The building industry consumes a lot of material, which causes depletion of material stocks, toxic emissions, and waste. Circular building design can help to reduce this impact, by moving from a linear to a circular design approach.
To reach a circular build environment, all disciplines should be involved, including fire safety design. However, there is a contradiction between the objectives of circular and fire safety design, either affecting the aim of protection of material sources, or protection against fire risk.
Timber is a material that has high potential in contributing to a circular building industry, as it is renewable, recyclable and can store CO2. However, timber is combustible, which increases the risk of fire. Therefore, mass timber building design has traditionally been restricted by building regulations. To enhance mass timber building design research on timber buildings has increased, to allow understanding of the risks. However, yet general guidelines or understanding on the fire behaviour and risk in timber buildings is lacking. This is a problem for the fire safety design and the potentials of timber contributing to a circular building industry.
Until now, there was no specific method available that quantifies this relation between material use and fire risk in mass timber buildings. This limits the possibility of fire safety design and mass timber design to contribute to a more circular building industry. By creating a method that allows comparison between the economic and environmental impact of material use and fire risk, a well-founded choice of building materials is easier to make.
The design tool created in this research quantifies the impact on material use for fire safety measures relating to CLT, encapsulation and sprinkler availability and their effect on the fire risk in mass timber buildings. This way insight is provided between the balance of material use and fire risk. By the sum of the impact on material use and fire risk, the total “circular fire safety impact” value is calculated. This value represents the total economic and environmental impact of the design based on the choice of building materials. By changing the fire safety design, the most optimal design variant can be determined. This is the variant with the lowest total impact value.
This way, a circular design approach is used to steer fire safety design in mass timber buildings towards a design solution that does not only provide sufficient safety for people, but also provides maximum economic and environmental safety from a material point of view.
As timber is being used for several millennia as construction material, glued laminated timber (glulam), a highly engineered timber product, exists for about hundred and fifty years. In Europe, it is nowadays common practise to make glulam from softwood species, though in the last few decades glulam made from different kinds of hardwoods emerged. Iroko glulam is part of this development, as iroko is a hardwood species from the African tropical regions. The aim of this thesis is to investigate the bending strength of iroko glulam, as well as strength influencing features. From literature it is expected that the following features are of influence: density, modulus of elasticity, tension strength of the lamellas, finger joint strength and size. Several researches conducted in the past experiments to determine these mechanical and physical properties, focusing mainly on iroko sawn timber. Only few investigated iroko glulam, and none of those focused on finger jointed iroko glulam. In this lies the originality of this work: determining bending strength values of finger jointed iroko glulam, as well as density, modulus of elasticity and investigating mechanical and physical properties of the base material: iroko sawn timber and iroko finger joints. The laboratory experiments included the following: tension tests on 38 unjointed and 38 finger jointed lamellas, and four point bending tests on 12 glulam beams. Also density, modulus of elasticity and moisture content were determined. The experimental results yield the following characteristic values: a lamella tension strength of 17 N/mm2, a finger joint tension strength of 29 N/mm2, and a glulam bending strength of 42 N/mm2 (including size effect according to NEN-EN 1995, 2011). The experimentally determined characteristic lamella tension strength is a little lower than values found in literature. This is due to a large scatter in the test results: a coefficient of variance equal to 0.37 was found. However, if the grain angle is equal or smaller than 5°, a higher lamella tension strength of 27 N/mm2 is feasible. Grain angle is as expected a significant strength influencing parameter for iroko sawn timber. And it would suggest that the strength class is as expected D40 if the lamella bending strength equals 0.6 divided by the lamella tension strength. The ratio of finger joint bending strength (30 N/mm2) and tension strength (29 N/mm2) on the characteristic level was found to be equal to 1.06. This is smaller than expected from theory: apparently the 1.4 ratio commonly assumed for softwood finger joint strength values does not hold for iroko finger joint strength values. The investigated iroko glulam beams with depth 108 mm yielded a mean bending strength of 66 N/mm2 and a characteristic bending strength of 42 N/mm2. Due to the size effect and quasi-brittle failure this figures lie lower for full scale glulam beams, however, strength class GL24h is indeed a safe assumption for iroko glulam beams. These aspects explain the higher mean glulam bending strength compared to the mean finger joint tension strength of 40 N/mm2. A strong mathematical relationship between characteristic glulam bending strength and both lamella tension strength and finger joint strength was not found; however lamella and finger joint tension strength do influence the glulam bending strength. Furthermore, density does not influence any strength or stiffness property for both iroko sawn timber, finger joints, and glulam beams. Although there is a slight positive correlation with both dynamic and local modulus of elasticity of lamellas and its tension strength.
