Search Results (12)

Laminated bamboo (LB) has shown enough exceptional performance to be used in constructions, but the performance of the bolted connections remains to be explored. To meet the criteria of low-carbon construction and fill the research gap in LB dowel embedment performance, this study examined the longitudinal dowel embedment behavior of LB. Failure modes, load–displacement curves, embedment strength, and elastic foundation parameters were examined after four sets of half-hole specimens with dowel diameters (6, 8, 10, and 12 mm) were tested in accordance with ISO 10984-2. The majority of the data was confirmed to follow a normal distribution by the Kolmogorov–Smirnov test. Interlaminar shear failure (dominant in 10 and 12 mm groups) and local crushing (dominant in 6 and 8 mm groups) were the primary failure modes. There were clear linear and nonlinear phases in the load–displacement curves (excellent ductility). The average elastic foundation modulus was 3565.55 MPa (0.39 times the compressive modulus); meanwhile, the average proportional limit, yield, and ultimate strengths were 35.48, 63.08, and 74.44 MPa (0.59, 1.06, and 1.25 times the parallel-to-grain compressive strength). The ultimate strength varied from 72.64 MPa to 76.71 MPa as the diameter rose; however, the elastic foundation beam coefficient dropped significantly. A novel calculation based on LB’s parallel-to-grain compressive strength accorded well with test results, while the existing code formulae (GB 50005, NDS, and CSA O86) overestimated LB embedment strength. The design of LB bolted connections is guided by this study, which also explains LB embedment criteria and offers design parameters and a prediction method. Full article

Steel–timber composite (STC) structures offer a sustainable and low-carbon structural solution. Steel–timber interface behavior is critical for the mechanical performance of STC structures. This paper introduces a novel connection for steel–timber composites (STC) that combines mechanical interlocking with adhesive bonding through an epoxy-bonded bolted design. Epoxy resin is injected into the timber dowel slots, followed by pre-tightening of the bolts, forming a composite dowel system where the ‘bolt–epoxy resin–timber’ components work in synergy. The load–displacement characteristics and failure modes of nine specimen groups were investigated through a series of double-shear push-out tests. The influence of a wide range of connector parameters on the stiffness, shear bearing capacity, and ductility of STC joints was systematically investigated. The parameters included fastener strength grade, thread configuration, diameter, number, and the use of epoxy resin reinforcement. The experimental results demonstrated that high-strength partially threaded bolts were crucial for achieving a synergy of high load-bearing capacity and commendable ductility, while full-threaded bolts exhibited vulnerability to brittle shear failure, a consequence of stress concentration at the root of the threads. Although screw connections provided enhanced initial stiffness through timber anchorage, ordinary bolt connections exhibited superior ultimate load-bearing capacity. In comparison with conventional bolt connections, epoxy resin–bolt connections exhibited enhanced mechanical properties, with an augmentation in ultimate load and initial stiffness of 12% and 11.8%, respectively, without sacrificing ductility. Full article

End-users can design personalized furnishing products using remote web-based CAD systems. However, if these designs fail to incorporate design for disassembly (DfD) principles, the furniture’s subsequent repair, reconfiguration, recycling, and disposal can be significantly hindered. To address this drawback, this study supports DfD, a strategy that enables the creation of easily repairable, reusable, and recyclable furniture to reduce waste and environmental impact. Consequently, this review aims to classify and evaluate available furniture joinery systems for their suitability within DfD frameworks, ultimately promoting their implementation within CAD environments. To this end, various solutions were evaluated, including traditional joints, dowel/biscuit, hammered, directly screwed, snap-on, expandable, and cam/bolt fasteners. Based on a literature review and practical observations, the analyzed joinery systems were categorized into non-disassemblable, conditionally disassemblable, and fully disassemblable categories. Only the fully disassemblable solutions effectively align with DfD principles. The study postulates a preference for expandable and cam/bolt fasteners in furniture designs, noting that although snap-on fasteners can potentially support DfD, this outcome is not always ensured. To guarantee that the designed furniture adheres to the DfD principles, the following eight furniture design guidelines were formulated: develop web-accessible disassembly instructions, prioritize access to fast-wearing components, prioritize modularity, standardize parts in modules, label components, enable independent component removal, use materials that withstand repeated disassembly, and employ fully disassemblable joints. Full article

