The effectiveness of seismic displacement response control for isolated bridges, which behave nonlinearly at both the columns and the isolators, is studied using the LQR optimal active control. A typical viaduct is analyzed for evaluation. An extensive parametric study of weighting matrices is carried out to examine the effect on reducing the displacement response. The results indicate that the active control is effective in reducing the deck displacement at small control force levels. Further, the effectiveness of saturation of control force is investigated for preventing excessive control at large control force levels. Finally, the active control is compared with the passive control using viscous dampers.

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In order to evaluate the deterioration characteristics during the lifecycle of bridge rubber bearing, a series of long-term accelerated exposure tests are performed on four kinds of rubber materials widely utilized for bridge bearings. Different degradation factors are applied in these tests, such as thermal oxidation, ozone, low temperature ozone, ultraviolet radiation, salt water and acid rain. The test duration lasts from 96 hours to more than 6,OOO hours. Mechanical properties of aged rubber specimens are measured and compared. The effects of pre-strain are investigated too. The ageing behaviors of each kind of rubber are made clear. The test results are fundamental to the prediction of rubber bearings' durability.

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The authors conducted running constant-load and vibration-load tests on RC beams and slabs to quantitatively evaluate the experimental load-carrying capacity and the dynamic effect. The load-carrying capacity of the beams and slabs under running vibration-load was nearly approximate to the maximum running constant-load and upper limit running vibration-load. The dynamic effect of running vibration-load was evaluated from the experimental impact coefficient based on deflections. The experimental impact coefficient of RC beams and slabs was approximately 0.24 to 0.49. Because it was larger than the amplitude of working load, the authors evaluated a dynamic effect coefficient as a function of load amplitude.

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Since experimental studies of the characteristics of ultimate shear strength in the structural system of U-shaped steel girders, generally called open cross-sectional box girders, under construction have not been made so far, this study attempts to identify the characteristics by conducting load tests using experimental girders. Basler's formula for calculating ultimate shear strength was applied to U-shaped steel girders with diagonal web members to validate the formula by comparing it with the experimental results. In addition, reproducibility of the experiments was analyzed using a program for analyzing elasto-plastic finite displacement. Thus, the programs for the analysis and the conditions used as a basis for numerical studies of the ultimate shear strength of girders are verified.

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This article analyzes the characteristics of travel demand concerning return-home trips after the Off-Miyagi Prefecture Earthquake of May 26, 2003. This type of investigation is essential for formulating disaster prevention and post-disaster travel demand management policies. As such, this examination of person trips was conducted by randomly sampling 1,239 residents of the Miyagi metropolitan region which suffered the brunt of damage during the earthquake. The results of this analysis showed that 9.7% of the travel demand on the day of the earthquake changed with regard to start time of return-home trips or means of transportation. Consequently, it was discovered that trip makers changed their means of transportation after the earthquake. For example, they switched from trains to other means of transportation, and those that previously used cars and buses returned home mainly on foot. Furthermore, I found that the timing shift of travel demands advances in three periods of contraction, expansion, and convergence, and that there are three distinct types of trip elements (non-response trip, delayed-response trip, and early-response trip).

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In composite two-I-girder bridges, at the position which intermediate cross beams are installed, lalge stress transfer between concrete slab and steel girder is produced. Since the rotation of upper steel flange is restricted by vertical stiffeners, large stress transfer occurs. This paper describes on-site experimental results and based on them, the design method of studs is proposed. The experiment includes a long-term observation and vehicle loading. It is predicted, under the condition that the headed stud is not installed top of the vertical stiffeners, that no fatigue damage in studs and welding part between upper flange and vertical stiffener occurs within 100 years or so. Furthermore, the way of finite element modeling of the connecting part for estimating the stress level is also presented.

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A steel railway through-truss bridge with SRC slab has advantages on the reduction of the slab height and so on. The fact that the main trusses restrict the SRC slab makes difficult to verify the behaviors of the slab. The authors conduct pull-load and dry-shrinkage experiments by using model slabs and apply these results to the designs of three-span continuous steel through-truss bridges.
In this study, the authors demonstrate the behaviors of the lower chord members, cross girders, slabs and so on by measuring stress and strain of each member of these truss-bridges and analyzing them by considering the cracks of the SRC slabs. Based upon these results, the authors also propose simple and practical design methods of the SRC slabs.

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The authors investigated that a honeycomb-WIB (Wave Impeding Barrier of honeycomb celles) works for vibration mitigation for the traffic induced vibrations from viduct when constructed to surround the foundation, especially in the low frequency range. The thin layered method is taken to analyze the involved wave field to determine the size of the WIB cells and their area for construction. The interaction of structure-foundation-soil is analyzed by the 3D substructure method to show the WIB effect for the ground response reduction. The comparison with the buried wall for an alternative measure demonstrate the superiority of the honeycomb-WIB, claimg the reduction more than several dB at the low frequencies.

