Dynamic measurements are widely used to perform structural health monitoring of existing structures and operational modal analysis. This paper describes the design steps and applications of a multi-channel modular data acquisition system to perform in-situ and laboratoryscale experimental and operational modal analysis. The main advantages of a modular system compared to a traditional data acquisition system are flexibility, easy and fast deployment, and minimal interference with the surroundings. Several experiments have been conducted in order to validate and evaluate the data acquisition system. The results show that the system is versatile and can acquire high-quality and reliable data.

There is a growing interest in timber buildings in Sweden and increased availability of Glulam (GLT) andparticularly Cross Laminated Timber (CLT) products. Timber buildings, though, often have difficulties in fulfilling theperformance requirements of a building project. The use of concrete elements in addition to timber elements in the load-bearing structure is a widespread solution, introducing timber-concrete hybrid buildings. The study presents responsesfrom interviews regarding ten different timber-concrete hybrid building projects in Sweden with a load-bearing structureabove the foundation level in both timber and concrete. Four main types of timber-concrete hybrids were found: a CLTstructure on top of a concrete structure, a post-beam system in GLT with CLT slabs and concrete walls, a post-beamsystem in GLT with concrete hollow core slabs, and a timber structure with some slabs in concrete. The results show thattimber-concrete hybrid buildings are flexible and suitable for various construction types. The reasons for using concretein timber construction were primarily to increase self-weight, obtain longer span lengths, and overcome shear wallcapacity issues. There is still a lack of competence in the design of structural timber projects, and at most, five differentstructural designers were involved in the load-bearing design of a single building. This highlights issues regarding projectmanagement of the design process within timber-concrete hybrid buildings

 This paper describes the in-situ ambient vibration tests of a lightweight timber frame building, performed in order to obtain its modal properties. Our case study is a six-story lightweight timber frame building in Varberg, Sweden. Five battery-driven wireless data acquisition units with a total of 14 uni-axial accelerometers were used to perform the in-situ measurements. Accelerations along the two horizontal directions were recorded with a duration of approximately 40 minutes. Two different only-output frequency and time domain Operational Modal Analysis (OMA) methods were used to evaluate the dynamic properties of the building. The modal parameters obtained from the in-situ measurements, such as natural frequencies and mode shapes, were compared with the parameters obtained from the Finite Element (FE) model of the structure. To perform a detailed numerical analysis of the light-frame timber building, all lateral-load resisting system components were modelled. The FE model was calibrated in function of the results obtained from the OMA of the building. Based on the obtained results from the calibrated FE model, it was possible to conclude that the non-structural elements have an influence on the global dynamic response of the building.

KL-trä är ett relativt nytt konstruktionsmaterial som lämpar sig som stomme i bostadshus, offentliga och industriella byggnader. Eurokod 5 är den europeiska standarden för dimensionering av träkonstruktioner som är obligatorisk att använda i alla länder. Den omfattar både dimensionering i normalfallet och branddimensionering. Nuvarande version för branddimensionering EN 1995-1-2:2004 publicerades 2004 [1]. Den saknar regler för dimensionering av KL-trä. En ny version av Eurokod 5 beräknas komma 2025, den finns idag som utkastet prEN 1995-1-2:2025 [2]. De två versionerna av Eurokod 5 jämförs för KL-trä i denna artikel. Artikeln baseras på ett examensarbete vid Linnéuniversitetet [3]. Endast konstruktioner med synlig träyta har analyserats.

Wood is widely used in the construction sector and gaining increased market share. It isinteracting with the surrounding so that its mechanical and geometrical properties (stiffness,strength, swelling, density, …) change with temperature and humidity levels. In a full-scalebuilding, the eigenfrequencies are hence also varying with the climate. In the current paper,results from a preliminary experimental study are presented. A beam made from cross-laminated timber was hanging freely supported inside a climate chamber. Enforced vibrationsfrom a controlled shaker were taken to obtain the eigenfrequencies. With decreasing moisturecontent, the first and third eigenfrequencies were increasing (bending modes) while the secondeigenfrequency was decreasing (torsional mode). A finite element study allowed for checkingwhich parameters is influencing to which degree so that individual changes can be combined.

