Timber-concrete hybrid structural systems : Examples, long and short-term dynamic monitoring, and numerical analysis

Abstract: Timber-concrete hybrid buildings are an innovative solution to increase the amount of timber materials in modern buildings. Due to its lower impact on the environment than materials like steel and concrete, the demand for timber products is rising as the construction industry aims to decrease its environmental footprint.Timber is naturally grown, and certain characteristics must be considered when used in buildings, such as strength and stiffness properties depending on variables like fiber direction and moisture content. In addition, timber is a lightweight material, which influences dynamic performance of timber elements and structures.To fulfill the requirements of a modern building, timber elements are sometimes combined with concrete elements, introducing timber-concrete hybrid buildings.This study aims to expand the use of timber-concrete hybrid buildings within the construction industry. The objective is to present different types of timber-concrete hybrid buildings and evaluate their structural performance to improve the level of knowledge for structural designers for the safe and robust design of such buildings. Typically, four different types of timber-concrete hybrid structures are found in building projects in Sweden. These types of building projects usually involve additional designers than regular projects due to a lack of knowledge in timber design. Additionally, different designers uses different statical models for their designs, even within the same building project. A mobile measurement system was developed to perform in-situ dynamic measurements. The system was used in a nine-story timber-concrete hybrid building during construction to investigate the dynamic properties and validate structural design models. A parameter study highlights different design parameters that have a large influence on these models. These parameters include the inplane shear stiffness of CLT wall elements, the foundation properties, as well as non-load-bearing internal walls. In addition, the long-term dynamic response of a four-story office timber concretehybrid building is presented. Over a three-years evaluation period, the results show a clear seasonal variation of the natural frequencies which correlates well with the moisture content within a CLT slab element. The results show that environmental effects are to be considered when comparing with finite  . A predictive model is presented that can be implemented in a structural health monitoring system for damage detection so that these environmental effect scan be filtered out.