|Budget Amount *help
¥1,600,000 (Direct Cost : ¥1,600,000)
Fiscal Year 1995 : ¥300,000 (Direct Cost : ¥300,000)
Fiscal Year 1994 : ¥1,300,000 (Direct Cost : ¥1,300,000)
In this research, some considerations have been made on the hydrodynamic behavior of a submerged tubular concrete bridge, anchored to the sea bed by the tension-type mooring system of plane framework. The main girder has the elliptic cross sections with thickness ratio of 2 and the framework is composed of a number of steel tubes linked together at their ends by universal joints.
The dynamic characteristics of this structural system was clarified analytically by using a modified transfer matrix method.
Next, a discrete vortex method was employed for the analysis of the two-dimensional unsteady separated flow past the bluff body in a stationary state. Thereby, the opening angles of the separation points were roughly estimated from the mapping of the experimentally obtained ones of a cylinder for a post-supercritical range of Reynolds number by Joukowski transformation.
The summary of the results obtained for the incidence, alpha, over the range, 0ﾟ*alpha*5ﾟ,is :
(1) The time average of drag coefficient <@DAC<@D2D@>D2(/)-@>DA is roughly taken to stay constant, <@DAna(/)-@>DAmely, C<@D2D@>D2<similar or equal>
(2) The time averages of lift and moment coefficients, <@DAC<@D2L@>D2(/)-@>DA,<@DAC<@D2M@>D2(/)-@>DA,change linearly with incidence alpha, namely, <@DAC<@D2L@>D2(/)-@>DA<similar or equal>0.054alpha and <@DAC<@D2M@>D2(/)-@>DA<similar or equal>0
(3) The Strouhal number S_h does not change with incidence alpha, S_h<similar or equal>0.36.
(4) The ratio of the natural frequency, f_n, of flexural oscillation in the vertical plane of the structural system to the vortex shedding frequency, f_s, is, f_s/f_n = (V_r・S_h)^<-1> <similar or equal>3.6, where V_r is the reduced velocity.