The development of polyurethane (PUR) adhesives for engineered wood products started in Switzerland in 1985. Those adhesives satisfied the need for formaldehyde free adhesives, which is mainly attributed to health and environmental reasons. However, due to new requirements concerning the high temperature resistance of adhesives, especially in North America, newly developed adhesives are basically banned from the market, and adhesive manufacturers face a new barrier to approve their new adhesive technologies on the market. The work presented in this thesis clarifies the influence of adhesives on the fire design of glued-laminated timber beams. Additionally, clear scientifically based requirements are identified, which should be met by adhesives used in glued-laminated timber beams in case of fire.
In this thesis, twelve different adhesives for both structural and non-structural applications were tested in large-scale fire tests on finger-jointed timber lamellas. Those fire tests indicated that structural adhesives certified according to current European testing standards exhibit sufficient strength in fire for the use in glued-laminated timber beams. Taking into account the crack pattern observed in the fire tests, no significant influence on the fire resistance was found between the studied structural adhesives. Therefore, it is not necessary to consider the influence of adhesives in the design of glued-laminated timber beams, given that the adhesive is approved according to current European testing standards.
The paper reports on the recent state of hardwood glulams technically approved in Europe and/or Germany for load bearing structures. Build-ups, mechanical properties, manufacturing specifics and issues related to strength equations including size effects are discussed. The high potential of this emerging structural timber product group is herein also revealed.
The driving forces for an increased attention in Europe towards glued laminated products made of hardwoods stems from several facts, the most important being: i) noticeable shortage and rapidly rising costs for softwoods, ii) high stocks of structurally so far not used hardwood resources in Central and Southern Europe and iii) a continuous shift in re-afforestation policies towards hardwoods due to better aptness of several broadleaf species versus soil and climate conditions.
Architects, engineers and researchers alike often cite practical reasons for building with wood. Since the development of curved glulam beams and columns over a century ago, the widespread use of massive structural timber elements has allowed architects and engineers to design and build in wood with unprecedented speed and scale. Moreover, rising concerns of climate change and the carbon-dioxide emissions associated with construction encourage the use of wood as a viable alternative to steel and concrete, due to CO2 sequestration in trees.
In mid- and high-rise buildings, the current shift from steel and concrete towards massive structural timber elements like glulam, laminated-veneer lumber (LVL) and cross-laminated timber (CLT) is evident in a number of recently completed timber buildings in Europe, ranging from seven to nine storeys. Several speculative design proposals have also been made for ‘timber towers’ of thirty, fortytwo and even sixty-five storeys, recognising that designing with massive structural timber elements in high-rise buildings is still in its infancy. This paper offers a new perspective on building with wood at this scale, beyond carbon sequestrationand construction.
This report comprises reslts from the work done within work package 1 in the WWN+ project "Silent Timber Build", WP 1: Prediction tools, low and high frequencies. The aim from this WP was to develop prediction tools applied for wooden constructions. Included in this is also to create necessary basis for enough accuracy for any European wood construction. It implies development of new methods but also to understand how input forces primarily from the tapping machine affects the resuts of impact sound levels. The WP also describes how models are developed, in order to provide expected accuracy and then how to further improve the models in order to optimize floor and wall assemblies. The Work Package has been closely linked to WP 2 but also WP3. Using the reults from WP 2, the prediction model results can be compared to expected values for any European construction. From that optimization of floor assemblies and refining of the model is possible.
