Studies Of Wind-induced Vibration And Wind-induced Fatigue On High-Rise Structures

High-rise structure is somewhat different from others because of being high, light, soft and slim. It has been widely used in some related fields such as power transmission, communication , broadcasting and television system. Due to its characteristic of shape, the dominating load of high-rise structure is wind load. With the growth of demand and progress of technique, it has been developed to be much higher, lighter and softer which increases its sensitivity to wind load.For the purpose of studying the vibration characteristics of high-rise structure under high wind speed, a model of single-rod transmission tower was tested in wind tunnel. The aerodynamic model was designed and manufactured with similar principle. The boundary layer was simulated in wind tunnel. The aerodynamic force coefficients in laminar flow and the dynamic response in turbulence flow were measured in the experiment. The results were converted to the real structure.The time series of turbulent wind velocity were simulated by wave superposition method for numerical calculation. The along-wind response was calculated in time domain. The equivalent static wind force was calculated by gust response factor method and load combination method respectively. The result was compared with that of the dynamic wind coefficient method. The infuence of coupling effect was taken into account and aerodynamic damping force was calculated. What's more, the across-wind response was analized by random vibration method. The results were compared with that of the wind tunnel test.Wind-induced fatigue of high-rise structure was analysed by means of S-N curve method which was based on accumulated fatigue damage theory. The distribution of stress amplitude was accounted by rain-flow method in time domain. The accumulated fatigue damage was calculated in frequency domain by equivalent stress method and equivalent narrow band method respectively. On the basis of equivalent narrow band method, a new method was proposed by dividing the wind-induced stress into background part and resonant part, which avoid complexity of calculating stress spectrum. The feasibility of this method was proved by comparing its result with that of other methods.In this essay, the application of fatigue crack growth theory to wind-induced fatigue was also studied. Taking the distribution of mean wind velocity into account, the random crack growth model under variable amplitude load was established. The time series of mean wind velocity with given Weibull distribution and time related funtion were simulated by zero-memory nonlinearity method. The sample of crack growth was calculated. The statistical quantities were gained by Monte-Carlo method. The equations of second-order moment method were infered. The distribution of crack length and reached time was approximated by lognormal model. The destruction probability was calculated. Some factors which influenced the crack growth were analysed at the end.