Eiki Yamaguchi

Bridge-Weigh-In-Motion by Two-Span Continuous Bridge with Skew and Heavy-Truck Flow in Fukuoka Area, Japan:

For clarifying maintenance requirements of National Highway 201 in the Fukuoka area, a project to investigate actual truck weights was initiated in the year 2002. To this end, the bridge-weigh-in-motion was employed. Nevertheless, a two-span continuous curved bridge with skew was the only bridge available in the area: the bridge is far from ideal for the weigh-in-motion. Preliminary field test taking account of various traffic situations was therefore conducted carefully to see if the project goal could be achieved with this bridge. The test result has confirmed that the bridge-weigh-in-motion employed in the present project can estimate truck weights with satisfactory accuracy, the error being 11.7% at most. The real-time weigh-in-motion system was then constructed and run for 237 days in the year 2004. The data thus obtained reveals characteristics of heavy-truck flow in National Highway 201 in the Fukuoka area.

Improvement of aeroelastic instability of shallow π section

Abstract From an economical point of view, a two-plate-girder bridge section has been examined as a bridge section for a long span suspension bridge. The two-plate-girder bridge section of H or π section inherently does not have good aerodynamic performances, as shown by the accident of the Tacoma Narrows Bridge with H section-type bridge girder. On the contrary, in the present paper, there has been an attempt to find the possibility of the aerodynamic performance improvement of the two-plate-girder bridge section of the π section by changing the intervals between the two plate girders. With respect to wind tunnel test results, in the vortex-excited vibration in heaving vibration mode, the on-set wind velocity and the vibration amplitude decrease with interval between two plate girders, and the flutter on-set wind velocity increases. These results show the possibility of aerodynamic performance improvement of the two-plate-girder bridge section.

Aerodynamic performance of improved shallow π shape bridge deck

Abstract Aerodynamic stability of π section, which is structurally economical, was studied. By locating the main girders at inward location, so that the ratio of the floor deck overhang C to the girder height D′, C/D′, to be 2.0, and also setting solid barriers at inward location, the wind-induced responses were much suppressed even under various angles of attack. Although, some wind-induced responses were still observed with the improved section, the magnitude of the negative aerodynamic damping that caused the vibration was found to be small, thus the section could be thought as a probable choice for long-span bridges. The stability due to the solid barrier location was accomplished by the separated flows mutual interference effect; the unsteady pressure on the upper surface of the deck decreased significantly for the torsional motion.

FEM-BEM superposition method for fracture analysis of quasi-brittle structures

Fracture analysis of civil engineering structures often requires appropriate modeling of discrete cracks propagating in an inhomogeneous or nonlinear material. For example, quasi-brittle materials, such as concrete, are characterized by formation of cracks with fracture process zone under tension and plasticity under compression. Application of either finite element method (FEM) or boundary element method (BEM) to problems involving simultaneously discrete cracks and inhomogeneities or plastic deformations faces certain difficulties. Therefore, we propose the FEM-BEM superposition method, which removes the respective methods disadvantages while keeping their advantages. In the proposed method, the original problem involving both material inhomogeneity or plasticity and discrete cracks is decomposed into two subproblems. The inhomogeneity or inelastic deformation is represented in only one of the subproblems, while the cracks appear only in the other. The former subproblem is analyzed using FEM and the latter one by BEM, so as to utilize the advantages of the two methods. The solution of the original problem is then obtained by superposing the solutions of the two subproblems. In order to verify validity of the proposed method we present numerical results of several examples, including both linear-elastic and nonlinear fracture mechanics. The results are compared with available analytical solutions or with data computed by other numerical methods, showing both accuracy and computational superiority of the proposed method.

Stress Concentration of Simply Supported Box Girder with Longitudinal Stiffeners Including Shear Lag Effect

This study is focused on stress concentration of longitudinally stiffened box girder accounting for shear lag effect by three-dimensional finite element analysis. For the practical design of steel box girders, longitudinal stiffeners are incorporated to add buckling strength of the girders. There were a few studies on shear lag effect of stiffened box girder reported in the past literatures. In the present study, the longitudinal stiffeners are added to the top and bottom flange plates of simply-supported box girder in order to examine the shear lag of flange plates. The size and number of stiffeners are designed according to AASHTO code. The loading conditions consist of concentrated loads at mid span and uniformly distributed loads along the girder length. The parametric studies on geometry of box girder are performed. The finite element mesh is paid attention through the use of multi-mesh extrapolation method to improve the solution accuracy. Based on the numerical results, stress concentration factors of box girders with stiffeners including the effect of shear lag are discussed. The empirical formulas are proposed to evaluate the stress concentration including effect of shear lag.