This study presents an analytical, experimental, and numerical investigation of full-scale glulam trusses connected through birch plywood gusset plates. Three trusses were joined through mechanical connectors, while three were adhesively bonded. Failure was designed to occur in the plywood plates subjected to a multi-axial stress state due to the convergence of three glulam elements in the node. The thickness of these plates varied between 9, 12 and 21 mm. This research aimed to evaluate the structural behaviour and failure mechanisms of birch plywood plates in timber connections. Experimental results showed that glued trusses generally exhibited larger ultimate loads and greater global stiffness compared to mechanically connected trusses. Nevertheless, the global stiffness was independent of the thickness of the central plywood plates. Analytical estimations for specimens that failed in the plywood generally showed good agreement with the experimental capacity despite a slight overestimation, which was attributed to the size effect of the plywood's mechanical properties. Glued trusses with thicker plywood plates (12 and 21 mm) exhibited failure in the glue line between the central plywood plate and the glulam member. Despite the size of the glued area being the same for these two trusses, the experimental capacity differed significantly due to the varying values of wood failure percentage in the glued connections that failed. Furthermore, 2D planar numerical models demonstrated good prediction of the global experimental stiffness for both glued and dowelled trusses.

The proper design of timber connections requires precise characterization of the embedment strength and stiffness values. Valid embedment data are usually sourced from experiments following different testing standards. However, these values have been known to be influenced by discrepancies among different test standards, making it challenging to compare available embedment test data from various literature sources and use these values in predicting the strength and stiffness of connections. Therefore, it is essential to investigate and understand the differences among embedment test standards, of which EN 383 and ASTM D5764 are the two most representative ones. In this study, embedment tests on nearly 200 specimens were conducted following specifications in EN 383. First, the loading procedures, specimen configurations, and orientations slightly varied among different test series, so the significance of certain subtle parameters within EN 383 was examined. Second, the measured values were compared with the literature data tested following ASTM D5764. Thereby, by considering the difference in veneer layups, the reduction factor for plywood was analytically derived based on the formula for LVL as recommended in Eurocode 5. A combined formula was thereby derived to predict the in-plane anisotropic embedment strength values and compared with the experimental embedment data.

This article investigates the dynamic behaviour of a pedestrian timber truss bridge by in situ testing and numerical modelling. The in situ dynamic tests were performed at three different construction stages: (1) on the finished bridge without the asphalt layer, (2) on the finished bridge with the asphalt layer at warm conditions and (3) same as stage 2 but at cold conditions. The interest of this study is that some modelling details that are usually not considered in the numerical modelling of pedestrian timber bridges are important for this bridge. The stiffness at the connections must be considered in order to obtain accurate numerical results for both lateral and bending modes. The stiffness of the pile foundations has an influence on the first bending mode. In addition, the experimental damping ratio for the first lateral mode is much higher than the values recommended in the design codes.

The use of wooden dowels has gained renewed interest recently, primarily as a means of connecting structural components in timber construction. Serving as an alternative to metal fasteners, wooden dowels offer mechanical compatibility with timber elements and potential environmental benefits. Due to their green credentials, high compatibility with timber members, and ease of disassembly and reuse, this type of fasteners requires appropriate models to predict their mechanical properties. Due to their load-bearing capacity and lateral stiffness, wooden dowels are commonly used in composite structures, effectively enhancing the composite action between two members. There is still a lack of studies on mechanics-based models focused explicitly on wooden dowels. In fact, they exhibit a unique failure mode that can involve not only bending and/or embedment but also shear and even compression perpendicular to the grain. This study aims to evaluate predictive models for the capacity of connections with wooden dowels. The authors tested glulam-to-plywood connections with fasteners made of either birch, beech, and laminated densified wood dowels. Additionally, reference tests were performed using conventional self-tapping screw connections, and the results were compared. Additional tests were also conducted on the dowels to estimate their bending, shear, and embedment strengths. Selected predictive capacity models are compared, including that in the new Eurocode 5 proposal.

