The estimate of overall behaviors of heterogeneous or damaged materials has been one of major concerns for engineers of various fields. From a micromechamcal point of view, identified are fundamental relations among the average field quantities from which overall responses of the materials can be determined. A new estimate method called the finite part approximation is proposed which may overcome deficiencies of existing estimate methods. A solid damaged by microcracks is considered as an illustrative example, and the overall moduli estimated by the proposed method are compared with those predicted by the existing ones.

View full abstract

The main objective is to investigate analytically the elastic interactive buckling strength and the post-buckling behavior of a simply supported panel subjected to combined loading of bending and shear. Special attention is paid to the effect of unequal end moments at both-side of a panel, which appear in the actual girder structures. The buckling modes are found to be governed mostly by the shear buckling mode. A simple-form formula to predict the buckling coefficients under combined unequal end moments and shear is proposed for the practical use. Moreover, the elastic post-buckling behavior and stress distribution are also discussed.

View full abstract

The following are some approaches in the study on the seismic wave characteristics for the earthquake resisting design. The seismic wave characteristics are in general explained by the statistical method using various records of strong earthquake wave and are expressed in the attenuation formula of the max. acceleration and also in the response spectrum. In this paper, we utilized the fault models modified from Haskell model and the specific barrier model for the magnitude (M) of earthquake on a scale of 6-8 and then we examined the seismic wave characteristics. Finally we have made comparison between the above results and those stipulated by the Specifications for Earthquake Resisting Design of Highway Bridges.

View full abstract

Analysis of seismic response of common ducts and internal pipes is presented here. A common duct is modeled as a uniform beam with a rectangular cross section and internal pipe as a rumped mass-spring system. First, based on the soil-common duct interaction to seismic waves, the axial and lateral responses of the common duct are analyzed. Then the internal pipe's response is investigated depending on the response of the common duct. Numerical computations are done mainly on the strains of the common duct and internal pipes. Results show that the common duct reduces the deformation of internal pipes, and the strain of the common duct concentrates at both ends in the case of large difference of motion between both ends structures and ground.

View full abstract

Recently, mamrtenance and rehabilitation of existing bridges have become important subjects. Therefore, new techniques are required for damage evaluation and judgement of strengthening efficiency. One of the suggested methods for bridge evaluation is to use vibration measurements.
In this paper, the strengthening of the substructure of a truss bridge aging about 65 years was used as a case study. The two columns of each pier were combined in a gravity-type pier. The vibrational behavior of the bridge before and after the strengthening were measured. Moreover, numerical analysis considering the supported conditions of the basement of piers was made to check the measured results. As a result, the change of vibrational behavior of the bridge was recognized.

View full abstract

It is accurate to use the theory of finite displacements and finite strains for the analysis of geometrical nonlinearity of structures. However, the governing equation for this theory becomes highly nonlinear and its direct use makes the solution procedure very much complicated. So approximate numerical methods, respectively referred to as the corotational method and the method with the Rigid Bodies-Spring Model, are often used to simplify the solution procedure for the framed structures. Herein, we precisely examine their theoretical accuracy as well as the convergence to the exact solutions. Based on this result, we further discuss an efficient method to be adopted in the analysis of frames considering finite displacements and finite strains.

View full abstract

Fracture phenomena at a debonded tip of partially bonded bimaterial half planes which are subjected to concentrated normal forces, couples and uniform traction are considered. Crack's initiating conditions are described by stress distribution before the initiation and energy release rate of the crack immediately after the initiation. Debonding's extending conditions are described by stress distribution and energy release rate of the debonding before the initiation. When both the crack and the debonding have chances to occur, or when both two material cracks have chances to initiate, the fracture phenomena is decided by comparing the ratio of energy release rate and the ratio of fracture toughness.

View full abstract

Mechanical behaviours of long bolt tension-type connections are significantly affected by faying surface conditions of the connections. In this paper, load transmission behaviours influenced by the faying surface conditions in the connections are studied by experiments. Experiments were performed using specimens with various faying surface conditions and variovs details of the connections. The influence of faying surface conditions on additional bolt axial forces due to external forces are firstly discussed. Secondly, stress distributions in the connection elements are investigated. Thirdly, contributions of the connection elements to load transmission are examined.

