser formula which has been considered reasonable from the theoretical point of view.

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Angular distortion and misalignment are the typical initial imperfections of welded-joint in steel structure. Stress and strain concentration at the root and the toe of welded-joint become larger when the welded-joint has misalignment, as misalignment causes a moment with applied force. Therefore, fatigue strength of the welded-joint with misalignment is inferior to that without misalignment.
In this paper, fatigue strength of such joint was investigated using the specimen, which was scale-up model of a cross section of U-shape trough rib. Stress concentration factor of the root was analyzed by the finite-element method and was measured by static loading test. Cyclic loading test was carried out to clarify the effect of root shape on fatigue life and the relation between fatigue crack propagation rate and stress intensity factor range. Also, the effect of scale-up rate of the specimen was investigated.

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This paper presents the experimental study on the ultimate strength of thin-walled box stub-columns with the longitudinal stiffeners subjected to compression and bending. Eight columns were tested up to failure under the conditions of uniaxial and eccentrical compressions. These results were arranged from various point of views and the ultimate strength was plotted as the interaction curves of compression and bending. By introducing a plate slenderness for the stiffened box stub-columns, an empirical formula for evaluating their ultimate strength was proposed herein.

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Stress analysis is carried out for a strip whose part is embedded and with a crack which emanates at a stiffened end between the embedded and unembedded parts. As loading conditions, a uniaxial tension and a bending in a plane of the strip are considered. Stress distribution before and after the occurrence of a crack is investigated. In particular, stress intensity factor for some crack length and Poisson's ratio is investigated. Stress analysis is carried out as a mixed boundary value problem in the plane elastic problem. Complex variable method and a rational mapping function of fractional expressions are used. A closed solution can be obtained for the rational mapping function.

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The object of this paper is to develop a finite displacement theory of naturally curved and twisted rods undergoing finite rotations. Particular attention is paid to investigate the coupling of finite rotations in space under the Bernoulli-Euler hypothesis. A finite rotation vector is employed to derive the displacement field available for finite rotations. A new variable is introduced as a fourth parameter associated with rotations of cross sections. Then the twist and curvatures after the deformation are expressed in terms of four parameters without using small-strain assumptions. The equilibrium equations and the associated boundary conditions, in which second order terms with respect to displacement components are fully taken into account, are derived from the principle of virtual work. The accuracy of the present equilibrium equations are confirmed through comparisons with those obtained by the equilibrium method.

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The governing equations for the finite displacement beam theory are often formulated through the principle of virtual work by introducing the pertinent kinematic field with displacement components defined in terms of the coordinates fixed in space. However, this formulation can hardly be applied for the theory of space beam without any restrictions on the magnitude of displacements, since the kinematic field becomes highly nonlinear largely due to the finite rotations in space.
This paper presents a new formulation which considerably simplifies the derivations through the principle of virtual work. By the formulation, the governing equations can be easily obtained even for the exact theory under beam assumptions.

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When a thin-walled plate girder is subjected to repeated shear, it is possible that fatigue cracks may be initiated along the web boundaries in regions where the tension field is anchored. They are caused by the secondary bending stress which is produced by out-of-plane deformation of the web. In this paper, first, the out-of-plane deformation and the secondary bending stress of a rectangular plate under in-plane shear are examined by the finite element analysis. Secondly, using the relation between in-plane shear stress and secondary bending stress, the fatigue strength is expressed in terms of the in-plane shear stress as a function of the web slenderness ratio. And the influence of various factors on the fatigue strength is discussed.

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An incremental equilibrium equation for a beam-cloumn with arbitrary open cross sections is derived in a stiffness matrix form by using a moving element coordinate system and an incremental variational principle. A segmentation method for the cross section is used to analyze the development of plastic zones in the cross section and the effect of initial residual stresses arbitrarily distributed in the cross section. Yielding of the material is judged as a bi-axial stress problem under normal and shear stresses by using the flow theory of plasticity associated with von Mises yield criterion. Validity and efficiency of the present method are shown by illustrative examples.

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Nonstationary earthquake motion prediction models are proposed on the basis of rock surface-ground motion dataset. Ground motions on rock surface with the shear velocity of 600-700m/sec are dealt with. The ninety-one components of acceleration time histories on rock surface level are arranged, which consist of (i) rock surface-ground motions estimated from the accelerograms recorded on alluvial and diluvial sites, (ii) rock surface-ground motions modified from bed rock ground motions, and (iii) ground motions recorded on rock surface. On the basis of this dataset, two earthquake motion prediction models are developed, one (EMP-IB Model), a prediction model for given magnitude and epicentral distance, and the other (EMP-IIB Model), an advanced model which deals with the effect of successive faulting and relative site locations on ground motion characteristics.

