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Timber connection capacity, in case of beam-column joint connection provides significant impact on the wooden building structures. Strength and stiffness of timber connections using reinforcement technique of wooden building structures have not been studied intensively. This paper studies the use of nails and modified-washer to improve wood connection’s performance. The experimental tests were conducted in the laboratory by comparing the partial connection between test specimen timber without reinforcement (standard type) and the reinforcement (PRP type). The testing was conducted based on partial connection beam-column joint test using Universal Testing Machine’s with a modified holder. Wood studied includes Meranti (Shorea spp.) and Mersawa (Anisoptera spp.). PRP type connection was using nails and modified-washer strengthening, and standard type connection was using a classic washer. Parameters studied were strength and stiffness of the connection, reviewed both: proportional limit load and ultimate limit load conditions. Result obtained from this research indicates that the use of nails and modified-washer make a positive contribution to improving the performance of the beam- column timber joint connections, in terms of strength capacity (both of proportional limit and ultimate limit loads) and stiffness capacity (displacement ductility ratio). Meranti beam-column timber joint is more brittle than Mersawa beam column timber joint, it has an impact on the results. PRP-type of Mersawa timber connection produces a higher ductility than the standard type, while the PRP-type of Meranti timber connection produces a similar ductility to the standard type.

Batak Karo is one of the ethnic group that exists in North Sumatra. Wooden house of Batak Karo called with Siwaluh Jabu. This wooden house has a structure system of pillars on top of stone foundations. This type of foundation is able to improve the performance of the overall structure due to lateral style caused by the earthquake. This research was conducted to know the behaviour of the structure of a wooden Batak Karo home especially the restoration of wooden style joints by comparing the results of a laboratory test, numerical analysis and analysis with SAP2000. Experimental testing in the lab do the test objects as much as 3 pieces. Testing by giving a cyclic load with a capacity of 10 tons in each of the test object to damaged object. Then conduct an evaluation the behavior of the structure consist of failure modes and moment-rotational angle relationship. After the experimental test was completed, the analysis continued with validate test results with laboratory of numerical analysis. Then conducted an analysis of the power structure by using SAP2000 program to know the power of elements against the maximum tension. The analysis conducted on the overall structure of the system and the structure of mast above the foundation stone. The program was conducted with input data: the work load, etc. As the output from these programs is the element force, etc. The final results of this program are the weaknesses and advantages of structural system observed from wooden Batak Karo.

The goal of the work was to evaluate mechanical performance of full-scale timber beams containing scarf joint with a dowel. Work focused on standard testing using modular system to obtain effective stiffness and strength of the beams with and without the joint. The work further researched a contact zone between two timber parts of the joint – at the scarf face. This was carried out using non-destructive optical technique – digital image correlation (DIC) and newly developed algorithm. The joint was made of Norway spruce, dims. 6×0.2×0.24 m and was loaded by two modes: a) 3-point bending and b) 4-point bending. During the loading, a sequence of images was acquired for further investigation of contact zone using the proposed algorithm. The joint with scarf and dowel provided enough effective stiffness, ie. 73–93% for 3-point bending test and 71% for 4-point bending with respect to MOE measured on reference solid beams. Effective strength of the joint was also relatively high and in a range of 55% and 60% with respect to reference solid beams in both 3-point and 4-point bending tests. Contact length differed for loading modes. Mean contact length in symmetrical 4-point bending was about 40%, for asymmetrical 3-point bending test, it was approx. 20% on face closer to support and 44% on a face closer to loads.

Many Javanese traditional timber structures have been destroyed by major earthquake. A lot of them tend to be dismantled due to a high cost of reconstruction and a demand for more reliable structures. In order to preserve this disappearing building as valuable and tangible culture, a deeper understanding on these traditional timber structures is necessary. Especially the restoring force of the traditional joints, which are the major earthquake-resisting elements has to be investigated. The static characteristic of these structural components has been investigated experimentally. A total of 12 full-scale specimens of 2 types made from glued Acacia-mangium were tested. The specimen simulated joint at middle part, which is a joint of column-tie beams interlocked each other. The horizontal cyclic load was applied on the specimen placed in pin joint frame from two mutually perpendicular directions. The cyclic loading protocol consists of 7 increasing target deformations from 1/200 radian to 1/15 radian, and finally until failure. As the test result, failures were caused by embedment, crack, and split in beams parallel to the load direction. All crack of beam started from corner of beam mortise and resulted in the split. From the curve of load and rotational relationship, occurrence of initial slip leaded to the larger deformation. It revealed the importance of joint tightness against future earthquake.

We, in this article, propose a manual calculation method for the skeleton curb of single bolted timber joint. The calculation method takes into account the edge distance, the end distance, and the slenderness ratio as the parameters. The validity of the proposed calculation method was confirmed by the experimental results, the edge distance of 1d, 2d, 4d, 6d, 7d, the end distance of 1d, 2.5d, 4d, 7d, 10d, the slenderness ratio of 0.625 d, 3.75d, 7.5d, 10d.

