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Herein, a beech wood dowel reinforced with a self-tapping screw (composite dowel in brief) is proposed. Composite dowels were welded into the predrilled holes by high speed rotation. Force-displacement curves were obtained using a single-shear and dual connection. A double-peaked pattern was found in the bearing process, indicating that the wooden dowel and the self-tapping screw had a synergistic bearing effect in the bearing process. Regarding the failure mode, the self-tapping screw and the wooden dowel were bent, whilst the default wooden dowel fractured. Further, the numerical simulation was carried out using the finite element analysis software ABAQUS, and the result differed from the test value by only 4.30%, showing a high prediction accuracy. The study of the bearing capacity of the composite dowels provides a theoretical basis for the practical application of wooden dowels reinforced by self-tapping screws. [ABSTRACT FROM AUTHOR]

Testing showed that the hysteretic behavior of nailed wood joints governs the response of many wood systems when subjected to lateral loadings. Unfortunately, commercially available software does not have the appropriate hysteretic element for a nailed wood joint, and the accuracy and versatility of the previously developed nail joint elements are not satisfactory. A general hysteretic model, Bouc-Wen-Barer-Wen, was modified to represent the hysteretic behavior of a nailed joint, in which the hysteretic constitutive law is characterized by a series of ordinary differential equations. It can produce versatile and smoothly varying hysteresis curves, is nonlinear, history dependent, and includes stiffness and strength degradation, and pinching. Based on the test data, the suitable parameters for different joint configurations can be estimated through genetic algorithms. This model was embedded in commercially available software, ABAQUS/Standard (Version 6.5), as a user-defined element which accounted for the coupling property of the nail joint action. A detailed shear wall was modeled and analyzed, and the results agreed well with the test data. [ABSTRACT FROM AUTHOR]

Widely used for light frame structures or for heavy laminated wood structures, dowel-type fasteners are the most commonly used kind of connectors in timber construction. The purpose of this work is to develop a tool for the semi-rigid analysis and design of such joints. Firstly, interests and approaches described in literature for the semi-rigid modeling of timber plane frames are summarized. Secondly, for a better understanding of the problem, the main characteristics of wood used as a structural material are presented. Finally, a method for an efficient study of joints built with dowel-type fasteners is proposed and developed. This method consists of the introduction of a specific finite element called 'Finite Semi-Rigid Element (FSRE)' between the ends of the jointed members. This joint element consists of two nodes, each with three degrees of freedom. These nodes will be tied with common beamelements during the FE analysis. The stiffness of the FSRE is computed from the geometry of the joints and embedding stiffness of all fasteners, along and perpendicular to the grain. The embedding characteristics of fasteners are defined with help of their experimental load-slip curves (fitted with Foschi's models) leading finally to the resolution of a FE non-linear problem. [ABSTRACT FROM AUTHOR]

Steel-timber composite structures have numerous advantages compared to steel only and timber only structures. One of the most important parts of a composite structure is the composite connection. Object of this research was a steel-CLT composite connection consisting of a steel profile, a cross-laminated timber (CLT) panel and a bolt with nut and washer. Aim of the research was to develop an efficient finite element (FE) model of a bolted steel-CLT composite connection and to validate it experimentally. The research process consisted of several steps: experimental testing of the considered connection using asymmetrical push-out test, numerical modelling and analysis of the connection using Finite Element Method (FEM), validation of the numerical model using experimental results, and parametric study of the proposed numerical model. For numerical analysis, an innovative method for timber modelling has been proposed. The comparison between the experimental and numerical research results demonstrated that the proposed numerical model was convenient for practical application in structure analyses. The parametric study showed that, in some cases, atypical failure modes of the connection occurred. Based on registered behavior, a recommendation is given to calculate the load capacity of the connection integrally, taking into account both the primary (Johansen's) and the secondary (rope effect) part of the connection strength, instead partially, as proposed by EN standards. [ABSTRACT FROM AUTHOR]

Gridshell nodes are key elements regarding structural performance, visual appearance and assembly of any gridshell that have been given little attention in recent research. This paper explores aluminium as a material for timber gridshell nodes. First, existing gridshell nodes are categorised regarding bulk materials, gripper types and connection methods and based on this, a set of novel node principles in aluminium are deducted and proposed for a timber gridshell on the geometry of the British Museum Great Court. A finite element analysis is done on the proposals to increase the understanding of the node principles' structural behaviour and feasibility. Together, the set of node principles, their evaluation and the utilised procedure can provide new options in the future design of gridshells and gridshell nodes. [ABSTRACT FROM AUTHOR]

