In this paper, a series of experimental bending and compression tests were performed on cross-laminated timber (CLT) products with ±45° alternating layers, to evaluate their performance against conventional panels of 90° orientation. Engineered wood products, such as CLT with ±45° alternating layers can provide opportunities for greater use in larger and more sustainable timber constructions. A total of 40 panels, manufactured in an industrial CLT production line with either of these two configurations, were tested and compared. Panels were evaluated in bending tests n=20 and the remaining ones in compression tests. Results showed that 35% increased the strength in the fourpoint bending tests for panels containing ±45° alternating layers compared with the 90° alternating layers. Compression strength was increased by 15%. Stiffness increased by 15% in the four-point bending and 30% in the compression. The results indicate that CLT containing ±45° alternating layers has increased strength and stiffness compared to 90° alternating layers. These findings suggest that further developments in CLT are feasible in advanced building applications.

Bending tests were conducted with cross laminated timber (CLT) panels made using an alternating layer arrangement. Boards of Norway spruce were used to manufacture five-layer panels on an industrial CLT production line. In total, 20 samples were tested, consisting of two CLT configurations with 10 samples of each type: transverse layers at 45° and the conventional 90° arrangement. Sample dimensions were 95 mm × 590 mm × 2000 mm. The CLT panels were tested by four point bending in the main load-carrying direction in a flatwise panel layup. The results indicated that bending strength increased by 35% for elements assembled with 45° layers in comparison with 90° layers. Improved mechanical load bearing panel properties could lead to a larger span length with less material.

Eucalyptus nitens has become a commercially important species in Chile and it isrepresenting one of the fastest growing wood-stock in the country. Today, it is widelyused for pulp and paper production, but the interest in using the solid wood has increasedin recent years. Before the sawn timber can be utilized, its moisture content must bereduced. Often during drying, hydrostatic tension forces within the cell exceed thecompressive strength of the thin cell wall of Eucalyptus nitens and the cell collapses. Thisphenomenon usually leads to severe surface deformation and both surface and internalcracks (honeycombing). Yield and quality of the final product, and thereby sawmills’profitability, are decreased by these cracks and deformations. The aim of this study wasto investigate, by CT-scanning samples throughout the drying process, if it is possible todetect when and how cracking and deformation occurs and develops in specimens ofEucalyptus nitens from Chile. Based on this knowledge, better drying schedules canhopefully be developed to improve the yield and provide a higher end-quality of the sawntimber.

This work proposes a multi-Fickian method to analyse the hygro-thermal behaviour of timber bridge elements under Northern Europe climates. A temperature-dependent wood hysteresis is included in the model and the thermal effects due to temperatures above and below zero are taken into account. As a case study, the model is used for the hygro-thermal simulation of a glulam beam of Älsvbacka bridge in North of Sweden that was monitored by using wireless sensors in a previous study. The model, implemented in Abaqus FEM code, is able to predict the states of moisture and temperature in protected parts of the beam by using as external loads the relative humidity and temperature of the air provided by in-situ measurements. Furthermore a simplified model using a wood hysteresis independent of temperature is found to provide similar results and appears easier to implement in finite element codes.

Fire safety is one of the six essential performance requirements to consider when building timber structures. Fire safety has to be proven for the whole building process and the end use of the building. On the building site during the execution there might be an increased risk for fire spread because of large amounts of unprotected timber and relatively open structures. Work processes dealing with high temperatures, smoking, vandalism or other reasons can lead to ignition of timber and end up with serious damages. Fire safety on the building site should be handled from the very beginning to the final stage of execution. During the execution the designed solutions have to be checked and followed. This paper gives the background and principles that should be considered in a new Nordic standard for execution of timber structures in terms of fire safety.

Bristande brandteknisk funktion hos byggnadstekniska detaljlösningar är ofta en starkt

bidragande orsak till brandspridning. Flera incidenter de senaste åren visar tydligt att byggsystem

med hålrum kan ha stor inverkan på brandförloppet och medföra stora egendomsskador i alla

typer av byggnader. Befintliga rekommendationer om att brandstopp måste installeras i hålrum

för att hindra att dolda bränder uppstår och sprids mellan brandceller följs tyvärr ofta inte inom

praktiskt byggande.

