No abstract

<p>The Shimotsui-Seto Bridge, Kita Bisan-Seto Bridge and Minami Bisan-Seto Bridge are highway- railway combined suspension bridges in the Seto-Ohashi Bridges, which connect Honshu Island and Shikoku Island in Japan. Cross sections of stiffening truss girders of the bridges are identical and have two levels for transportation. Upper level and lower level are for highway and railway, respectively. In order to satisfy the aerodynamic stability, open gratings are installed at the center divider and both sides of road deck. However, since small objects may drop through them and endanger railway operation, it is disadvantageous to use them in terms of maintenance.</p><p>In order to minimize range that requires open gratings, aerodynamic stability of the bridges was re-evaluated by three-dimensional flutter analysis. This analysis method was developed after the completion of the Seto-Ohashi Bridges. From the analysis, it was found to be possible to minimize the range that requires center gratings. Also, it was found to be possible to close all center gratings by installing center barrier.</p>