The identification and control of large-scale structures are considered to be difficult due to structural complicacy and system uncertainties. In this paper, based on the concept of localized control and neural networks, a computational algorithm for earthquake response control of large-scale structures is proposed. In this algorithm, the control-structure interaction (CSI) and actuator dynamics are considered. Moreover, electro-hydraulic actuators as practical applications are designed to simulate the proposed control algorithm. Results from the numerical simulations have shown great promise for the control of large-scale civil engineering structures with localized control using neural networks.

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Random lattice networks generally exhibit spurious heterogeneity that can overshadow important aspects of material behavior, particularly when modeling fracture in homogeneous materials. This issue is resolved through the innovative use of a crack band model for fracture within the Rigid-Body-Spring Network approach. Analyses of concrete compact tension specimens are conducted to demonstrate model objectivity with respect to size and geometry of the network components. During mode I cracking, fracture energy consumption is uniform along the crack path, independent of the meshing strategy.

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LPFDM (Lagrangian Particle Finite Difference Method) is presented for analyzing large deformations of soils. The explicit time-marching solution scheme of LPFDM, in which no global matrix is formed, reduces the computational time considerably. All Lagrangian parameters calculated at each time step are carried by Lagrangian points, which, as a cluster, describe a mass of the material. The updated Lagrangian parameters are then mapped back, for the next calculation cycle, on the stationary Eulerian lattice. LPFDM is thus viewed as an Eulerian way of describing solid motions (LPM, Sulsky et al.) obtained through the Fast-Lagrangian scheme of calculation (FLAC, Cundall), and retains the merits of both FLAC and LPM.

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A conventional method predicting seismic damage, using vulnerability functions, requires a lot of labors, the use of a huge data and a variety of forecast methods. Therefore, to design a new method to evaluate the disaster as simple as possible is thought to be very important. We proposed a new simplified method to evaluate the seismic risk in local areas by employing the qualification theory base on the data obtained by the conventional method.

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This paper presents an experimental study on the seismic retrofit of circular reinforced concrete bridge columns by carbon fiber sheets. Cyclic loading tests were conducted for six specimens; Two were tested under as-build condition and four were retrofitted by wrapping carbon fiber sheets horizontally to enhance ductility. It was found from the tests that stable flexural capacity range increased from about 3% drift to 5% drift by wrapping the carbon fiber sheets. The ductility factor of columns confined by carbon fiber sheets in two layers was smaller than that of columns confined by carbon fiber sheets in one layer. Flexural strength and ultimate displacement was evaluated using stress vs. strain relation of concrete confined by carbon fiber sheets.

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Recently, in order to improve the construction procedure, composite piers have been actively developed and adopted for tall piers. This study proposes a hollow RC pier with densely arranged spiral confinement zones. It is called “DASC” pier. To investigate the seismic performance of DASC pier, a series of cyclic loading tests for five hollow reinforced concrete models with the same column size and the same amount of longitudinal reinforcements were conducted. It was found from the experiment that displacement ductility factors of DASC columns were larger than those of the regular hollow RC columns. It was also found that the ultimate displacements of DASC columns can be satisfactorily predicted by the fiber model.

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A method of conducting model experiments on wave propagation phenomena caused by irregular ground was developed. Acrylamide gel was used as the ground model material, which slows down the wave phenomena because of its low elasticity. The ground model layers were made on a rigid base. The left-side layer of the ground model and two right-side layers were connected at the center of the model. By inducing SH waves in the vertical direction, wave phenomena due to the irregular ground were researched. The following results were obtained in (1) Love waves in the horizontal direction produced in the two-layer ground were verified. (2) In the vicinity of irregular part, wave phenomena depended strongly on body waves. The applicability of this method was thus demonstrated.

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In Menshin design it is recommended not to elongate the natural period so that the deck response displacement does not become excessively large. Under such a design requirement, not only an isolator but also a column undergoes inelastic range when the bridge is subjected to a strong ground shaking. This results in the plastic hinge at both the isolator and the column. Since nonlinear interaction between an isolator and a column has not been studied, a cyclic loading test was conducted. It was found from the experiment that inelastic response of the column increases when the nonlinear restoring force of isolator reaches the yielding force of the column, and that the energy dissipation occurs more in the column than the isolator.