View full abstract

This paper presents an estimation method of the shear resistance force and the earth pressure of the fill materials in the steel made Sabo structure by experimental approaches. The experiments have been carried out by applying the horizontal load to the top of the simple shear steel frame of rectangular type and bench type with four kinds of fill materials, respectively. An experimental estimation equation has been proposed for the shear resistance force and earth pressure of fill materials in the rectangular type shear test. By using this equation, the shear resistance force and earth pressure of fill materials in the bench type shear test have been estimated and compared with experimental values. It is found that the proposed estimation method is good agreements with experiments and, as such, it can apply to the design of the steel made Sabo structure such as bench type with fill materials.

View full abstract

This paper presents several investigations on application of time domain boundary-finite element hybrid method to dynamic problems of sediment-filled valleys. For the sake of stability of the solution, numerical dissipation is introduced into the higher modes of finite element solution by employment of Hilber-Hughes-Taylor (H-H-T) method and the coupling interface is located in the exterior region far from the dipping boundary. In time domain coupling, the interpolation of boundary element equations in two successive time steps is combined with the finite element equation. Under the above-mentioned coupling procedure, influences of the time increment ratio and element size on the accuracy of the solution are examined.

View full abstract

Deployable flexible members utilizing an elastic buckling phenomenon have been studied in order to improve the packing efficiency of space structures. However, these studies are primarily restricted to straight members such as columns and beams. Herein, we present an interesting buckling phenomenon of a ring which considerably reduces its original volume and could be applied to a deployable ring. First, we show an accurate method which can be used to analyze this buckling phenomenon accompanying finite rotations in space. Then, with this method, we theoretically examine the effect of structural parameters on the buckling behavior.

View full abstract

This paper deals with the residual stress and initial deflection of steel plates with closed cross-sectional stiffeners. Through the measurement of residual stress for three full scale stiffened plate models, the distribution of residual stresses of the plate panel in the transverse and longitudinal directions, as well as the distribution of longitudinal residual stress in the stiffener are investigated, and then a formula is proposed for predicting these residual stress distributions. A lot of initial deflections of plate panels and stiffeners were also measured for the steel deck plate of an actual Nielsen-Lohse bridge. These initial deflections are statistically investigated. The measured initial deflections are compared with the tolerance in the Japanese Spescifications for Highway Bridges.

View full abstract

This paper presents a supporting system for evaluation of the safety of bridges by maintenance engineers. The system consists of three subprocesses: On the first, the dominant factors for evaluating the safety of bridges are determined using the hierarchical diagraph developed by ISM. On the second, pair-wise comparisons of bridges characterized with the factores are done by maintenance experts, and a safety-order-diagram is drawn automatically by the supporting system. On the third, through the discriminant analysis of the diagram bridges are numerically classified into three categories; safety, a slightly danger and danger.
We do experiments on evaluation of 24 bridges by three experts of different professional background and also make camparison between the results gotten by this system and the ones by the phisycal evaluation of dynamic characteristics of bridges.

View full abstract

A rigorous and efficient optimum design method for steel cable-stayed bridges is developed, in which cable anchor positions on main girder, height of pylon are dealt with as the design variables together with the sectional dimensions of the member elements of main girder, pylon and cables. The design problem is formulated as a minimum cost design problem subjected to the stress constraints which are taken from the Japanese Specifications for Highway Bridges. In the stress analysis, the stresses in the cantilever system at erection closing stage and in the continuous girder system at service stage are considered as the working stresses. The cost minimization problem is solved by using dual method with mixed direct/reciprocal design variables. The optimum solutions can be obtained quite rigorously and efficiently by the proposed design method. The optimum values of the design variables obtained are quite reasonable and well-balanced from the static analysis viewpoint. The significance of dealing with cable anchor positions and height of pylon as the design variables is also emphasized for the minimum cost designs of cable-stayed bridges.

