Effect of Live Load on the Dynamic Performance of Joisted Timber Floors

Abstract

Timber constructions has increasingly grown popular over the last decades due to the environmental benefits compared to concrete and steel. Although there are many other benefits such as the high strength to low mass ratio, lowering gravity load and the foundation cost, there are still challenges. A lot of research has been done on timber construction and a new Eurocode 5 for timber construction is being discussed. Vibration serviceability of timber floors is one of the challenging topics. As timber has a relative high strength-to-mass ratio, the floors are often highly susceptible to vibration from excitation of different kinds. Human-induced vibration due to occupants activities including walking is a main concern. There are different types of timber floors used in constructions, including cross laminated timber (CLT) floors, joisted timber floors, timber-concrete-composite floors, and more. This study focuses on joisted timber floors. The influence of different structural characteristics and non-structural parts such as partition walls and floor finishing, has been investigated by several researchers indicating their potential to affect the vibration performance. This study investigates via experimental testing, the influence of furniture on the vibration performance of joisted timber floors. In this study, tests have been performed to capture the modal characteristics in terms of the natural frequencies, mode shapes and damping of different configurations of floors with and without furniture. Time-history acceleration response from walking excitation has been measured and analysed to evaluate the vibration response and human perception using peak acceleration, root mean square acceleration, weighted root mean square acceleration and vibration dose values. The results indicate that placing furniture on joisted timber floors can significantly affect the vibration response of joisted timber floors exposed to walking excitation and alter the modal characteristics of the floors. The vibration response is generally lowered, and vibration comfort enhanced. The natural frequencies are generally lowered, and damping is generally increased when adding furniture (considering the first two modes). However, these effects vary greatly between different floors and different arrangements of the furniture. Thus, quantifying any effect in relation to imposed mass to floor mass ratio require further studies. Lastly, imposed load with lower centre of gravity was used to investigate the impact of elevating the centre of gravity on the modal characteristics of the floors. The results indicate that elevating the imposed mass amplify the effect of lowering the fundamental frequency of the floors.