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Dynamic response characteristics of a wharf with coupled batter piles were investigated by a series of shaking table tests. The 1:30 scale model was tested under four different conditions of ground stiffness and two different loads applied on the slab. Axial and bending stiffness and ground stiffness of the model were scaled down in order to reflect the properties of a full-scale wharf. Test results showed that vibration response of a wharf with coupled batter piles was mainly affected by base ground motion whereas a wharf with all-vertical piles has proved to be affected by near surface ground motion. Axial forces acting on the batter piles were calculated from the acceleration response of the slab; the bending moment acting on the top of pile was found to be mainly caused by the ground motion.

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A force reduction factor (R factor) is widely used to estimate the inelastic strength demand from the elastic strength of a bridge. In many seismic codes, a constant value is used for the R factor, although it has long been pointed out that R factor depends on the various factors. This paper presents how natural period of the system, the damping ratio and the ground condition affect the R factor, and a new model, which is formulated by a simple function with two parameters, is proposed to estimate the R factor. The parameters were obtained from the computation of the R factors for elasto-plastic SDOF systems for 70 ground motions. From these results, it was found that the proposed model predicts the mean values of R factors.

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This study presents a method of sequential data processing of seismic damage information for rapid and appropriate decision making in post-earthquake emergency management. First, a real-time estimation of damage rate is conducted using seismic intensity information and fragility relations, providing a prior distribution of damage rate. Next, according to reported damage information, the distribution of damage rate is updated using Bayesian approach in a sequential manner. A technique of SPRT (sequential probability ratio test) is then applied to judge when to make a decision of emergency response. Numerical examples are shown using hypothetical and existing lifeline systems.

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In this paper, we first set up a mathematical model of a single pile subjected to axial load with initial horizontal displacement in elastic soil, then obtained critical loads and expressed them in nondimensional parameters. Based on the results obtained from parametric study, we found that the critical load decreased with the increment of the initial displacement, and its effect of it was very small, but, the effect of the reduction of soil spring coefficient due to liquefaction on the decrease of the critical load was significant.

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In this paper, we first set up a mathematical model of a single pile subjected to axial load with initial horizontal displacement in elastic soil, of which pile head is free; then obtained critical loads and expressed them in nondimensional parameters. Based on the results obtained from the parametric study, we found that the critical load decreased with the increment of the initial displacement, but the effect of it was very small. On the contrary, the effect of the reduction of soil spring coefficient due to liquefaction on the decrease of the critical load was significant. Finally, the effect of the difference of the boundary condition at the pile head, i. e, free vs hinge, could be seen for short piles, but the effect could not be seen for long piles.

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Although nonlinear dynamic ground properties are necessary for a backward calculation to identify an incident wave in time domain, it is difficult to select the suitable parameters for a set of vertical array records. GA (Genetic Algorithm) and the non-iterative time integration method are applied to the parameter selection. Numerical examples are conducted to examine the accuracy of the identified incident wave, and dynamic ground parameters at Port Island vertical array point are computed to verify the applicability for a large-degree-of-freedom. These results show the availability of the parameter estimation method for the backward calculation of incident wave.

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The plastic hinge length is one of the important factors to assess the ductility capacity of reinforced concrete columns under seismic loading. It has been suggested that the plastic hinge length is affected by column size, column hight, longitudinal bar diameter, hoop spasing, etc, however, there are few researches on the plastic hinge length. This paper presents the analytical studies on buckling of longitudinal reinforcement in columns with use of the FEM analyses and compares the theoretical buckling length with that obtained from the column loading tests. Furthermore, the simplified procedure for assessing the plastic hinge length of reinforced concrete columns is proposed based on the analytical studies on the buckling of longitudinal reinforcement with taking account of the inelastic behavior.