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In this study, aerodynamic characteristics of square prism in a uniform flow with respect to various angles of attack were investigated using LES turbulence model. As a result, mean forces, drag and lift, mean surface pressure, and mean flow patterns for all attack angles were met well with the experiments. It was found that computational domain in the spanwise direction gave strong impacts on fluctuations, drag, lift, and pressure, indicating that spanwise length should be long enough to evaluate quantitatively. Regarding power spectral density for fluctuating aerodynamic forces, the predictions were in good agreements with experiments in dominated frequencies. Finally, we proposed an estimation method of fluctuating aerodynamic forces with no spanwise length dependency, and confirmed the validity of the approach using the numerical results.

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Based on lessons from a large number of bridge failures during the 1995 Kobe earthquake, rubber bearings and isolation bearings have been rapidly adopted in new bridges as well as existing ones. The bridge with new bearings is expected to cause longer natural period of superstructure and larger response displacement of girders. However, few researches have done on behaviors of automobile running on elevated bridge under strong ground motions. This research examines measures to improve seismic resistance of elevated bridge from the viewpoint of driver's safety.

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As an estimation method of low cycle fatigue strength of welded joint in extremely large strain field, fatigue assessment method based on peak strain approach was verified. T-shape welded joints were employed for the low cycle fatigue test. The local strain field around welded portion and the peak strain at the cracked point was analyzed by elasto-plastic finite element method. The relationship between the peak strain and the fatigue life was consistent with the fatigue strength curve proposed by the authors. Consequently, it was demonstrated the fatigue assessment method based on peak strain approach was available even in extremely large Strain region.

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A hybrid approach of computational fluid dynamics and mesoscale modeling, Dynamical statistical downscaling procedure was proposed for wind climate assessment without onsite measurement and verified at Tappi Cape. The atmospheric stratification at Tsugaru Strait during summer causes flow convergence, which results in high wind speed at the cape throughout the year. Idealizing and realizing approach with computational fluid dynamics can take the effect of local terrain into account and the prediction error of annual mean wind speed at Tappi Wind Park was 7.6 percent. Compared to the spatial conditional nesting and temporal conditional nesting, proposed method reduce the prediction error of annual and monthly mean wind speed at Tappi Lighthouse from 29.8 percent to 4.6 percent and from 19.3 percent to 5.9 percent respectively.

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The advantage of the volume integral equation is in that it is possible to clarify the relationship between fluctuations of the wave field and radiation of waves. It is necessary, however, to hadle a dense and large size matrix to solve the volume integral equation in the case that the region for the fluctuation of the wave field spreads to a wider area. In this paper, a numerical method is proposed to obtain a sparse matrix for the volume integral integral equation. The formulation employed here is based on the wavenumber domain solution together with usage of the Haar scaling functions. The usage of the unitarity of the Fourier transform in terms of the Haar scaling functions reveals that the integral equation is transformed into a linear algebraic equation with a sparse matrix. Numerical calculations are carried out to verify the present formuluation.

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This paper presents an accelerated Green's function method for wave diffraction analysis of a very large floating structure (VLFS) in infinite water depth. The formulations have been made for multipole expansion of Green's function in infinite water depth and the expressions for conversion of the expansion coefficients, which are required for application of the fast multipole algorithm. Then, wave diffraction analysis around a very large floating structure in infinite water depth using accelerated Green's function method has been presented. Numerical examples have shown the efficiency of O(N) in computation time, where N is the number of unknowns for the velocity potential.

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The general theory of elastic stability was developed to elucidate the mechanism of the imperfection sensitive reduction of buckling strength of structures. Yet the application of this theory to real structural systems has been problematic in that they involve numerous number of initial imperfections. In order to settle this problem, we focus on the fact that, for a bilateral symmetric structure, a symmetric imperfection and an asymmetric imperfection have different imperfection sensitivities. Initial imperfections are decomposed into symmetric and asymmetric imperfections, and a generalized imperfection sensitivity law is derived through the assemblage of the influence of each symmetric and asymmetric imperfection. This law enables us to evaluate the influence of a number of initial imperfection in a systematic manner. The validity of the law is assessed through the comparison of the theoretical and actual strength of a simple four-bar truss for an ensemble of 100 random initial imperfections.

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As a tentative repairing method for fatigue cracks in steel bridges, resin injection method was investigated. The method aimed to restrain the crack closing behavior by the resin injected into the crack while it was temporary opened by local heating near the tip. The delay effect on crack propagation rate was clearly observed in fatigue tests when the proposed processings were applied to the specimens. An analytical prediction method for fatigue life extended by the proposed method was also proposed.

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