A wider deployment of nearly zero energy buildings (NZEBs) is expected to contribute to the transition to a decarbonized and energy-efficient building sector in Europe. This study proposed an integrated energy-economic analysis to exemplify the feasibility of NZEB renovation in temperate climate. A parametric analysis was performed to identify technical building system configurations that give minimum share of renewable energy systems contributing to NZEB level. Final energy savings, global costs and cost-effectiveness of renovating a building to NZEB level are analysed, considering active and passive energy efficiency measures (EEMs). The active EEMs included efficient water taps and heat recovery ventilation, and the passive EEMs encompassed insulations to roof, exterior walls and ground floor, and improvements of windows and doors. The building had initial final energy use of 133 kWh/m2 year for space heating, domestic hot water production (DHW) and facility electricity. The results show that NZEB level is achieved with active and passive EEMs, without renewable energy systems for scenarios with low discount rates and high future energy price escalations. The annual final energy use for space heating, DHW and facility electricity is reduced cost-effectively by 37-54%. Furthermore, increasing size of PV-system enhanced cost-effectiveness by lowering total global costs.

The aim of this pilot study was to identify the existing level of digital competence and skills at wooden house manufacturers and to understand the future perceived needs they have in relation to these competences. This is motivated by the acknowledgement that digitalization has been emphasized both as a critical necessity and significant challenge for this industry.

The number of responding companies in the study is rather low, offering a partial snapshot of the current state of the industry and potential future directions. However, it does provide valuable insights and considerations for future strategies for digitalization of the industry.

The wooden house manufacturing industry is facing challenges relating to the overall business cycle as well as the effects of war, inflation, and increased competition. Despite these challenges, the industry appears to be aware of the potential possibilities that digital technologies may offer. Overall, they are rather content with the current level of digitalization and the level of digital competence among their staff. At the same time, they realize the need to continue investing in hardware and software as well as continued enhancement of digital skills for the staff. Presently, only a very small portion of total investments in the industry is allocated to digitalization.

Most companies employ similar technologies and a variety of similar strategies to enhance their competences. The primary focus in terms of digital competence lies in the areas of production, marketing, communication, and sales. Areas such as customer support, decision-making, testing, and certification are not prioritized. Most of these companies recognize the need of digital competence development for their staff to effectively use contemporary digital technologies. Furthermore, they see a growing demand for digital competence over the next three years, particularly in domains such as artificial intelligence (AI), cybersecurity, infrastructure, and social media/marketing.

The dynamic action of footbridge users in different forms of activity (especially during walking andrunning) may cause an excessive vibration of the footbridge deck and may disturb the comfort of use of the structure. Thedynamic susceptibility of the footbridges varies depending on the construction material used to build the footbridge andthe typical construction solutions (construction details) resulting from the construction material used. The paper presentsthe basic dynamic characteristics of timber footbridges of various structural solutions, collected during dynamic field testsof these structures. The obtained results indicate relatively high dynamic resistance of timber footbridges to the dynamicloads generated by users under normal conditions of use. In addition, the results show that in the case of timberfootbridges, it is possible to consider changing the requirements of international standards defining the range of naturalfrequencies sensitive to the dynamic impact of users. In the case of timber footbridges, characterized by a relatively highself-weight (compared to steel footbridges), high stiffness and high damping, it is possible to consider changing therequirements for performing forced vibration analyses only for structures with fundamental vertical vibration frequency f_v <= 3.0 Hz instead of the currently defined f_v <= 5.0 Hz.

Timber-concrete hybrid buildings are an innovative solution to increase the amount of timber materials used in modern buildings. This study presents a dynamic evaluation of a nine-story timber-concrete hybrid residential building during construction. The building consists of a seven-story structure in cross-laminated timber (CLT) on top of two stories in concrete. Ambient vibration tests were conducted seven times during the 13-month construction period, including tests with only the structural elements in place and tests of the finished building with the façade, non-structural walls, and other internal finishing. The results show a clear decrease in the natural frequencies of the building as the building gets higher and more elements are installed. However, a slight increase in the natural frequency was observed following the installation of the non-structural walls in the final construction stage. A corresponding finite element analysis is presented for each test, providing additional insights into the parameters typically used in the structural design process. The study demonstrates the importance of properly selecting reduction factors for CLT elements in a dynamic finite element analysis. It also shows the importance of considering non-structural walls, both regarding weight and stiffness, even in buildings where the number of non-structural walls is relatively small compared to structural walls.

Birch plywood has superior mechanical properties compared with plywood made from most softwood species, which makes it suitable for structural application. Plywood is also more environmentally friendly, cost-efficient, and less prefabrication demanding than steel plates. For a proper design of birch plywood as joint plates in timber-timber connections, the embedment behavior of mechanical connectors into plywood needs to be properly investigated. In this study, the authors performed embedment tests of dowel connectors into birch plywood specimens under five different angles from parallel to perpendicular to the face grain with a step size of 22.5 degrees. Dowel connectors with three different diameters were utilized to study the influence of dowel diameter on embedment strength and stiffness. Besides, test series using self-drilling screws and acetylated birch plywood specimens were conducted to study the effect of both fastener type and acetylation. Moreover, full-hole and half -hole test results were compared. The embedment strengths were calculated analytically according to different term definitions. The test results were then compared with the analytical results based on formulas reported in the literature, e.g., Eurocode 5 and other design standards.