With the growing popularity of timber structures, the requirement for reliable and non-destructive methods to assess the quality and condition of structural joints becomes increasingly essential. A novel coaxial correlations method is investigated to assess the degradation of panel-to-panel moment joints in timber structures. The method involves analysing the response data obtained from accelerometers placed on both sides of the joint and comparing the readings to evaluate the joint's condition. A specific joint solution to simulate the degradation of the moment joint in laboratory conditions is selected based on its simplicity and the ease with which its degradation can be simulated. The joint consists of angle brackets joined with timber screws and bolts to plywood panels. Gradually unscrewing the timber screws reduces the joint's stiffness to simulate wear and tear over time. The experimental setup includes static loading and finite element modelling (FEM) to determine the rotational stiffness of the investigated joint at each degradation level. A dynamic experiment using vibration loading with sweep signal in the frequency range of 10 Hz to 2000 Hz is conducted to assess the quality of the joint. The conducted research provides valuable insights into the behaviour of timber panel-to-panel connections. The findings highlight the relationship between joint stiffness, vertical displacements, and the proposed dimensionless parameter, volume root mean square value (RMSvol), which offers a more comprehensive assessment of the joint's condition in three spatial directions. As a result of the research, it has been established that, in the case of linear-type connections, unlike point-type joints, there is a possibility of signal scattering, so it is recommended that power comparisons and evaluations of the response signals from both accelerometers at the initial stage of applying the coaxial correlations method are performed. [ABSTRACT FROM AUTHOR]

The wood industry faces the dual requirements of improving the quality of timber products and minimising waste during the manufacturing process. The finger joint, which is an end-to-end joining method for timber boards, is one of the most important aspects of engineering wood products. This study presents a numerical and optimisation investigation of the effects of finger-joint design parameters on the flexural behaviour of finger-jointed timber beams. A numerical model based on advanced three-dimensional finite element analysis was developed to model the behaviour of finger-jointed beams. Using the validated finite element (FE) model and automated parameterisation, a parametric study was conducted to assess the impact of each design parameter of the finger joint, including finger length, tip thickness, and the number of finger joints. The results indicate that the number of fingers and finger length significantly influence the maximum load capacity, while the tip thickness has a marginal effect on performance. This study identifies a design threshold of five fingers and a 14 mm finger length for achieving efficient, high-performance finger-joint designs. In addition, the multi-objective modified firefly algorithm (MOMFA) was proposed to maximise the finger joint resistance while simultaneously minimising the material waste. The optimisation shows that there will be a significant amount of wood waste when using traditional single-objective optimisation that only focuses on structural performance. In contrast, the proposed method achieves comparable load capacity while significantly reducing waste (up to 53.31%) during the joining process. The automated finite element modelling framework and holistic optimisation developed in this study can be used to design and optimise engineering wood products for construction applications. [ABSTRACT FROM AUTHOR]

Results of tests performed on joints used in timber-frame construction allow characterizing the variability of their mechanical behavior, which differs substantially from one joint to the next. The parameters of a constitutive model of the joints and their variability are identified. Finite element (FE) models of a shear wall and a timber-frame house are used in nonlinear dynamic calculations to study the propagation of uncertainty through the structure. It demonstrates that for a single-story 6 m × 6 m house, the variations in mechanical strength of each connection do not significantly affect the structural behavior of the house. Both the numerical and experimental results (on a shaking table) are quite similar, proving the model accuracy, its ability to study the propagation of uncertainty and its relevance for future development (non-regular, multi-story buildings...). Moreover, a sensitivity analysis performed on a FE wall model under uncertain seismic loads reveals the importance of earthquake motion modeling. [ABSTRACT FROM AUTHOR]