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Multiple regression analyses of duration of earthquake ground acceleration are presented. Duration is defind as the time interval between the time when accleration amplitude firstly exceeds a times (0<a<1) of peak ground acceleration and the time when acceleration amplitude becomes less than a times of peak ground acceleration in the last. Employed were 394 components of horizontal strong motion acceleration records obtained at 67 free field sites in Japan. Empirical formulae of the durations in terms of earthquake magnitude and epicentral distance are propose for three subsoil conditions.

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Multiple regression analyses for vertical peak ground motions (peak ground acceleration, peak ground velocity and peak ground displacement) and absolute acceleration response spectra with damping ratio of 5% of critical are presented. Employed were 119 sets of vertical strong motion acceleration records obtained at 53 free field sites in Japan. Empirical formulae of these characteristics in terms of earthquake magnitude and epicentral distance are proposed for three subsoil conditions. Peak ground motions and absolute acceleration response spectra of vertical components were compared with those of horizontal components, and characteristics of vertical components were discussed in comparison with the characteristics of horizontal components.

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We here report a method for synthesizing design earthquake motions at a short epicentral distance that makes use of microearthquake records. Characteristics such as the corner frequency and flat level were analyzed from displacement spectra determined from the digitized time histories of microearthquakes. A statistical model of microearthquake motions then was constructed by applying the nonstationary second-order autoregressive moving average (AR-MA) process. The attenuation laws of the AR-MA parameters were derived from a regression analysis. A waveform that satisfied these attenuation laws was regarded as a statistical Green function. Strong earthquake motions were synthesized by superposing the statistical Green function. In order to make this superposition, a new scaling law was derived taking into account the difference of stress drop between large events and microearthquakes. Peak accelerations and response spectra of synthesized accelerograms in the region near the source were large in comparison to the values which had ever proposed.

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Scattering problems of antiplane waves incident upon inhomogeneous alluvial valleys are studied by using the integral equation methods. Three types of integral equation approaches are presented and compared each other. The first one is the boundary-domain integral equation based on the static fundamental solution for a homogeneous body. The second one is identical to the first one, except that the dynamic fundamental solution is employed. The last one is the boundary integral equation for the scatterer with ad hoc inhomogeneity, for which the fundamental solution is obtained. The numerical results show that the soft surface layer in alluvial valleys induces the large amplification and long duration of surface motions, which reflects the important problem in earthquake engineering.

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The strain behavior at the connection plate between main girder and transverse bracing in a simply supported composite plate girder is studied in order to find the causes of fatigue cracks. These cracks occur mainly at the upper end of stiffening plates and rib plates for connection, and propagate into the web plates of main girders. The strains measured in field tests are analyzed and fatigue investigations are carried out using Miner's Law. As the result, it is clear that cracks are initiated by cyclic high stress due to unequal deflection of main girders and deformation of slab plate at the front toe of fillet welds between flange plate and stiffener or rib.

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For a partially penetrated corner joint, estimations of the fatigue crack size and the crack growth behavior are investigated using the ultrasonic imaging method. Experimental results are obtained as follows:
1. An approximate estimation of the crack size is possible basing on its relation to the ultrasonic defect image.
2. The crack growth behavior can be estimated with reasonable accuracy from the increase of defect image size.

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The displacement and strain distributions for a plate segment comprising open cross section are derived considering the pre-buckling deflection of beam axis. Applying the higher order theory obtained to I-beams bent about their major axes by equal end moments, the effects of pre-buckling deflections on local, distortional and lateral-torsional buckling are investigated. Solving eigen-value problems, it is clarified that the stress corresponding to distortional buckle of an I-beam is conservative compared with that neglecting the pre-buckling deflections and the stress corresponding to lateral-torsional buckle occuring at long lengths are progressive compared with the results of Timoshenko.

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It is very advantageous to represent various probability distributions by respective standardized variates with zero mean and unity variance, as well as the normal distribution. Then, useful figures and tables on them can be prepared, and a probability distribution can be compared numerically and visually with the others based on the same standard. Some figures are shown for distributions commonly encountered in structural reliability. Characteristics of these distributions are briefly presented and the characteristic value defined by the normal distribution in the limit state design is discussed on validity of its use for the other distributions.