Design for efficient assembly is essential to further enhance the competitiveness of cross-laminated timber building systems for multi-story timber structures. This requires a holistic view from the design of the load bearing structures by structural engineers, over the production, pre-fabrication, and transport to the assembly of the structural elements on-site, which often is done by different companies with input from different stakeholders in the construction process. Especially the design of connections between CLT elements, and CLT and other construction materials and products, as well as the size of CLT elements and possibilities for pre-fabrication are crucial for an efficient assembly process. The paper summarizes findings from expert interviews with a focus on Sweden along the before-mentioned value chain, with the aim to identify current practice and potentials for further improvements. Design for efficient assembly starts at the early-stage design and involves all stakeholders in the design construction process. The reduction of uncertainties in the design and assembly process of multi-storey CLT structures as well as knowledge and experience transfer could lead to more efficient design. The identified requirements for efficient assembly should be combined with a life cycle analysis to quantify the potential for a reduction of the carbon footprint of CLT-based building systems, which is the aim of the ongoing research project ‘Improving the competitive advantage of CLT-based building systems through engineering design and reduced carbon footprint’.

The foundation of the circular economy in the construction sector is based on implementing the deconstruction and reuse of buildings, providing the potential for a closed loop of building materials within the supply chain. Mass timber buildings using large, prefabricated elements and certain types of reversible mechanical connections are deemed to have great potential for post end-of-life (EoL) options, including recycling and reuse. To fully characterize the benefits of reusing post-use mass timber in new construction projects, it is crucial to conceptualize a ‘grave-to-gate’ approach, including the complete analysis of post-EoL activities and impacts on the material’s second life. In this study, a comparative life cycle assessment (LCA) including different EoL and post-EoL options for a virtual reference mid-rise mass timber building in the Pacific Northwest (PNW) of the United States was conducted. Among four different deconstruction and reuse scenarios examined in this study, a case of nearly complete reconstruction of a mass timber building for the second service life used as an idealized reference established an optimistic limit for reduction of global warming potential (GWP) by 13-41% compared to the ‘demolish and landfill’ decision, depending on the scenario. The demolition and landfill scenario had the lowest net impact since the GWMP calculations accounted for the carbon storage benefits in the landfill in addition to the carbon stored in the building.

The paper focuses on the finite element modelling of a floor slab made of prefabricated hollow core floor units. The subject of the numerical analysis is a floor that has been investigated experimentally in VTT, Finland. The DIANA finite element analysis software has been used. Internal forces and displacements, as well as a failure load obtained from the finite element model, are compared with selected provisions given in the literature. The numerical analysis confirmed the inconsistencies and unreliability of existing models mentioned in the authors’ previous papers. The modelling technique presented in the paper, which takes into account the possibility of cracking of longitudinal joints between prefabricated units, provided reliable results consistent with experimental results.

This chapter deals with the fire properties and performance of wood products and structures. It starts with two subchapters on the basic physical and chemical properties under fire conditions including fire-retardant treatments to obtain higher reaction to fire classes. A new European standard to evaluate their long-term fire performance is included. The third subchapter gives an overview of the fire safety design of wood products in buildings. The European system for fire safety of construction products is explained with the two main fire scenarios to be considered: the initial fire where visible wood surfaces may contribute, and the fully developed fire, which is important to limit the fire to the room of origin. Generally speaking, wooden structures can obtain high fire resistance, whereas the surface properties in the initial fire are less favorable. The European reaction to fire class D is fulfilled for most wood products. North American systems are different and their classification of wood products is described briefly. Methods for calculating the fire resistance of wood elements according to Eurocode 5, and US systems, structural detailing, and fire safety at building sites are presented. The chapter ends by explaining the possibilities for using performance-based fire safety design and active fire protection by, for example, sprinklers. 

Building codes around the globe dictate the design and construction of buildings. For most buildings, designers will follow prescriptive code provisions to demonstrate code compliance. However, some buidling codes allow the use of performance-based design to demonstrate code compliance. Performance-based design is usually more complex but allows for greater flexibility in the use of materials and systems. Regardless of the code compliance methods, the combustibility of timber structures and wood products needs to be well understood and properly accounted for in building designs. This paper describes the develpment of a new international guidance document on fire safety in timber building within the Fire Safe Use of Wood (FSUW) network, written by 13 lead authors assisted by more than 20 experts in over a dozen different countries.

