Effects of separation distance on wind-induced response of parallel box girders

Wind-induced response characteristics of parallel bridges were studied with various separation distances. Section models of box girders for a proposed and an existing cable-stayed bridges were tested in smooth flow. The two box girders have different cross-sections, and different response characteristics were observed with the opposite wind directions. Mostly, larger response was observed when the bridges were located in parallel than for the single bridge case; but in a few cases, smaller response was observed when the bluffer girder was located close leeward of the other girder. General conclusion could not be obtained, but the results of this study will serve as an example of complicated parallel bridge response characteristics. It was observed that the interference effects between the bridges built in parallel can be significant even with a separation distance as large as 8 times the deck width.