We, in this article, propose a manual strength calculation method of single bolted timber joint loaded parallel to the grain. The strength calculation method takes into account the edge distance, the end distance, and the slenderness ratio as the parameters. The validity of the proposed calculation method was confirmed by the experimental results, the edge distance of 1d, 2d, 4d, 6d, 7d, the end distance of 1d, 2.5d, 4d, 7d, 10d, the slenderness ratio of 0.625d, 3.75d, 7.5d, 10d.

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.

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 work presents the development of a three-dimensional lattice material model for wood and its application to timber joints including the potential strengthening benefit of second order effects. A lattice of discrete elements was used to capture the heterogeneity and fracture behaviour and the model results compared to tested Sitka spruce (Picea sitchensis) specimens. Despite the general applicability of lattice models to timber, they are computationally demanding, due to the nonlinear solution and large number of degrees of freedom required. Ways to reduce the computational costs are investigated.Timber joints fail due to plastic deformation of the steel fastener(s), embedment, or brittle fracture of the timber. Lattice models, contrary to other modelling approaches such as continuum finite elements, have the advantage to take into account brittle fracture, crack development and material heterogeneity by assigning certain strength and stiffness properties to individual elements. Furthermore, plastic hardening is considered to simulate timber embedment.The lattice is an arrangement of longitudinal, lateral and diagonal link elements with a tri-linear load-displacement relation. The lattice is used in areas with high stress gradients and normal continuum elements are used elsewhere. Heterogeneity was accounted for by creating an artificial growth ring structure and density profile upon which the mean strength and stiffness properties were adjusted.Solution algorithms, such as Newton-Raphson, encounter problems with discrete elements for which ’snap-back’ in the global load-displacement curves would occur. Thus, a specialised solution algorithm, developed by Jirasek and Bazant, was adopted to create a bespoke FE code in MATLAB that can handle the jagged behaviour of the load displacement response, and extended to account for plastic deformation.The model’s input parameters were calibrated by determining the elastic stiffness from literature values and adjusting the strength, post-yield and heterogeneity parameters of lattice elements to match the load-displacement from laboratory tests under various loading conditions.Although problems with the modified solution algorithm were encountered, results of the model show the potential of lattice models to be used as a tool to predict load-displacement curves and fracture patterns of timber specimens.

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.

In the field of timber engineering, adhesive bonding remains a promising, though poorly developed, joining technique that may increase the structural stiffness and capacity of timber joints and structures. Selecting ductile adhesives may further allow to conceive ductile joints, which can compensate for the missing material ductility of timber. To demonstrate the potential of this approach, adhesively bonded double-lap timber joints were manufactured using a ductile acrylic adhesive and then subjected to axial tension and compression. The load–displacement responses were captured and compared to those of the same joints composed of a brittle epoxy adhesive. The effect of the different adhesives on the joint ductility has been studied and quantified.

In traditional Japanese timber structures, nuki-column joints are used as seismic elements. However, the elastic stiffness of their moment resistance performance is rather small. In this research, hardwoods were used for nuki in three ways to improve the performance of the joints. Moment resistance tests of the joints were conducted to evaluate their structural performance and clarify the differences depending on the wood species, the nuki cross sections, and reinforcing effects of hardwoods discussed. In some specifications, it was shown that using hardwoods for nuki improved the structural performance of the joints. A significant effect was observed on some characteristic values of the joints.

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.

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.

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.

In the current European standards for design of timber structures, the issue of timber-to-timber joint type is addressed only to squared timber, which makes the pinpointing of the round timber bolted joints load carrying capacity near-unfeasible due to the insufficient support in the current standards. There have been made series of tests of round timber joints in different inclinations of the loading force and also the reference tests of squared timber joints to compare the behaviour of this type of joints. Mechanical behaviour of the round and the squared timber bolted joints was tested in the laboratory of the Faculty of Civil Engineering in Ostrava. This paper presents results of static tests in tension at an angle of 0 degrees, 90 degrees and 60 degrees to the grain of squared and round timber bolted joints. Load carrying capacity was determined according to the applicable standards and theories of fracture mechanics. The test results of laboratory tests were then compared with the results of theoretical calculations. Web of Science 39 61 56

In the current European standards for the design of timber structures, the issue of timber-to-timber joint type is addressed only for squared timber, which makes the pinpointing of the round timber bolted joints carrying capacity near-unfeasible due to the insufficient support in the current standards. To compare the behavior of this type of connections have been made a series of tests of round timber joints in different inclinations tensile load to the grains but also the reference tests of squared timber joints. Mechanical behavior of round and squared timber bolted joints were tested in the laboratory of the Faculty of Civil Engineering in Ostrava. This paper presents results of static tests in tension at an angle of 0°, 90°, 60° to the grain of squared and round timber bolted joints.

