Wind-Induced Dynamic Responses of Structures with Outrigger Systems
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Determination of the Strouhal number based on the aerodynamic behavior of rectangular cylinders
The Strouhal number is an important nondimensional number which is explanatory of aerodynamic instability phenomena. It takes on the different characteristic constant value depending upon the cross-sectional shape of the body being enveloped by the flow. A number of investigations into this subject, especially on the drag test, surface pressure test and hot-wire test, have been carried out under the fixed state of the body in the past. However, almost no investigations concerning the determination of the St on wind-induced vibration of the body have been reported in the past even though the aerodynamic behavior of the body is very important because the construction of wind-sensitive structures is recently on the sharp increase. Based on a series of wind tunnel tests, this paper addresses a new method to determine the Strouhal number of rectangular cylinder in the uniform flow. The central idea of the proposed method is that the Strouhal number can be obtained directly by the aerodynamic behaviors of the body through wind-induced vibration test. The validity of proposed method is evaluated by comparing with the results obtained by previous studies in three B/Ds at attack angle and a square cylinder with various attack angles. The values and trends of the proposed Strouhal numbers are in good agreements with values of previous studies. And also, the Strouhal numbers of B/D
Preliminary analysis of high-rise braced frames with façade riggers
In this paper, a simple method of analysis for preliminary analysis of facade rigger stiffened braced frames in tall buildings subjected to horizontal loading is presented. The facade riggers in the structure are located in the exterior frames in the direction of the lateral loading. The interaction between the braced frames and facade riggers is through the floor diaphragms adjacent to the chords of the riggers. The method of analysis requires the calculation of five stiffness parameters: bending and racking shear stiffnesses of the braced frames and facade riggers in addition to a bending stiffness of the exterior frames in which the riggers are located. The method allows a graphical procedure for obtaining the optimum level of the facade riggers in addition to a rapid assessment of the influence of the facade riggers on the performance of the high-rise structure such as the reduction in lateral deflection at the top and the overturning moment at the base of the braced frame.