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The addition of prestressing not only improves the force resistance of glulam beams, but also provides a potential solution to improve their fire resistance. An in-depth study of the fire behavior of prestressed glulam beams (PGBs) under fire and the force behavior after fire is essential for their fire resistance design and evaluation. In this paper, fire tests and post-fire four-point bending experiments were conducted on the PGBs aiming to investigate the thermal response of the PGBs as well as their force resistance after fire. The results showed that fire significantly affected the mechanical properties of the PGBs, not only reducing the prestressing force during the fire, but also decreasing the residual load carrying capacity after the fire. After 60 min of standard fire exposure, the prestress and load capacity of the PGBs decreased by 10 % and 33.33 %, respectively. Increasing either prestress or reinforcement ratio can effectively improve the resistance performance of the PGBs after fire. In the same fire action time, if the prestress was increased by 59.46 % or the reinforcement ratio was increased by 0.53 %, the residual ultimate load capacity of the PGBs was increased by 17.14 % and 22.19 %, respectively. The study also indicates that fully utilizing the synergistic effect of prestressing and reinforcement ratio enhancement can significantly improve the overall performance of the PGBs. In addition, a theoretical calculation model is proposed to accurately predict the residual flexural capacity of the PGBs after fire, which provides a theoretical support for the fire-resistant design of the PGBs before fire and the assessment of residual load capacity after fire. • Experimental studies revealed the damage mechanism of PGBs under fire. • Prestressing bars improve the mechanical properties of glulam beams after fire. • Theoretical models effectively predict the carrying capacity of PGBs after fire. [ABSTRACT FROM AUTHOR]

For structures that experience a fire event without collapse, determination of the residual capacity is required. The objective of this research is to determine the residual properties of glued laminated (glulam) timber after exposure to elevated temperature to enable post-fire structural evaluation. The residual compressive and shear properties of glulam were experimentally measured after exposure to a range of elevated temperatures (50, 100, 150, 200 and 250 ℃), considering also the effect of heating duration (30, 60 and 90 min) and cooling method (air cooling and water cooling). To account for transient temperature gradients, an effective temperature of the specimen was defined based on the dynamic time-temperature profile. For parallel-to-grain compressive strength, the reduction in residual strength remains within 20% of the initial strength as long as the effective temperature has not exceeded 170 ℃, but it drops severely to exceed 50% at 210 ℃. For shear strength, the permanent reduction is also within 20% after exposure to effective temperature lower than 190 ℃ and air cooling. Water-cooling leads to greater permanent reduction of mechanical properties compared with air-cooling. After first temperature exposure, additional cycles of heating-cooling (by air) do not further degrade the properties. Based on the test results, predictive formulae are proposed for the residual mechanical properties of glulam. • Test the post-fire performance of glulam with a total of 450 specimens. • Consider the variation of heating temperature, heating time and cooling method. • Assess the residual elastic modulus and strength under compression and shear. • Propose the concepts of air temperature, maximum and effective glulam temperature. • Establish and verify the equations to calculate post-fire properties of glulam. [ABSTRACT FROM AUTHOR]

This paper presents a method to expand the availability of wood in construction by establishing a computational design and robotic fabrication workflow. Digital tools enable the evaluation of the structural, material and geometric properties of pieces of unknown origin to create beams from unprocessed reclaimed timber using clay and natural fibers. Methods to overcome challenges such as material irregularities, embedded fasteners, size variation, and surface toxins allow for timber that would otherwise only be downcycled to serve a structural high-value use. A full-scale prototype beam was fabricated to test the fabrication process, and structural testing was conducted to demonstrate design specific span and loading performance. • A workflow for building laminated beams from unprocessed reclaimed timber elements. • Use of computational design addresses the irregularities of reclaimed materials. • Use of clay and natural fibers as binding material creates a disassemblable system. • Clay encapsulation mitigates emission of toxic substances in the coatings. • An end effector design and fabrication process for fiber wrapping are demonstrated. [ABSTRACT FROM AUTHOR]

In recent years, wood has become an increasingly popular building material for its environmental friendliness. Large-span timber structures are in high demand, of which the spliced joints play an important role for the main structural members. In this research, six specimens with two connection configurations, i.e., the slotted-in-steel-plate connection (SC) and the cover-plate connection (CC), were designed and subjected to cyclic loading tests. Besides the traditional data acquisition system, contact-free displacement measurement was also applied. The feasibility was verified since the moment-rotation curves obtained through the two methods showed strong consistency. Through the analysis of the mechanical properties of the joints, different methods for the determination of the yielding point of the specimens were compared and discussed. The test results show that the ultimate strength and stiffness of the CC connection were 59.04% and 187.7% higher than that of the SC connection, whereas the ductility of the former was 77.02% lower than that of the latter. Factors influencing on their mechanical properties were further analyzed. It is noted that while the ultimate strength is dominated by the steel plates, the stiffness and ductility depend more on the glulam elements and fasteners. Recommendations were also proposed as a design basis for the two types of connections. • Two types of spliced joints for large-span timber structures were designed. Six full-scale specimens were tested. • The mechanical properties of the connections were compared and analyzed, and suggestions for improvement were proposed. • PTV was applied to obtain the displacement data. The applicability of contact-free measurement was verified. • Methods for the yielding definition were compared. EEEP method is suitable for specimens with obvious brittleness. [ABSTRACT FROM AUTHOR]

• A new type of bamboo and timber composite material (CLBT) was developed by bidirectionally assembling and gluing bamboo-based glulam (glubam) and timber. • CLBT beams have similar and even larger bending stiffness and capacity compared with CLT beams. • In addition to the experimental method, advanced analytical models are also applied to investigate the flexural response of CLBT beams. • Some optimal patterns are provided for the design of CLBT beams to achieve a favorable flexural performance. The flexural behavior of cross laminated bamboo and timber (CLBT) and cross laminated timber (CLT) beams are studied to explore the potential of using glued laminated bamboo (glubam) in CLT panels to obtain similar or even better mechanical performance and other constructional and environmental merits. The 4-point bending experiments were conducted for full-scale model CLBT and CLT beams, assisted with using deformation instrumentations including the digital image correlation method (DICM) and conventional methods (LVDT and strain gauges). All the experimental results show that the CLBT beams have the similar even better bending stiffness and capacity than corresponding CLT beams, and the advantage is more significant for beams under in-plane bending condition. Analytical models based on two-dimensional (2D) elasticity theory are also applied to predict the flexural response of CLBT beams. The accuracy of the proposed analytical models can be verified by comparing the results with experimental results. Some parametric studies for CLBT beams with different combination configurations of glubam and wood layers are also conducted to provide several design suggestions to achieve favorite flexural performance for this type of cross laminated bamboo and timber beams. [ABSTRACT FROM AUTHOR]

