A long-span truss bridge with 980 m long, is located in the Hanshin Expressway near Osaka port and has seismic risk which cause failure to not a few main members due to scenario level II earthquakes. In this project, a damage controlled design concept is employed to achieve rational retrofit from a view of risk management. The concept differentiates main members that support vertical load from sub-members for lateral force such as seismic force. According to this design, main members should be liner and sub-members are allowed to perform nonliner and provide damping. In this paper, floor seismic isolation system and buckling restrained brace system are introduced based on the design concept and their response reduction effects are also described.

View full abstract

This paper presents an improvement of the current wind zone map of the Philippines. The Generalized Extreme Value (GEV), Gumbel and point process models were used in characterizing the extreme wind speeds in the Philippines. Available daily maximum wind data from 50 stations in the Philippines were also used in the analysis. The results show that the standard errors in the point process model are lower than the GEV or Gumbel models making it a better model. Finally a regional wind zone map (6 zones) was developed using extrapolated 30, 40 and 50 year return wind speeds from the point process approach. Wind zone maps were developed using kriging interpolation method of ArcGIS Geostatistical Analyst.

View full abstract

Multi-channel planar array probes had been developed in order to improve detectability of three-dimensional defects. The ultrasonic system, which is applicable to the planar array probes, was developed in order to make the compact and fast detection system. Specific 3D SAFT algorithms were proposed for the planar array probes. Experiments for verifying the improvement in detectability of three-dimensional defects and the advantage of the 3D SAFT processes were performed. The results show that the planar array probes and the 3D SAFTs show great improvement in detection and information of defects in three dimensions.

View full abstract

The paper addresses the fatigue problem of traditional connection detail for steel structures and provides the answer for the issue; replacement of the conventional ribs with the newly developed U-shaped ribs will maximize the fatigue strength of the rib-reinforced connection. Fatigue test for pole base structure has been performed to clarify that U-shaped rib configuration provides a dramatic fatigue property improvement in comparison with the orthodox rib configuration. Evaluation in accordance with the JSSC recommended S-N curve resulted in “stronger than grade C” for the newly invented rib, as opposed to “grade G” for the traditional rib structure.

View full abstract

Identification of external forces applied on a structure during its operational life is of practical importance for structural design and maintenance. Especially, identification using dynamic measurement has attracted much research interest because of its relative advantage in measurement. In this study, forces in 3 different types are identified experimentally, i.e. impact force, inertia force and sound pressure using Laser Doppler Vibrometer. Identification methods employed are: pseudo-inverse method and regularization method. Error obtained from each identification method and each experimental case is evaluated and the proposed method is shown to have wide applicability to various loading cases.

View full abstract

The paper is focused on composite deck with curved concrete and steel-plate forms. By the permanent curved forms, arch action can be expected during concrete casting and for live loads after concrete hardening. Fatigue tests using a wheel running machine were carried out to certify the fatigue durability of the composite decks. Also, the arch action and the composite effect between the concrete and these forms were made clear through specimens different in the shape and the structural type. The with the experimental results and analyses, the author derived formulae to predict the punching shear capacities for these arch shape decks by considering the arch action, eccentric loading and composite effect. Finally, the degrees of improvement on the fatigue durability of these arch-shape composite decks were verified.

View full abstract

It has been pointed out that the ground with an irregular surface causes complicated seismic responses. However, the process of generating this complex response is not yet clarified. In this study, boundary element-perturbation method has been developed to investigate scattering of seismic waves due to an irregular surface. This method is based on the boundary element method in frequency domain and perturbation technique employing the Neumann series. By using this method, the ground response can be separated into those induced by incident waves and scattered waves. Numerical results showed that the amplitudes of the scattered waves are affected by both distance and direction of the irregular surface to the observation points.

View full abstract

The vector ARMA model is structured by the contrability transformation of the discrete state equation for the dynamic equation of a highway bridge. Structural identification for the vector ARMA model is performed by the impulse testing using least-squares method. The discrete bridge-vehicle system equation is constructed by the vector ARMA model of bridge generated by the experiment and discrete vehicle equation. The covariance equation for the discrete bridge-vehicle-road surface model is derived. Authors proposed the estimation method for the bridge vibration level (r.m.s. value).