Forced vibration tests have been conducted on the seven-storey timber building Eken in Mariestad inSweden. The main objective is to estimate the building’s dynamic properties from test data. The eigenfrequencies, modeshapes and their scaling are useful to calibrate numerical models. However, the most important outcomes are the estimatesof the modal damping values. The reason is that the damping impacts the acceleration, and thus the serviceability of thebuilding, and at the same time, it is very hard to model damping. So, during the design phase, one must rely on previoustest data (of which very few exist for taller timber buildings) or rule of thumbs. It is therefore important to gain knowledgeabout the damping for timber buildings in order to enable good designs of future and taller timber buildings. The test datashows that the modal damping is roughly equal to 2% of the critical viscous ones for the eigenmodes extracted. The testcampaign on Eken is made as a part of the project Dyna-TTB in which vibrational tests have been performed on eighthigh-rise timber buildings, in Europe, of which Eken is one.

Within the project Dyna-TTB, vibrational tests have been conducted on eight high-rise timber buildings, in Europe. A main objective of the project is to gain knowledge about damping in timber buildings to assist in predicting the accelerations, at the top of a building, due to wind-induced vibrations.One of the buildings is Eken (the oak) in Mariestad in Sweden. That building is seven stories tall, thus questionable as a tall timber building, yet an interesting test object. The building structure is made up of glue laminated timber beams and columns stabilized with glulam trusses.Forced vibration were conducted on Eken with the aim to estimate the building’s dynamic properties from test data. Estimates of the eigenfrequencies, mode shapes and their scalings are useful both in the calculations of wind-induced vibrations and to calibrate numerical models. However, the most important outcome is estimates of the modal damping values. The damping impacts the acceleration, and thus the serviceability of the building, and at the same time, it is very hard to model damping. So, during the design phase, one must rely on previous test data (of which very few exist for taller timber buildings) and rule of thumbs. It is therefore important to gain knowledge about the damping for timber buildings in order to enable good designs of future and taller timber buildings.

The limitations in performance of band-pass filters to accurately process rapid decaying signals in lower frequency bands is an obstacle for some measurements within building acoustics. For instance, it would be beneficial to be able to accurately measure reverberation times down to the 20 Hz one-third octave band for impact sound in timber buildings.

Here, it is tested whether calculations with FFT with small incremental steps may be a way to achieve discrete frequency time signals with faster performance than traditional band-pass filters. The tests show that incremental FFT gives accurate estimations of the reverberation time corresponding down to 0.1 seconds at 20 Hz with a spectral resolution of 2 Hz. Using the one-third octave limits it is possible to form approximate one-third octave band results. It is seen that accurate estimations of reverberation time are achievable for BT ≥ 0.5 (T = 0.1 seconds for the 20 Hz one-third octave band) and possibly even lower, if the dynamic range in the interrupted noise signal is sufficient. The higher one-third octave results show to work as well. A disadvantage with the method is that during short reverberation times (0.1 seconds) there is a severe spectral leakage to the side bands. Also, the method requires higher dynamic range decay signals compared to band-pass filtered signals. If a one-third octave resolution is requested, a dynamic range of 50 dB or greater is preferable. With a coarse resolution of e.g., 10 Hz and having no averaging into one-third octave bands, it is possible to measure short reverberation times (0.1 s) with signals having close to the same dynamic range used in classical band-pass filtered reverberation time measurements.

Measurements of reverberation time is often used to obtain information about sound absorption of rooms within building acoustics. A limitation of the common method used today is the performance of band-pass filters to process rapidly decaying signals in the low frequency range. This occurs when the reverberation time (T) and bandwidth (B) product is less than 16. This is a limitation infor instance multi-story timber buildings where low frequency range, below 50 Hz is of interest for impact sound performance. Here, an alternative method is tested. Using incremental short time steps between each FFT calculation creates “moving average” signals, one for each frequency spectral line. A disadvantage is that the methodrequires a high dynamic range of the interrupted noisesignals, which increases with frequency resolution. Here itis tested to fit in the frequency resolution to the one-thirdoctave band frequency limits with as small errors as possible. It is shown that the dynamic range can be decreased a bit compared to a previously presented version. Two disadvantages with just one spectral line for each third octave band is that the signals are less stable and to produce the different frequency resolutions for each one-third octave requires more calculations.

