Wind Tunnel Test Study of Aerostatic Drag Shielding Factor of a Truss Bridge Section

In truss structures, the aerostatic drag coefficients are different between trusses in windward and leeward due to the shielding effect. To solve this problem, the shielding factor is introduced in Wind-resistant Design Specification for Highway Bridges (2004) of China which refers to BS5400-1 (1988) of British Standard. But it doesn’t take the shielding factors of non-zero wind attack angles into consideration in these two specifications. When calculating the shielding factor of the truss girder bridge which has a bridge deck system, it is necessary to add the height of bridge deck pavement into the windward truss and to include the windward area of bridge deck pavement to the overall truss for calculating the spacing ratio and the solidity ratio. Based on pressure coefficients from 24 measurement points, the shielding factors for different wind attack angles (from -10° to 10°) can generally be obtained. The results show that the shielding factor decreases with increasingly different wind attack angle and a ‘linear’ fit equation is demonstrated as a possible way to find the shielding factor of truss girder bridges.