Issue 47

Y. Mizuno et alii, Frattura ed Integrità Strutturale, 47 (2019) 209-220; DOI: 10.3221/IGF-ESIS.47.16 211 B ASIC THEORY his work relies on Kubota’s [4] previous research, which describes the form of fundamental bridge types and force acting upon them. A new method is developed to elucidate the transition of structural forms in the construction process. R ELATIONSHIP BETWEEN FORCE AND FORM OF FUNDAMENTAL BRIDGE TYPES enerally, five types of forces can be imposed on a bridge. These can be classified as follows according to the dimensions of the space where they can exist: axial force, that is, tension and compression, for one dimension; bending moment and shearing force for two dimensions; and torsional moment for three dimensions. Tab. 1. shows the forces acting on a bridge, dimensions that the forces that can exist within, typical structural systems that resist these forces, and corresponding fundamental bridge types. As ordinary bridges are usually constructed to cross at a right angle to obstacles, such as rivers, roads, or railways, and cross straight to the other side, torsional moment seldom becomes a major factor when selecting the bridge type. Thus, torsional moment does not correspond to any of the structural systems and bridge types in this table. In practical applications, there are obviously more bridge types. In addition, the forces acting on a real bridge are more complicated as several types of forces often act simultaneously on a member. However, it is important to understand that the dominant force imposed on a structure has a great influence on the form of the bridge. Therefore, this analysis pairs four bridge types (suspension, arch, girder, and truss) with their corresponding forces. The abovementioned four fundamental bridge types are related to each other, and the relationships are illustrated in Fig. 2. There are six combinations of two bridge types. Figure 2 : Continuous relationships between fundamental bridges [5]. Figure 3 : Interrelationships among four fundamental bridge types [5]. In this figure, the relationship between the suspension bridge and arch bridge is expressed as continuity. However, it could also be expressed as symmetry. Fig. 3 illustrates the interrelationships among the four fundamental bridge types related to T G