Issue 47

Y. Mizuno et alii, Frattura ed Integrità Strutturale, 47 (2019) 209-220; DOI: 10.3221/IGF-ESIS.47.16 213 C LASSIFICATION OF ELEMENTS OF TRANSITION OF STRUCTURAL FORM coordinate system for a bridge incorporates movement, which occurs during the construction of the bridge. This is described by a combination of six degrees of freedom in three-dimensional space (Fig. 6). The x-axis is the bridge’s axial direction, the y-axis is the direction in a horizontal plane at right angles to the x-axis, and the z-axis is the vertical direction. The coordinate origin is set at the point where the rotation of the structural system is the simplest on the x-axis. Rot-x can support small rotations such as when the structure supports a dead load, but this ability decreases drastically as the rotation angle becomes large. Rot-y is effective in beam systems, but it cannot achieve the cantilever status in spanning system (suspension and arch). Therefore, its support base, such as suspension tower and bearing, moves vertically. Rot-z can occur only in a beam system (diagonal system structure and web system structure) because it can become a cantilever system. Figure 6 : Movement and rotation of the bridges. The element variations of structures include four typical structural systems are shown in Tab. 2. First, the structural condition of bridges is classified into the “spanning system” and “cantilever system” (Tab. 2). Then, the “spanning system” is classified into the free rotation condition (Rot) and fixed rotation condition (Fix) of the end point in the y-z plane. This classification can describe typical structural conditions of bridges, such as simple structure, consecutive structure, both- ends-fixed structure, and cantilever structure. Thus, all structural conditions can be described in the area enclosed by a heavy line in Tab. 2. Basic transitions of structural form in the construction process can be explained as a combination of them. Table 2 : Adaptability to spanning/cantilever systems and movement within six degrees of freedom . A