Different test setups have been reported in the literature for the determination of the embedment strengthin timber elements. These variances hinder a straightforward comparison between available test data. It is difficult todetermine if the source of variability lies in intrinsic timber properties or is related to the test protocol used. This paperaims to provide a better insight into the influence of embedment strength test methods, comparing experimental resultsfrom different test setups within the guidelines of EN 383 and ASTM D 5764-97a for Scots pine wood (Pinus sylvestris)and Spruce (Picea Abies). A robust statistical analysis was performed to identify statistically significant differencesbetween the groups evaluated. The analysis of the parallel to grain embedment strength showed that the results differedbetween standards, pointing out the potential bias inserted in the embedment properties given their evaluation method.Moreover, the thickness of the specimen tests also proved to influence the yield and ultimate embedment strength for thewood species tested.

A major challenge in building energy renovation is to cost effectively achieve notable energy savings. This paper investigates cost-effective passive energy-efficiency measures for thermal envelope retrofit of a typical Swedish multi-apartment building from the 1970s. Here, the use of different types of insulation materials for the retrofits of roof, exterior walls, and ground floor are analyzed along with changing windows and doors with varying thermal transmittance values. The cost-effectiveness analysis is based on the net present value of the investment costs of the energy-efficiently measures and the achieved energy cost saving. Different economic scenarios and renovation cases are considered in techno-economic analyses to determine the cost-effective energy-efficiency retrofit measures. The results indicate that improved windows reduce energy demand for space heating by up to 23% and yield the highest final energy savings. However, additional mineral wool roof insulation is the most cost-effective measure under all economic scenarios. This measure gave the lowest ratio of cost effectiveness of about 0.1, which was obtained under the stable scenario. The final energy savings that can be achieved in a cost-effective manner vary between 28% and 61%, depending on the economic scenario and renovation case. This analysis emphasizes the influence of different renovation cases and economic parameters on the cost effectiveness of passive energy-efficiency measures.

A mechanically induced phase transition in tin-tellurium (Sn-Te) system and its dependence on the milling time of the masses of metastable Sn-Te phase(s) produced during ball milling have been investigated. The synthesis approach involves top-down ball milling of elemental Sn and Te powders in an argon environment with a milling time of 1 to 5 h at a low ball milling speed of 300 RPM. The Sn-Te solid solution forms as particles, resulting in large masses due to the ball milling operation. Ball milling of initial micron-sized powders of Sn and Te resulted in a homogenized nano-sized powder mixture. This mechanical mixture of Sn and Te powders exhibiting in-termediate phases with a crystal structure similar to that of elemental Sn and Te were detected in the ball-milled mixtures at various milling times, which resulted in a stable phase that ultimately transformed into a Sn-Te solid solution. Morphological and structural modifications at different stages of ball milling were investigated through X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, differential scanning calorimetry, dynamic light scattering, density measurement, and surface analysis. Subsequently, dense pellets were fabricated by spark plasma sintering from synthesized Sn-Te solid-solution powders produced by ball milling for 5 h. The sintered samples showed excellent structural integrity with densities of up to 6.35 g/cm3. It is to be noted that the formation of large quantities of uniform Sn-Te powder alloy produced by ball milling is reported for the first time in this study. These findings could be extended in the future to prepare bulk quantities of many solid solutions of the elements of the same periodic group.

This chapter aims at highlighting the benefit of numerical methods and their broad application in the field of wood, engineered wood-based products (EWPs), structural elements including glued-laminated and cross-laminated timber, and engineered timber structures. It focuses on the hygrothermo- viscoelastic material behavior of these elements and structures as a consequence of the behavior of wood materials. After motivating the need for models of wood, different types of numerical models and their application for determination of mechanical properties and dimensional stability of wooden boards, strand- and veneer-based engineered woodbased products, including glued-laminated and crosslaminated timber, as well as of connections in EWPs are reviewed and application examples are given. Methods and application examples are furthermore provided for moisturerelated stresses and deformations in timber structures, the influence of connections on the structural response, instability of structural systems, and modeling of prefabricated frame structures, before modeling of historical structures of wood is discussed. The chapter ends with discussing bottlenecks in modeling of wood materials and timber structures, which might be a starting point for further improvements and novel modeling strategies. © Springer Nature Switzerland AG 2023.