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Using a model box girder, this study, attempts to obtain data on welding strengths by measuring the restraint intensity of one of the significant elements that suffer from cold cracking on steel structures. The study also employs an analysis with the finite element method to compare with the measured values. The results can be summarized as follows. 1) The strength of fillet welded joints can be expressed by the geometric average values of thicknesses among the flange, web, and rib of the main girder. 2) Although the restraint intensity varies with the boundary conditions of the steel plates in the box girder and with the measuring positions, it is shown that the restraint intensity does not exceed 70 times the thicknesses of normally used plates.

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In this study, a modeling of vehicular loads in a fully congested traffic stream state on urban expressway networks is presented. The statistical analysis of randomly spacevaring vehicular loads is performed by using the simulation technique and the observed data on traffic streams, provided by the Hanshin Expressway Public Corporation. The parametric analysis for the statistical nature of vehicular loads is done for the various cases of the traffic stream conditions. To demonstrate the effectiveness of the present model, the probabilistic characteristics of the response of a continuous two-span girder to random vehicular loads are calculated numerically by using the correlation theory of random processes and compared with the simulation results.

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This paper presents an analytical study on the ultimate strength of intermediate transverse stiffener in the web plate of horizontally curved girders. Firstly, the shear buckling strength is analyzed by the theory of shallow shell. Secondly, the ultimate shear strength is also inquired through the collapse model. Based upon these analyses and some experimental data, the behaviors of the transverse stiffener are discussed. Finally, a beam-column model for evaluating the strength of the transverse stiffeners is proposed and a design recomendation to determine the strength and corresponding rigidity of the transverse stiffeners of curved girders in the ultimate state is given by this paper.

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Various constitutive models for the description of the elastoplastic deformation with an anisotropic hardening and also a smooth transition from the elastic to the distinctyield (fully-plastic) state have been proposed in the past. Among them the two surface model extended from the kinematic hardening model would be one of the most available models, and many costitutive equations have been presented using this model. They have not been formulated, however, in mathematically rational forms applicable to the generalized material with not only hardening but also softening behaviours. In this paper, a reasonable formulation of the two surface model is given by deriving the mathematical condition which must be satisfied in order that the surfaces do not intersect at their relative translation and which will be a “non-intersection condition” and by assuming a reasonable measure to describe a distance from the outer yield surface

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In the design of bridge, the designer's subjectivity enters into the form of bridge, willynilly.
Accordingly, in this paper, a means giving the objective data in examination of the form is proposed from a standpoint of application of PSYCHOMETRICAL TECHNIQUE. This technique includes “Method of Paired Comparisons”, “Method of Rank Order” and “Method of Successive Categories”.
It is thought that these methods are not only the form but also applicable for the colour and scene of bridge.

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One of the remaining problems in field welding is application to members under loading. There is a few study in this problem. The authors reported “Deformation behaviors of plates welded under loading” and “Welding to pipe column under axial compressive load”. These studies are related to initial imperfection of members and load carrying capacity after welding.
This paper describes experimental study on mechanical properties and residual stress of joints welded under tensile or compressive loading, and F. E. M. analysis on transient stress during weld heat conduction and residual stress.

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In steel-concrete composite beams under repeated negative bending moment, the steel flange plates on which stud shear connectors were welded are subjected to combined fatigue stresses of flexural tensile stress in the plates and shearing force on the connectors.
The fatigue tests which were conducted on beam-type specimens and on coupon-type ones, showed that the fatigue strength of the flange plates decreased in proportion to the shear forces acting on the stud.
The effects of the shear force were clarified by the three dimensional finite element stress analysis at the stud base and evaluated reasonably by using an equivalent stress at the toe of weld upset.

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A finite element method based on the modified Hellinger-Reissner's principle is applied to compute the elastic-plastic post-buckling behavior of plate-assembled steel column segments. The effects of both welding residual stresses and initial plate deflections are allowed for in the analysis. Load-shortening curves of uniaxially loaded single plates are shown to be in good agreement with Little's results which are supporsed to be the most reliable solutions. Moment-thrust-curvature (M-P-Φ) curves of locally buckled box column segments are computed and, based on the results, an interaction formula for predicting the ultimate strength of box column segments in combined compression and bending is proposed.

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A theoretical study is presented on the local and overall interaction buckling behavior of steel compression members. The analysis begins with constructing moment-thrust-curvature curves (M-P-Φ curves) of locally buckled stub-columns with residual stresses and initial plate deflections, and proceeds to integrating, along the member axis, the M-P-Φrelations to obtain the overall load-deformation characteristics of compression members. The effect of initial member deflection is allowed for in the integration procedures. The present paper outlines numerical procedures for the latter half of the analysis. The numerical results are first compared with available test results of eccentrically loaded box columns and then utilized to check the adequacy of the design formulas proposed in previous papers.