This study compared two groups of furniture joints, i.e., a so-called ready-to-assemble (RTA) plastic biscuit joint from Lamello©, while the second group consists of four types of eccentric joints with beech dowels. L-shaped specimens were prepared with the help of the selected joints and a three-layer particleboard with dimensions of 150 × 150 × 400 mm. These L-shaped specimens were tested for bending moment capacity under compression and under tension. Cam joints with wooden dowels can withstand high stress. If Lamello© Bisco P-15 joints are added to the plastic Clamex P-14 joint, this joint will achieve 13% higher values for bending moment capacity under compression and 22% under tension. During testing, the worst result was achieved by the Tenso P-14 joint. The best values achieved during the testing of bending moment capacity under compression and under tension were for an eccentric joint with the use of a metal-capped bolt and Euro screw. This joint achieved 147% higher values for bending moment capacity under compression than a standard eccentric joint with a euro screw bolt and 213% higher values for bending moment capacity under compression than the Lamello© and Clamex P-14 joints. This study aimed to determine how the joints differ, how they behave during testing, and what deformations occur. Full article

Timber–concrete composite (TCC) systems present a viable alternative to conventional timber or reinforced concrete systems. TCC leverages the advantages of both materials, resulting in an enhanced composite structure. Historically, traditional mechanical connectors such as nails, bolts, and dowels have been used in TCC systems to join timber and concrete components. However, these connectors often fall short in providing sufficient load transfer efficiency. Therefore, the use of screws and, more recently, inclined screws in TCC systems has increased due to their enhanced load transfer efficiency and greater stiffness compared to traditional connections. This review paper consolidates findings from contemporary experimental studies and analytical models, examining the influence of factors such as screw type and inclination angle on the performance of TCC systems for both connection and beam specimens in ultimate and serviceability limit states. Key issues addressed include the shear strength, stiffness, and long-term behaviour of the connection type. By offering a comprehensive synthesis of existing knowledge, this paper aims to inform design practices and contribute to the development of more resilient and efficient TCC systems, supporting their increased adoption in sustainable construction. Full article

A comprehensive understanding of the embedment behavior is of great importance in the design of contemporary bamboo constructions with connections utilizing dowel-type fasteners. The objective of this research was to assess the embedment behavior of bamboo scrimber using full-hole embedment tests. To investigate the effect of the loading angle and bolt diameter, a series of tests were performed using bolts of varying diameters (16 mm, 18 mm, and 20 mm) and loading angles (0° to 90°, with an increment of 15°). The experimental results demonstrated that the loading angle has a considerable influence on the embedment behavior. As the loading angle was increased, the failure mode underwent a change from a brittle failure mode, which was dominated by shear mechanisms, to a ductile failure mode, which was dominated by fiber crushing. The yield and ultimate embedment strengths showed an M-shaped response to changes in the loading angle, with the lowest values being 0°, 45°, and 90°. The bolt diameter was found to have no impact on the failure mode of the specimen. However, an increase in bolt diameter resulted in a reduction in the embedment strength when the specimen was loaded at 90°. Full article

Joints in timber structures are today typically designed in a simplistic manner, i.e., by assuming linear elastic behaviour or neglecting their real stiffness by assuming ideal pinned or fixed conditions. While such assumptions may be acceptable for simple structures, they do not reflect the real behaviour of joints in complex structures, and could, in some cases, lead either to an over-conservative or even unsafe design. Therefore, a more accurate and realistic representation of the nonlinear behaviour of joints with mechanical fasteners is needed. The most common modern timber joints with mechanical fasteners are realized with dowels, bolts, glued-in rods, or self-tapping screws. In this paper, an overview of the impact of the most influential parameters on the shape of the load-displacement curves of these joints under common static loading is given. The joints were differentiated according to the characteristics of their nonlinear load-displacement behaviour. Different analytical models from the literature for the description of the load-displacement curves of timber joints were reviewed. The performance and suitability of these models for describing the variety of nonlinear load-displacement behaviours of joints were evaluated and the advantages and limitations of each model were identified. It was found that the Richard–Abbott model is the most suitable to parametrize a variety of timber joints and to capture the variability of the test data by its parameters. Such an analytical model can be used to incorporate a parametrized, more realistic, nonlinear load-displacement representation of the behaviour of joints in reliability analyses, structural design software, and design guidance for modern timber structures. Full article