© 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.

A new type of moment resisting timber joint has been developed. The joint is made up of steel plates, bolts and cotters. The plates and the bolts are embedded with timber element of frame structure. By combining those elements with steel cotters, moment resisting joints can be constructed easily. Static loading tests of the joint have been performed, and results of the tests made it clear that the joint have rotational rigidity and strength required from constructing moment resisting joint. In this report, three kinds of racking tests were performed to simulate the moment-rotational angle. “A tests” were prototypes, and “B tests” and “C tests” had each kinds of joint. The simulation results of moment-rotational angle curves by three kinds of tests agree with the prototype tests results.

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.

A new type of moment resisting timber joint has been developed. The joint is made up of steel plates, bolts and steel cotters. The plates and the bolts are embedded with timber element of frame structure. By combining those elements with steel cotters, moment resisting joints can be constructed easily. Static loading tests of the joint have been performed, and results of the tests made it clear that the joint have rotational rigidity and strength required from constructing moment resisting frame. And when we design the structure of wooden residence, we must use the shear elements. So, we simulate of shear-displacement curves of shear elements. In this paper, we show the results.

Timber constructions made of round timber components are becoming more and more popular. Given that in the current European standards for the design of timber structures, timber-to-timber joint type is solved only for squared timber. This paper presents results of static tests in tension at an angle of 0°, 90°, 60° to the grain of round timber bolted joints. This research looks into reinforcement with modified washers or self-drilling screws, as these are the least labour-intensive (while economically advantageous). The joints samples were experimentally tested in the laboratory of the Faculty of Civil Engineering VŠB TU Ostrava.

Post-tensioned timber joints have been studied at the ,nstitute of Structural Engineering at the ETH =urich. A post-tensioned beam-column timber joint has been developed using glued laminated timber with local hardwood reinforcement. 2nly a single straight tendon is placed in the middle of the beam and post-tensioned to restrain the rotation of the joint. 1o additional steel elements are used. The developed joint is characterised by a high degree of pre-fabrication and easy assembly on site. The glue-laminated timber moment-resisting frame featuring this joint shows great potential for timber frame structures especially for multi-storey buildings. Robust performance-based design criteria are a necessity for a s uccessful market implementation of the proposed system. A simplified analytical model was developed in order to predict the structural performance of the post-tensioned timber connection and facilitate preliminary performance-based design. This model was implemented in 2penSees using a bi-linear rotational spring approach. The model was verified against an analytical model and validated against tests on a post-tensioned timber joints under gravity loading and under horizontal loading. Moreover, a complex numerical model was developed using 2penSees to check the accuracy of the proposed preliminary design model. The preliminary design model was used to design fictitious moment-resisting post-tensioned glue-laminated timber frame structures using the loads prescribed in the Swiss code. The design process showed that neither the gravity loads nor the seismic load controlled the design. The design was governed by the lateral deformations due to wind. Based on this finding it is recommended to focus further research on increasing the connection stiffness or on adding additional structural elements to address the seismic performance of post-tensioned timber frames in regions of high seismicity.

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.

This paper provides a review of research being conducted at The University of Hong Kong (HKU) on the strengthening of concrete, metallic and timber construction materials with externally bonded fibre-reinforced polymer (FRP) composites. The motivation of such research is to enhance our understanding of the interfacial behaviour between the FRP and the three different substrate materials via FRP-to-concrete, -metal, and-timber joint tests. Of the three substrate materials, concrete has clearly experienced the most research activity to date by the wider research community, followed by that of metal and then that of timber. In order to progress the extensive knowledge base of FRP-to- concrete behaviour, research at HKU is aimed at enhancing the bond strength of the FRP via the addition of anchorage. The anchor of choice is the so called FRP anchor and its effectiveness in anchoring FRP flexural strengthening applied to reinforced concrete (RC) slabs is also presented. For the metal and timber substrate materials, HKU research is more focused at this stage on understanding the influence of key fundamental variables affecting interfacial behaviour such as FRP geometry, surface preparation and substrate material characteristics.

A proper understanding of the interfacial behaviour between timber and bonded fibre-reinforced polymer (FRP) composites will assist in the rational and optimal design of FRP strengthening works for timber structures. To enhance this understanding, a series of single-lap FRP-to-timber joint shear tests are reported herein in which the strength of the bond between the FRP and timber is examined. The shear tests are conducted on softwood (Pine) which has been strengthened with carbon FRP with the main test variables being the FRP bond length and the growth characteristics of the timber. Extensive strain gauging of the FRP has enabled the onset and propagation of debonding cracks to be monitored. An effective bond length is identified, however, the results also show that timber is a variable material which requires continued investigation.