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Optimum design of steel compression members (columns and beam-columns) is undertaken by means of SUMT method, one of the nonlinear programming techniques. The cross-sections being considered are both unstiffened and stiffened square box sections. Design formulas proposed previously by the present authors for the local and overall interaction strength of compression members are utilized in the optimization process, together with some side constraints (i. e. maximum slenderness ratio and minimum thickness) specified in the current Japanese design code for highway bridges. All the computed results are presented in graph with nondimensional basis so that they could easily be used for practical design.

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This paper presents the experimental researches on the lateral-torsional buckling behavior of welded steel girders. The test program was designed to clarify the effect of moment gradient in the inelastic range. Test results, including material properties, residual stress distributions and initial lack of straightness of compressive flange and web panels, are presented. The experimental ultimate load-carrying capacity of girders is compared with the analytical predictions by the finite displacement theory. The lateral-torsional strengths of welded girders under moment gradient are then proposed by a simple formula.

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This paper presents the probabilistic procedure for estimating fatigue resistance of highway bridge cable to vehicle loads, which takes account of the stochastic properties of both live loads and cable strength. The statistical model of the live loads can be constructed on the basis of the field measurements of traffic loads previously performed in the usual traffic conditions on actual bridges. The ranges and frequencies of cable stress amplitudes are directly estimated from its random wave samples produced by the live loads with the aid of the associated influence lines, and it can be shown that the exponential distribution function is very well fitted to the histogram. Miner's rule is applied to fatigue analysis, in which the fractile of strength distribution can be used to estimate the probability of fatigue failure. Examples are given for the cases of a cable-stayed bridge.

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In recent years, many cable-stayed girder bridges with a long span length more than 400m have been planned and these projects are mostly planned as structures with multipie cables. Nevertheless, the materials for basic planning of them have not been prepared sufficiently so far.
In this paper, the materials for basic planning of them are presented. That is to say, the determining method of prestress quantity of the cables which is most important on designing the cable-stayed bridges is discussed and presented relating to the anchoring points of the cables to the girder. Furthermore, the materials for selecting the ratio a side span length to a center span length are presented.

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This paper presents equations and figures for evaluating the sectional forces of each members of the cable-stayed girder bridges with multiple cables. These results are useful not only for the understanding of the static behavior of the bridge but also available for the check of the results obtained by the electric computer which is inevitable in the design stage. Especially, BEF analogy is used for the evaluation of the sectional forces and a new parameter concerning the rigidity ratio between the bending stiffness of the girder and axial stiffness of the cables is presented.

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This paper is concerned with the computational procedure of displacements and stresses of an elastic multi-layered half-space due to harmonic loads acting in the interior of the half-space. In calculating the fundamental solutions of displacements and stresses, the authors propose a transfer matrix method taking advantage of a vectormatrix form which expresses the general solutions of displacements and stresses being used in the derivation of dispersion function of an elastic multi-layered half-space. The results shown in this paper can be used as the fundamental solutions in the Boundary Element Method. As numerical examples, the stresses of an elastic half-space due to vertical and horizontal concentrated loads are calculated for the various non-dimensional frequency ωH₁/V_s1.

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The aerodynamic lift responses of geometrically simple bluff prismatic sections to a sharp-edged gust are studied for the purpose of evaluating the gust responses of bridge deck sections in the time domain. A towing water tank that can simulate a sharp-edged gust was specially designed and used in the experiment. The results obtained are: 1) A satisfactory form of a sharp-edged gust is obtained. 2) The indicial aerodynamic lift responses of the models ase qualitatively similar to but quantitatively different from that of an airfoil. 3) Flow patterns around the models are characterized by the leading-edge separation bubbles that are formed and shed downstream during the passage of a sharp-edged gust.

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Strong-motion and hydrodynamic pressure records obtained on the Ofunato breakwater which consists of rock-fill mound of 19m high and concrete caissons of 20m high on the mound were analyzed. The maximum acceleration ratio of the caisson's top to the base rock decreased with the increase of the maximum acceleration of the base rock. The first-order natural frequency estimated from the transfer function between the caisson's top and the base rock decreased with the increase of the base rock acceleration. These seismic behaviors were due to the nonlinear characteristics of the mound's material. The hydrodynamic pressures observed at vertical surface of the caisson were a little small compared with those calculated from the Westergaard's formula.