Værnes church is one of the oldest mediaeval stone churches with the original wooden roof in Norway. The roof is made of several crossed layers of wooden boards connected with a large number of wooden dowels and has stood for centuries, but there are visible deformations in the lower parts of the structure. In this work, finite element models of the roof are presented in an attempt to characterise the behaviour of the wooden connections in the diaphragm. Two main scenarios are discussed: a first scenario that takes into consideration only the frame with line loads, considering the wooden boards merely as loads and a second scenario where the wooden boards are considered collaborating planks that influence the behaviour of the structure. As result of the work, it is possible to state that the wooden planks provide a stiffening effect, distributing the load on the gable walls.. [ABSTRACT FROM AUTHOR]

In this study, an experimental and numerical analysis of the bond-slip model is made on timber-to-timber bonding connections. The variables examined in this study are the types of adhesives used for bonding, the length of adhesion, and the types of reinforcement used to increase the adherence to the adhesion surface. Two different types of adhesives were used namely polyurethane and epoxy. Three different bonding lengths of 180, 250, and 350 mm were chosen as the bonding length. For each variable, four different test specimens were produced and tested under axial tensile force as a nonreinforced reference test specimen and aluminum, fiber, and steel net type as a reinforced bonding strength. In the experimental study, a total of 24 test specimens were tested and the bond-slip behavior of the timber connections and changes in the axial strain values along the timber adhesion zone were measured. By interpreting the experimental results, a bond-slip model is proposed for the timber bonding connections. In this proposed bond-slip model, the effects of the variables examined in the experimental study are interpreted. In this study, the most successful bond-slip behavior and load-carrying capacity have shown in the test specimen, which is reinforced with steel material reinforcement mesh, using epoxy adhesive, and 350 mm adhesion length. By using the experimental results, the bond-slip behavior is verified by numerical modeling with ANSYS software, and a finite element model was formed. [ABSTRACT FROM AUTHOR]

Nowadays, the use of timber as a building material is gaining more prominence. When designing timber structures, it is necessary to pay increased attention to the design of their connections. The commonly used connections are dowel-type connections, which are often used in combination with steel plates slotted into cut-outs in timber members. The presented paper deals with the behavior of double-shear bolted connections of squared timber and round timber with slotted-in steel plates. Several variants of connections with different distances between the fastener and the loaded end were selected for the experimental testing. A total of six types of test specimens were made from spruce timber, for which their selected physical properties were determined and evaluated before the experimental testing. Test specimens of bolted connections were first tested in tension parallel to the grain until failure under quasi-static loading. The connections were broken by splitting. Ductile failure preceded brittle failure. The actual load-carrying capacities were lowest for the lowest end distance. The load-carrying capacities for the middle and the longest end distances were comparable. The results of the experiments were then used for comparison with calculation procedures according to the standard for the design of timber structures and with calculations according to the theory of linear elastic fracture mechanics. The experiments and the analytical models were supported by a simple numerical analysis based on the finite element method. [ABSTRACT FROM AUTHOR]

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. [Copyright &y& Elsevier]

In this article, the rotational behavior of typical bolted glulam beam-to-column connections with slotted-in steel plate was studied in the numerical method. In order to describe the complicated behavior of wood more closely, an elastic–plastic damage constitutive law combining the Hill yielding criterion and a modified Hashin failure criterion was embedded in the commercial ABAQUS software in the form of a VUMAT subroutine. Subsequently, a three-dimensional finite element model based on the constitutive law proposed was established, with the failure mode and moment–rotation curve compared to some similar experiments. Based on this finite element model, a parametric study concentrating on the influence of the width of the beam, bolt diameter, and assembly clearance was carried out. It was found that the numerical method using the proposed constitutive law showed a good capacity to study the rotational behavior of the connections. Besides, the initial rotational stiffness increased with the increase in beam width and bolt diameter, and the assembly clearances between bolts and bolt holes would affect the initial rotational stiffness while the assembly clearance between beam and column affected little. [ABSTRACT FROM AUTHOR]

Finding new efficient connectors or improving existing ones are important issues in timber construction. This research investigates an innovative large-diameter dowel-type connection by using a finite elements model calibrated with experimental results. This connection is made of a large-diameter single dowel reinforced by means of a steel plate with a vulcanised rubber layer. The steel plate shape, thickness and dimensions, the rubber stiffness, the steel mechanical properties, etc., are parameters that may influence the critical load of the plate. The joint load-bearing capacity is also highly depending on the load direction to the grain. Those parameters are investigated using FE modelling and discussed in order to propose design recommendations. [ABSTRACT FROM PUBLISHER]