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The relationship between the site amplification of the response spectra and the ground condition was investigated using a total of 3, 990 strong motion records measured at 77 JMA stations in the period of over 8 years. The site amplification ratios of the response spectra were obtained from the station coefficients of the attenuation relationships derived from the JMA records, The combined use of the geomorphological land classification and the surface geology was found to give the best estimate of the spectrum amplification ratios, the same as the cases for the peak ground acceleration and velocity, This result suggests that the Digital National Land Information may be conveniently used for the estimation of the response spectrum distribution in a large area in Japan.

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Corrosion is major cause of deterioration of steel bridges, and corrosion damages seriously affect on the durability of steel bridges. So, corrosion damage must be carefully evaluated and the damaged part of members must be repaired or restrengthened. In many restrengthenning ways, reinforcement by cover plates is often selected because of its simplicity and effectiveness. But, in case of application to corroded members, there are some indefinite points. This report describes an investigation of reinforcement by cover plates that are connected with high-strength bolts and both use of high-strength bolts and adhesives.

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This paper discusses engineering effects of the short-period surface waves caused by the lateral inhomogenuity of ground from both viewpoints of vector and tensor. The former viewpoint focuses on the irregular amplification of ground motions and the latter the behaviors of strains. First numerical simulations of earthquake response are carried out for model grounds with typically lateral inhomogenuity using the Pseudo-Spectral Methopd. Basic effects of the short-period surface waves are made clear by these simulations. Next an array observation system of earthquake motions, which has been deployed at a site characterized by lateral inhomogenuity, is used to confirm such effects resulting from the simulations. Finally it is concluded that the short-period surface waves play possibly an important role in earthquake damage.

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Kamiyama and Yoshida proposed a method to estimate the nonstationary variation of the stiffness from the time histories of strain and stress by using the complex envelope. They applied the method to the strong motion records of the 1995 Hyogoken Nanbu Earthquake. In this paper, the method is theoretically and numerically investigated and it is shown that in general the method does not give a precise value of the stiffness. It is, however, shown that under a condition that the stain does not include low frequency component and the stiffness does not include high frequency component, the method evaluates a correct value. It is also shown that even if the condition is not rigorously satisfied the method can give a good approximation of the true value of the stiffness.

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The distribution of building damage due to the 1995 Hyogoken-Nanbu earthquake was interpreted visually using aerial television images taken by high-definition television (HDTV) cameras. Comparing the interpretation results obtained by different people, the accuracy of the interpretation for wooden building damage was inspected. These results were compared with the results of the ground survey. For wooden buildings, severe and moderate damages were mostly recognized in the aerial HDTV images. Almost the same result was obtained, regardless of who performs the determination. The damage level of non-wooden buildings extracted from the aerial images corresponded to collapsed and severe damage in the ground survey. Hence, aerial television images may be used to grasp overall damage distribution of urban areas due to earthquakes at an early stage.

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In Japan the way of determining seismic intensity by JMA (Japan Meteorological Agency) changed from perceptual to instrumental in 1996, immediately after the Kobe earthquake. This new instrumental seismic intensity is known as a useful measure to estimate the earthquake ground motion. We here examine the relations between seismic intensities and various quantities of earthquake observation records such as peak acceleration, peak velocity, spectral intensity, etc., focusing especially on the seismic intensity range equal to or higher than 4 on the JMA scale. The response spectral characteristics of two records with the same seismic intensity are compared. The peak values of the spectrum and predominant periods are found different and this evidence facilitates the necessity of introducing a combined seismic intensity, that is, of modifying from a single-valued one to a three-valued seismic intensity, especially at making clear the difference of damage to structures with shorter and longer natural periods.

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The purpose of this study is to present the relation between cyclic plastic strains and the decrease in the fracture toughness of structural steels. The fracture toughness of structural steels subjected to cyclic plastic strains is investigated by Charpy V-notch impact tests. It is shown which is more suitable, the plastic skeleton-strain or the equivalent plastic strain, for relating the decrease in the fracture toughness due to cyclic plastic strain to that due to monotonic plastic strain. The relationship between the decrease in the fracture toughness and the increase in the stress due to plastic strain and aging is established. A way to assess the decrease in the fracture toughness of structural steels due to cyclic plastic strains is proposed.