Syftet med projektet är att utveckla en lämplig metodik för att verifiera funktionen hos olika

typer av brandstopp i byggnader, att dokumentera funktionen hos några typer av brandstopp

enligt relevant metodik samt att ge underlag för riktlinjer om hur brandstopp ska utformas och

användas. Resultaten ska även kunna användas för att bedöma befintliga detaljlösningar.

Arbetet har inriktats främst på brandstopp för hålrum i modulhus. Olika typer av brandstopp för

sådana hålrum har studerats bland annat genom provningar i modellskala. Befintlig

provningsteknik har vidareutvecklats och en reviderad metodik har föreslagits.

Som ett första resultat för praktisk användning har riktlinjer tagits fram för hur brandstopp ska

utformas och användas i modulkonstruktioner. De främsta målgrupperna är bygg- och

byggmaterialindustrin samt brandkonsulter

In the collaborative forum Positive footprint housing® Riksbyggen is building the Viva residential quarter, which is a sustainability project at the very forefront of what is possible with contemporary construction. The idea is that this residential quarter should be fully sustainable in ecological, economic and social terms. Since 2013, a number of pilot studies have been completed under the auspices of the Viva project framework thanks to financing from the Swedish Energy Agency.

The various building frame alternatives that have been evaluated are precast concrete, cast in-situ concrete and solid wood, all proposed by leading commercial suppliers. The report includes a specific requirement for equivalent functions during the use phase of the building, B. An interpretation has been provided that investigates the building engineering aspects in detail, as well as an account of the results based on the social community requirements specified in Viva, durability, fire, noise and energy consumption in the Swedish National Board of Building, Planning and Housing building regulations (BBR), plus Riksbyggen’s own requirements, Sweden Green Building Council’s Environmental Building Gold (Miljöbyggnad Guld) and 100-year life cycle. Given that the alternatives have different long-term characteristics (and also that our knowledge of these characteristics itself varies), these functional requirements have been addressed by setting up different scenarios in accordance with the EPD standard EN 15978.

Because Riksbyggen has specified a requirement for a 100-year life cycle, we have also opted for an analysis period of 100 years.

The results show no significant differences between concrete and timber structures for the same functions during the life cycle, either for climate or for primary energy. The minor differences reported are accordingly less than the degree of uncertainty involved in the study.

The available documentation on the composition of the relevant intumescent paint coating on solid wood frames differs from source to source, so it was not possible to fully allow for the significance of this.

The LCA has not included functional changes in the building linked to load-bearing characteristics, noise, moisture, health or other problems that may result in increased maintenance and replacement. The concrete houses have been dimensioned for 100 years, for instance, in accordance with tried and tested standards and experience. The solid wood house is not dimensioned in the same way, and this has led to us having to assume various scenarios.

The results also show the following:

• The uncertainties involved in comparing different structures and alternative solutions are very significant. The results are affected by factors such as life cycle, the functional requirements taken into consideration, transportation, design and structural details, etc.

• Variations in the built items and a considerable degree of uncertainty in the assumptions make it difficult to obtain significant results on comparisons. Only actual construction projects with known specific data, declared from a life cycle perspective that takes into account actual building developer

requirements and involving different scenarios (best, documented and worst-case) for the user stage can currently be compared.

• In the other hand, comparisons restricted to different concrete structures only, or to different timber structures only, ought to involve a lower degree of uncertainty, These would then provide results that are significant as well as improvement requirements that are relevant.

• There is potential for improving concrete by imposing requirements on the material

• There is potential for improving solid wood frames by developing and guaranteeing well-documented long-term characteristics for all functional requirements.

The LCAs were performed as an iterative process where all parties were given the opportunity to submit their viewpoints and suggestions for changes during the course of the work. This helped ensure that all alternatives have been properly thought through.

