The number of tall timber buildings being constructed in recent years is on the rise. This makes the topic of robustness increasingly relevant. With the use of carbon fibre reinforced polymers (CFRP), timber elements can be reinforced to improve strength properties and make failure modes more ductile. An investigation has taken place on the ability of CFRP reinforced softwood glued laminated timber to form catenary action in full-scale specimens. A novel setup has been used to perform a series of full-scale experiments. In order for catenary action to be activated, horizontal restraints are required. The setup comprises hinges to allow free rotation however no horizontal displacements. These idealised boundary conditions are a starting point to gain a better insight of the combined flexural and tensile actions occurring inside the beams during loading. In order to allow for the comparison with and validation of existing analytical models, the tensile force in each specimen is monitored using strain gauges, whilst deflections, rotations and strains are measured using a combination of LVDTs and optical measurement systems.

Cross laminated timber (CLT) is a wood-based product increasingly utilized in construction. It comprises multiple layers of boards arranged orthogonally to each other, providing the resulting panel with bearing capabilities in both bending and in-plane directions. Nevertheless, the computation of load-bearing properties for CLT remains challenging, as highlighted by recent studies. One of the primary challenges is establishing a comprehensive link between structural CLT properties and the base materials and layup parameters. Due to the inherent variability of wood and the orthotropic arrangement of CLT, extensive testing is necessary to determine mean and characteristic values.

To tackle this issue, this contribution proposes an efficient computational model. Initially, a layerwise plate model is developed to reduce computation costs compared to a full three-dimensional model, while maintaining precision in stress field calculations, particularly at layer interfaces. The resultant 2D multilayer plate model is implemented in the FEniCSx open-source finite-element package. Subsequently, damage models are devised to simulate crack initiation and propagation within or between layers, capturing the interaction between these diverse damage mechanisms. Anisotropic phase-field models are notably employed to regularize intra-ply damage localization. Following initial validation of individual damage mechanisms, the model will be calibrated and its predictions tested against available experimental data from various failure tests.

A novel multi-layered solid wood-concrete-composite floor system with combined shear connectors based on a structural design of the traditional “Dippelbaumdecke” (dowel beam floor) is introduced and investigated by means of its long-term static load-bearing and deflection behaviour on varying assessable scales.

The presented publication aggregates the results of the related experimental and analytical long-term investigations and gives an insight into the consequential time-dependent load-bearing behaviour of the assessed structural system under short-term loads, as well as into the arisen deflection behaviour of the structural component and its related creep mechanisms under permanent long-term loads.

As mentioned initially, the paper primarily focusses on the long-term static load-bearing and deflection behavior of the assessed novel structural system. These studies cover experimental and analytical investigations on varying assessable scales, as the properties of the examined composite floor system can ideally be described based on a combination of large-scale and mid-scale level explorations (overall structural floor system level resp. shear connector level).

In more detail, the investigations thereby are executed in form of flexural tests for the large-scaled explorations as well as in form of double symmetric push-out tests for the mid-scaled explorations. Furthermore, as the investigated structural system contains combined shear connectors, all experimental and analytical investigations are conceptualized and conducted for each stand-alone typology as well as for the combined typology.

Based on this chosen setup of structural investigations it becomes possible not only to describe the assessed structural system and its time-dependent properties on varying length scales, but also to characterize the explicit interactions between the used stand-alone shear connector typologies. In conclusion, decisive general parameters, as well as resulting explicit temporal effects within the composite system can be gained experimentally and can be pursued analytically. Furthermore pertinent statements regarding the ongoing standardization process of timber-concrete-composite structures can be derived thereof.

As a replacement of concrete and steel, timber is increasingly being recognized and used in the construction industry in the past decade thanks to the emergence and spread of Engineered Wood Products (EWPs). There are two scales of adopting hybrid structures: on the system level by adopting different materials for each building component, e.g. timber columns combined with concrete floor and steel beams, and at the building component level by combining different construction materials in one building element, e.g. CLT-concrete composite floor slabs. Building components formed by timber-concrete are often referred to as Timber-Concrete Composite (TCC) components. The connection/bonding mechanisms for TCC typically include dowel type fasteners, notches, notches combined with steel fasteners, and adhesives. To promote timber-based hybrid structures with sustainability goals, advanced computational tools to predict long-term behavior are required. The analysis and prediction tool also needs to be adapted for the specific use cases on the structural scale while keeping a fundamental multi-physics framework for scientific soundness.

The author proposes a multi-scale multi-physics modelling framework for timber-concrete hybrid structures. The proposed modelling framework starts from the micro-macrostructure of wood looking into moisture transport and diffusion, then upscales to timber element scale linking to time-dependent mechanical behavior, lastly incorporates the connections between timber-concrete and the mechanical responses on the structural scale. The formulation for timber and composite elements builds on the previously developed multi-scale multi-physics aging framework for concrete by the author and coworkers, which was implemented in the specialized modeling software MARS. As the hygroscopic and mechano-sorptive behavior of timber display similarities to that of concrete, it provides high feasibility to adapt the aging framework to fit the mechanical responses and long-term behavior of timber and TCC.