• Coating locations and inclined angles of timber can affect fire-retardant efficiency. • Investigation of the fire dynamics on fire-retardant coated timber surfaces. • A novel synchronised multi-wavelengths and Schlieren imaging system for fire research. • Developed conceptual models for revealing coating's heat transfer inhibition mechanisms. The impact of intumescent flame-retardant (IFR) coating location on the fire-resistance of inclined timber samples was studied using a multi-imaging system that integrated visible wavelength, short-wavelength infrared (SWIR), long-wavelength infrared (LWIR), and Schlieren techniques. Weight loss post-initial ignition was monitored using a weight scale, and a scanning electron microscope (SEM) was employed to observe the microstructure of both coated and uncoated surfaces post-burn. Samples were inclined at 30˚, 45˚ and 60˚ to study the effects of inclination on fire-retardant efficiency. Four coating strategies were compared: top surface, bottom surface, one side surface, and both side surfaces, against an uncoated control. Quantitative results revealed significant reductions in burning intensity and fire spread when coating was applied to the bottom surface and both side surfaces, attributed to the inhibition of convective heat transfer from underneath the timber samples. The mechanisms of this inhibition were considered to be the termination of gas-phase combustion and impediment of pyrolysis product escape. Furthermore, the fire-retardant efficiency diminished with increasing inclination angles, especially for samples coated only on the top or one side. Conceptual models were developed to understand the mechanisms of fire-retardance and heat transfer inhibition. This work offers critical guidance for the application of fire-retardant coatings and may enhance cost efficiency in fire safety, particularly for individual elements of timber structures such as beams, columns, and frames. [ABSTRACT FROM AUTHOR]

• A new concept of bio-based prestress technology. • Experimental proof-of-concept on bamboo-timber composite beams. • Industrial level of trial production of prestressed bamboo-timber composite beams. • Thorough lab investigation on the proposed new bio-based composite beams. This paper presents a pioneering experimental proof-of-concept study to validate a novel concept of prestress technology that used only pure bio-based composite materials while achieved consistent prestressed stress distribution within the structure member, and provided in-situ flexibility, improved structural performance, and maximised the rate of utilisation of each material. Industrial level of facilities were used during this development. The prestress is achieved by pressurised/forced lamination of multiple components with different materials and geometrical properties. The prestressing process is activated during the pressure release stage during which the components are interacting with each other, creating different stress statuses that would favour the weaker and adverse the stronger components to maximise the strength exploitation of different materials. Using laminated bamboo and timber as an example pair, twenty-two glulam, non-prestressed and prestressed laminated bamboo-timber composite beams were manufactured, tested, and analysed to provide an in-depth understanding of the structural behaviours of these novel structural members. Failure modes, yielding, ultimate and serviceability limit loads, and corresponding deflections, as well as the histories of strain development at key positions of the specimens were examined. The experimental study confirmed the feasibility, effectiveness and industrial scalability of the proposed technology. The novel concept provides a new approach for developing the prestress technology for bio-based materials, and this experimental study laid the foundation for its future analytical development and numerical studies. [ABSTRACT FROM AUTHOR]

• Timber dowel-type connections with slotted-in steel plates tested with and without reinforcing screws. • Connections without reinforcing screws exhibit brittle shear failure with little to no ductility or energy dissipation capacity. • Addition of self-tapping screws as perpendicular-to-grain reinforcement prevent brittle shear failure. • Screws were most effective for connections that had similar row shear and yielding failure capacities. • Reinforced connections with larger dowel slenderness had more significant improvements in ductility and energy dissipation capacity. Braced frames are a common lateral force-resisting system in mass timber structures. In timber braced frames, timber-steel dowel connections are relied upon to provide ductility and energy dissipation capacity under earthquake loads. However, the ductility and energy dissipation capacity of these connections can be limited by the onset of a brittle failure mechanism (e.g., row-shear or group tear-out) prior to significant dowel yielding. This paper presents an experimental campaign investigating the structural performance of timber-steel dowelled connections reinforced with self-tapping screws. Twelve connections were tested; with 8 tested under monotonic loading and 4 tested under a cyclic loading regime. The tested connections included two different fastener diameters of 11 mm and 16 mm, with one or two internal steel plates, both with and without reinforcing screws designed to prevent brittle shear failure. The results demonstrate that the reinforcing screws are most effective for improving the ductility and energy dissipation for connections with similar design values of dowel yield and row shear capacities. In addition, the increases in ductility and energy dissipation with reinforcement were greatest for connections with high slenderness (defined as the ratio of dowel diameter to timber thickness) dowels. There was little improvement in the ductility of connections whose design capacity was dominated by row shear, although there was improvement in the energy dissipation of the connections. Overall, results of this study demonstrate the potential for using self-tapping screws to reinforce steel dowel connections and improve the seismic performance of mass timber braced frames. [ABSTRACT FROM AUTHOR]

• Non-linear bending models for wood considering composite reinforcement. • Selected issues in estimating and numerical modelling stiffness and strength of FRP-reinforced timber beams. • Application of the generalised Hill yield criterion with a distinction between compressive and tensile yield stresses. The paper presents selected methods for modelling bent timber beams strengthened with fibre-reinforced polymers (FRP). The assumptions are described, and the main analytical models representing the non-linear bending behaviour of wood are shown. Based on the models presented, analytical approaches considering reinforcement in the tension zone are proposed. The problem of determining the appropriate material parameters of the wood used in analytical calculations and numerical models is discussed. The main numerical methods used in timber analyses are presented. The Hill yield criterion and the generalised Hill yield criterion are discussed in more detail. A method for retrospective estimation of material properties of wood taking into account non-linear material models and fitting the generalised Hill yield criterion is described. Experimental bending tests of technical-scale beams reinforced with composites are presented. The numerical analysis was carried out and discussed. The generalised Hill yield criterion was applied to represent the behaviour of the wood, distinguishing the different yield stresses in compression and tension. The suitability of using non-linear models and advanced strength criteria in the numerical analysis of timber elements is discussed. [ABSTRACT FROM AUTHOR]

Glue-line tests provide the shear resistance and failure mode of samples extracted from laminated timber products. Several papers questioned the practical use of such tests affirming the lack of correlation between the capacity of the beam and the outcomes of glue-line tests. However, no studies provide a probabilistic framework for interpreting glue-line tests. This paper presents and discusses the largest database of glue-line tests ever published, consisting of approximately 17000 tests on glued laminated timber (GLT) beams, carried out at the Treteknisk, the Norwegian Institute of Wood Technology (Norway). This database has been used to develop in Abaqus a stochastic FE model to predict the shear capacity of glued laminated timber beams (GLT) using advanced modelling concepts, including discrete cracking and plasticity. The authors examine the dependence of the shear capacity on the beam size to assess the shear size effect in GLT components. The methodology is based on Montecarlo simulations. The mechanical properties of the elementary volumes composing the beam are assigned using a random field model calibrated on the glue-line tests. • Screw reinforcement for timber specimens under compression perpendicular to grain. • Experimental tests on 54 specimens with different geometry and load conditions. • Validation of the capacity model according to the Eurocode 5 proposal. • The model does not seize the failure mechanism by the screw tips. • The model is slightly conservative for the failure by the load steel plate. [ABSTRACT FROM AUTHOR]