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This paper deals with the optimal repair timing of concrete structure on the viewpoint of not only mechanics but also human impression from out-looks of the structure. Questionnaire is made on the time series picture images of a damaged concrete structure. The used images are made by photo-retouch software on a personal computer system. The results of the questionnaire show the relationship between mechanical damage level and impression of damage level.

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The present paper has dealt with the train track-ground interaction vibration due to a moving load on the track and the induced ground vibration transmission alongside. The track is modeled by a bending beam. The ground is modeled by either a halfspace or stratum on a rigid base. First, the ground characteristic is investigated in the frequency-wave number domain for the wave propagation. Secondly the loading on the ground through interaction with the track is evaluated. Thirdly the transient track and ground vibration is computed to find drastically changed by the source moving speed Finally, the ground surface response is viewed versus the source moving speed. The findings from the above are useful for predicting the train induced vibration.

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A simulation method of earthquake ground motions on engineering bedrock is proposed. The essence of the method is identification of parameters prescribing Fourier spectrum, so that the peak values of the motions generated by proposed models of Fourier amplitude spectrum and envelope function, fit the peak acceleration, velocity and displacement obtained from attenuation equations. The method can be used to generate acceleration time series on engineering bedrock for various magnitudes of earthquakes, distances and focal depths.

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This paper describes the elasto-plastic behaviors and the load carrying capacity of the steel suspension bridge under various combinations of the safety factor of the main cable, hanger and tower. Rational combination of safety factor by considering both of the initial yielding state of each component and the ultimate state of the bridge is emphasized. From results of this study, we propose the combination values of γ_T1.5, γ_H=2.2, and γ_C=1.8 as the rational safety factor. The main selective reason is as follows: (1) The load parameter at initial yielding first agrees with that under the present safety factor. (2) Each component at the hanger, main cable and tower yield before reaching a ultimate state. (3) The ultimate load parameter of bridge is greater than the required safety factor α=2.4.

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A method to a priori estimate the equivalent material behavior of the elastic-plastic heterogeneous bodies is developed within the frame work of the multi-scale modeling based on the mathematical homogenization theory. To estimate the macroscopic elastic-plastic properties, such as the macroscopic yield surface, we carry out a series of numerical experiments for the periodic microstructures called unit cells. Through its quantitative evaluation, the macroscopic initial yield surface is approximated by a quadratic function in the macroscopic stress space, and the evolution of the yield surface with anisotropic hardening is numerically investigated.

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The calculation of LCC will be the important subject in the establishment of BMS. The LCC includes the initial construction cost, the maintenance cost, the exchange and rehabilitation cost and UC. These costs are sometimes shown concretely, but UC has been shown only the word. However, in the relation of the road network around the bridge, it is anticipated that UC becomes large. For UC, the evaluation of the increase by the detour traffic in running time, the economy evaluation, and the social evaluation are included And here, only the time increase due to detour traffic is evaluated In this paper, the numerical example of LCC of RC bridge based on seismic performance design method shows the importance of UC in the decision making of the design and the bridge management strategy.

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Slightly damaged steel members were reused in repairing the bridges suffering from the 1995 Kobe Earthquake. The earthquake loads may have induced cyclic plastic strains into the steel members. The cyclic plastic strains will decrease the high-cycle fatigue strength for the vehicular loads afterward. In this study, regarding the cyclic plastic strains as low-cycle fatigue, we investigate the influence of the damage generated by the low-cycle fatigue on the high-cycle fatigue strength. The columnar speciments with stress concentration are damaged by low-cycle fatigue, and then they are subjected to high-cycle fatigue. Based on the obtained results, we establish the S-N formula for the steels subjected to cyclic plastic strains.

