Aerodynamic Admittance Research on Wide-body Flat Steel Box Girder
Abstract: Aerodynamic admittance is a key parameter affecting the analysis accuracy of the bridge buffeting response. However, few articles have covered the issue of the wide-body flat box girder with much smaller depth-width ratio (such as 1/12 studied in this paper). Therefore, to explore the real buffeting force of the wide-body flat box girder, experiments of the static force coefficients and aerodynamic admittance are carried out in wind tunnel. Wooden segmental model has a scale ratio of 1/60 to an actual 42 m wide suspension bridge girder. Using the high-frequency-force-balance (HFFB) equipment fixed with the segmental model under the conditions of different wind speeds and different wind attack angles, wind power spectrums of the buffeting force are measured and the variation of aerodynamic admittance parameters is analyzed. The results show that the aerodynamic admittance of the box girder measured in the experiment with this so much smaller depth-width ratio differs from the corresponding classical Sears expression. Some inspiration can be presented for the future study of the buffeting response for this kind of much wider bridge with the similar ratio in this paper.
Characteristics of distributed aerodynamic forces on a twin-box bridge deck
Abstract To facilitate an effective assessment of stress-related bridge performance and safety, stress-level buffeting analysis of a long-span cable-supported bridge is necessary. A stress-level buffeting analysis requires knowledge of characteristics of distributed aerodynamic forces on the surfaces of a bridge deck. This paper first presents a formulation for distributed aerodynamic forces on the surfaces of a bridge deck based on the quasi-steady theory. The characteristics of distributed aerodynamic forces, such as pressure coefficients, pressure admittances and span-wise pressure coherences, are introduced in the formulation. In consideration of different characteristics of incident and signature turbulences, the empirical mode decomposition is then adopted to separate their effects on the distributed aerodynamic forces. Wind tunnel pressure tests of a sectional motionless bridge deck model were conducted to identify the characteristics of distributed aerodynamic forces on the surfaces of the Stonecutters cable-stayed bridge with a twin-box bridge deck as a case study. The results indicate that the separation of incident and signature turbulence effects is necessary and that the proposed framework is feasible although more works need to be done towards a complete stress-level buffeting analysis.
Laminar heat or mass transfer in rectangular channels and in cylindrical tubes for fully developed flow: comparison of solutions obtained for various boundary conditions
Abstract A comparison is made of results obtained with various boundary conditions at the wall of the channels. By comparing blood Sherwood numbers for finite wall resistance with those for constant concentration boundary condition only a small variation is found for various points along the blood channel.