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The comprehensive experimental study examining the general load-displacement behavior, stress distributions and shear stress-shear-displacement behaviors in the connection area when wood structural elements are combined with adhesive or adhesive with mechanical anchorages have been found in very limited number of studies in the literature. Therefore, an experimental study was planned. In this study, the general load-displacement behavior of the timber connection regions which are connected by adhesive and mechanical anchorages together with adhesive, with varying lengths of 180, 240 and 350 mm are investigated experimentally. Besides, the effect of changing the number and location of mechanical anchorages used in the connection area on the general load-displacement behavior and shear stress-shear-displacement behavior was also investigated. Using the load-displacement graphs obtained as a result of the experimental study, a generalized material model is proposed for the shear stress-shear-displacement interfacial adhesion surface for wood-wood junction points. This material model, which is proposed for wood-wood connection points with mechanical anchors, is a model that can be useful and can be used in the analysis of structural systems containing such connections using finite element software. It is thought that the overall capacity and load-displacement behavior of structural systems containing such connection points can be calculated more realistically using the proposed interfacial material model.

This paper presents exploratory research on behavior of a lap scarf timber joint used in restoration of historical constructions in the Czech Republic. The joint with oblique faces and a dowel was tested in full-scale and was subjected to both three- and four-point bending where standard, optical and numerical techniques (FEA) were employed. The joint keeps 70–92% and 55–57% of the corresponding solid beam MOE and bearing capacity respectively. The FE analysis revealed the angle of the joint has the highest impact on its MOE. Paper demonstrates the advantages of coupling of full-field measurement technique and FEA in analysis of a timber joint, especially for model verification based on measured displacement of the structure.

This paper analyses the optimisation studies of a pre-stressed embedment-type timber joint system, the Kusabi–Nageshi (K–N) timber joint system, designed to be used for structures in seismic-prone countries. The K–N joint is composed of a triangular-sectioned beam and wedges in combination with bolts. Its resistive mechanism utilises the embedment strength of timber and the pre-stress in association with friction. In addition, elastic energy deposited in the bolt as storage fills the gap as it is deformed during the embedment. With the aim of optimising both mechanically and physically, several alterations were tested in terms of shape (taper angle) and of combining densified veneer wood (DVW) with the joint members. A cyclic loading test of the cross joints was made to examine their structural behaviour. The use of less tapered wedges showed higher stiffness and strength, but the beam beneath was undesirably embedded. Different combinations of reinforcement with densified veneer wood showed that the use of the wedges alone provided high optimisation, and an increase in bolt axial force. The successful test results observed in the alteration using the densified veneer wood are expressed using the ‘analytical K–N joint diagram', an analytical method modified from a conventional joint diagram used in mechanical engineering, which showed itself to be an applicable method to predict the trend of the altered K–N joint. The use of the new tapered angle and densified veneer wood for optimisation, and the performance predictions using the analytical K–N joint diagram, will need further precise investigations but their great benefits are potentially promising.

Embedment is a key feature of timber joints envisioned as the ultimate solution in avoiding the devastating full collapse of timber structures in seismic countries. The Japanese traditional timber post-and-beam structural system utilizes moment-resisting joints based on embedment. Despite the joint's advantages having the ductile and energy-absorptive behavior continuously to the post-elastic phases, a primary shortcoming needs to be resolved - specifically of having the low and unreliable initial stiffness due to the gap formation between the contacting members. Further, large-dimensioned timber most suitable for the embedment-type joint is scarce and the lower quality of available timbers is making the modern applications difficult. A new timber joint capable of sustaining future seismic impacts is being pursued using various approaches. As a result of the optimization to satisfy the manifold studies, two traditional elements, namely Kusabi wedge and side-penetrating Nageshi beam, are combined and tightened by the penetrating steel bolt. Its tightening system eliminates the gap formation in the joint, and heightens its performance over the traditional embedment-type joints. Additional features, such as the damage-inducing and fast seismic-retrofitting ability, are also integrated. This new proposal for the Kusabi-Nageshi (K-N) timber joint system aims to provide a new alternative to the joints used in seismic countries.

