The dynamic characteristics of a structural system are identified. The relevant neural network characteristics of a learning algorithm are discussed in the context of system identification. Because of the self-learning nature of the neural network the dynamic characteristics identified are strongly affected by the level of noise contained in the teaching signals. A method to identify the dynamic characteristics of a structural system proof against contaminating noise in teaching signals has been developed with the aid of the Kalman filtering technique. Numerical examples to identify dynamic response characteristics of linear and nonlinear structural systems are worked out to demonstrate the stability and robustness of the proposed algorithm.

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This paper presents test results on lateral-torsional buckling of welded monosymmetric I-beams with unequal flange width or thickness. Seven different types of sections including doubly symmetric ones are tested under a central concentrated load at a simply supported span. All the beams correspond to compact section, and four span lengths ranging from 1.5m to 3m are chosen for each of the sections. The effects of beam monosymmetry on the deformation capacity and the ultimate strength are investigated by using various slenderness parameters. Test results are also compared with some design stregnth curves.

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In this research, about 2000 painted specimens have been exposed at 4 different corrosive areas since 1988. From the result of this exposure test for 6 years, performances of heavy duty anti-corrosive paintings for newly-built steel bridges were mainly investigated. As a result, corrosion rates of 4 exposure areas were found to differ greatly each other mainly caused by the differences of environments. Appearances of corrosion such as areas, average depths and steel weight reductions were also found to differ greatly in each exposure area. In addition, performances of paintings against corrosion were also found to be influenced strongly by the kind of paint system in addition to the difference of the climate.

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Fatigue strength of the joint between diaphragms and longitudinal ribs on lower flange in box girder of suspension bridge was investigated by means of fatigue tests and stress analyses. Fatigue tests were carried out on large scale specimens which were models of transverse section of box girder and had various size of cope holes at the crossing joints. It was found that smaller cope hole was appropriate for reducing the local stress and increasing fatigue strength. However, when no cope hole existed, high stress concentration occurred at the flange plate inside of through rib and fatigue strength became low.

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Local stresses around the cope hole in I-section members of steel bridges were investigated by finite element analysis in order to propose a simple method to estimate the stress concentration factor for the detail from geometrical parameters and loading conditions. Based on the results, fatigue design method for this detail including the influences of shear deformation of the flange plate inside of cope hole was proposed.

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Low cycle repetitive loading tests are carried out using steel beam-to-column joint specimens in order to investigate low cycle fatigue behavior of the joint. Fatigue cracks are developed from the fillet weld toe at the stress-concentrated portions in the corners of beam-to-column joints. These cracks are initiated in the very early stage of cyclic loading. The crack initiation life of steel beam-to-column joints can be evaluated by means of elasto-plastic finite element analysis, using three-dimensional models and the cyclic stress-strain curve.

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The equivalent vibration system for water in TLD is useful in calculating earthquake responses of the structure installed with TLD. This system is already well known concerning the horizontal vibration of rectangular and cylindrical TLD. When a structure whose rigidity and gravitational axis do not correspond is struck by earthquakes, TLD vibrates around vertical axis with the structure. In this paper, the equivalent vibration system is obtained theoretically when rectangular TLD vibrates around vertical axis. Then, the values of the system for water in rectangular TLD are obtained by experiments. Finally, the validity of the theoretical expressions is shown.

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The rubber devices to distribute the seismic lateral force for the multi-span continuous girder bridge was developed utilizing its compressive deformation. First, the force-displacement relationship was verified from the loading tests of the specimens, which resulted in the highly nonlinear relationship showing the hardening effect of rubber material. Then, the inelastic earthquake response analysis of the multi-span continuous bridge with the rubber elements was conducted to verify the effect for the distribution of seismic lateral force. Though the girder showed the acceleration response with some impulses, the deformation of the girder was suppressed to be small. Furthermore the maximum reaction force of each pier was almost identical.

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In severe earthquakes such as the Kobe, it is reasonable to allow minimum repairable damage to elevated highway bridges. To keep damage under control, earthquake-induced damage must be allocated to each structural element appropriately. In this paper, optimal allocation method of damage is proposed considering the seismic performance of the total structural system. First, the relationship between damage to each element and its repair cost is established, and that between the initial cost and seismic performance is also derived. Then, optimal damage allocation to minimize total cost is obtained by combining these relationships with nonlinear dynamic analysis of a foundation-pier-isolation-bearing system.

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We had studied on earthquake resistance and damage by Hyogoken-nanbu earthquake of reinforced concrete viaduct between Sumiyoshi and Nada on JR Tokaido Line, in order to find the earthquake resistance on design required to this earthquake. The viaduct had been damaged most heavily in railway structures on Hanshin-awazi earthquake disaster, January 1995. As a result of using the response acceleration in case of elestic behavior as a index of earthquake resistance, it was found that the structures which have earthquake resistance of 1, 000-1, 200 gal do not collapse only sinking and transformation, more than 1, 200 gal is slight damage or below the fall of cover concrete.

