Probabilistic effectiveness of visco-elastic dampers considering earthquake excitation uncertainty and ambient temperature fluctuation

Abstract

The mechanical property of the visco-elastic damper (VED) is dependent on the loading frequency and the ambient temperature. Due to the frequency-dependency, the effectiveness of VED varies as the earthquake excitation alters. However, such an excitation-sensitivity is usually ignored in the design and evaluation of VED. To rationally quantify the VED effectiveness considering the excitation uncertainty, a probabilistic analysis scheme is proposed. In the scheme, multiple response history analyses (RHA) are conducted to reveal the probabilistic properties of the VED effectiveness. The required number of RHA is studied based on three earthquake databases and three VED-structure models with different natural periods. It is shown that at least 30 RHA analyses are needed to get a good result. Due to the temperature-dependency of VED, the probabilistic results are notably influenced by the ambient temperature. Unfortunately, by far, there is no approach to account for the effect of temperature fluctuation on the probabilistic effectiveness of VED. To address this problem, the Fourier series are adopted to model the building thermal environment. By doing so, the seasonal fluctuation of temperature is well incorporated, and the probabilistic property of the working temperature of VED is obtained. Based on the law of total probability, a probabilistic framework for evaluating the effectiveness of VED is established by integrating the effects of excitation uncertainty and temperature fluctuation. The framework consists of two major steps. In step one, the probabilistic effectiveness of VED is computed under a series of pre-defined temperatures. In step two, the probabilistic results under the specific temperatures are integrated over the fluctuating range of the temperature. An example is provided to illustrate the application of the proposed framework. From the example, the temperature fluctuation has little influence on the expectation of the VED effectiveness, but it notably affects the dispersion of the probabilistic effectiveness of VED. In this study, two types of VED (Acrylic and Diene) are considered. The conclusions drawn from the two types of VED are alike.