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This paper deals with the dynamic stiffness (i. e., the complex stiffness) under rigid rectangular foundations resting on an elastic two-layered medium. This is a problem belonging to mixed boundary value problems which are not easily solved by an analytical approach. To overcome the difficulties of analysis the authors employ a numerical method, in which the contact area of the foundation is divided into a finite number of rectangular sub-regions, and a system of linear simultaneous equations with respect to the unknown contact pressures is derived by introducing the influence functions. In this paper the authors mainly investigate the effects of the layering on the dynamic stiffness and the difference in the dynamic stiffness between the relaxed and welded boundary conditions on the contact plane.

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An online-graphic computer program (ERISA-G) has been developed to facilitate engineering decision making concerning design earthquake loads. ERISA-G utilizes a simple Poisson model, together with historical data of past earthquake occurrences. The man-machine interactive system and its graphic display capability enable the engineer to understand not only the final results but also the process of earthquake risk analysis. The data files consist of mapping data (about 20000 points), active fault data (about 2000 segments) and two sets of earthquake data catalogues of different characteristics (each with about 1900 and 18900 earthquakes). Using a small number of input data and the choices made by the engineer at different stages of the program, ERISA-G produces some 40 different graphic displays in addition to a variety of line-printed output.

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A method is presented for using historical earthquake data and active fault data jointly for seismic hazard estimation. Japan and its vicinity are divided into 22 regions, and then earthquake occurrence rates are estimated for each region on the basis of information combined from historical earthquakes and active faults.
On the basis of simulation results, iso-seismal maps are developed in terms of peak ground acceleration, peak ground velocity, and ground motion duration.

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Earthquake observations have been carried out on a road bridge supported by piles where dynamic strain gauges are attached on their surfaces for the purpose of the clarification of earthquake response behavior of piles penetrating through soft soil deposit.
External factors which govern the earthquake response of pile foundation are analyzed quantitatively and dynamic behavior characteristics of battered pile foundation are investigated. Effective data for establishing aseismatic design of pile foundation applicable for real conditions are presented.

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Seismic Design Methodology for typical highway bridges with reinforced concrete piers is developed. This methodology presented herein is based on a cost/benefit formulation for a rational choice of the two important parameters in seismic design requirements of typical highway bridges; the seismic design coefficient and the displacement ductility factor. Procedures require to quantify the hazard of earthquake shaking, the likelihood of bridge damage, the relationship between damage level and post earthquake performance of bridges, and the cost for increasing the required earthquake resistance of bridges. These quantities are quantified by utilizing the experimental and analytical results of damage degree for reinforced concrete piers, the experiences on post earthquake performance of bridges, and the statistics of damage cost collected on highway bridges during the past earthquakes. As an illustrative application, the methodology is applied to the choice of design requirements for typical highway bridges in Tokyo, and the values for the seismic design coefficient and the importance factor in the conventional design code are discussed.

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With the aid of currently available finite element method results, an approximate analytical solution is developed for the effective seismic motions of cylindrical embedded rigid foundations having the two embedment cases as follows: Case 1; embedded in a viscoelastic surface layer with the foundation base resting on a much stiffer bedrock, Case 2; embedded in a viscoelastic surface layer with the foundation base resting within the surface layer. The characteristics of the solution are compared with the results of the laboratory tests by shaking table and also with the responses observed at an actual embedded foundation during an earthquake, where the original data were available by other investigators. It is found from the comparisons that the solution developed in this paper well agrees with the experimental and observed data.

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This paper examines the influences of the foundation flexibility and the initial irregularities on the seismic response of cylindrical tanks. A calculation method for describing those behaviors is showed and dynamic shaking table tests are performed. The results of dynamic tests agreed fairly well with the results obtained by numerical calculations. It is concluded that the base fixty conditions will significantly change the seismic response of tanks. It is also concluded that significant high radial accelerations are induced on account of the irregularities, however, stresses induced by the irregularities are less significant.

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This paper describes an effective method of obtaining covariance responses in recursive form for a multiply-supported structural system, such as bridges and buried underguound pipes, subjected to multiple-support seismic excitations. The seismic excitations are expressed as an autoregressive model for multiply-correlated stochastic processes. By utilizing white noise characteristics of the AR model, this covariance response matrix equation is derived from a state space matrix equation with mixed excitations are expressed as an autoregressive model for multiply-correlated stochastic model, subjected to mutually correlated stationary and nonstationary random excitations, is demonstated.

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