We present a new and alternative proposition for the traditional Asian timber column-and-beam connection, using the Kusabi-Nageshi (K-N) joint system. The mechanical behaviour is complex and relies on the embedment strength of the timber, pre-stress, friction, and elastic energy storage. Using a systematic comparative analysis, the advantages of the K-N joint over more traditional joints can be made clear. The comparison of the hysteresis from cyclic loaded cross-joint tests with varied pre-stress clarifies the enhanced mechanical behaviour of the K-N joint system. © 2009 Elsevier Ltd. All rights reserved.

A large number of joints are developed as a result of various timber construction techniques, structural efficiency and cultural differences. Many joints are not used because they are not adapted or are inconvenient for modern manufacturing and construction technologies. Nonetheless, this construction heritage can be harnessed and adjusted for contemporary use. Significant cultural and social differences in timber jointing and construction technologies are reviewed. The Geometric Breakdown Method is developed to analyse the geometry of timber joints for structural, carpentry and construction considerations. Using this method, traditional and modern joints can be understood better and designers can use accumulated construction knowledge to create new joint designs in a systemic manner. Un grand nombre de joints sont fabriques en raison des diverses techniques de construction en bois, de l'efficacite structurelle et des differences culturelles. De nombreux joints ne sont pas utilises parce qu'ils ne sont pa...

This paper investigates the feasibility of employing timber pegged joints in modern seismic-resistant structures or for retrofitting existing structures. The behavior of timber pegged connections has been investigated for about twenty years, but seismic design aspects are not treated in existing standards. In the framework of the force-based design approach, this paper analyzes and defines seismic design aspects and rules for timber pegged connections that are easy-to-use in engineering practice. A large database (more than 350 test results) has been elaborated and the data processed with the purpose of (1) analyzing the effectiveness of the European Yield Model for evaluating the maximum strength of the connection, accounting for the particular embedding behavior due to the presence of timber peg; (2) assessing and defining the capacity design rules to design the dissipative regions (i.e., overstrength factor); and (3) defining the available ductility of the connection with identification of ductility class intervals. The obtained results proved that timber pegged joints have a good potential to be used in seismic-resistant structures. In fact, data processing identified a suitable value for the overstrength factor (useful to project the joint with the capacity design) similar to that used for steel-dowelled connections, and defined a likelihood range of ductility classes. Finally, it is highlighted that the European Yield Model can be a practical tool to calculate connection strength, provided that some modifications are included to consider peg behavior.

Tests investigating the fatigue performance of a bolted timber buttsplice connection containing wood splits are presented. Relationships of compressive axial load to joint slip at the bolt nut and of load to average and relative joint slip relationships are studied to explain the fatigue failure of this type of joint when cyclic loads are involved. None of the three joint slips alone was sufficient to indicate when a particular joint would fail; however, considering the interaction between the joint slip at the bolt nut and the relative joint slip between the bolt nut and head allowed a failure hypothesis to be established. The test results indicate that the fatigue resistance of the connection is more adversely affected when a split is located near the bolt hole on the bolt‐head side of the connection than when a post has no splits or has splits located near the bolt hole on the nut side of the connection.

The present study addresses the loading or deformation rate effect on the yield loads of nailed timber joints. Four different types of joints, which differed with respect to the thickness of the members and the angle of load to grain, were tested. The bearing strength of the wood and the bending strength of the nails were also tested in order to analytically verify the dynamic ultimate capacity of the joints. All tests were run with deformation rates from static loading values up to approximately 1 m/s (40 in./s). The pilot study results show that the strength of the nailed joints can be expressed in terms of the deformation rate. A logarithmic expression for the strength of the joints was obtained from regression analysis of approximately 200 results. The values obtained analytically agreed well with the experimental ones for the various joints tested.

