The positive bending moment capacity of composite steel girders is examined through parametric study employing elasto-plastic finite displacement analyses. The effects of initial bending moment on the bending moment capacity and on the web slenderness limit for section classification are investigated. Observations made during the numerical study indicate that the noncompact web slenderness limits in conventional design standards, which are based on tests of steel I-sections, are conservative for composite sections. Many sections, which are classified as slender by current specifications, demonstrate sufficient flexural capacity as noncompact. The conventional web slenderness limits for noncompact sections, independent of initial bending moment seems inappropriate for composite I-girders. The initial bending moment has considerable effect on the noncompact web slenderness limits. The web slenderness limits for compact and noncompact sections are proposed on the basis of the parametric study.

View full abstract

To minimize residual displacements in reinforced concrete columns, a design is proposed whereby a longitudinal post-tensioning tendon replaces some of usual longitudinal mild reinforcing bars. The seismic performance of such partially prestressed, reinforced concrete columns was investigated through a series of earthquake simulator tests. The effects of unbonding of longitudinal mild reinforcement and providing a steel jacket were also investigated. The partially prestressed, reinforced concrete columns studied performed remarkably well under strong ground excitations. Very small permanent deformations were observed after the tests, especially when the longitudinal mild reinforcement was unbonded and a steel jacket was provided.

View full abstract

In this study, a program for dynamic response simulation of a floating bridge subjected to both winds and waves have been developed. The program is able to handle the following matters at the same time: 1) the elastic deformation of the floating bridge, 2) the memory effect of the radiation wave forces, and 3) nonlinear restoring force characteristics of the mooring systems. The oblique incidence of waves and winds are able to be handled also. The developed program has been compared with the experimental results using the wave tank located in a wind tunnel, and good agreement between the simulated results and the experimental results has been obtained.

View full abstract

Attenuation relationships are proposed for PGA, PGV, spectrum intensity (SI), instrumental seismic intensity, and acceleration response spectrum of ground motion at the Class I, II, and III ground and engineering bedrock using about 11,000 strong motion records observed in Japan. The attenuation relationships include short period level of acceleration source spectrum as one of variables besides moment magnitude and source distance. After taking the short period level of each earthquake into consideration, errors of the regression analyses become remarkably smaller than those without short period level. Dependence on magnitude and regional difference of short period level are also discussed.

View full abstract

Properties for low-friction bearings, which have been developed for the floor isolation system of a long-span truss bridge, have not revealed. Therefore shaking table tests and analytical studies considering amplified vertical acceleration by main structure as well as horizontal acceleration have been carried out. The results show that the friction coefficient under the high speed is smaller than that under the low speed, and the effect of vertical input can be neglected under the design grond motion. In addition, a simplified design model is here proposed. It is rigid-plastic model appling the equivalent coefficient concept considering the velocity-friction coefficient curve below the design maximum velocity.

View full abstract

A rate-independent damage-elastic-plastic constitutive model for single crystals is proposed and incorporated with the method of two-scale analysis method to characterize both the deformation characteristics and the strength of polycrystalline metals. First, we introduce a relevant kinematics associated with the multiplicative decomposition of the deformation gradient into elastic, plastic and damage deformation components. Next, the evolution equations of state variables are formulated with the principle of maximum dissipation in the framework of multisurface plasticity, and the associated state update algorithm is developed along with the corresponding consistent tangent moduli. After examining the basic characteristics of the proposed constitutive model, we demonstrate the promise and potential of the developed two-scale analysis method.

View full abstract

Stiffness modification method is presented as a strong and pertinent means for the bifurcation analysis at a multiple bifurcation point with multiple critical eigenvectors. It hitherto has been problematic to find the directions of bifurcated paths with reference to the critical eigenvectors when the multiplicity is large. In order to resolve this problem, we revise the stiffness modification method, which is a systematic method to modify the entries in a few rows and columns of the tangent-stiffness matrix to reduce the symmetry of the system. The modification is conducted so as to reduce the apparent geometrical symmetry, and, in turn, to obtain the critical eigenvectors corresponding to the directions of bifurcated paths. The validity and usefulness of the present method improved herein are ensured by systematically obtaining a complete set of bifurcated paths of regular polygonal truss domes and honeycomb structures.

View full abstract

In order to utilize the bridge thermal deformation to the health monitoring, the temperatures of the bridge members as well as those deformations due to temperature variation have been monitored continuously over two years at the existing box girder bridge with orthotropic deck system. Those characteristics and relations are, then, investigated.
As the results, it is clarified that the thermal deformations strongly correlate with the temperatures and those relations are very stable for long term. Furthermore, it is shown that the monitoring of thermal deformation has possibility to detect the damage, by extracting the dominant temperature of the members to the deformation and proposing the evaluation method of the correlations.

View full abstract

A method to integrate information from seismic intensity and satellite SAR imagery has been formulated for post-earthquake estimation of building damage. By applying Bayesian updating theory, initial estimates based on seismic intensity are updated using the satellite SAR intensity imagery which detects the difference between pre- and post-event ground surface conditions due to building damage. Likelihood functions and fragility functions for damage estimation have been modeled on the basis of data from the 1995 Hyogo-ken Nambu earthquake. Making the best use of the two information sources, building damage rates and their uncertainty can be estimated quantitatively.