• Glued-in rod connections instrumented with distributed fiber optic sensors (DFOS) were tested. • Strain sensors used to measure distributed strain profiles along the rod-adhesive and adhesive-timber interfaces. • Experimental strain distributions in good agreement with Volkersen theory. • Distributed strains from DFOS can be used for bond-slip measurement. • Challenges surrounding use of nylon-coated fiber optic cables for short bond lengths. The rise in popularity of mass timber structures globally has increased the demand for high-performance timber connections. Glued-in rod connections which are advantageous compared to other dowel-type connections because of their high strength and stiffness, have been the subject of extensive research in the literature; However, the lack of an in-depth understanding of their behavior and a uniform set of guidelines for their design continues to limit the use of glued-in rods in practice. To develop an improved understanding of the behavior of glued-in rod connections this paper examines, for the first time, the use of distributed fiber optic sensors to measure the complete strain distribution along the length of a glued-in rod connection. Axial pullout tests were conducted on twenty-five glued-in rod connections in glued-laminated timber with varying embedment lengths and glue-line thicknesses. Results of the study demonstrate the ability of fiber optic sensors to capture the full strain distribution along the length of the steel rod and along the epoxy-adhesive interface, enabling the study of localized behavior that would be difficult to measure using conventional strain gauges. In addition, results demonstrate the ability of distributed fiber optic strain sensors to infer axial stress and force distributions along the length of a glued-in rod connection, which are compared with theoretical distributions from the Volkersen model, as well as measure bond-slip behavior. [ABSTRACT FROM AUTHOR]

At present, the popularity of timber as a structural material is booming. However, the current knowledge on disproportionate collapse prevention and extreme loading of timber buildings is scarce. To prevent disproportionate and progressive collapse, catenary action is an important mechanism, where the axial capacity of bending members is activated. Because of the brittle behavior of timber in the relevant failure modes, it can only achieve catenary action via strengthening. In this paper, analytical expressions are derived for the elastic, plastic, and catenary capacity of laterally loaded wood and timber beams with a tension-side strip reinforcement. A load-path dependent M - N interaction diagram with damage accumulation explains the ultimate catenary capacity and the transition between the bending- and catenary-dominated load-carrying mode. The analytical expressions are validated and discussed based on tests on beech clearwood specimens reinforced with carbon fibers in a polyurethane matrix. Furthermore, a case study on glued laminated timber beams is presented to demonstrate the potential of reinforcing timber beams subjected to extreme loading. [Display omitted] • Analytical models for strip-reinforced wood and timber beams are presented and validated. • A load-path-dependent M-N interaction diagram with damage accumulation is shown. • The models are validated against tests and a case-study is presented. • The strength parameters are the most important. • Strengthening led to multi-fold increases in impact resistance and flexural rigidity. [ABSTRACT FROM AUTHOR]

This paper presents an experimental campaign conducted on the glue laminated timber (glulam) joints with epoxy bonded-in GFRP rod aiming to investigate the bond-slip mechanism between glulam and GFRP rod. The tests were conducted in pull-pull configuration. To measure the axial strains of GFRP rods during testing, strain gauges were internally installed in the GFRP rods in advance of bonding. The test results were summarized and discussed in terms of typical failure modes, load-slip behavior, distributions of GFRP rod strain, bond stress and relative slip. The local bond stress-slip relationships at different locations along the bonded length were obtained based on the obtained bond stress and relative slip distributions. It was founded that the local bond stress-slip relationships at different locations differ from each other. The local bond stress-slip curves near the loaded end are generally stiffer than those close to the anchorage end, which indicates that it might not be reasonable to do finite element modelling using an unified bond-slip law. The local bond-slip stiffness distributed nonuniformly along the bonded length confirming the differences among the local bond-slip relationships at different locations again. Finally, the analytical models were used to predict the bond-slip behaviour of the specimens. The results showed that the analytical models can predict the bond-slip behaviour between the glulam and the GFRP rod effectively. This study expanded the data base of the timber joints with glued-in rod and provided some references for the structural analysis and design of the glued-in FRP timber joints. [ABSTRACT FROM AUTHOR]

This study investigates the secondary failure of Malaysian Dark Red Meranti ( Shorea spp.) and Spruce ( Picea abies ) finger joints in a glulam beam in a fire test using a bench-scale test set-up. Secondary failure is the occurrence of failure of the bond lines due to fire and the falling off of the outermost tension layers, exposing the uncharred inner layers to a sudden increase of fire intensity. The lack of published work and the difficulties in describing the behaviour of the finger joints after the secondary failure in a full-scale fire test has identified the need for a simple bench-scale method, incorporating the conditions of the standard fire test. This paper focusses on the performance of the finger joints which together with other defects such as knots and splits are generally the weakest component in the glulam beam. The finger joints were bonded with structural adhesives, specifically phenol resorcinol formaldehyde (PRF) and polyurethane (PUR). They were tested in tension to imitate the failure of finger joints on the tension side of a standard fire test of a glulam beam. Constant heat flux was introduced to the finger-jointed specimens to replicate the secondary failure of a glulam beam in the standard fire test. The results of this study indicate a relationship between the charring rate and density of the specimens, with higher density Dark Red Meranti showing lower charring rate compared to the lower density Spruce specimens. Factors such as constant heat flux as opposed to the time-increasing heat flux exposure and specimen size influenced the charring rate of the specimens. The char rate was measured at the early stages of the fire test, which is known to have higher values since the build-up of the charred layers was not sufficiently substantial to protect the inner unburnt wood. Overall, the bench-scale fire test set-up was able to differentiate the fire performance of the adhesives, with PRF showing better fire performance compared to the specimens finger-jointed with PUR adhesive. In addition, tensile tests at ambient temperature showed no significant difference in tensile strength between finger joints bonded with different adhesives for the same wood species. The tensile strengths of the finger joints bonded with different adhesives were influenced by the temperature profile through the joint. The proposed bench-scale fire test was used to compare the quality of the adhesives in a fire situation, specifically with respect to secondary failure. The PRF was selected as the reference adhesive. [ABSTRACT FROM AUTHOR]

In order to achieve larger spans of timber arch bridges, glulam massive timber sections must be spliced on-site by moment resisting and rotationally stiff joints. In this paper, a novel timber splice connection utilizing long threaded rods and grout-filled couplers is presented. Flexural characteristics of the splice joint were investigated by full-scale experimental tests and 3D finite element models. An analytical model is proposed for determining the moment capacity and the rotational stiffness of the splice connection. The experimentally measured efficiency of the splice connection with regard to moment capacity and rotational stiffness was 69% and 66%, respectively. [ABSTRACT FROM AUTHOR]

Cracks are easily observed in glulam bolted joints due to the high moisture transport rate in the area and constraint stresses caused by the presence of steel fasteners. The purpose of this research is to explore to what extent initial cracks affect the mechanical performance of bolted glulam joints. Experiments were conducted on full-scale specimens with different bolt diameters, bolt layouts, and combinations of different crack patterns (e.g. crack length, location, etc.) were considered. This paper presents the failure modes and the reduction in several mechanical parameters of cracked glulam joints. It is found that initial cracks have a significant effect on the mechanical behavior of the joints. The cracks lead to a reduction up to 52% in the stiffness and a reduction up to 61% in the ductility ratio of the joints, respectively. In addition, an analytical method based on the yield theory and fracture mechanics was proposed to predict the load carrying capacity of the cracked glulam joints, and the proposed model was further verified by the experimental results. [ABSTRACT FROM AUTHOR]