This paper proposes a numerical model capable of predicting the mechanical behaviour and the failure mechanism of typical wall-to-floor connections for Cross-Laminated Timber structures. Such systems are assembled with angle brackets and hold-downs, anchored to the wall and floor panels with profiled nails and bolts. The metal connector and the elements to which it is fastened are modelled using 3D solid bodies, while the steel-to-timber joints are simulated as non-linear hysteretic springs. Shear and tension tests are reproduced on two connection systems and results are compared to the test data obtained from similar configurations. Simulations lead to accurate predictions of the mechanical behaviour (i.e. elastic stiffness, maximum load-carrying capacity, and shape of the hysteresis cycles) and energy dissipation. Finally, the performance when lateral and axial loads are applied simultaneously is investigated. Analyses are carried out by varying the inclination of the load, with respect to the axis of the connector, between 0° and 90°. Results exhibit a quadratic interaction relationship between shear and tension loads, and prove that their coupled effect influences the stiffness and the maximum load-carrying capacity.

Self-Tapping Screws (STSs) are commonly used to realize many geometrical configurations for connections that are characterized by enhanced stiffness and load-carrying capacity. The analysis of STS joints and composite systems, however, usually requires designers to account for several aspects in their actual load transfer mechanisms, and most of them require refined calculation tools. In this paper, an extended Finite Element (FE) investigation is proposed for timber-to-timber slabs with STS joints, based on full 3D brick models inclusive of Cohesive Zone Modelling (CZM) techniques and damage constitutive laws for the materials in use. The final goal of the study takes advantage of the global and local performance assessment of a selection of STS joints, with careful consideration for their response under a conventional Push-Out (PO) test setup or a full-size bending configuration. As shown, major FE outcomes are discussed to elaborate a design procedure that can be developed on the base of correlation coefficients for maximum force and stiffness calculations in a given slab and loading condition. Major effects due to variable loading configurations are in fact explored at the screw level. Further, geometrically simplified spring-based FE models, that hardly capture the complex behaviour of the examined systems but are largely used in design practice, are presented in comparison to refined FE approaches and literature efforts. As shown, the variation of maximum force and stiffness parameters for STSs is emphasized in the paper for a selection of configurations, and fitting curves are proposed to estimate the STS performance along a given full-size slab, thus suggesting the feasibility and possible generalization of the procedure.

In this paper, a Finite-Element (FE) numerical investigation on timber-to-timber joints and composite beams with inclined self-tapping screws (STSs) is presented. Based on past experimental data and numerical literature efforts, full 3D solid FE models of selected geometrical and mechanical configurations of technical interest are implemented in ABAQUS software package and analysed under static loading conditions . The typical push-out samples include GL24h timber members with several types (WT-T-8.2, 190 mm and 220 mm their length), layouts (2 + 2, 4 + 4, 2 + 2 X-shaped) and inclination of screws (up to ±45°). For the full-scale beam samples in bending (8 m their span), composite systems consisting of GL24h timber beam, wooden plank, spruce floorboards and STSs are investigated. There, the STS joints take the form of two-rows or X-shaped connections, respectively (45° or 90° their inclination), including four screw types and different spacing. In both the push-out and full-scale cases, simple modelling approaches are taken from the ABAQUS library and adapted to the timber-to-timber structural system under investigation, so as to explore their structural performance in the elastic and post-damage phases, up to failure. A key role in the typical FE models is assigned to input material properties and mechanical contacts, including damage constitutive laws so as to reproduce possible local failure phenomena in the timber or steel components, as well as cohesive damage interactions for the joints. The presented FE models are calibrated in accordance with past research studies, and validated – for the examined structural typology – against experimental results available in literature. Comparative calculations are hence presented, based on the collected numerical, experimental and analytical estimations for the selected samples. As shown, the examined modelling approach can reasonably capture the expected performance of timber-to-timber joints and composite systems.