In this study, Malaysian Dark Red Meranti (DRM) was used to manufacture glulam beams, following closely the requirements of BS EN 14080:2013 so as to emulate commercial production. Phenol resorcinol formaldehyde (PRF), commonly used in structural glulam production, was used in the fabrication of finger joints and laminations of the glulam beams. Factors influencing the mechanical properties of finger joints and bonding performance of laminations were investigated. Full size glulam beams were manufactured and tested in bending with partial and complete carbon fibre reinforced polymer (CFRP) reinforcement on the tension face and compared with the performance of unreinforced beams. A bench-scale fire test was proposed to describe the behaviour of DRM finger joints in tension under fire condition, in order to simulate the failure of finger joints on the tension side of a glulam beam in a standard fire test. Overall, DRM finger joints exhibited better bending strength than Spruce finger joints which represented softwood used in European glulam. Wood density and end pressure were shown to affect the strength properties of the finger joints. Higher cramping pressure was needed to produce DRM laminations with higher shear strength. The glulam beam with CFRP reinforcement had a higher bending strength than the unreinforced glulam beams but partial reinforcement had an adverse effect on beam strength. In the bench-scale fire test, DRM finger-jointed specimens exhibited lower charring rate than Spruce. Furthermore, PRF finger-jointed specimens showed better fire performance than finger-jointed specimens bonded with polyurethane (PUR) adhesive. In conclusion, it is hoped that results from this research will motivate engineers and architects in Malaysia to design and build structures from less-utilised local timber, specifically in the form of glulam, encouraging the timber industry in Malaysia to produce them commercially.
In timber engineering, self-tapping screws, optimized primarily for axial loading, represent the state-of-the-art in fastener and reinforcement technology. Their economic advantages and comparatively easy handling make them one of the first choices for application in both domains. This paper focuses on self-tapping screws and threaded rods applied as reinforcement, illustrating the state-of-the-art in application and design approaches in Europe, in conjunction with numerous references for background information. With regard to medium to large span timber structures which are predominately erected by using linear timber members, from e.g. glued laminated timber, the focus of this paper is on their reinforcement against stresses perpendicular to grain as well as shear. However, latest findings with respect to cross laminated timber are included as well.
Timber-concrete-composite (TCC) systems have increasingly been used in recent decades. One of the main reasons for this development is related to applications that could not be built with timber alone, but that become possible with a TCC solution. This paper first gives a short overview of the use of TCCs, the relevant regulatory framework, and then presents several case studies of TCC applications. The perspectives and examples are from Europe, North America and Oceania to give a worldwide perspective from regions where TCC systems are being used. The structural systems presented in the case studies include bridges and floors in public buildings. For each project, details of the application are presented and the way each one contributed to extend the use of timber in construction.
This paper presents an experimental and analytical investigation on the application of laminated veneer lumber (LVL) made of European beech wood (fagus sylvatica L.) in timber truss structures. Particular focus is laid on developing improved design approaches for dowel-type connections and on promoting ductile failure behaviour, as the connections in timber trusses are generally governing the performance of the whole structure. Embedment tests were carried out in order to assess the embedment strength values for beech LVL, which are necessary to design dowel-type connections. The results showed higher values for beech LVL, as compared to estimations using existing formulas from design codes. A series of tensile connection tests showed that, using cross-layered beech LVL, ductile dowel-type connections with high load-carrying capacities can be designed, given that premature brittle failures are prevented. Lastly, tests on full truss structures confirmed that the favourable behaviour of dowel-type connections in cross-layered beech LVL can be implemented in truss systems, improving the global behaviour of the whole structural element.
The report includes an overview of different floor assemblies used all over Europe. They have been selected and evaluated carefully and from that the floor assemblies are divided into different groups in order to fit to limit the number of possible setups. Hence the grouping is made in a manner that will facilitate modelling of floor assemblies using the different methods as developed within this project, Silent Timber Build. It can also be used in order to recommend different floor assemblies for different buildings and usage. The software that has been used and further developed within this project is a French software adapted to wooden building floor and wall components, “SEA Wood". In addition FEM software is used in order to improve and verify the results particularly in the low frequencies, which is of particular interest for structural solutions in wood.
Within several research projects and with the aim to optimize energy efficiency and ecological characteristics of structural building components the Department of Structural Design and Timber Engineering (ITI) at the Vienna University of Technology (VUT) developed several wood-based composite systems, which combine timber products with other conventional building materials and components. As a representative example for these developments, the application of wood lightweight concrete composites illustrates the extent of interrelationships in the development of complex system solutions when focusing on the increase of resource efficiency. The environmental assessment shows the ecological advantages of the developed concept compared to conventional concrete elements and underlines the potential for further developments. Assessment of structural wood-based wood lightweight concrete composites are illustrated in this paper.