Seismic Response of a Concrete Viaduct Reinforced by Steel Braces

After the Hyogo-ken Nanbu Earthquake of 1995 in Japan, the code of seismic design of highway bridges was revised to meet the new requirements. Meanwhile, the seismic strengthening of viaducts has becomed very important for protecting the structures from damages caused by intensive earthquakes. In this paper, an existing reinforced concrete viaduct was taken as an example to check its seismic behavior following the new Japanese seismic design code. The viaduct was modeled as a 3-dimentional frame skelton (Fig. 1). The reinforced concrete members were simulated by fiber models (Fig. 2), in which the nonlinear behavior of the concrete and the reinforced bars and their interaction could be included. The seismic capacity of the viaduct was firstly checked by static nonlinear analysis(pushover analysis) and then the dynamic response to an intensive input motion was carried out. It was found that the viaduct might suffer to a shear failure during an severe seismic event such as the Hyogo-ken Nanbu Earthquake. Hence, strengthening by using steel braces was proposed to upgrade the seismic capacity of the viaduct. Checked by both static and dynamic response, the strengthened viaduct showed enough seismic capacity due to the limitation of the deformation by installing the steel braces properly. Figure 1 Analysis Model Figure 2 Concept of Fiber Model for Reinforced Concrete Member