The mechanical behaviour of steel-to-timber joints with annular-ringed shank nails is investigated using numerical modelling and a component approach. These joints are used in Cross-Laminated Timber (CLT) buildings to anchor metal connectors such as hold-downs and angle brackets to the timber panels. At first, a general hysteresis model is introduced, where a single fastener joint is schematized as an elasto-plastic beam embedded in a non-linear medium with a compression-only behaviour. A second hysteresis model is then presented, where the mechanical behaviour of the joint is simulated by a non-linear spring with three degrees of freedom. Both models are calibrated on the design rules prescribed by the reference standards. Moreover, average strength capacities are determined from the corresponding characteristic values assuming a standard normal distribution and suitable coefficients of variation. As first applicative examples of the proposed models, shear tests are simulated on single steel-to-timber joints with annular-ringed shank nails and on a connection made of an angle bracket and sixty nails. The scatter of mechanical properties in steel-to-timber joints is also taken into account in the simulations and a stochastic approach is proposed, demonstrating acceptable accuracy.

The research deals with a 49.0 mm in diameter mechanical fastener to which load perpendicular to grain is applied. The experimental research was divided in two series: the first series was carried out with locally reinforced, and the second with non-reinforced timber specimens. The local reinforcement of timber elements with textile sheets between lamellas in a layer of adhesive was made in the production process. Furthermore, research on finite element models using Abaqus/CEA software package was carried out. UMAT subroutine and cohesive contact between surfaces were used for modelling complex timber mechanical properties and cracks opening. The research results have shown that glass fiber textile placed between lamellas in adhesive layer effectively increases the resistance and splitting capacity of timber joint. Analytical approach has been proposed for predicting the splitting capacity of the reinforced joint.

This paper investigates the mechanical and the hysteretic behaviour of steel-to-timber joints with annular-ringed shank nails in Cross-Laminated Timber (CLT). These fasteners are used to anchor typical metal connectors, such as hold-downs and angle brackets, to the CLT panels. The experimental programme presented in the paper was carried out at the Institute of Timber Engineering and Wood Technology, Graz University of Technology (Graz, Austria). Average and characteristic values of the experimental strength capacities are evaluated and compared to the analytical predictions determined according to current structural design codes and literature. Furthermore, to fulfil the requirements of the capacity-based design, the overstrength factor and the strength degradation factor are evaluated and conservative values are recommended.

Rammed earth-timber joints without enlarged ends have been used in rammed earth buildings for several hundreds of years. Due to the embedment nature, the joint has a certain degree of flexibility, allowing the floor and roof beams to slide without damaging the rammed earth, enabling dissipating energy during earthquakes. The energy dissipation mechanism of rammed earth-timber joint has not yet been fully understood. This study studied the energy dissipation characteristic of eight rammed earth-timber joint specimens via cyclic pull-out/push-in experiments, investigating the effects of compressive loading, embedment length, and surface roughness on joint performance. Results show that the joint stiffness under cyclic loading was reduced nonlinearly with the increase of pull-out displacement until the occurrence of slippage. The high vertical compression from the upper level, the deformability of timber frames, and the plasticity of rammed earth were found to be the primary energy dissipators. A linear frictional and nonlinear geotechnical hysteretic model, combining frictional and soil mechanics theories, was established to represent the joint behavior. In addition, a simplified multi-linear hysteretic model was developed for the same purpose. The predictions and the measurements had good agreement, suggesting that geotechnical methods should be employed to analyze the joint, maintaining the assumption that both the timber frame and the rammed earth are linear-elastic.