This paper investigates the mechanical behavior of dowelled steel-to-timber moment-resisting connections. Two configurations of joints were tested, and the experimental results were used to validate a three-dimensional (3D) nonlinear finite element method (FEM) model. The model uses the Hill criterion to manage the plastic yielding of timber. The brittle character of timber in shear and tension perpendicular to grain is managed through the damage evolution based on the Hoffman failure criterion. The numerical model represents with good accuracy the behavior observed during experiments. The analytical model based on the theory of plastic limit analysis was evaluated through the application to the tested connections. [ABSTRACT FROM AUTHOR]

In structural analysis, because of its anisotropic behavior, wood requires an appropriate constitutive law covering different behavior modes, such as ductile compressive behavior and brittle character in shear and tension. In this study, nonlinear material models were proposed to describe the behavior of timber in a finite-element method (FEM) model. An anisotropic elastoplastic constitutive law with hardening according to Hill yield criterion was used to describe the compressive behavior. Brittle behavior in tension and shear were modeled by using the progressive failure analysis approach, which is based on a failure criterion representing the evolution of damage in timber by a reduction of the elastic modulus. The wood material model was implemented in a three-dimensional FEM model to simulate the nonlinear behavior of timber joints with various types of loadings. The numerical model reliably predicted the stiffness and failure load of the joints. Furthermore, the failure index provided by the numerical model was used to evaluate the potential brittle failure position. Moreover, the initiation of damage and growth in timber members was modeled by using the element removal controlled by stress checking on the basis of the failure criterion. Good agreement was observed between numerical simulations and experimental measurements of failure modes. [ABSTRACT FROM AUTHOR]

Single-sided punched metal plate fasteners have been used in construction industry for a few decades. However, its double-sided version is relatively new and is increasingly attracting more users due to its advantages on fire resistance and aesthetics. Owing to complex nature of such fastener, limited research has been undertaken up to date. In this paper, a finite element method-based inverse modelling technique was developed for optimization analyses of a prototype double-sided fastener. The non-unique nature of inverse model solutions makes assessment of model sensitivity to input material properties imperatively. This paper uses validated numerical models for sensitivity analysis of joint modelling output. Joint stiffness is most sensitive to wood elastic moduli. Ultimate strength is significantly influenced by steel yield strength and wood embedding strength and shear strength. The coefficient of friction, steel yield strength, wood shear and embedding strengths have significant effects on joint slip. [ABSTRACT FROM AUTHOR]

Abstract: The behaviour of dowel-type steel-to-timber joints loaded in tension perpendicular to grain is analyzed experimentally and numerically. Two main types of failures are observed in the experiments such as wood splitting and embedding. The experimental results are used to validate a three-dimensional (3D) non-linear finite element model. The non-linear model uses the Hill criterion to control the plastic yielding of wood material. The Hoffman failure criterion, controlling the damage evolution in wood, is used to take into account the brittle failure in shear and tension perpendicular to grain. The comparison with experimental results shows that the numerical results are in good agreement with them. The validated model is used to investigate the effect of some influential parameters on the splitting strength of the joints loaded in tension perpendicular to grain. Besides, the splitting strengths given by the numerical model are used to evaluate the accuracy of some analytical formulae available in the literature. [Copyright &y& Elsevier]

Blockhaus systems represent a traditional construction technology in which structural resistance is obtained by direct contact between multiple timber surfaces obtained through carvings, notches, and ancient joints. Native of forested areas, this technology is currently used for the construction of log buildings also in earthquake-prone areas. Their seismic structural behavior hence represents an interesting and not well known research topic. In the paper, experimental results obtained by cyclic and monotonic tests recently performed on Blockhaus shear walls with three different types of joints are presented and discussed. At the same time, sophisticated finite-element numerical models able to take into account the complex structural behavior of log-walls subjected to in-plane seismic forces are described. Performed numerical simulations highlighted that in general multiple factors affect the global structural response of Blockhaus shear walls, including the presence of imperfections (small gaps) in the joints, the contribution of friction phenomena, the mechanical properties of timber, and the interaction between in-plane seismic forces and vertical permanent loads. However, careful calibration of timber mechanical properties and contact interactions between overlapping logs can provide accurate numerical predictions and good correlation with full-scale experimental results. [ABSTRACT FROM AUTHOR]