View full abstract

We propose a multi-scale analysis method for heat conduction problem of porous media based on the homogenization method. For the implementation of multi-scale heat conduction analysis, we discuss the differences and characteristics of the homogenization for heat conduction problem in comparison with that for deformation problem particularly by focusing our attention to the definition of micro-structure (unit cell). First, we formulate the homogenization method for heat conduction problem considering the heat transfer at porous boundaries in micro-scale and specify the points to notice of the formulation. Secondly, we examine the validity of the proposed method of multi-scale heat conduction analysis based on the homogenization method by carrying out simple several numerical experiments. Finally, a 3-dimensional numerical example for porous medium at elevated temperature is presented to demonstrate the capability of the method.

View full abstract

A new seismic upgrading method that employs a controlled rocking mechanism is proposed to improve the performance of upper-deck type steel arch bridges under transversely input earthquake waves. In this method, a rocking behavior that accompanies uplifts is allowed both for end piers and arch ribs. Furthermore, the rocking behavior is controlled by the energy dissipation rods installed at the bases of piers and arch ribs. The validity of the newly proposed seismic upgrading system is numerically examined under severe earthquake waves. As a result, the damages and the reaction forces observed in the original arch bridges are considerably reduced by the use of the new upgrading mechanism. Specifically, reduction of the damages and reaction forces in arch bridges is remarkable in case when the end piers and the arches have high shear rigidity and large aspect ratio. Since the proposed seismic upgrading system is installed at the bases of piers and arch ribs, this system will be easily implemented in the existing bridges. In addition, the installation or change of the energy dissipation rods is possible under dead load because the arch bridges can carry the dead load without these rods.

View full abstract

In this study, standoff detonation tests for reinforced concrete (RC) slabs with and without cover soil using Toyoura standard sand have been carried out to establish the blast resistant design and protective methods of RC shelters. The test parameters were mass of Pentolite explosive and standoff distance. After the tests, the damage caused in the slabs was investigated for craters, spalls and breaches. The main results obtained are as follows: 1) The cover soil is obviously effective as a shock absorber against blast loadings. 2) The damage of the RC slabs without cover soil may be better predicted using the method which is based on the McVay’s prediction method for spalling damage and proposed in this study.

View full abstract

Strong motion simulation technique using site-dependent amplification and phase characteristics, whose applicability is already shown for short-period ground motions, is applied to basin-induced surface waves with periods of several seconds. First, empirical site amplification factors are estimated for strong-motion sites in Kyushu region, Japan, including sites in calderas. Then, the tequenique is applied to simulate ground motions from the Kagoshimaken-Hokuseibu earthquake of March, 1997, with special reference to predominant basin-induced surface waves in the calderas at preriods of several seconds. The good agreement between the synthetic and the observed ground motions indicates the applicability of the method to ground motions with periods of several seconds.

View full abstract

In this paper, we propose a new attractor-based structural damage detection technique using chaotic excitation. We reconstruct attractors from responses and obtain quantitative features from the response attractors by using Recurrence Analysis. We use this feature as damage indicator. By comparing indicators between intact and damage structures, we detect and localize structural damage. The robustness against noise and sensitivity to minor damage of the proposed method are shown through numerical examples, in which we assume minor damage to a structure and high noises on input excitation and observed data.

View full abstract

A method for the analysis of elastic wave field is presented by means of the volume integral equation. The usage of the unitarity of the Fourier transform as well as the piecewise constant basis functions lead to a large scale non-Hermite sparse matrix from the integralequation. It is found from the numerical analysis that the Bi-CGSTAB method which is one of the iterative methods for the linear algebraic equation can be applied successfully to the matrix obtained from the integral equation. The numerical solutions of the integral equation showed good agreement with those from the surface spherical harmonics expansion. The behaviour of the scattred elastic waves are found to be well explained by the numerical solutions as well as the spectral structure of the scattered waves.

View full abstract

Because there is effectively no strong motion records in the near-source region of a huge subduction-zone earthquake, much of its characteristics remains unknown. In this article, near-source strong ground motions from the scenario Tokai earthquake are evaluated using empirical site-dependent amplification and phase characteristics. The site amplification factors are obtained using spectral inversion technique. Records from a M_J5.3 earthquake are used to verify the method used. The estimated near-source strong ground motions for the scenario Tokai earthquake are quite site dependent and, at some locations, even stronger than the near-source records from the 1995 Hyogo-ken Nanbu earthquake.

View full abstract

The ultrasonic test could be applied to evaluate welded joints of steel bridges. The time of flight diffraction (TOFD) technique was developed in the United Kingdom in the 1980’s and the technique has been applied to pressure vessels of power plants. However, the applicability of the TOFD technique to steel bridges has not been investigated sufficiently. A collaborative study was organized by the Ministry of Construction. The collaborative study focused on the applicability of the ultrasonic testing to the steel bridges, including the TOFD technique. A round robin test of the TOFD systems was carried out. Considering the ratios of detection and overdetection, the performance of the systems was evaluated. This paper describes the round robin test and some remarks on the applicability of the TOFD systems.

View full abstract

Composite orthotropic steel deck systems with SFRC pavement was proposed as an effective preventive work for fatigue damage based on the investigations on the effects on the stresses on the deck systems. The systems were applied to the actual structure for the first time, to the lower deck of Yokohama Bay Bridge. The effect of stress reduction by SFRC pavement were verified by FEM analysis and staric loading tests on the actual bridge. Furthermore, in order to evaluate the effects of SFRC pavement for long term, the monitoring system was developed by using optical fiber sensors.

View full abstract