In this study, the life cycle environmental implications of modular multi-storey building with cross-laminated timber (CLT) volumetric elements are analysed, considering the product, construction, service life, end-of-life and post-use stages. A bottom-up attributional approach is used to analyse the environmental flows linked to the global warming potential (GWP), acidification potential (AP) and eutrophication potential (EP) impacts of the building for a 50-year reference study period. The result shows that the building’s life cycle impacts can vary considerably, depending on the energy production profile for the operation of the building. The product, construction and end-of-life stages constitute a significant share of the life cycle impacts, and the importance of these stages increase as the energy production profile evolves towards a low-carbon energy mix. For the GWP, the product and construction stages constitute 13% of the total life cycle impact when the operational energy is based on a coal-based marginal electricity. The contribution of this stage increases to 81% when electricity is based on a plausible long-term Swedish average mix. The patterns of the life cycle EP and AP impacts are also closely linked to the energy production profile for the assessment. The analysis shows that a 5% reduction in the GWP impact in the product stage is achievable with emerging solutions for the improved structural design of CLT buildings. This study highlights the need for strategies to improve the life cycle environmental profile of modular CLT buildings.

Embedment strength and stiffness of steel dowels in spruce and birch solid wood were investigated in an experimental study, taking into account the moisture and connection assembly history. Thus, in addition to the effect of different mechanical properties of wood at different moisture contents, the effect of changes in the moisture content between the steps of: drilling the dowel hole, assembly of the dowel, and testing of the specimen on the embedment strength and stiffness was studied. Full-hole embedment tests with 12 mm steel dowels showed a decrease in embedment strength with increasing wood moisture content, while the elastic embedment stiffness was not influenced. Drying the wood specimens after the dowel was inserted yielded up to 50% higher elastic embedment stiffness compared with connections drilled and assembled when the equilibrium moisture content was reached. Application of an artificial crack showed only a moderate effect on embedment strength and stiffness, while the ductile embedment behavior was maintained.

Material properties of wood under compression perpendicular to the grain and rolling shear are important for the engineering design of timber structures. This regards the short-term stiffness and strength, their dependence on the moisture content of wood, as well as the time-dependent behavior. Norway spruce clear wood properties in the transverse plane of wood were studied inan experimental campaign exploiting an earlier developed biaxial test setup. The moisture dependence of the stiffness and strength and the short-term time-dependent creep deformations under compression in the radial direction and under rolling shear were characterized. Loading and unloading stiffness, as well as the strength, were determined in quasi-static tests at five different moisture contents from 4% to 29%. The elastic and viscous stiffnesses were identified in creep tests at three compressive stress levels of 0.50, 0.75, and 1.00 N/mm2, and at two rolling shear stress levels of 0.33 and 0.50 N/mm2. The test data complements the existing experimental database, especially with novel data regarding the moisture dependence of the rolling shear strength, which showed less moisture dependence than the compressive strength perpendicular to the grain. The results of the creep tests revealed different material properties for the different loading and material directions of wood.

Light-frame timber shear walls have been used as load-bearing elements in buildings for several decades. To predict the performance of such structural elements under loading, numerous analytical and numerical models have been developed. However, little focus has been on the prediction of the plastic damage behaviour and unloading of the walls. In this paper, a parametric Finite Element (FE) model is further developed by introducing elasto-plastic connectors to simulate the mechanical behaviour of the sheathing-to-framing connections. To verify the accuracy of the elasto-plastic model, full-size walls were tested and compared with results from simulations. The numerical results, from a few loading cycles, indicate that the model achieves reasonable accuracy in predicting both the nonlinear elastic and plastic deformations. Both experimental and simulation results demonstrate the importance of opening locations relating to the external racking force. The results also indicate that for a double-layer wall, its racking strength can be achieved by summation of the separate contribution from each layer. Furthermore, the internal layer was observed to contribute significantly less than the external layer since its nail pattern was based on the sheathing pattern of the external layer.

The aim of the research presented herein is to investigate the mechanical behaviour of cross-laminated timber (CLT)-to-concrete dowel-type connections. For reliable timber-concrete-composite structures, mechanical connections between the two construction materials are of great importance. This paper investigates the nonlinear load-displacement behaviour, giving access to the stiffness and strength, as well as ductile connection failure modes, of a CLT-to-concrete composite connection using a Beam-on-Foundation (BoF) model. The latter is a numerical model that utilizes non-linear springs for the interaction between the fastener and the surrounding CLT and concrete materials. The influence of: (i) fastener diameter, (ii) initial slip, (iii) concrete embedment properties, and (iv) axial fastener resistance due to friction, on the connection shear capacity and slip modulus, was investigated in a parameter study. The nonlinear load-displacement response, connection stiffness and strength predicted by the BoF model were moreover compared to laboratory tests and the European Yield Model (EYM), which supported the validity of the BoF model. In addition, it was shown that the BoF model could enhance the prediction of the slip modulus compared to the current design regulations in Eurocode 5.