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This study investigates a redundancy index R_E in order to discuss the reserve capacity of a complex lifeline system. This index R_E is defined by an information entropy of damage modes conditioned on damage occurrence. First, mathematical relationship between R_E and other index R_Z proposed by Ziha is established, and it is clarified that R_E is more sensitive to the probability of disconnectivity, and therefore more useful than R_Z, though they are linearly related. A model for a water supply network is studied for the reserve capacity by using R_E.

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In estimating fatigue resistance of existing steel bridges, applied stresses are not always perpendicular to weld toes. Fatigue tests of non-load-carrying fillet welded joints with inclined ribs are carried out. The ribs are inclined at 0, 15 and 30 degrees to perpendicular direction of applied stress. Fatigue cracks for the specimens with inclined angle of 0 degree are initiated at multiple points along the fillet weld toes, and then coalesce with adjacent cracks to propagate in a same plane. On the other hand, numerous fatigue cracks are initiated along the weld toes and propagated in different planes for the specimens with inclined angle of 15 or 30 degree. This fatigue crack propagation pattern yields increase in fatigue life as the inclined angle increases. The test results show that the normal stress perpendicular to fillet weld can be used for estimating fatigue life of inclined non-load-carrying fillet welded joints.

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In the performance-based design method, serviceability such as the evaluation of vibration of the vehicle and the bridge structure, and the crack width of the concrete slab is required to be checked. Therefore, the vehicle-bridge vibrational problem, which includes the nonlinear restoring characteristics in some members of the bridge, is required to be solved.
In this paper, first, the vehicle-bridge vibrational problem, which includes the nonlinear restoring characteristics in some members of the bridge is formulated. Secondly, it is confirmed the efficiency of the numerical analysis method through the numerical examples which deal with the crack width of concrete slab and horizontal shear forces applied to shear connectors in continuous composite girder bridge.

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In order to detect damage in structures by using changes of vibration characteristics, it should be made clear whether the changes are caused by damage or within the range of uncertainty. This paper addresses a method to calculate changes of vibration characteristics caused by uncertainty based on Bootstrap analysis, in which vibration characteristics are assumed to be probabilistic variables. Furthermore, a significance testing method using Bootstrap distribution is also proposed. These methods are applied for identification from actual seismic records of a base-isolated bridge and ambient vibration records of a reinforced concrete building. For the former, it is shown statistically and objectively that the change between two earthquakes is significant due to non-linearity of the building. On the other hand, for the latter, it is considered that the changes through one year are caused by uncertainty.

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RC columns supporting the ceiling slab of Daikai subway station, a box tunnel constructed using the cut-and-cover method, totally crumbled in the 1995 Hyogo-ken-Nanbu Earthquake; that failure was followed by a couple of meters subsidence of its overburden soil over the entire 90m extent of the crushed station. This damage stimulated a sharp rise in research activities for possible measures for avoiding that fatal destruction. Among a variety of tunnel members, center columns sustaining the weight of overburden soil are the most important key members, and therefore should not be destroyed. Insertion of a flexible joints on upper and/or lower ends of these columns would be a possible measure. This paper presents a possible shape of a column joint that will meet the necessary requirements for the device sustaining a heavy oveburden soil mass and reducing the induced shear force and moment.

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Elastic wave propagation was examined by ray theory. A Love wave was propagated through a model elastic layer on a rigid base, and displacement time histories due to wave propagation were measured clearly in certain exciting frequency band. In this frequency band, experimental and numerical analyses both revealed that displacement responses were predominant. The ray theoretical investigation successfully ascertained such phenomena qualitatively.

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In order to clarify the dynamic inelastic behavior of the steel pier, it is pointed out that the geometrical nonlinearity should be taken into account in the analysis. On the other hand, the effect of shear stress on the yielding of the steel material is generally ignored in the analysis. In this paper, the dynamic inelastic behavior of the steel pier is examined by employing the rigid-body-spring model analysis, where the geometrical nonlinearlity and the effect of the shear stress on the yielding of the steel material are incorporated, and these effects on the dynamic inelastic behavior of the steel pier is investigated quantitatively. Moreover, the effect of the initial crookedness on the dynamic inelastic behavior of the steel pier is investigated.

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