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Hysteretic models for pier base-to-footing connections are presented with a view to applying them to the dynamic analysis of steel piers under seismic loading. First, the hysteretic behavior of double anchor-beam type connections and that of single-anchor beam type connections are experimentally investigated. Then, based on these experimental results, a semi-empirical model and three simplified models are proposed for both types of pier base-to-footing connections. The accuracy of the proposed connection models is examined by comparing with the experiments. In addition, it is examined how the overall behavior of steel bridge piers is influenced by the modeling of connections. Finally, taking all the results into consideration, we discuss a practical connection model which can be used for design.

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The authors have conducted analytical simulation studies focusing on the failure of box conduits with intermediate columns. The effect of surface geology to the responses of ground were evaluated by the multi reflection theory, the seismic responses of soil structure interaction system were evaluated by 2-dimensional dynamic equivalent linear method with taking account of the nonlinearity of soil by the equivalent linear method as well. The calculated ratio of applied force to ultimate strength in shear of intermediate column revealed that the column was critical in shear failure. By the static 3-dimensional FEM nonlinear analysis, it was predicted that shear failure of the intermediate columns occurred in prior of reinforced bar yielding in all structural members.

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The authors derived a 3-dimensional time domain Green's function for a rectangular distributed moving load on a uniform soil stratum. The integral transform procedure was applied to obtain the solution and the discrete wave number method for the inverse transform. Alternatively, the time domain analysis was conducted for time dependent loading functions whose intensities vary with time from the convolution integral with use of the time domain Green's function for an impulse through a discrete convolution method on space and time steps. Regarding the speed and frequency of the moving load, case studies were demonstrated which gave useful information to evaluate vibration effect as induced by certain loads associated with initial conditions.

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We propose a method to theoretically estimate response spectra at the points where the seismic records are not available during earthquakes. Spectral characteristics of earthquake motions at the ground surface are evaluated considering effects of rupture process of faults and the nonlinear amplification through shallow ground. The expected value of maximum response acceleration of a single-degree-of-freedom system is evaluated by using spectral moments of the predicted motion in frequency domain. We apply the method to estimate the acceleration response spectra at several points in the severely damaged area during the 1995 Hyogoken-Nambu earthquake. A method is also proposed to modify the theoretical response spectra with observed seismic records.

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Field stress measurements were carried out for a typical box girder bridge with orthotropic steel deck both in summer and in winter. The measured stresses in summer, when the temparature of deck plate was over 40 degrees, were similar to the stresses measured after the asphalt pavement was removed. When the temparature was low, the stiffeness of the asphalt pavement seemed to increase, and the measured stresses decreased accordingly. Fatigue assessment of the structual details of the orthotropic steel deck, considering the temparature effect of tha asphalt pavement, revealed that butt-welded trough ribs had little possibility of fatigue cracking. However, longitudinal fillet welds of the trough ribs to the deck plate showed relatively short fatigue life.

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Kurushima Bridge is a group of three suspension bridges and it constitutes one of the Honshu-Shikoku Bridges, the Nishiseto Expressway. It consists of 6 main towers 2P, 3P, 5P, 6P, 8P and 9P. It was predicted that vortex-shedding vibrations occur under construction of these towers, and therefore, mechanical vibration suppressers were implemented in order to ensure the construction works and to protect the erection machines. This paper introduces an active mass damper (AMD) system and a pair of tuned mass dampers (TMDs) installed in the tower 5P, and describes the result of the vibration tests and the field observations conducted during the free standing state. It is confirmed that the performance of the AMD system and the TMDs satisfy the required damping of the each erection step. It is also shown that the AMDs system is efficient for suppressing vortex-shedding vibration.

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This paper reported the loss factor of beams covered partially and separately by constrained viscoelastic layer. The loss factor of three layered sandwich beam was calculated by strain energy analysis. Four support conditions, Pin-Pin, Fix-Fix, Fix-Free and Fix-Pin were considered in analysis. At low vibration mode, loss factor of partially covered sandwich beam becomes higher than that of fully covered one, not related with support conditions. However, this phenomena was disappeared at higher vibration mode due to distribution of bending moment. When the viscoelastic layer covered fully is divided into a few sections, loss factor becomes higher depending on the number of separation, material properties and vibration mode.

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This paper presents a method to estimate the effect of measurement noise on identified parameters in structural parameter identification problems. The effects of noise is given as a confidence region of identified parameters using the propagation law of errors and sensitivity of parameters with respect to errors. Furthermore, regarding an identification method based on the concept of prior information, a similar formula for the confidence region is derived. The validity of the formula is confirmed by numerical simulation.

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