Numerical analyses relating to real-scale research of prestressed crane girders were carried out. Modelled beams had a low transverse reinforcement ratio. Moreover, the cable anchorages did not have any corrosion protection. Numerical analyses were conducted in phases, to simulate prestressed member operation (according to the research). Also, to simulate cables’ anchorage failure, bonding transmission of the prestressing force and bonding anchorage of the tendons. A total of 29 numerical simulations were performed. Based on the calculation results, an analysis of the effect of the transverse reinforcement ratio and the effective prestressing force magnitude on the load carrying capacity of the girders was performed. Numerical analyses mapped experimental studies with satisfactory compliance. Therefore, analyses enabled research to be extended. Numerical analyses indicated, the reinforcement marginally affects the load carrying capacity of the investigated elements. Also, failure of the top cable’s anchorage negligibly influences the load bearing capacity. On the other hand, the failure of bottom cables’ anchorages significantly reduces the carrying capacity of the analysed elements.

The use of cross laminated timber (CLT) for construction has increased greatly in recent years and the large volumes ofwood used for CLT means that it is important to optimize the use of the material. This requires relevant grading of lamellasand knowledge of relationships between lamella and CLT properties. In the present study, the relationship between dynamicaxial modulus of elasticity (MoE) of lamellas and the quasi-static out of plane bending stiffness of CLT is investigated. Bymeans of four-point bending test, it is shown that the effective quasi-static MoE of lamellas in CLT is only 2–6% lower thanthe average axial dynamic MoE of the individual lamellas. With this knowledge, producers of CLT can easily predict andcontrol the important out of plane bending stiffness of the produced CLT. Moreover, it is shown that effective rolling shearstiffness of layers in CLT can be accurately determined by means of digital image correlation performed in connection tofour-point bending of CLT, even for long test spans. For layers of lamellas of Scots pine of size 40 × 190 mm2the averageapparent or effective rolling shear modulus was determined to be 159 MPa. The average rolling shear modulus of the samematerial was determined to be 56 MPa.

Korslimmat trä (KL-trä) tillverkas av brädor som limmas ihop korsvis i flera skikt. Skivorna som erhållsanvänds som byggelement, mestadels för väggar och bjälklagselement. Utgångsmaterialet trä tarstår i jämvikt med det omgivande klimatet och kommer därför ändra fuktkvoten. I studien undersöktesen skiva av KL-trä under varierande fuktförhållanden i en klimatkammare hos Linnéuniversitetet.Egenfrekvenser samt fuktkvoten följdes upp och sambandet med klimatet studerades. Det visade sigatt första och tredje uppmätta egenfrekvensen (böjning) visade negativ korrelation med omgivandefukten, den gick upp när fukten minskades (och tvärtom). För andra egenfrekvensen (torsion)däremot visade sig ett mer komplicerat samband. Ett flertal möjliga orsaker presenteras som förklaring. Medverkande organisationer var Linnéuniversitetet som huvudpart samt SödraSkogsägarna och Saab som bidragit som stödfunktionen och bollplank.

Structural floor systems made of Timber-Concrete Composites (TCC) slabs are becoming more and more popular in office and residential buildings as well as in systems used for the renovation of old ceilings. Timber elements can be constructed as beams or solid slabs (massive CLT). Regardless of the main structural layout, individual components require using interlayer connections, which provide composite action in cross-sections. The most used connection types for TCC are mechanical fasteners, grooved or notched connections, and bonded shear joints. Bonded connections with rigid thin-layer adhesives provide high load capacity, but they are characterized by brittle failure due to their low ductility and introduced stress concentrations. An innovative flexible adhesive joint that ensures the transfer of high loads and high deformations simultaneously is presented in the paper. This connecting structural element, named PolyUrethane Flexible Joint (PUFJ) was examined experimentally in double shear lap tests of connections formed between two external CLT slabs of dimension 120 × 350 × 400 mm3 and a central concrete slab of dimension 100 × 250 × 400 mm3. Shear connections between the composite elements were made of a two-component polyurethane PS type adhesive layer of thickness 3 mm. The tested specimens were prepared in two variants of the application: wet application in the form of liquid adhesive and dry application in the form of prefabricated polyurethane layer glued to the elements by thin polyurethane adhesive. The effect of the adhesive application method on the stiffness and capacity of the TCC joint was investigated. In the paper, the analysis of the experimental tests’ results is presented.

