An experimental determination of damping ratio of a multi-storey building subjected to aerodynamic loadings

Abstract

The present study focused on an experimental determination of damping ratio of a multi-storey building subjected to aerodynamic loadings. It used the methods of model construction, wind tunnel and dimensional analysis for the investigation. Although, the wind tunnel and dimensional analysis were successfully used in the past and in different ways by many Scholars and Engineers to investigate the problem of wind effects on buildings; but such solutions or efforts, did not include the influence of the building deflection (δ). The results of the study show that depending on the phase of the force with respect to motion, self-excited forces can be associated with the displacement, the velocity or acceleration of the structure. Due to the influence of these associations, these forces can be thought of as “aerodynamic contributions” to stiffness, damping and mass, respectively. The building deflection is therefore, considered to be an important structural quantity which affects structural quantities such as forces, moments, velocity and acceleration which severely affect the human perception criteria of occupants using multi-storey buildings. The damping ratio also proved to have been influenced by dependent variables such as stiffness, amplitudes of vibration, H/B ratio, Strouhal and Lo numbers at a basic wind speed of 52.5 ms-1. Therefore, it can also be inferred that the relationship in the variations of the values of H/B ratio and Lo number are inversely proportional to the values of the Strouhal numbers and damping ratio along the model height. Whereas, the amplitude of the vibrations progressively increased, while, a critically damped model and its stiffness decrease with increase in model height. All these are likely to provide wider areas of applicability in structural analysis and in particular, experimental use of wind tunnel for structural modeling and similitude. Key words: Dimensional analysis, Strouhal number, Bernoulli universal constant, wind loads, wind tunnels, multi-storey buildings, damping ratio, aerodynamics.