Mechanical behavior of the shear connections has a significant influence on both the load-carrying capacity and the bending stiffness of timber-concrete composite (TCC) beams. All the studies reported so far have concentrated on the performance of TCC connections in mature concrete. The performance of shear connections for TCC beams at early concrete ages, however, has not been investigated yet. This information is essential to evaluate the structural behavior of TCC floors or bridges during construction. In this paper, a total of 18 push-out tests with concrete ages ranging from 12 h to 28 days are performed, to investigate the early-age performance of lag screw shear connections in the lightweight concrete. Development of concrete strength with time is also analyzed. At the concrete ages shorter than 7 days, both the stiffness and strength of the screw connectors increase evidently with time, which follows the same growth trend with the concrete strength. After a 7-day cure, screw shear connections reach almost 100% of both the 28-day serviceability slip modulus and shear strength. Material properties of the glulam and the screw fastener are decisive in the shear performance of connections when the concrete hardens to some degree. Based on the experimental results, the accuracy of the design methods proposed in Eurocode 5 is evaluated. In addition, by non-linear regression of the experiment data, expressions to predict the development of load-carrying capacity and serviceability slip modulus for screw shear connections before 28 days are established. [ABSTRACT FROM AUTHOR]

Glued-laminated bamboo (glubam) is a new type of structural material, which is developed as a potential alternative to the glued-laminated lumber or glulam. Similar to modern timber structures, connecting the glubam elements using steel joints requires a good understanding of the shear behavior of the material. In this study, glubam boards with three different bamboo strip (or fiber) configurations are manufactured and studied. Three types of glubam boards were manufactured and tested, including glubam with two bidirectional fiber arrangements at the ratios of 4:1 and 1:1, respectively, in the two orthogonal directions, and also the unidirectional fiber arrangement. The shear strengths in different loading conditions are experimentally investigated, following testing specifications for conventional wood. The study found that the in-plane shear strength values follow a normal distribution well, whereas the out-of-plane shear strength values can be statistically expressed by Weibull distribution. Based on the test results, the out-of-plane shear strengths and the in-plane shear strengths of glubam are studied, and the characteristic values and the design values are suggested. The relationship between the out-of-plane shear strength and the bidirectional ratio of bamboo strip (or fiber) has also been obtained with reasonably good correlation to the test results. [ABSTRACT FROM AUTHOR]

The orthogonal structure of cross laminated timber (CLT) diaphragms under shear can cause three possible shear failure mechanisms: (i) gross-shear (in case of narrow-face bonded laminations), (ii) net-shear and (iii) torsion. While the resistance against torsion has been investigated comprehensively, the determination of in-plane gross- and net-shear strength remains a challenging task. Whereas gross-shear properties are proposed in analogy to glulam, for net-shear only properties derived from testing single CLT nodes are available. The verification of these approaches for full CLT elements has yet to be confirmed. We aim on verifying the applicability of a corresponding novel test configuration. For this aim and for evaluation of net- and gross-shear strength and modulus, an experimental study comprising in total 23 series featuring different parameter settings was conducted. In doing so, the operational efficiency of the test configuration together with reliable shear failure of all tested CLT elements was observed. With regard to the conducted parameter study, results qualitatively correspond with tests on single CLT nodes. Gap execution and layer thickness are confirmed to be the main parameters significantly influencing in-plane shear properties. Based on gathered experiences, characteristic shear properties and a conclusive design concept are proposed. [ABSTRACT FROM AUTHOR]

Thin-strand composite panels and subsequent mass timber beams were produced using thermally modified wood strands in a pressurized system. The effects of thermal modification (TM) temperature and dwell time on the mechanical, moisture, and decay performance of panels were studied. TM reduced moisture sorption and increased decay resistance. The thin-strand composites were evaluated in flexure and benchmarked against commercially available structural products. Moreover, the mass timber beams' out-of-plane bending was accurately predicted with traditionally used laminated beam theory. The study shows that TM, under controlled conditions, enables the production of high-performing wood-strand panels with improved dimensional stability and decay resistance. [Display omitted] • Thermal modification (TM) effects on strands produced from small-diameter timber. • TM improved the physical performance and decay resistance of strands. • Cross-laminated strand veneer lumber (CLSVL) was produced using the modified strands. • The CLSVL out-of-plane bending is predictable and has structural grade performance. • Panels with reduced moisture sorption and improved decay resistance were obtained. [ABSTRACT FROM AUTHOR]

This paper reports testing results of various connections for composite beams made of concrete slab and glue-laminated bamboo (glubam) beam. Six types of composite connectors, commonly used in timber-concrete composite (TCC) beams, were tested under direct shear condition. The shear force-slip relationships were measured and all the relevant mechanical properties such as slip moduli and shear capacities were obtained. Compared with typical TCC beam connections, the Glubam-concrete composite (BCC) systems present several different characteristics. The shear failure along the notch, typical in TCC notched connectors was not observed for BCC system, however, the delamination cracking along the lamination layers occurred in some types of BCC connections. Based on the test results and analysis, six types of connectors can be classified into two categories, one with higher strength and stiffness but low ductility, and the other with lower strength and stiffness but higher ductility. A set of regression equation with a bilinear descent segment is also provided for simulating the shear-slip behaviors of each type connector. It is found that some of the connection systems including the notched connector, steel mesh connector, screw connector and pre-tightening notched connector, are more suitable and recommended for constructing BCC structures. [ABSTRACT FROM AUTHOR]

Moisture induced stresses were studied in glulam beams, which were made from hydrothermally treated poplar ( Populus deltoides ) wood in the current research work to understand whether the hydrothermal wood modification can reduce those stresses or not. Wood blocks with dimensions of 6 (R) × 10 (T) × 73 (L) cm 3 were cut and hydrothermally treated in a stainless steel reactor at temperatures of 140 and 160 °C for a holding time of 30 min. The treated wood blocks were dried to achieve moisture content of 12%. Afterwards, the glulam beams (4-ply) were manufactured by using polyurethane (PUR) adhesive. In order to evaluate cross sectional moisture induced stresses (MISes) and bending properties of glulam beams; wood density, equilibrium moisture content (EMC) of wood, 4-point bending of the glulam beams (according to ASTM D 198-02), 3-point bending of the treated and untreated wood (according to ASTM D 143-09) and the moisture induced stresses in cross section of the glulam beams were determined. The results showed that the hydrothermal treatment reduced the cross sectional moisture induced stresses as well as relevant moisture gradients and also it caused increase of the bending strength as well as stiffness of the treated wood and the glulam beams. [ABSTRACT FROM AUTHOR]