As long-term investigations are often too time- and cost-consuming, short-term experimentsare introduced for investigating the behaviour of connections in timber-concrete-compositeelements. The paper presents a proposal for short-term double shear tests with adhesive andmechanical connections for investigating their time-dependent behaviour. The proposedevaluation method determines the elastic and visco-elastic parts of the slip modulus of theconnection. The validity of the identified parameters needs to be verified by long-term tests.

In a Finnish-Swedish consortium project, a large amount of sound insulation tests wasconducted for several intermediate floors in laboratory conditions to serve variousscientific research questions. The dataset contains 30 wooden and 8 concreteconstructions which are commonly used between apartments in multistorey buildings.Impact sound insulation was determined according to ISO 10140-3 standard usingboth tapping machine and rubber ball as standard sound sources. Airborne soundinsulation was determined according to the ISO 10140-2 standard. The data arespecial since they have a broad frequency range: 20-5000 Hz. Data are reported in1/3-octave frequency bands and the single-number values of ISO 717-1 and ISO 717-2are also reported. Detailed construction drawings are available for all reportedconstructions. The data are highly valuable for research, education, and developmentpurposes since all data were obtained in the same laboratory (Turku University ofApplied Sciences, Turku, Finland), and all the constructions were built by the same installation team.

Laminated veneer products (LVPs) are veneers glued together into a predetermined shape. Experimental and numerical investigations were performed under lamination and simultaneously bending of veneer laminate to study the stress distribution in the laminate. Laminates of different thicknesses were made of peeled veneers of European beech. The veneers were coated with adhesive, inserted in a mould which had the shape of a semicircle, and finally pressed at 20 degrees C to a laminate. Two Teflon-polymer films including sensors for measurement of the contact pressure were placed on both sides of the laminate to measure the local contact pressure (contact stress) between the laminate and the mould. At the beginning of the bending process, the contact stresses were locally distributed over the laminate in a similar pattern as in a three-point bending; after the laminate was further bent, the stress distribution rearranged to be as in four-point bending. In the end of the moulding, the local contact stresses increased over the entire laminate and reached a 'peak-value' over bent area in the middle part of the mould. A finite-element model was created to study the bending process. Regarding the overall development of the contact stress variations, the experimental and the numerical results agreed.

Wooden floors usually have worse impact sound insulation (ISI) at low frequencies than concrete floors having the same rating level. Rating level is usually expressed by single-number quantities (SNQs), such as weighted impact sound pressure level Ln,w. Psychoacoustic research among wooden floors is very limited although a controlled laboratory experiment is the strongest method to point out the most adequate SNQs to be declared for the floors. The purpose of our study was to determine how four standardized SNQs of ISO 717-2, Ln,w, Ln,w +CI, Ln,w +CI,50, and LiA,Fmax,V,T, and a recently proposed SNQ, Ln,w +CI,25, are associated with the annoyance of natural impact sounds transmitted through wooden floors. Fifteen floors were built in the laboratory based either on cross laminated timber (heavy) or open box wood (light) slabs. Different coverings and suspended ceilings were applied on these slabs. The ISI was tested within 25-3150 Hz using both tapping machine and rubber ball. Thereafter, five natural impact sounds were recorded for each floor: rubber ball drops, steel ball drops, walking, jumping, and chair pushing. Fifty-two people rated the annoyance of these 75 recorded natural impact sounds in psychophysics laboratory. Annoyance was best associated with Ln,w for all the five impact sound types. That is, measurement of ISI within 100-3150 Hz is sufficient from subjective point of view. All four SNQs based on tapping machine explained annoyance better than the SNQ based on rubber ball. Our results can significantly guide the future research, development, and regulations of wooden floors.

Ambient vibrations of a six-story lightweight timber frame building were measured under different environmental conditions in order to obtain the modal parameters of the structure. Changes in temperature and relative humidi-ty in timber can influence its response in terms of modal parameters. Namely, a moisture content change in the timber can affect stiffness, strength, and shape of the elements as well as the properties of the connections. Monthly measure-ments have been performed on a six-story lightweight timber frame building in Varberg, Sweden, built in 2021. The in-situ tests were performed using five bat-tery-driven data acquisition units with 14 uni-axial accelerometers. Additional-ly, the building is permanently monitored using temperature and humidity sen-sors, starting ever since its construction phase. The ambient vibration data have been analyzed using two different only-output methods. The results obtained under different temperature and humidity conditions were compared in order to assess the effect of the environmental conditions in the building. This infor-mation can be used to ensure the building meets safety and performance re-quirements, as well as to identify potential issues that may need to be addressed during building design.