The aim of the Bachelor’s thesis was to describe and evaluate the most common connection details between steel-concrete composite (SCC) beam DELTABEAM® and Cross-Laminated Timber (CLT) slab in two variations: with and without concrete topping. The purpose of the thesis was to provide a basis for future studies that are to expand the CLT range of appliance in Finland. The thesis was based on a theoretical description of the four different connectors that utilize the same working principles as the connections used for joining concrete floor slabs and the beam using the German standard details. The calculations were done according to the Eurocode 1995 and German timber design code DIN1052. The result of the thesis was the connection details library. The result of the study allows to conclude that by using described connection details, the CLT slabs and DELTABEAM® form a reliable flooring system.
Concentrated loads on Cross Laminated Timber elements (CLT) in areas of point supports or load applications cause high local shear stresses. Inclined self-tapping screws with continuous threads have turned out to be an effective reinforcement. As neither the German design standard DIN 1052 nor technical approvals cover this construction method a research project funded by the AiF was conducted to gather basic information for its application. These basics include the determination of shear stresses next to concentrated loads, the interaction of compression perpendicular to the grain and rolling shear stresses as well as theoretical and experimental examinations of the load bearing behaviour of reinforced CLT-elements. This paper presents the main research results. A design concept validated by means of the test results is proposed.
An experimental study of the influence of an exposed combustible ceiling on compartment fire dynamics has been performed. The fire dynamics in compartments with combustible cross-laminated timber ceilings vs non-combustible reinforced concrete ceilings in otherwise identical compartments with three different ventilation factors were investigated. The experimental results are compared against predictions from two theoretical models for compartment fire dynamics: (a) the parametric fire model given in EN 1991-1-2, and (b) a model developed at Technische Universität Braunschweig, which are the parametric fire models currently used in Germany. It is confirmed that the introduction of a combustible timber ceiling leads to higher temperatures within the enclosure, both under fuel-controlled and ventilation-controlled scenarios. It is also demonstrated that the theoretical models considered in this article require refinement in order to adequately represent all relevant scenarios when combustible ceilings are present. A refinement of the German model, by adding the fuel from the combustible ceiling to the occupancy fuel load, was shown to not adequately capture the response for the ventilation-controlled fires.
CLT is becoming global. New countries and regions increasingly realize the potential of what can be done with CLT. As a result, new markets are forming and new companies are entering the industry. Every new region or country that opens its doors to CLT has its own challenges and opportunities. However, there is the unique opportunity to learn from the existing Original Market in Europe and the companies that have been successful there for many years. Especially the German-speaking alpine region was, and still is, the cradle of CLT innovation. Therefore, this research,using qualitative methods, analyzed market characteristics and business models of this region. Lessons learned over the years were identified such as the importance of high-level timber education, the role of designing for building services, hype versus reality with respect to tall wood buildings and how careful design processes are key to competitiveness of CLT buildings. Threats and challenges in the North American CLT market were also identified there. The combined findings give an enhanced understanding of how the implementation of CLT in North America, as an example of a new global market, can be fostered.
Within the German research project “Fire resistance of primary beam - secondary beam connections in timber structures” solutions for a fire-safe design have been developed. The project concentrated on connections with self-tapping full thread screws and joist hangers. This paper describes the investigations, calculations and experiments on the former type of connections. Herein, a series of loaded fire tests and numerical simulations were conducted with the objective to develop design rules and determine the load-bearing capacity.
Acetylierte Radiata Kiefer, das Produkt einer speziellen Holzmodifikation, besitzt eine verbesserte Dauerhaftigkeit und Formstabilität. Sie ist grundsätzlich für die Herstellung von Brettschichtholz frei bewitterter Konstruktionen geeignet. In der Forschungsarbeit werden entsprechende Kennwerte, die für die Bemessung von Bauteilen und von Verbindungsmitteln erforderlich sind, mit wissenschaftlichen Verfahren hergeleitet.
The usage of holes in glulam and LVL beams is a common practice in timber constructions and requires in many cases the application of reinforcement. At present, Eurocode 5 does not contain design rules for holes, nor for their reinforcement, which are, however, regulated in the German National Annex to EC5. Although it has been proven that internal rod-like reinforcements improve the shear force capacity of a beam with holes, several problems still remain, particularly the inability to successfully reduce peak stresses at the periphery of the hole, especially shear stresses. Inclined internal steel rod reinforcements were studied and compared with vertically oriented rods, which is currently the only regulated application. The analysis revealed a reduction of both perpendicular to grain tensile stresses and shear stresses, which for the case of vertical rods are not reduced at all. A first attempt at the design of such inclined reinforcements was made by deriving an equation based on the results from FEM simulations. The design approach was then applied to an example case. Experimental verification of the theoretical observations is still necessary and ongoing, though a very promising approach for an improved internal reinforcement and its respective design can already be observed.
A residential building with cross-laminated timber structure in Granada (Spain) was analyzed using the life cycle assessment methodology, life cycle energy analysis and sensitivity analysis to changes in efficiency of operating energy, materials database, transport distances and different scenarios for C&DW. The environmental impacts of the materials and construction production and embedded energy were relatively significant. The global warming impact category was very low due to the CO2 sequestration of wooden materials. Sensitivity analysis revealed that the most significant reduction in environmental impact was achieved through improvements in energy efficiency, high uncertainty in the impacts of the environmental product declaration, the low effect of long-distance transport on the overall impact and the feasibility of the objective of recovery of the Waste Framework Directive by 2020 (above 70%).
A newly developed reinforcement system for glulam, actually representing a new generic wood com-pund, is presented. The composite consists on a hybrid cross-section, composed of intercalated layers of GLT and LVL, glued together along the width-direction of the beam. The specific build-up improves in first instance the mechanical properties of the glulam in the direction perpendicular to the grain significantly. Hence, the composite is especially well suited for the reinforcement of arrays of large holes in wide cross-sections. Secondly, the layers were tailored in such a manner, that the bending load capacity equalls that of the gross-cross-section. A parametric study was performed by means of the finite element method, to study the redistribution of stresses perpendicular to the main axis of the beam in the region of stress concentrations at one of the hole corners. Specifically, the load sharing of the vertical tensile force F_t,90 described in the German National Annex to EC5 was analyzed, and an analytical relationship depending on the thickness, elastic modulus and moment-to-shear-force ratio was developed.
Timber construction has become completely modernized. It has gained considerably in market share with respect to competing building materials and is dominated by systems such as frame and solid timber construction.
Every timber construction is determined by its structure. Hence it is essential to know the connections and relationships from the design stage right through to the construction phase. Systems in Timber Engineering takes a whole new approach to this subject. It is a comprehensive, analytical, and visually organized treatment, from the simple single-family house to the large-scale multistore structure. It includes the building envelope, which is so important for saving energy, and systems for ceilings and interior dividing walls, which are so essential from the vantage point of construction.
This work uses plans, schematic drawings, and pictures to show the current and forward-looking state of the technology as applied in Switzerland, a leading country in the field of timber construction.