View full abstract

The ultimate strength of steel beam-columns under biaxial bending is investigated numerically by an elasto-plastic finite displacement analysis considering characteristic values of the measured initial imperfections. And the appropriate interaction strength formulae for beam-columns which are modified from Chen's interaction formula are proposed for the members with box section and I-section, respectively. The proposed formulae are verified by the comparison between the prescribed results and the experimental data. The efficiency of the proposed formulae is demonstrated by the comparisons of several existing design codes.

View full abstract

In the practice of earthquake-resistant design, the peak ground motions such as the maximum acceleration A_max and the maximum velocity V_max are used as a measure of earthquake intensity. However, they are not always reasonable. In elasto-plastic response of structures, the spectrum intensity SI, the integral of squared acceleration P and PT₉ (T₉ is a predominant period of ground motion) are more appropriate. By studying the variation of response of a SDOF system excited by simulated ground motion having four populations, the authors compare the five measures of earthquake intensity (A_max, V_max, SI, P and PT₉), and obtain following results:
1) The variation of T₉ gives rise to a lot of variations of response especially whenA_max or P is used as a measure of earthquake intensity
2) When the variations of predominant period T₉ and the strong-motion duration of earthquake t_d are taken into account, PT₉ and P are the most appropriate measures on earthquake intensity to the response of long period structures and to the response of short period structures, respectively.

View full abstract

A new method of damage evaluation for complex secondary networks of lifeline systems is proposed. A similarity between natural and man-made supply network systems are explored. Rivers and veins are examples of the former and gas and water pipelines are those of the latter. It is shown that both possess fractal nature in the statistical sense so that any part of an abovementioned network is statistically similar to that of any other parts or that of an entire network. When a lifeline network system is received seismic damage, the total effective length of the network, which is defined as the supply rate, decreases. Using the actual data from Off-Miyagi Earthquake in 1978, it is found that the change in the total effective length is linearly related to the change in the fractal dimension. It is also found that the supply rate due to hypothetical damage can be estimated from the linear relation obtained thoroughly from the actual data. This shows a possibility that a supply rate-fractal dimension curve may be used to predict the extent of damage due to an upcoming event.

View full abstract

Model vibration tests and these numerical analysis were carried out in order to comprehend the seismic behavior of the parallel tunnels laid under the submarine embankment being revetted by steel jackets in both sides. The model was made in the similitude of the portion of slipway at Ukishima area of Trans-Tokyo Bay Highway. The experiment was conducted with three continuous large scale water vessels only one of which was put on a shaking table while the remains were fixed on the base mat so as to enable us to simulate the behavior of any offshore structure during an earthquake. The numerical simulation for the experiment was carried out on the basis of the equivalent linear analysis taking account of nonlinear soil properties. As the results of above studies some new information pertaining to the seismic behavior of the portion of slipway has been obtained.

View full abstract

A new closed-open-loop optimal control algorithm is proposed that has been derived by minimizing the sum of the quadratic time-dependent performance index and the seismic energy input to the structural system. This new control law provides feasible control algorithms that can easily be implemented for applications to seismic-excited structures. To apply the developed continuous-time control algorithms to a real structural system we must take into account the time delay not only for digitizing the observed input motion and system response but for calculating the control force and for applying it in the form of stepwise functions through A/D converters. We developed the discrete-time formulations of active structural control which include the time delay compensation.
To compensate the time delay of control force the input earthquake motion must be predicted for the period to be used for generating the control force. We assumed an earthquake ground motion to be defined as an autoregressive process. We also developed a prediction method of earthquake motion for a few time step ahead of observation time by using Kalman filtering technique.

View full abstract

In order to assess durability of steel bridges against fatigue, service stress measurements were carried out on several types of bridges. Under the service condition, histogram recorder was used to measure stress ranges and their frequencies in service. Fatigue life was evaluated by using the Miner's cumulative damage rule. Classification of joint details and design S-N diagrams were quoted from ECCS recommendations for the fatigue design of steel structures. It was found that evaluated fatigue life was longer than a few hundred years in the main members. However, some secondary members showed much shorter fatigue life than the main members. Actually some of the secondary members had experienced fatigue cracking. Therefore, the fatigue life computed from the measured stress range histogram was good indication of severity against fatigue.

View full abstract