Changes in Vibration Properties of the High-Rise Building 50 Years after Construction

Abstract

This study examines the changes in vibration properties of a 120 m high-rise steel building 50 years after its construction. Microtremor measurements and forced vibration tests are carried out to understand the changes in vibration properties and to analyse the factors behind these changes. Vibration properties are measured for the first to third-order modes of the two translational and rotational components. The eigen periods, damping constants and mode shapes will be compared. Forced vibration tests are conducted with several forces, and the amplitude dependence of the vibration properties is evaluated. Furthermore, the influence of earthquakes and strong winds on the vibration properties are examined analytically to consider the factors that cause the changes. The experimental and analytical results showed that the primary natural period of the building increased from 2.3 s to 2.7 s, about 15%, in the 50 years after construction, and that the analytical change in natural period due to the effect of PC steel bar bracing on each floor and the actual one were generally consistent, indicating that the PC steel bar bracing may be a significant reason for the natural period increase.