Seismic design of a steel-concrete hybrid cable-stayed bridge - the Shin-Minato bridge

Toyama New Port is an important international port in the Hokuriku area facing the Sea of Japan, which is located near Toyama city, Toyama prefecture. Toyama city has a population of around 400 000, and is an important city in the Hokuriku area from the economic, culture and politics viewpoints. The port is an international multipurpose terminal and provides the berth for passenger ships and cargo ships transporting raw materials such as timber, coal etc. In order to attain smooth distribution of products from this international multipurpose terminal, the Ministry of Land, Infrastructure & Transport is now in charge of constructing a harbor road connecting the east and west sides of the port. This harbor road links the left bank (Kaiou-machi, Izumi city) and the right bank (Kairyu-machi, Izumi city) of Toyama New Port (see Fig. 1). The Shin-Minato Bridge, a cable-stayed structure, is located on the middle section of this road. In order to ensure safe navigation for large ships, a clearance exceeding 270 m wide and 47 m high is necessary. Therefore, a continuous cable-stayed bridge with steel-concrete hybrid main girder and steel towers was chosen. The center span of this cable-stayed bridge is 360 m long and the towers rise 127 m above sea level. The central span between the towers is a twin-box-type steel girder with an orthogonally stiffened steel deck; each side span girder comprises a three-cell PC box girder. Since the side spans are relatively short, a steel-concrete hybrid system was selected. This paper describes design issues relating to earthquake-resistant or earthquake-control design.