In Japan, many high-rise buildings adopt the passive control devices, such as steel damper, oil damper, viscose damper, viscoelastic damper etc., to decrease the response of building. It has been recognized that the viscoelastic (VE) dampers have significant advantage over other types of dampers in controlling response of building against not only earthquake but also wind excitation. VE materials are typically made of polymers or glassy substances. Typical harmonic response based on the relation of force and deformation of VE damper is shown in Figure 1. It is commonly known that dynamic characteristics of VE damper are represented by K'd and K"d , and these are depending on the frequency and tempera-ture (Kasai et al. (1993), Sato et all (2007)). When a building with viscoelastic dampers is subjected to wind excitations, its dynamic properties such as vibration period and damping ratio can vary, depending on the frequency components of the excitation. This is due to frequency sensitivity of the viscoelastic damper, and contradicts the basis of the conven-tional spectral modal analysis method using the constant dynamic properties evaluated at resonant state of the building. This paper points out the need for considering frequency sensitivity of a building when it possesses velocity-dependent dampers such as viscoelastic dampers, and proposes for the first time a new spectral modal analysis method to predict the wind-induced response, considering the frequency sensitivity of the viscoelastic dam-per.
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