System Identification of a Six-Story Lightweight Timber Frame Building Using Ambient Vibration Measurements at Different Environmental Conditions

Ambient vibrations of a six-story lightweight timber frame building were measured under different environmental conditions in order to obtain the modal parameters of the structure. Changes in temperature and relative humidity in timber can influence its response in terms of modal parameters. Namely, a moisture content change in the timber can affect stiffness, strength, and shape of the elements as well as the properties of the connections. Monthly measurements have been performed on a six-story lightweight timber frame building in Varberg, Sweden, built in 2021. The in-situ tests were performed using five battery-driven data acquisition units with 14 uni-axial accelerometers. Additionally, the building is permanently monitored using temperature and humidity sensors, starting ever since its construction phase. The ambient vibration data have been analyzed using two different only-output methods. The results obtained under different temperature and humidity conditions were compared in order to assess the effect of the environmental conditions in the building. This information can be used to ensure the building meets safety and performance requirements, as well as to identify potential issues that may need to be addressed during building design.