Because, during the project, Riksbyggen opted to procure a concrete frame, in the final stage the researchers involved focused on ensuring the procurement process would result in the concrete frame as built meeting the requirements set out above. As things currently stand, the material requirements for the concrete are limited by the production options open to the suppliers, and this is therefore being investigated in the manufacture of precast concrete frames for the Viva cooperative housing association.

In the collaborative forum Positive footprint housing® Riksbyggen is building the Viva residential quarter, which is a sustainability project at the very forefront of what is possible with contemporary construction. The idea is that this residential quarter should be fully sustainable in ecological, economic and social terms. Since 2013, a number of pilot studies have been completed under the auspices of the Viva project framework thanks to financing from the Swedish Energy Agency. The various building frame alternatives that have been evaluated are precast concrete, cast in-situ concrete and solid wood, all proposed by leading commercial suppliers. The report includes a specific requirement for equivalent functions during the use phase of the building, B. An interpretation has been provided that investigates the building engineering aspects in detail, as well as an account of the results based on the social community requirements specified in Viva, durability, fire, noise and energy consumption in the Swedish National Board of Building, Planning and Housing building regulations (BBR), plus Riksbyggen’s own requirements, Sweden Green Building Council’s Environmental Building Gold (Miljöbyggnad Guld) and 100-year life cycle. Given that the alternatives have different long-term characteristics (and also that our knowledge of these characteristics itself varies), these functional requirements have been addressed by setting up different scenarios in accordance with the EPD standard EN 15978. Because Riksbyggen has specified a requirement for a 100-year life cycle, we have also opted for an analysis period of 100 years. The results show no significant differences between concrete and timber structures for the same functions during the life cycle, either for climate or for primary energy. The minor differences reported are accordingly less than the degree of uncertainty involved in the study. The available documentation on the composition of the relevant intumescent paint coating on solid wood frames differs from source to source, so it was not possible to fully allow for the significance of this. The LCA has not included functional changes in the building linked to load-bearing characteristics, noise, moisture, health or other problems that may result in increased maintenance and replacement. The concrete houses have been dimensioned for 100 years, for instance, in accordance with tried and tested standards and experience. The solid wood house is not dimensioned in the same way, and this has led to us having to assume various scenarios.

The results also show the following:

• The uncertainties involved in comparing different structures and alternative solutions are very significant. The results are affected by factors such as life cycle, the functional requirements taken into consideration, transportation, design and structural details, etc.

• Variations in the built items and a considerable degree of uncertainty in the assumptions make it difficult to obtain significant results on comparisons. Only actual construction projects with known specific data, declared from a life cycle perspective that takes into account actual building developer requirements and involving different scenarios (best, documented and worst-case) for the user stage can currently be compared.

• In the other hand, comparisons restricted to different concrete structures only, or to different timber structures only, ought to involve a lower degree of uncertainty. These would then provide results that are significant as well as improvement requirements that are relevant.

• There is potential for improving concrete by imposing requirements on the material

• There is potential for improving solid wood frames by developing and guaranteeing well-documented long-term characteristics for all functional requirements.

The LCAs were performed as an iterative process where all parties were given the opportunity to submit their viewpoints and suggestions for changes during the course of the work. This helped ensure that all alternatives have been properly thought through.

Because, during the project, Riksbyggen opted to procure a concrete frame, in the final stage the researchers involved focused on ensuring the procurement process would result in the concrete frame as built meeting the requirements set out above. As things currently stand, the material requirements for the concrete are limited by the production options open to the suppliers, and this is therefore being investigated in the manufacture of precast concrete frames for the Viva cooperative housing association.

Fire resistance of timber structures is an important topic of research and discussion. A popular method for protecting timber members against fire is the use of protective non-combustible claddings. For these, the most widespread material is gypsum plasterboard. A method for calculating the fire resistance of timber frame assemblies is the improved component additive method which will be introduced to the next version of the European standard EN 1995-1-2. Currently there exist formulas only for material groups. In this work two more materials are added and the implementation procedure is described. Four horizontal model scale furnace tests were conducted. Thermal simulations of the tested configurations were conducted by the finite element software SAFIR v2014a1. The thermal parameters of the studied materials were calibrated in order to obtain the same temperature rise curves as were shown in the fire tests. The calibration procedure developed was implemented on cellulose fibre insulations. With the suitable effective thermal parameters, another set of simulations was run based on the work of Vanessa Schleifer and material specific formulas derived. These were compared with results of separate full scale test results to verify the safety of the calculations.