• Timber long-term behaviour under variable environmental conditions are evaluated. • Analytical model for the deflection evaluation in timber elements are proposed. • Timber time-dependent creep factor is considered. • Timber mechano-sorptive and pseudo-creep components are considered. • Creep damping under cyclic environmental conditions is incorporated. The variability of the physical and mechanical properties of wood requires that the analysis of its long-term behavior take into account all the factors capable of modifying these properties. The environmental conditions of humidity and temperature are factors that alter these properties, conditioning long-term behavior, a situation that is especially decisive in the case of structural elements in bending. The design standards establish simple corrective factors based on the type of environmental exposure that allow creep deformation to be estimated in a final stage from an initial instantaneous deformation value. A new analytical model is proposed that allows estimating the behavior at any stage from the knowledge of the environmental conditions to which the structural element has been subjected. The model is applied to different elements in various environments, from camera control situations to outdoor situations of 3-year seasonal cycles. In all cases, the precision of the model and the simplicity of its use are verified due to the basic factors on which it is based. [ABSTRACT FROM AUTHOR]

• Loading temperature could not cause any significant impact on the wood density. • Thermal cycling has a meaningful impact on the modulus of elasticity of glued laminated beams composed of one wood species. • Temperature cycling also has a significant effect on the bending strength of beams glued together from one species. • Temperature cycling had no significant impact on the mechanical properties. • The combination of wood species influences mechanical properties, including MOE and MOR. This study investigates the effect of cyclic temperature variation on the bending properties of glued laminated timber made from combinations of wood species. One hundred sixty timber beams were created from three species, Norway spruce (Picea abies (L.) H. Karst.), Black alder (Alnus glutinosa (L.) Gaertn.), and European beech (Fagus sylvatica L.), which were chosen to represent hardwood and softwood species. Beams were glued together using one-component polyurethane (1C PUR) adhesive according to a combination key, with the verification series consisting of beams glued together from a single species. The beams were split into four groups, with three of them undergoing temperature cycling (-25 °C and + 60 °C) and the fourth serving as a reference. The bending characteristics, namely modulus (MOE) of elasticity and bending strength (MOR), were investigated. As a result, the cycling of our chosen temperatures does not affect the density change in the beams. The modulus of elasticity (MOE) was significantly negatively affected for the single species beams, while it was not affected for the combinations of wood species. Bending strength (MOR) was also negatively affected by temperature, especially for the hardwood species; generally, there was an increase in bending strength for the combined GLT. Density in combined beams showed an increase compared to alder and spruce and a decrease compared to beech. The mechanical properties were affected by a significant increase compared to the softwood species. [ABSTRACT FROM AUTHOR]

• Twenty-seven specimens were designed and four-point bending experiments were carried out. • The failure modes, elastic stiffness, bearing capacity, and ductility coefficients of the solid beam, hollow beam, stiffened hollow beam were compared and analyzed. • Numerical models were developed to analyze the mechanical performance of stiffened hollow beams and were validated by the experimental results. • The calculation equations for ultimate bearing capacity and bending stiffness of glulam beam with three different section forms were established. Inspired by the section structure of natural bamboo, a rectangular hollow glulam beam with stiffeners is proposed. In this paper, experimental study and finite element simulation were carried out for such glulam beams. The results showed that compared with hollow beam, the initial bending stiffness, ultimate bearing capacity and ductility of the stiffened hollow glulam beams improved significantly, indicating that stiffeners enhanced the local stability behavior of the webs and the bottom plates. Meanwhile, the calculation equations for ultimate bearing capacity and bending stiffness of glulam beam with three different section forms were established based on the material mechanics and constitutive model. The accuracy was verified by experiments and finite element analysis. This paper shows that the proposed stiffened hollow glulam beam can be used as a replacement for solid timber beam, which can save material while maintain a desirable mechanical performance. [ABSTRACT FROM AUTHOR]

In the present paper, the withdrawal stiffness of axially loaded threaded rods screwed into timber elements is investigated using theoretical, numerical and experimental methods. The theoretical approach is based on the application of classical Volkersen theory on axially loaded connectors. An experimental investigation of withdrawal of threaded rods from glulam elements is presented. The parameters of this investigation are the embedment length and the angle between the rod axis and the grain direction. The theoretical and numerical estimations are compared to the experimental results. [ABSTRACT FROM AUTHOR]

This paper describes an experimental test program and theoretical analysis which examines the reinforcing in flexure of glued laminated timber (glulam) beams using bonded-in carbon fiber reinforced polymer (CFRP) bars. A series of four-point bending tests were conducted till failure on unreinforced, passively reinforced and prestressed Douglas fir glulam beams in a simply-supported scheme. The focus of this research was to evaluate the reinforcing efficiency of both passively reinforced and prestressed beams. Test results showed that the flexural capacity of the reinforced, prestressed, prestressed & reinforced (bottom prestressed and top reinforced) beams greatly increased by 64.8%, 93.3% and 131%, respectively. While the maximum improvement of the bending stiffness reached 42.0%. Another important finding was that the extreme fiber tensile strain of timber beams at failure could be remarkably increased due to the presence of the tension reinforcement, which indicated it overcomes the effects of local defects and therefore the failure mode was changed from brittle tension failure to ductile compression failure. Based on the experimental results, a theoretical model was proposed to predict the flexural capacity of unreinforced, reinforced and prestressed timber beams, which was validated by the test data. [ABSTRACT FROM AUTHOR]

This paper describes an experimental test program and theoretical analysis which examines the reinforcing in flexure of glued laminated timber (glulam) beams using fiber reinforced polymer (FRP) and steel materials. A series of four-point bending tests were conducted till failure on both unreinforced and reinforced Douglas fir glulam beams in a simply-supported scheme. The focus of this research was to evaluate the effects of reinforcing materials, reinforcement ratio and arrangement on the flexural behavior. Test results showed that the flexural capacity, flexural global stiffness and timber tensile strain at failure were all improved considerably for reinforced timber beams when compared to the unreinforced control beams, in which the average improvement reached 56.3%, 27.5% and 49.4%, respectively. On the bases of the experimental results, a theoretical model was proposed to predict the flexural capacity and flexural stiffness of the reinforced timber beams. Most of the differences between theoretical and experimental results for both flexural capacity and flexural stiffness were within 10.0%, which showed a high accuracy of the proposed model. Subsequently a parametric analysis, which includes the axial stiffness ratio of reinforcement to timber, the relative location of tensile reinforcement, and the strength ratio of reinforced timber between flexural tension and compression, was undertaken to investigate the effects of the influential factors for both flexural capacity and flexural stiffness. [ABSTRACT FROM AUTHOR]

When rocking structures are designed, dampers may be required to substitute conventional connections to provide load resistance and dissipate the rocking motion. This study investigates the applicability of High-Force-to-Volume (HF2V) damping devices in rocking timber structures. HF2V devices present an attractive solution since the device does not suffer stiffness or strength degradation and can be reused after an earthquake. Laboratory tests on loaded and unloaded timber walls using two HF2V devices per wall were carried out. The applicability of the devices in timber walls was investigated focusing on damper functioning, the influence of the vertical load on the self-centering behaviour of the dampers, and possible slip in all connections. The results show that the devices functioned as intended and no significant damage occurred in the devices or the timber walls. HF2V devices present a feasible solution for rocking timber walls when a damage free structural behaviour is aimed for. [ABSTRACT FROM AUTHOR]

