Cross-Laminated Timber (CLT) has significantly increased the potential for the use of wood in sustainable multi-story mass timber buildings. This paper explores the structural modeling of bracing systems in mid-rise CLT buildings under both static and dynamic loading conditions. The study aims to enhance the understanding and application of engineering models, ranging from simplistic hand-calculation methods to complex three-dimensional finite element models. For realistic modeling, the structural behavior at various levels, including connections, CLT elements and their interfaces, floor plans, and the overall structural system, must be described and discussed comprehensively.

Stress-strain properties of commonly used connections are described for both linear and non-linear analyses based on design codes and scientific literature. The horizontal displacement behavior of CLT shear walls is influenced by the element build-up, the connection stiffness, and the level of vertical load. At floor plan level, the distribution of reaction forces due to horizontal loads may be determined on a 2D-stiffness approach.

For dynamic analysis, the building can be modelled as a single three-dimensional Timoshenko beam element, a space frame model, or a finite element shell structure. The beam model, utilizing cross-section values from 2D-Stiffness calculations supports simplified engineering models. 3D structural models incorporate additional factors, such as the in-plane stiffness of the bracing ceilings, edge interconnections of walls across corners, and ceiling bending rigidity.

The study compares various analysis models, emphasizing the potential of push-over analysis in accordance with Eurocode 8 - Design of structures for earthquake resistance. The investigation also explores the potential of vertical prestressing with crenellated interlocking of wall elements. The paper concludes with a practical use case demonstrating the application of these modeling techniques at different complexity levels, highlighting critical findings and proposing directions for future research to develop robust, reliable, and efficient design tools for CLT buildings.

The research project Sys.Wood is supported by the Austrian Research Promotion Agency (FFG): FFG Project number: FO999896268

A concrete core usually provides the lateral stiffness of tall timber buildings. To further decrease their carbon footprint and construction time, lateral stiffening systems comprising only timber would be highly beneficial. Given the flexibility of timber, wind-induced serviceability displacements and accelerations are often the governing design criteria. However, the ultimate limit state should not be neglected and may sometimes be governing. In this paper, we present a parametric framework to assess and compare the serviceability and ultimate limit state of tall timber buildings with lateral stiffening systems comprising timber members. The framework assesses both gravity and lateral wind loading. Based on the building geometry, material properties, vertical loads and wind characteristics, it determines the relevant load combinations and the corresponding utilizations. The framework serves as an important tool to determine the relevance of various parameters on the limit states, and can optimize the structural systems and material use of tall timber buildings.

The number of timber buildings is increasing worldwide and many different typologies, use cases, and structural systems are found. The timber-construction industry has yet to reach the same level of standardization as the conventional construction industry. There is simply less experience since timber as a high performing, mass product is on the market for not more than 25 years.

In this research work, multiple buildings have been analyzed and the performance of the realized as well as the designed building has been compared. Realized buildings were evaluated through monitoring of the dynamic behavior, the test campaigns consisted of (a series of) one-time measurements during construction phase or in the completed building, respectively. This was made possible using a self-developed data acquisition system which allowed quick deployment without disturbing the residents or the construction process. In parallel, design models were created using commercial software. For the models, realistic parameters regarding material, foundation, the effect of non-structural walls, and connection properties were deployed.

The comparison between the models and the measured values often shows significant differences: while the mode shapes are basically identical, the eigenfrequencies regularly deviate significantly between model and reality. Interestingly, deviations in both directions are found. Parametric studies highlight the significance of different properties, the sensitivity of the properties often become evident. Using this method of comparison and the parametric study, the “most important” parameters can be identified. It is proposed that those parameters should be focused on in the design when selecting the “most appropriate” values.

Timber chock is one of the most important standing support systems widely employed in underground mining operations. This type of standing support system offers numerous benefits, including cost-effectiveness, rapid installation, and minimal service requirements. The structures of timber chocks are made by stacking several timber end-notch components, providing a full contact area between layers and an interlocking structure, which is constructed from Australian hardwood timbers, particularly the Gum family. The timber chock can stabilize mining areas where the roof is uncontrollably deforming, resisting converging loads from both the roof and floor to maintain underground stability and productivity at a high level. Thus, investigating timber chock is crucial for improving mine safety during operations. However, there are instances where overestimating the load-bearing capacity of the supports leads to collapse. This paper presents an investigation into the mechanical characterization of timber chocks. To this end, several experiments were conducted to determine the mechanical properties of timber chock structures. First, several small and clear sample tests, such as compression perpendicular to the grain and static bending tests, were conducted based on British standards. Additionally, visual grading of hardwood timber components was conducted to determine the structural grading of timber components. Then, as timber chocks have a full-contact structural configuration, compression tests were conducted on two-row timber chock structures to examine their behaviour at the contact level. Lastly, the effect of aspect ratio was studied to obtain the stiffness, load-carrying capacity, and dominant failure modes of the timber chocks under compression. The findings contribute to a deeper understanding of the mechanical behaviour of timber chocks subject to critical underground loading scenarios.

In this contribution, experimental modal analyses for a cross-laminated timber (CLT) plate are presented. The plate with dimension 1.2x1 m, consisting of three layers, is supported freely and excited by an electrodynamical shaker while the vibration response is recorded by a Laser-Doppler vibrometer in a frequency range from 50 to 750 Hz. Two series of experiments are discussed where the average moisture content differs by 2.6% as a consequence of drying due to in-door storage of the plate. Although the mass of the plate is reduced by drying, natural frequencies of the plate are reduced due to shrinkage. This is particularly the case for torsion-dominated modes (the first natural frequency is reduced from 95 to 91 Hz, for instance). This leads to the conclusion that the opening of joints in between the narrow faces of the timber boards is mainly responsible for this loss of torsional stiffness.
In accompanying finite element simulations employing a higher-order plate theory, effective elastic material properties (Young’s and shear moduli, respectively) are obtained by model updating for both sets of experimental data. Assuming homogeneous behavior throughout the plate, it is concluded that both the Young’s modulus in fiber direction and the in-plane shear modulus is reduced by approximately 10% due to shrinkage. These results are confirmed by more detailed 3D finite element simulations considering frictional contact between the narrow faces.
Hence, this contributions demonstrates the relatively grave effect of a low amount of drying shrinkage on the elastic and dynamic properties of CLT plates which complicates the assessment of the dynamic properties of these structures in practice.