The moment-rotation-behaviour of a post-tensioned beam–column timber joint has been analysed extensively with a series of static bending tests. The timber joint was loaded at the end of the beams in order to apply a moment to the connection. The tests were conducted with various forces in the tendon, from 300 kN up to 700 kN. The bending tests were performed with a controlled load level, so that no failure perpendicular to the grain in the column occurred. The maximal allowable vertical load to be applied was estimated using a simple spring model. A final bending test was conducted in order to study the failure mode of the post-tensioned timber joint. The vertical load on the beams was increased until the tendon elongation got so high that the test had to be aborted. The results of bending tests of the post-tensioned timber joint are presented herein. Attention will be given to the structural behaviour and to the influence of the applied post-tensioning force on the connection stiffness. The experimental results will be compared to the results obtained using a simplified analytical calculation model.

A theoretical model is presented to calculate the stress distribution around a pin-loaded hole in a timber joint and to predict brittle failure modes in bolted connections. The analytical solution uses the stress functions expressed in terms of complex parameters, and it can be considered an application of Lekhnitskii’s theory on stress distributions in anisotropic plates. The influence of the end distance and material properties on development of failure due to the splitting and shear-plug is shown for a dowel-type timber joint. Laboratory experiments on timber joints with 15.9-mm and 9.5-mm bolts loaded parallel to grain have shown good agreement with the model predictions.

The multiple shear connection with slotted-in steel plates and dowel-type fasteners is a very efficient timber joint for large timber cross sections. It is used in practice, mainly due to its high capacity and its better performance under fire. However, when the number of inner plates is increased, instead of a ductile mechanism, brittle failure may govern its capacity. No standard deals explicitly with this kind of joint. A set of tests has been performed in order to study the brittle failure of this kind of connections. The test results are then compared with the available prediction models that study both ductile and brittle failure modes to assess their prediction accuracy. An improved model for the assessment of the brittle failure mode for the multiple shear connections with slotted-in steel plates and dowel-type fasteners is then proposed.

© 2017 Elsevier Ltd Despite a large number of studies on estimating the effective bond length from the characteristics of the component materials, key parameters governing the effective bond length for FRP-to-timber joint have not been suggested by any of the current Codes and developed theories to date mostly cover FRP-to-concrete joints. Also, most theoretical bond strength models have been derived based on effective bond length. Therefore, to achieve a satisfactory bonded joint, the effectiveness of bond length is required to be accurately considered. This research study investigates 136 FRP-to-timber joints subjected to pull-out tests in order to determine the stress and strain distribution profiles along the interface and subsequently analyses the results to undertake direct measurement of the effective bond length. In addition, a modified test set up has been developed and is presented. A novel theoretical model has been established through regression analysis of bond length data and accordingly a new predictive model for effective bond length for FRP-to-timber joints has been developed. A comparative analysis between the results of the experimental pull-out tests results and those predicted from the analytical model indicates a satisfactory correlation is achieved between measured and predicted effective bond length, verifying the validity of the new model.

This paper presents an experimental program for testing glued-in rebar timber joints. Twenty five glulam specimens, each with a single glued-in rebar parallel to the grain were tested to evaluate the effects of anchorage length and glue-line thickness on pull-out strength and bond behaviour of glued-in rebar timber joints. Tests were conducted in pull-pull configuration. The test results showed that both the anchorage length and glue-line thickness had a significant influence on these two properties. Failure modes were characterized by pull out failure of the rebar, either alone or combined with the shear failure of timber along the glue line, longitudinal splitting of wood and bar yielding. For the same anchorage length, the average bond stress at both interfaces showed different variations (increasing by 11.6% at the bar/adhesive interface, and decreasing by 12% at the adhesive/timber interface) since the glue-line thickness increased from 2 mm to 6 mm. The load–slip relationship and initial stiffness of specimens were analysed in terms of anchorage length and glue-line thickness. An empirical bond–slip model for glued-in rebar timber joint was proposed by regression analysis based on the experimental data. It was observed that the proposed model fit the bond–slip relationship of glued in rebar timber joints with less than 15% deviation. Finally, the test results were compared with the design proposals reported in the literatures. It can be concluded that the prediction of Rossignon design proposal was more closely to the test results, and the Steiger design equation was unsafe, however, the Riberholt design equation was too conservative for the joint design.