The design of details is an important aspect in durability design of rain-exposed timber structures. Joints are considered the weak-points of these structures as they accumulate moisture and facilitate deterioration by decay. The present study aims to study the influence of detail design, and its effect on the service life, by estimating the decay rate in a number of rain-exposed timber components and joints, typically found in timber bridges. A test-setup was exposed outdoors over a period of one year while the moisture content was measured in specific measuring points. The test-setup included groups of beams, columns and joints commonly found in timberbridges. For the beams and columns, the effectiveness of typical protective measures was also tested. The annual decay rate was estimated using two different decay prediction models. Compared to a reference beam, the results show that structural protection reduced the risk of decay while joints and end-grain tended to be at increased risk. The lowest service life, estimated to 3-4 years, was found close to end-grain where drying was hindered but moisture could accumulate. In general, the discrepancy between the two decay models was large for low to medium exposure and decreased with increasing exposure.

The hypothesis is that a good cladding system in wood should be characterized by a homogeneous dimensional behaviour with minimal variation between individual panel boards to minimize maintenance, i.e. repainting or, in the worst case, replacement of whole panels. Four different types of cladding panels were tested: a regular spruce panel, a quality-sorted P-marked spruce panel, a regular panel of pine heartwood and a spruce glulam panel, 50 panels of each type. The objective was to study the dimensional changes under changing moisture conditions in order to find the cladding material with the smallest possible dimensional and distortion movements. The shape stability of the panels was measured and expressed in terms of bow, spring, twist and cupping. The spruce glulam panels showed the best shape stability, proven significantly different in comparison to the other two spruce panel systems. Panels of pine heartwood showed a tendency greater dimensional stability than the spruce panels, but not enough to be considered statistically significantly different in this study.

The purpose of this paper is twofold. The first aim is to develop a numericalanalysis procedure, by combining FRFs from FE-models with analyticalformulas for sound emission and transmission from the ceiling anddownwards within a room with four walls. The aim is to, by applying thisapproach; accomplish a tool which calculates the relative impact soundbetween different joist floors, in the low frequency range. The second aim is tobenchmark a thin hybrid wooden based joist floor with similar thickness,surface weight and global bending stiffness as a concrete hollow core floorstructure. What will be the difference in sound transmission? The question isrelevant since it may be necessary to make thinner wood based joist floors inhigh rise buildings, if wood should stay competitive against concrete. Theresults show that the direct transmissions of impact sound are very similararound the first bending mode. As the frequency increases, the modes in thestructures differ significantly. Below 100 Hz, the concrete floor has 4 modes,while the hybrid joist floor has 9 modes. As the frequency increases the soundradiation characteristics differs. The results show that it is possible to havesimilar sound transmission properties around the first bending modes for ahybrid based joist floor and a hollow core concrete floor structure with similar thicknesses. At the first modes of the structure, the information about thesurface weight and global bending stiffness are useful for prediction of soundtransmission properties but for higher modes, they are not sufficient.

The project included product development and materials research. The aim was to produce a wooden façade system with an attractive modern appearance and good constructive design with the help of modern woodworking technology. Important requirements to consider were that the system should have a contemporary, attractive expression and that the façade system should provide a product with high quality ambitions in terms of environmental impact. It should also be flexible and easy to use for architects and designers who want to create unique façades. The main focus in this study was about the visible wood surface appearance where the intention was to create a varied surface with interesting innovative designs, with a method that make it possible to always create new patterns. Two different façade cladding systems were developed by combining woodcraft tradition, new research, digital design tools and industrial processes in the wood construction industry. Prototypes with patterned surfaces on both individual boards joined together and on a system based on multi-layer solid wood panels were tested.