This paper examines the embedment behaviour of single-dowel connections in Scandinavian Spruce Glulam by means of experimental and numerical investigations. First, the experimental results of a series of single-dowel tests on samples of different geometry and grain directions are presented. The evolution of local strain concentrations around the fastener at increasing levels of bearing deformation, is reported in detail by means of non-contact field strain measurements and its implications are discussed. Detailed Finite Element simulations are also carried out and subsequently employed to highlight the main features of the response of doweled connections in glulam. A foundation model, initially developed for Douglas-fir ( Pseudotsuga menziesii ) timber, is upgraded and adapted for Scandinavian Spruce Glulam ( Picea abies ) elements subjected to loads acting perpendicular and parallel to the grain direction. The proposed model is based on the definition of equivalent material parameters for the crushing region around the dowel hole. To this end, relationships for the estimation of material characteristics as a function of the crushing volume are suggested. The validity and accuracy of the proposed modified foundation models are examined against the experimental results. It is shown the improved foundation model is able to simulate the embedment stiffness, capacity and inelastic behaviour of single-dowel connections on glulam with reasonable accuracy for strains of up to 8%, and can therefore be used for design and assessment purposes. [ABSTRACT FROM AUTHOR]

Glued-laminated timber (Glulam) – allowing for large span and curved elements to be produced – had revolutionized the way timber could be used in structural applications. As the importance of assessing large timber structures is growing, so is the interest of the professional community in assessment methods for existing timber structures. The performance of Glulam elements depends on the quality of the individual laminations, the quality of the finger joints, the quality of the glue-lines and the integrity of the cross-section. This paper presents and discusses feasible methods to: (i) create a general overview of the structural integrity of Glulam elements; (ii) assess the environmental conditions in which these are placed; (iii) determine their moisture content; (iv) map cracks; and (v) assess the integrity of glue-lines. There are multiple methods available; each method, however, only allows assessing a certain type of property or damage. Therefore the application of just one method might not be suitable to enable confident decisions, making it necessary to combine different methods to derive a full picture about the integrity of Glulam elements. As a consequence, expert’s reports treating the safety of a structure featuring Glulam oftentimes are set up from a standpoint which can be summarized as “safe on the best knowledge we have”. [ABSTRACT FROM AUTHOR]

In this paper, the performance improvement of glulam post-to-beam connections reinforced by plain round rods (PRRs) and self-tapping screws (STSs) were compared. Five non-reinforced post-to-beam bolted connections, five PRR-reinforcing connections and five STS-reinforcing connections were experimentally investigated under monotonic and low frequency cyclic loading. Their stiffness, ductility, moment resistance capacity, failure modes and seismic behavior were analyzed. The findings indicated that both of these two reinforcements could mitigate wood splitting, and change the failure mode from brittle failure to ductile failure. The maximum moment and failure rotation of PRR-reinforcing connection were increased by 29% and 6% respectively, compared with those of non-reinforced connection. In addition, those of STS-reinforcing connection increased by 86% and 145% respectively. Furthermore, the comparison of PRR-reinforcing and STS-reinforcing connections indicated that the connection ductility reinforced by self-tapping screws enhanced more significantly; 106% higher than that of PRR-reinforcing connection. Moreover, under the low frequency cyclic loading, PRR-reinforcing and STS-reinforcing connections dissipated more energy (336% and 641% respectively) with a lower stiffness degeneration rate and a higher equivalent viscous damping ratio than those of non-reinforced connection. Besides, the dissipation energy and equivalent viscous damping ratio of STS-reinforcing connection were larger than those of PRR-reinforcing connection. [ABSTRACT FROM AUTHOR]

Composite beam elements made of glulam beams and cross laminated timber (CLT) panels, and connected with a new shear connection system were tested under four point bending. The beams tested represent a section of a cassette floor element to be used in a multi-storey CLT construction system. The shear connection is primarily made of double-sided punched metal plate fasteners, connecting the CLT and glulam members to form a T-cross-section. Due to the uncertainty about the capacity of the double-sided nail plates to resist possible separation forces between the timber members, the shear connection may be secured with screws. Bending tests were performed with three shear connection configurations: double-sided punched metal plate fasteners only, inclined screws only, and double-sided punched metal plate fasteners combined with inclined screws. An additional test with a screw-glued connection was made for comparison. The results show that a shear connection with double-sided nail plates can be designed to provide a sufficiently high level of composite action and load-carrying capacity and represents an alternative shear connection system for glulam–CLT composite floors. [ABSTRACT FROM AUTHOR]

Glued laminated timber (glulam) is widely used as a construction material to make up lightweight and large span structures. The basic principle of this material consists in bonding together a number of layers of dimensioned timber with structural adhesives, in order to increase strength and stiffness of the member, and allowing to make up sustainable structures with great visual impact. Recent applications showed the effectiveness of fibre-reinforced polymer (FRP) composites in enhancing the structural performances of glulam beams, with particular reference on their flexural and shear strength. In fact FRP reinforcements could be used to strengthen existing structures or to reduce the dimensions of new structures to be designed. Considering the importance of the latter application, the present work shows the results of four-point bending tests on fifteen small scale glulam specimens, reinforced with glass (GFRP) or carbon (CFRP) cords, varying the kind of adhesive (epoxy resin or melamine glue). Eight further large-scale beams were tested in order to evaluate the role of the scale effect. Finally, an analytical model was developed, able to predict the behaviour of multilayer heterogeneous wood sections and which takes into account the effect of the reinforcements. [ABSTRACT FROM AUTHOR]

In the present paper, the withdrawal capacity of threaded rods embedded in timber elements is investigated using both theoretical and experimental methods. A theoretical approach based on Volkersen theory, assuming a bi-linear constitutive law is developed. Moreover, an experimental investigation of withdrawal of threaded rods from glulam elements is presented. Results for specimens covering a wide range of varying embedment lengths and rod-to-grain angles are provided. The agreement between theoretical estimations and experimental results is good. A nearly linear relation between embedment length and withdrawal capacity, predicted by the theoretical approach, is validated by the experimental results. [ABSTRACT FROM AUTHOR]

Near Surface Mounted (NSM) reinforcement is an effective strengthening technique for timber engineering. This study investigated the flexural behaviour of glulam beams reinforced by NSM–CFRP laminates. A total of twenty-four glulam beams, including eighteen reinforced glulam beams and six unreinforced glulam beams were tested up to failure to evaluate the reinforcing effect in terms of the flexural strength and the flexural stiffness of the beams. Two types of timber, namely, Douglas fir and Poplar were taken for the tests. The ratio of reinforcement arranged from 0.331% to 1.322%. The experimental results indicate that the flexural strength and the flexural stiffness were significantly improved by 34.2%–52.3% and 8%–28.5%, respectively. Several reinforced beams exhibit the pseudo-ductile behaviour in comparison to the linear elastic behaviour of the unreinforced beams characterized by the brittle tensile failure. The strain profile distribution indicates that the compressive behaviour of the timber can be improved by using NSM–CFRP reinforcement at the tension zone of the beams. Theoretical analysis was adopted for the prediction of the flexural strength of the glulam beams and the predicted results was observed in good agreement with the experimental results of the tested beams. [ABSTRACT FROM AUTHOR]

