Improvement of the Database of Natural Periods for Reinforced Concrete Buildings in Thailand

Abstract

This study aims to improve the database of natural periods for reinforced concrete buildings in Thailand by investigating the relationship between natural periods across multiple vibration modes and the building height. A total of 112 buildings located in Bangkok, its metropolitan area, Chiang Mai, and Chiang Rai were analyzed based on ambient vibration measurements. The dynamic properties were extracted using the Stochastic Subspace Identification (SSI) technique, which enables accurate identification of not only fundamental modes but also higher order and torsional vibration modes-an aspect rarely addressed in previous research. The analysis revealed a power-law relationship between the natural period and building height, with the first vibration mode showing the highest correlation (R² = 0.9162). Regression equations for the first three vibration modes were developed, providing refined estimations for use in seismic design. Additionally, the inclusion of low-rise building data helped expand the range and balance of the database, enhancing its applicability. This research helps fill the knowledge gap in existing studies and contributes toward future updates of national seismic design standards.