The aim of this study is to characterize the mechanical behavior of connections timber-to-timber joist hangers with specific nail fasteners. The methodology proposed by technical design standards is based on the hypothesis of an elastic and linear joint behavior. However, the local behavior of joint is semi-rigid characterized by the ductility of wood material in embedment and the non linear behavior of the nail fasteners in bending. Hence, in this study, the combination of a comprehensive experimental setup and a numerical approach is developed to analyze the evolution of the forces in the joint. Firstly, various tests are realized on specific nail fasteners, using different glulam species, in accordance with European test standards. They concern the withdrawal push-out test, the single plane shear and the yield bending moment. Besides, the adequacy of the methodology proposed by Eurocode 5 for dowel-type fasteners is discussed. Secondly, a similar investigation is carried out on a whole timber-to-timber joint, with nailed tridimensional metal plates. Considering the hypothesis of a semi-rigid behavior of the joint, the stiffness of each fastener is identified in tension and shear slips. Finally, a finite element model is applied and discussed considering the fasteners represented by bi-directional mechanical springs. The stiffness of each spring is considered as the slip modulus of each fastener defined by tests. A semi-rigid formulation was adopted and the overall joint behavior is apprehended numerically.

The mechanical performances of timber joints are particularly important for timber engineers involved in the design of the wood structures. In general, joints are often one of the weakest points in a timber structure. However, to simplify the problem, most previous investigations have considered the effects of individual parameters on the mechanical behavior of timber joints. Thus, it is difficult to undertake an analytical study due to interactions among parameters. In this paper, a finite element model for a dowel-type timber joint is proposed to investigate the mechanical performance of un-reinforced and reinforced timber joints affected by the various parameters. Moreover, a stress-interaction based failure criterion is proposed to predict the strength of such joints. The numerical prediction of the proposed finite element method model overall agrees with the experimental results of mechanical testing.

A nailed or screwed sheathing-to-timber joint may fail in one of two possible modes when subjected to a load applied along the axis of the fastener: fastener head pull-through of the sheathing material and shank withdrawal from the timber. Currently, the Canadian timber design code does not provide specifications to check the first mode of failure. In this study, tests were conducted to determine the head pull-through strengths of some common hammer and power-driven nails and wood screws in plywood and in oriented strand board. These are compared with the calculated shank withdrawal strengths of the same fasteners from timber, assuming it to belong to the Douglas fir–larch species group. The test results show that there is no significant difference in strengths between plywood and oriented strand board. Head pull-through strength appears to increase with fastener diameter. The major conclusion reached is that, except for small size nails (less than 2 in. long), fastener head pull-through in sheathing prevails over shank withdrawal from timber in sheathing-to-timber joints when loaded axially.Key words: nail, wood screw, head pull-through, withdrawal strength, timber, design capacities.

Brittle premature failure caused by splitting parallel to the timber grain is a common failure mode in glulam joints made with solid dowel type fasteners. It is thought that this problem can be alleviated by using hollow steel dowels as the fasteners and reinforcing the timber locally in the area of the joint. In this way, by varying the wall thickness of the dowels and the thickness of the reinforcing members, a chosen combination of strength and stiffness should be attainable together with a ductile failure mode. In this paper, three-dimensional nonlinear finite element models are developed to simulate (i) the structural performance of a timber joint made with a single hollow steel dowel and (ii) a moment transmitting joint made with a number of the dowels, each type being locally reinforced by densified veneer wood. The models incorporate suitably defined elastoplasticity and orthotropic elasticity and also allow for large deformations of the joints as well as for frictional contact between the timber and the dowel. They are calibrated against physical test data from joints loaded to failure.Key words: glulam, densified veneer wood, resin injected, hollow dowel fastener, moment transmitting, ductile failure, finite element.