Cross-Laminated timber (CLT), and other engineered timber products, are under high demand due to their prefabricated nature and environmental benefits. A key concern surrounding the application of CLT in buildings is its combustible nature and subsequent contribution to a compartment fire. Previous research has shown that exposed CLT, under certain circumstances, can achieve self-extinguishment. This research aims to further experimentally investigate the fire performance of small-scale compartments containing exposed CLT. The focus of this study is threefold, namely to investigate: i) the influence of (commercially available) adhesives used in CLT panels on fire behaviour; ii) the influence of CLT panel configuration on fire behaviour and iii) the ability of design guidelines to predict experimentally obtained fire behaviour. By investigating these aspects, a detailed investigation into fire behaviour of compartments with exposed CLT is presented to characterise the influence of CLT on enclosure fire behaviour and assess the ability of CLT to reliably self-extinguish. In general, it was found that reliable self-extinguishment is promoted when small-scale compartment fire tests reveal the avoidance of burn-through behaviour (and a second flashover), due to the combined effect of CLT adhesive type and CLT panel configuration. The particular observations recorded in this research project (relating to adhesive type and CLT panel configuration) serve as a base on which to conduct further research (especially by conducting experiments at real compartment scales). In addition, the investigation into the ability of a design guideline to predict fire behaviour, namely a Parametric Fire Curve (PFC) calculation method that includes the contribution of exposed CLT to the fuel load, provided mixed results. Further refinement is required to improve the model’s ability to predict compartment behaviour.
International Scientific Conference on Hardwood Processing
An innovative approach using laminated veneer lumber (LVL) hollow sections for temporary geotechnical slope stabilisation is being presented within this article. The use of circular laminated veneer lumber hollow sections as reinforcement elements in soil nailing walls demands load bearing elements, primarily loaded in tension, with a length up to 10 m. Thus finger-jointing was found to be an efficient method of a longitudinal load-carrying connection in combination with a minimized cross section reduction at the joint. This paper discusses the applicabiltiy of finger jointing on beech wood laminated veneer lumber hollow sections and presents the results of large scaled tensile under variaton of the joint arrangement.
The Cradle-to-Cradle Certification at Platinum level, awarded to products which perfectly embody the principles of Cradle-to-Cradle design, is perhaps one of the most esteemed standards of excellence in sustainability circles. Currently, there is no Platinum-level product which can deliver the classic postand-beam structural system. This literature review investigates the possibility of a timber beam product filling in that gap, and the potential design specifications necessary to do it. Findings suggest that the resin component of current glulam beams harm the Cradle-to-Cradle assessment rating, therefore posing a challenge to find eco-friendly alternative. Potential candidates such as lignin and casein resin are studied, along with the novel technology of welded dowel-laminated timber.
Ongoing development of timber and timber products made from European hardwoods like ash and
beech influences the selection of acceptable methods for connecting these elements and thus demands validation and application of current design methods for softwood and glulam. For the last 20 years, despite many national and international research projects and practical applications of glued-in rods in timber structures, there is still no universal standard with respect to their design. The use of adhesives available for bonding rods and timber is limited to softwood. This work shows the performance of different timber species Norway spruce (Picea abies Karst.), European ash (Fraxinus excelsior L.) and European beech (Fagus silvatica L.) and engineered timber products (laminated veneer lumber made of Norway spruce and European beech) based on comprehensive pull-compression tests of glued-in rods. For characterizing the elastic and elasticplastic behavior, failure loads as well as stiffness and ductility were considered whereby the rod diameter and anchorage length were maintained constant. The aim of the research was to show that glued-in rods cannot only be used in softwoods and glulam members but also in hardwoods and in wood-based products such as LVL.