View full abstract

Bridges are mainly made of two types plate component, slab and girder. Such components are vibrated by road traffic, and radiate structure borne sound. In this paper calculation methods for the structure borne sound are derived by the theory of thin plate vibration. Test-run of heavy trucks on different type bridges and vibration force measurement with hammer impact on bridge surface are carried out. From those tests the vibration force caused by traffic is estimated. With the aid of the vibration force and the calculation formulas, the radiated sound is calculated. Also we compared the calculated results with measured sound and could explain the sound field with this method. It is shown that a good agreement is obtained between the theoretically predicted value and the measured one.

View full abstract

A series of compression loading tests was conducted to develop a confined model for high strength concrete cylinders. It is found that the confinement effect on the peak strength, strain at the peak strength and stiffness of the deteriorating branch decreases as the concrete strength increases. An empirical formulation for the peak strength, the strain at the peak strength and the stiffness of the falling branch was developed depending on the concrete strength. Also, a stress-strain model that represents an entire range of stress-strain relationship was developed. The proposed stress-strain model provides an accurate estimation for concrete with the strength from 30MPa to 90MPa and the volumetric hoop reinforcement ratio from 0.45% to 1.36%.

View full abstract

Dynamic cracking analyses were applied to evaluate earthquake-resistant safety of concrete gravity dams during large-scale earthquakes. Since occurrence and propagation behavior of cracks within dams are mentioned to be sensitively affected by damping characteristics of the structure, the proper estimation method of the damping characteristics of dam was firstly discussed by comparing existing shaking table test results of a plain concrete dam-shaped model with the results of dynamic cracking analyses using the smeared crack model. Dynamic cracking analyses based on the estimation were next performed to predict the crack occurrence and its propagation behavior of a real-scale dam considering base rocks during large-scale earthquakes. Moreover, the relationship between crack propagation length and input acceleration at the base was investigated to evaluate seismic safety of the gravity dam.

View full abstract

It is important to estimate the ultimate strength of U-shaped steel girders before the concrete slabs hardening under construction. Therefore, it is necessary to grasp the feature of the ultimate strength of U-shaped steel girders. However, only few experimental studies have so far been made at the ultimate strength of U-shaped steel girders. The purpose of this study is to investigate the characteristic of the bending strength of U-shaped steel girders by experiments. Furthermore, the method of evaluating the bending strength of U-shaped steel girders is developed by extending the previous method for I-shaped steel girders and the validity of the proposed method is confirmed by comparison with experimental results.

View full abstract

It is known that the bending strain of pile foundations is generated not only by the inertial interaction due to superstructure, but also by the kinematic interaction due to large deformation of soft soil layers. Therefore, it is highly necessary to investigate the characteristic of pile bending due to kinematic and inertial interactions. The present study focuses on the appropriate diameter that minimizes the bending strain at the top of the piles when subjected to these interactions simultaneously. In this research, the relation between the diameter of pile and its bending strain is evaluated based on theoretical approaches. As a result, the appearance of the adequate diameter that minimizes the pile bending strain and its conditions are found and their characteristics are investigated.

View full abstract

In order to investigate the driver's reactions during an earthquake, the present authors have performed a series of virtual tests using a driving simulator. Based on the results, traffic accidents may occur in case of heavy traffic because of strong shaking. The Japan Meteorological Agency (JMA) have a plan to establish a system to issue “Nowcast Earthquake Information”, which is an early warning of seismic motion. In this study, the effects of early warning to drivers are investigated based on the driving simulator experiments. The reactions of drivers with/without warning are compared to reveal the effects of early warning.

View full abstract

The purpose of this study is to verify the accuracy of the hierarchical plate/shell element and solid element in the case of thermal stress analysis. By using numerical examples of the plane stress analysis of a circular plate with a hole and thermal bending analysis of plates, the accuracy and convergence of these elements are demonstrated. Because the convergence of displacements and stresses becomes worse in comparison to the case of ordinary plate bending, singular elements are used to improve the accuracy. And, closed-form solutions based on Mindlin's plate bending theory for thermal bending of rectangular plates are obtained using Lévy's method.

View full abstract