Prefabricated elements to provide environmentally friendly, energy- and cost-efficient solutions for the building envelope have been studied. The newly developed element system has a high level of flexibility since it is possible to adjust the length of the connection rods according to the building's energy requirements and it can be mounted on timber, concrete and brick structures. Adjustability to different types of buildings structures, materials, tolerances, geometries and energy requirements makes it very applicable and efficient.

The first European design guide for fire safety in timber buildings has been developed that presents information for architects, engineers, educators, regulatory authorities and building industry professionals for the fire-safe use of timber structures and wood products in buildings. The guide, available in nine languages, aims to provide the highest scientific knowledge with regard to fire safety on the European level. The guide covers the use of design codes (such as Eurocode 5 Design of timber structures), European fire standards, practical guidance and examples for fire safe design and principles of performance-based fire design.

The design guide is focusing on structural fire protection by providing the latest detailed guidance on load-bearing and separating functions of timber structures under standard fire exposure. New modelling not yet included in Eurocode 5 is presented. The guide includes information on the reaction to fire performance of wood products according to the new European system. The importance of proper detailing in building design is stressed by practical solutions. Active measures of fire protection are presented as important means in fulfilling fire safety objectives.

The combustibility of timber is one of the main reasons that many building regulations strictly limit the use of timber as a building material. Fire safety is an important contribution to feeling safe, and an important criterion for the choice of building materials. The main precondition for an increased use of timber in buildings is adequate fire safety. This paper reviews the opportunities and challenges to reach this goal by implementing Fire Safety Engineering and Performance Based Design principles.

Bristande brandteknisk funktion hos byggnadstekniska detaljlösningar är ofta en starkt bidragande orsak till brandspridning. Flera incidenter de senaste åren visar tydligt att byggsystem med hålrum kan ha stor inverkan på brandförloppet och medföra stora egendomsskador i alla typer av byggnader. Befintliga rekommendationer om att brandstopp måste installeras i hålrum för att hindra att dolda bränder uppstår och sprids mellan brandceller följs tyvärr ofta inte inom praktiskt byggande.brandprovning.

Several long term experimental studies on the maintained reaction to fire performance of fire retardant treated (FRT) wood products over time are presented. They are performed according to a European system based on earlier Nordic and North American systems and include accelerated ageing according to different procedures and natural weathering up to ten years. Main conclusions are: The hygroscopic properties are unchanged compared to untreated wood for most FRT wood products used commercially. The reaction to fire properties of FRT wood may be maintained after accelerated and natural ageing if the retention levels are high enough, but several FRT wood products loose most of their improved reaction to fire properties during weathering. Paint systems contribute considerably to maintain of the fire performance at exterior application and are usually needed to maintain the fire performance after weathering.

Several long term experimental studies on the maintained reaction to fire performance of fire retardant treated (FRT) wood products over time are presented. They are performed according to a European system based on earlier Nordic and North American systems and include accelerated ageing according to different procedures and natural weathering up to ten years. Main conclusions are: The hygroscopic properties are unchanged compared to untreated wood for most FRT wood products used commercially. The reaction to fire properties of FRT wood may be maintained after accelerated and natural ageing if the retention levels are high enough, but several FRT wood products loose most of their improved reaction to fire properties during weathering. Paint systems contribute considerably to maintain of the fire performance at exterior application and are usually needed to maintain the fire performance after weathering.

Wood is combustible, but can still perform very well in fire, especially for load bearing structures. However, visible wood surface may not fulfil the fire requirements in building codes and fire retardant treatments may be an option. The highest reaction to fire classification for combustible products may then be reached. However, the excellent fire performance of the virgin fire retardant treated, FRT, wood products may degrade over time, especially in outdoor applications. Two cases of long term durability of FRT wood products exist and standard procedures are available for limited hygroscopicity and maintained fire performance after weathering. Structural degradation may also occur, but is relevant only for load-bearing uses. Recommendations on end uses and suggestions for further research are included.