In this research the effect of using the combustible material CLT as the main bearing structure is investigated. As a combustible material, unprotected CLT can burn along with the fuel load present in a compartment.
This master’s thesis aims to increase insight into the fire behaviour of unprotected CLT structures in a compartment burnout, conservatively assuming no active measures. The main research question of this work is: “Under what conditions is there a potential for self-extinguishment of cross-laminated timber?” A model of self-extinguishment of CLT was created which consists of various phases of a compartment burnout. Under the influence of an initial fire due to burning of room contents, the exposed CLT becomes involved in flaming combustion. Once the room contents have been largely consumed and the initial fire decays, the CLT contribution is expected to decrease as well, transforming from flaming to smouldering combustion. Finally, there will be a transition from smouldering to self-extinguishment. Two series of experiments were conducted to investigate this model and the conditions under which the transitions can take place.
A housing project comprised of 72 units is located in IJ Burg— a new suburb east from the center of Amsterdam. More specifically, the project sits on a man-made island called Steigereiland North, on a ‘left-over’ green strip of land. Two types of dwellings (A and B) are disseminated around the site forming various permeable blocks of living and working units. These apartments consist of free-standing, row, and semi-detached typologies, depending on their arrangement and orientation. The capacity of these units to grow and change over time is a key feature of this project. The project has an additional activity strip between the waterside and the housing fabric border which will aid to serve as a lively catalyst for the neighbourhood. This ‘mat’ consists of landscaping and supplementary functions such as: tennis courts, a soccer field, playgrounds, picnic zones, pergolas, a climbing wall, a dance studio, and storage facilities. The newly-added layer of economical, community-driven activities reinvigorates IJ Burg. Introducing light production as well as the creative and working classes into the urban fabric will also result in an extrovert and well-functioning community.
During this MSc thesis it has been carried out an extensive literature review on fire safety engineering, on timber behaviour on fire and on fire safety regulations in different countries. A preliminary design for a high rise cross laminated timber building (CLT) has been carried out in order to obtain a minimum thickness of the structural elements needed for the load bearing structure. This thickness has been verified according to prescriptive fire regulations. Furthermore, fire safety analyses have been performed to evaluate a more realistic fire behaviour of exposed timber structures. The finite element program SAFIR and the fire model OZone have been used in the advance calculations. Finally, it is shown that timber buildings should be designed according to advance fire safety approach and suggestions are given for developing a timber fire model.
Proceedings of the Institution of Civil Engineers - Structures and Buildings
This paper discusses the long-term mechanical behaviour of timber-to-concrete joints made with dowel-type fasteners. Despite the influence that the long-term behaviour of joints has on the mechanical behaviour of a timber–concrete structure and consequently on its design, there is still a lack of research in this area. This paper presents experimental research, carried out at the University of Coimbra and Delft University of Technology, on seven joint configurations using different types of fasteners and different materials. For each joint configuration, either four or ten tests were performed resulting in a total of forty tests. A comprehensive description of the test specimens and test setup is given. The experimental creep–time curves were fitted to a creep–time model and used to predict joint creep values over longer timeframes (10 and 50 years). The values obtained were compared with values available in the literature for timber-to-concrete joints with other types of fasteners and timber-to-timber joints with dowel-type fasteners. The approach for timber-to-timber joints suggested by Eurocode 5 was used to determine creep values for timber-to-concrete joints. The results obtained were compared with test results to assess the accuracy of predicting creep values of timber-to-concrete joints with dowel-type fasteners. It was concluded that creep values measured in long-term experimental tests are usually higher than those obtained from the model indicated in Eurocode 5, particularly for environmental conditions corresponding the service class 2.