The commercial development of composite reinforced timber beams manufactured using low-grade laminated wood would be considerably enhanced if the same adhesive was permitted to be used both at the wood–wood bond interfaces as well as the FRP plate–wood bond interface. This paper describes a programme of tests undertaken to assess the structural performance of low-grade glued laminated timber reinforced with glass fibre reinforced plate (GFRP) bonded using the conventional wood laminating adhesive, phenol resorcinol formaldehyde (PRF). The use of a practical reinforcement percentage of 1.86% of the cross-sectional area resulted in a moderate stiffness enhancement of 18% and considerable improvements in the ultimate moment capacity of 31%. Strain profiles demonstrated that utilisation of the compressive behaviour of the timber was improved in the reinforced beams. Most importantly, at no stage during testing of any of the reinforced beams was the quality of the FRP–wood bond compromised. The results from a nonlinear finite element model showed excellent agreement with the experimentally determined ductile load–deflection behaviour of the reinforced beams. Furthermore, satisfactory comparisons are obtained between the predicted and measured failure loads and strain profile behaviour. Slip at the FRP–wood interface, bonded using a wood laminating adhesive, was considered negligible. The research proposes an improved alternative whereby the same adhesive is permitted to be used for all bond interfaces in the reinforced beam and the use of more expensive epoxy adhesives at the FRP–wood bond interface is avoided. [ABSTRACT FROM AUTHOR]

• Sliding achievable by yielding of base shear connections can act as an energy dissipation mechanism. • Two types of connections were tested: one to yield in fasteners and the other one within a perforated zone. • The strength, stiffness, ductility, and failure mechanisms were determined. • Perforated connections provided 3 to 5 times greater ductility than the ones yielded in fasteners. • Perforated base shear connections could be used to achieve moderately ductile connections. When cross-laminated timber (CLT) shear wall is designed for seismic loads, the Canadian timber design standard recognizes rocking as the sole energy dissipation kinematic mechanism to meet the capacity design requirement. The sliding mechanism, achievable by yielding of the base shear connections of CLT shear walls, is currently excluded. The focus of this research was on the yielding mechanism of base shear connections for mass timber shear walls as potential source for dissipating energy during major seismic events through sliding. Two types of base shear connections were evaluated: one was designed to exhibit ductile behavior through fastener yielding and the other was designed to yield within a perforated zone of steel bracket that was connected to the timber member with over-designed fasteners (i.e., capacity protected). In both cases, self-tapping screws (STS) were used as fasteners. Monotonic and cyclic tests were performed. The strength, stiffness, ductility, over-strength, and failure mechanisms were determined to investigate the use of these connections as reliable energy dissipating mechanisms. It was found that perforated steel plates provide a reliable yield mechanism with predictable yield and ultimate strength and displacement, and that damage in timber elements can be avoided when the fuses are combined with capacity-protected dowel-type fasteners. Both types of base shear connections under consideration behave in a ductile manner with some limitations under cyclic loading. While the perforated plate detail has the potential to qualify as moderately ductile connection, the other connection with fastener yielding mechanism may only exhibit limited ductility. An analytical model for predicting the yield and ultimate strengths, and ultimate deformation of the perforated plate was developed. [ABSTRACT FROM AUTHOR]

• Bonding pressure and glue type influence the bonding quality of CLT and glulam. • CLT or glulam made from pure oak delaminated more than the mixed oak-poplar. • The residual shear strength of pure oak specimen is comparable to mixed poplar-oak. • The residual shear strength is a better criterion to evaluate the bonding quality. The objective of this study is to evaluate the influence of manufacturing parameters on the bonding quality of CLT and glulam made from oak and mixed poplar and oak species. The bonding parameters studied were bonding pressure and glue type. To test the bonding durability, the specimens were subjected to a vacuum pressure cycle followed by drying to the initial weight. The bonding quality was then measured from delamination, residual shear strength, and wood failure percentage (WFP). Bonding pressure and type of glue appeared to have a significant influence on the bonding quality of CLT or glulam, with also significant interactions with the kind of species bonded. If a 0.8 N/mm2 bonding pressure seemed to provide better results, vacuum-pressed (0.085 N/mm2 bonding pressure) mixed poplar-oak CLT or glulam glued with PUR were very close to reaching the requirements of the standards. Generally, CLT or glulam made from pure oak delaminated more than the mixed specimens. However, their residual shear strength can be comparable or even superior to what was obtained with mixed poplar-oak specimens. As a result, residual shear strength after delamination test may be interesting to consider as an additional criterion to assess the glue line integrity of hardwood CLT or glulam products. [ABSTRACT FROM AUTHOR]

• Three types of novel connectors, named reactive powder concrete (RPC)-steel composite connectors, were designed and tested for developing fully prefabricated glued laminated bamboo (glubam) and concrete composite (BCC) beams. • Experimental results from the push-out tests on the proposed composite connectors with various configurations were presented. • This investigation validated that the proposed RPC-steel composite connectors effectively combine the high shear stiffness, high shear capacity and excellent ductility as well as convenient assembly on site. This study focused on developing novel connections with high shear stiffness and deformability for fully prefabricated glued laminated bamboo (glubam) and concrete composite (BCC) beams. Three types of reactive powder concrete (RPC)-steel composite connectors were designed and tested in the current investigation. Experimental results from the push-out tests on the proposed composite connectors with various configurations were presented, including the failure modes, shear force-slip responses, shear stiffness, capacity, and ductility. The results indicate that the RPC section can substantially improve the mechanical performance of the composite connectors. Moreover, a type of parametric model was also provided for predicting the shear stiffness and shear capacity of the proposed composite connectors based on the correlation analysis between the configuration parameter and the load bearing efficiency. Compared with the conventional cast-in-situ connectors, the experimental results validated that the easy assembly RPC-steel composite connectors have high shear stiffness and capacity as typical notched type connector as well as the excellent ductility of typical dowel type connector reported in previous studies. Feasibility evaluation revealed that the proposed composite connectors are suitable for a variety of fully prefabricated BCC structures. [ABSTRACT FROM AUTHOR]

• The use of stiff shear-key connectors in multi-panel CLT shear-walls is investigated. • An experimental campaign at joint and wall level on shear-key connectors is conducted. • The behaviour of shear-key connectors is compared to that of screwed connections. Multi-panel Cross Laminated Timber shear-walls with stiff vertical joints may represent a valuable structural solution for multi-storey timber buildings in low seismic prone areas. In this study, the opportunity of using shear-key connectors in the assemblage of stiff vertical joints as an alternative to short-spacing traditional dowel-type mechanical fasteners is evaluated. The mechanical behaviour of two types of stiff shear-key connectors is investigated through an experimental campaign conducted at joint and wall level. Shear tests were firstly carried out to determine the mechanical properties of panel-to-panel joints assembled with the shear-key connectors. The results are compared with those obtained from shear tests on joints with screwed connections (half-lap and spline joints). Full-scale shear-wall tests were then performed to determine the mechanical performances of the connectors at wall level. Joints with a single shear-key connector showed values of stiffness and strength comparable to those that would be obtained for vertical spline joints with approximately thirteen couples of 6 mm screws. The failure modes on the joints with shear-key connector were characterized by either a localized crushing in the wood or the shear failure in outer lamination of the CLT panels with no plastic deformation of the connectors. [ABSTRACT FROM AUTHOR]