The paper deals with the analysis of the load-carrying capacity of a timber semi-rigid connection created from a system of two stands and a rung. The connection was made from glued laminated timber with metal mechanical dowel-type fasteners. Not only a common combination of bolts and dowels, but also fully threaded screws were used for the connection. The aim of the research and its motivation was to replace these commonly used fasteners with more modern ones, to shorten and simplify the assembly time, and to improve the load-carrying capacity of this type of connection. Each of these two types of connections was loaded statically, with a slow increase in force until failure. The paper presents results of the experimental testing. Three specimens were made and tested for each type of the connection. Experimental results were subsequently compared with numerical models. The achieved results were also compared with the assumption according to the currently valid standard. The results indicate that a connection using fully threaded screws provides a better load-carrying capacity. Full article

The paper deals with the analysis of the rotational stiffness of a semirigid connection created from a system of two stands and a rung. The connection was made from glued laminated timber with metal mechanical dowel-type fasteners. Not only a common combination of bolts and dowels but also fully threaded screws were used for the connection. The aim of the research and its motivation was to replace commonly used fasteners with more modern ones, to shorten and simplify the assembly time, and to improve the load-carrying capacity of this type of connection. Each of these two types of connection was loaded to the level of 60%, 80%, and 100% of the ultimate limit state value. Subsequently, the rotational stiffness was determined for each load level after five loading and unloading cycles. This paper presents the results and comparison of the experimental testing and the numerical modeling. The obtained results were also compared with the assumption according to the currently valid standard. Full article

The present study deals with the innovation and the possibilities of improving the design solution of a frame connection for two selected types of fasteners. All specimens were made of glued laminated timber. Dowel-type mechanical fasteners, a combination of bolts and dowels, and full-threaded screws were used for the connection. The main goal of this research was to replace the typical solution (common dowel-type fasteners) with a more modern, faster, and easier solution in order to improve the load-carrying capacity, ductility, and deformation capacity of this type of frame connection. This article also aimed to provide a detailed evaluation of the mechanical properties of the used glued laminated timber and fasteners in order to comprehensively evaluate the research task. For the design solution, a frame connection created from a system of two struts and a partition was chosen as the basis of the experimental program. Dowel-type mechanical fasteners, as well as combinations of bolts and dowels, were used for the connection; however, in addition to these standardly used mechanical fasteners, full-threaded screws were used. The article describes the use of static destructive testing to determine the ductility of the connection, considering different variations in the strengthening of the individual segments of the mentioned connection means. In the first variation, the individual components of the frame were not reinforced in any way. In the second, the crossbar was reinforced with two full-threaded bolts. In the third, the webs and the crossbar were reinforced with two full-threaded bolts. In the article, these ductility values were compared with each other and the procedure was set by the currently valid standard. Full article

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. Full article

The lateral resistance of dowel-type connections with CLT is related to its lay-up, species of the laminations and even the manufacture method. Treating the CLT as homogeneous material, current methods develop new equations through test results or make use of the existing equations for the embedment strength already used in design codes; thus, the lateral resistance of dowel-type connections of CLT can be calculated. This kind of approach does not take the embedment stress distribution into account, which may lead to inaccuracy in predicting the lateral resistance and yield mode of the dowel-type connections in CLT. In this study, tests of the bolted connections and the screwed connections of CLT were conducted by considering the effects of the orientation of the laminations, the thickness of the connected members, the fastener diameter and strength of the materials. The material properties including yield strength of the fasteners and embedment strength of the CLT laminations were also tested. Using analysis of the dowel-type connections of CLT by introducing the equivalent embedment stress distribution, equations for the lateral resistance of the connections based on the European Yield Model were developed. The predicted lateral resistance and yield modes were in good agreement with the test results; the correctness and the feasibility of the equations were thus validated. Full article