The accumulation of self-mass and the resultant permanent deformation are critical in the design of high-rise timber buildings, especially in the case of compression perpendicular to the grain (CPG). Metal fasteners, e.g., self-tapping screws, are conventional and standardized reinforcements against CPG in timber members. As a comparison, wooden rods provide a more environmentally friendly and cost-efficient solution. This study utilizes glued-in wooden rods and laminated densified wooden (LDW) rods as CPG reinforcements. Test series are first planned to characterize the single-fastener behavior by applying direct loading on the single rod. Thereafter, the global behavior of reinforced glulam specimens, following the loading of Case A and Case B as defined by prEC5, is investigated. All possible associated failure modes are observed and classified. The capacity and stiffness data are utilized to validate the proposed analytical loading mechanism of Case A. The number of glued-in wooden rods varied with the specimen geometry to investigate whether the effective numbers apply. Digital image correlation measurements were also performed on featured Case B specimens to visualize the stress dispersion and the reinforcing effect of the rods. Stiffness-related parameters are also discussed for all investigated specimens.

In timber connections, adhesively bonded connections are, in general, cheaper, stiffer, and stronger compared to typically adopted mechanical connections. However, bond line quality is sensitive to various process-related parameters; thus, it is generally preferable to do the gluing in the factory with these parameters controlled during assembly and then transport the entire structure to the construction site. This leads to a limitation on the size of the timber structure owing to the limited transportation capacities. Another concern regarding fully glued timber-to-timber connections falls in their non-ductile behavior prior to the ultimate failure, which is crucial, especially in seismic regions. This paper focuses on the design of two innovative connection systems aimed at overcoming these two key limitations. Both systems offer the advantages of indoor adhesive application and on-site adhesive-free assembly. The first connection system involves a hybrid solution connecting prefabricated elements by means of steel rods and special ‘‘wheel-geared’’ notches of birch plywood, while the second connection system employs pure plywood notched connections during the on-site assembly. These two novel connection systems have potential for use in both moment- and force-resisting applications. In this study, they were introduced and designed in the format of a frame corner, where bending moment, axial force, and shear force are present. Analytical models predicting the capacity for each possible failure mode were developed and then validated by the test results. It can be found that the first connection system exhibits moderate ductile behavior, and its load-bearing capacity is considered to be satisfactory. The capacity can be further improved to be as strong as the fully glued connection if thicker plywood plates are utilized. The second connection system possesses lower strength and stiffness. However, it could still be applied in non-critical connection regions where no substantial external load exists.

Research on dowel-type moment-resisting joints has traditionally focused on metal dowels. When adequately designed, and, when necessary, completed with suitable reinforcement methods and specific measures, this type of joint can provide sufficient stiffness and ductility. However, can wooden dowels be a viable alternative to metal dowels in moment-resisting joints? Wooden dowels are emerging as promising biobased alternatives to metal fasteners and chemical adhesives, offering a reduced environmental footprint. They are fully compatible with wood substrate, enabling easy disassembly, recyclability, and reuse of structural elements. This study investigates the behavior of moment-resistant joints with wooden dowels and plywood plates. Eight joints were tested, incorporating two types of wooden dowels: birch and beech laminated densified wood. The objective was to compare these two types of dowel in terms of stiffness, load-bearing capacity, and ductility. In addition, two mechanics-based predictive models were evaluated to estimate the joint behavior. One model assumed an elastoplastic response for each fastener, while the other assumed an orthotropic elastic model to characterize the force distribution among the dowels. The goal was to analyze the two models and calibrate the mechanical parameters of the constitutive model used to predict the dowel response in the nonlinear analyses. Finally, the study assessed the poor adequateness associated with using the bending strength obtained from the dowel bending tests to estimate the connection capacity through the European Yielding Model, comparing it with the calibrated values from experimental curves.

This study reveals the magnitude of stress spread angles in the design of plywood gusset plates when subjected to uniaxial tension, with a specific focus on mechanical connections. Plywood plates with elevating widths at three different load-face grain angles were destructively tested. The test series continued with consecutively increased plate widths until the measured forces reached plateaus. Two models, namely, the classic and modified stress spread models, adopted from the Whitmore effective width theory, were investigated to account for the observed phenomenon. The classic stress spread model considers a rigid fastener array and an evenly distributed stress block. A closer-to-reality modified model considers the summation of stress blocks contributed from each fastener line. For both models mentioned, the magnitudes of corresponding spread angles were calibrated utilizing a fitting scheme considering maximized R-square values. The validity of both models was later examined and validated versus the previous experimental data reported in the literature. It was found that the classic model, despite some close predictions, gave over-estimations on the load-bearing capacities of several connection patterns. The modified model was found to be conservative for almost all investigated fastener patterns. Accordingly, a hybrid adoption of stress spread models was suggested.