This paper describes a series of four-point bending tests that were conducted, under service loads and to failure, on unreinforced, reinforced and post-tensioned glulam timber beams, where the reinforcing tendon used was 12 mm diameter toughened steel bar. The research was designed to evaluate the benefits offered by including an active reinforcement in contrast to the passive reinforcement typically used within timber strengthening works, in addition to establishing the effect that bonding the reinforcing tendon has on the materials performance. The laboratory investigations established that the flexural strength and stiffness increased for both the reinforced and post-tensioned timbers compared to the unreinforced beams. The flexural strength of the reinforced timber increased by 29.4%, while the stiffness increased by 28.1%. Timber that was post-tensioned with an unbonded steel tendon showed a flexural strength increase of 17.6% and an increase in stiffness of 8.1%. Post-tensioned beams with a bonded steel tendon showed increases in flexural strength and stiffness of 40.1% and 30% respectively. [ABSTRACT FROM AUTHOR]

A new shear connection system was tested in order to be used in off-site manufactured cassette floor elements made with glulam beams and cross laminated timber (CLT) panels. This type of floor element can present advantages from weight, structural and assembly point of view in multi-storey timber construction. The shear connection proposed is made of double-sided punched metal plate fasteners, connecting CLT and glulam members to form a T-cross-section. Inclined screws are used in combination with the double-sided nail plates to secure the shear connection. Shear test results are presented and compared with a simple calculation model for estimating the mean load-carrying capacity and stiffness of the combined joint according to methods available in the literature. [ABSTRACT FROM AUTHOR]

• Glued-laminated (glulam) timber beams were tested in 4-point bending. • Distributed fibre optic strain sensors (DFOS) used to assess structural behaviour. • DFOS can be used to identify timber defects including knots, cracks, and finger joints. • Distributed strains from DFOS can be used for in-situ measurement of elastic modulus. • Two-part epoxy adhesives optimal for bonding DFOS to timber. Global efforts to reduce the environmental impact of the construction industry have fueled the use of mass timber as a building material. However, the behaviour of mass timber elements is not fully understood, including the effects of localized anomalies (e.g., knots and joints) on global structural performance. To address this need, this study uses distributed fibre optic sensors (DFOS) to better understand the structural behaviour of mass timber elements through the testing of three glued-laminated (glulam) beams instrumented with DFOS under four-point bending. Results of the study demonstrated that DFOS data can be used to identify anomalies (e.g., knots, cracks, and finger joints) in glulam members, capture local strain distributions, and examine the influence of local effects on global structural response. Furthermore, distributed sensing was also found to be an effective tool to measure the in-situ elastic modulus of the timber material. [ABSTRACT FROM AUTHOR]

• A concept for a moment-resisting, beam-to-column, timber connection is presented. • The connection consists of inclined screwed-in threaded rods and metallic coupling parts. • Expressions for the stiffness and the forces in the rods are derived based on a component method. • The analytical predictions for stiffness were validated by full-scale tests. The use of moment-resisting frames with semi-rigid connections as a lateral load-carrying system in timber buildings can reduce the need for bracing with diagonal members or walls and allow for more open and flexible architecture. The overall performance of moment-resisting frames depends largely on the properties of their connections. Screwed-in threaded rods with wood screw thread feature high axial stiffness and capacity and they may be used as fasteners in beam-to-column, moment-resisting timber connections. In the present paper, a structural concept for a beam–to-column, moment-resisting timber connection based on threaded rods is presented and explained. Analytical expressions for the estimation of the rotational stiffness and the forces in the rods were derived based on a component-method approach. The analytical predictions for stiffness were compared to experimental results from full scale tests and the agreement was good. [ABSTRACT FROM AUTHOR]

• Introduction of a high-performance timber composite based on laminations from spruce. • Proof of significantly improved torsional stiffness properties by the rotation of individual layers to each other to a certain angle. • High capacity for biaxial load-bearing, as required for point-supports. • Resource-conscious building due to higher efficiency of structures made of DLT compared to CLT. • Bending stiffnesses of DLT in global x and y direction remain at almost the same level as for CLT with the same thickness. This paper deals with the development and implementation of diagonal laminated timber (DLT), a composite timber product, consisting of individual layers which are rotated to each other to a certain angle to increase its torsional stiffness. For the investigation we chose a specific DLT characterized by layers arranged at angles of ±45° respectively ±30° (±60°). The adjusted layup increases stiffness properties and provides ideal product properties for plates under biaxial bending. The load-bearing behavior and efficiency of diagonal laminated timber was investigated by means of theoretical and experimental investigations. The applied parametric numerical models explain the influence of the layer arrangement as well as the influence of width and thickness of the laminations on the torsional stiffness. The results prove a considerable increase in torsional stiffness of diagonal laminated timber compared to conventional cross laminated timber. This renders DLT an interesting option for floor systems which are governed by serviceability limit states such as deflections or vibrations. [ABSTRACT FROM AUTHOR]

Highlights: [•] Evaluated the flexural properties of solid rubber wood and laminated rubber wood. [•] If laminated wood could be suggested as a replacement to the solid wood. [•] Evaluated laminated wood flexural properties with different lamina thickness and jointed lamina. [•] Evaluated joint efficiency, wood adhesive bond strength, durability of the adhesive bond. [•] Rubber wood is found suitable for laminated and structural wood products. [Copyright &y& Elsevier]

Highlights: [•] Fracture place was changed from shear side to compression side by increasing of GFRP layers in glulam timbers. [•] GFRP materials improve mechanical properties of timbers. [•] Produced the highest ultimate strength and stiffness in bending test. [Copyright &y& Elsevier]

Highlights: [•] Structural beams were made from glue-laminated fibre composite sandwich panels. [•] Glued sandwich beams were tested under asymmetrical shear. [•] Beams with edgewise layers are twice stronger than beams with flatwise layers. [•] Beams with edgewise layers exhibited a progressive failure behaviour. [•] Theoretical evaluations were in good agreement with the experimental results. [Copyright &y& Elsevier]

• The moisture cycles present in timber bridges are simulated in this study. • The influence of moisture cycles on the bending strength is significant. • The influence of moisture cycles on the elastic modulus is not significant. • The zones of different local moisture in glulam can be discretized by patch sensors. Glulam timber is currently an interesting solution for building environmentally friendly and mechanically strong structures. However, little is known about the impact of Wetting/Drying (W/D) climatic conditions on glulam durability. This study evaluates the effect of W/D cycles on the bending mechanical properties of glulam. The results of this experimental study show that W/D cycles have significant influence on the bending strength. On the other hand, no significant effect is found on the elastic modulus. The moisture content of specimens is also monitored and the results provide an understanding of the sorption/desorption mechanisms in wood during cycling. [ABSTRACT FROM AUTHOR]