Dowel Connections Research Articles

Cyclic Behavior and Damage Assessment of Superelastic SMA Dowel Connections for Braced Timber Frame Applications

Cyclic Behavior and Damage Assessment of Superelastic SMA Dowel Connections for Braced Timber Frame Applications

Shear strength and ductility of novel steel fibre-reinforced concrete dowel connections for composite beams

In this paper, a novel steel fibre-reinforced concrete (SFRC) dowel connection without traditional steel bar reinforcement is proposed for steel-concrete composite beams. Push-out tests on thirty-six specimens were conducted to investigate the shear strength and ductility of SFRC dowel connections with varying dowel sizes, concrete densities, fibre content and type. Even without the presence of reinforcing bars, the SFRC dowels were able to resist substantial loads and maintained a ductile load-slip behaviour. The shear strength of SFRC dowels increased with an increase in the fibre content, dowel size, and concrete density. Further, dowels with higher steel fibres content exhibited enhanced ductility, displaying a near elastic-plastic load-slip behaviour, with an ability to resist up to 80 % of the ultimate load even at 6 mm slip. A unique analytical model to predict the ultimate load and the load-slip curve is proposed in this study. The model was able to predict the ultimate load to within 6 % of test results, on average, while the mean load at 6 mm slip was predicted to within 3 % of the test results, with standard deviation of 17 % and 13 % respectively. The general shape of the load-slip curve was also well predicted. The study also proposes simplified equations, which predicted the shear strength of SFRC dowels to within 2 % of the test results with a standard deviation of 13 %.

Effect of Connection Detailing on Reverse Cyclic Behaviour of Precast Beam to Column Grouted Cementitious Billet Connections

In reinforced concrete framed structures exposed to high lateral loads, the performance of the beam to column joints has been acknowledged to have a significant impact on the overall behaviour of the structures. The present study conducted an experimental investigation on four 1/3rd scale Precast Concrete (PC) beam-to-column grouted cementitious billet connections subjected to reverse cyclic loading. Their performance was compared with a reference monolithic connection. The various precast connections studied are Billet with Dowel (BD) connection, Billet with Dowel-cleat Angle (BD-CL) connection, and Extended Billet with Dowel-cleat Angle (EBD-CL) connection. The ultimate load-carrying capacity, ductility factor, hysteretic behaviour, load ratio, energy dissipation, and stiffness degradation of the monolithic (MO) and precast (PC) specimens were studied, and a comparison of their performances was made. The results show that the EBD-CL connection has comparable ductility and strength.

Mechanical properties of multi-bolted Glulam connection with slotted-in steel plates

The Bolted Glulam Connection with Slotted-in Steel Plates (BGCSSP) is widely employed in modern timber structures due to its advantages of convenient installation and reliable force transmission. However, the current design methods lack rigorous mechanical derivation and fail to consider various influencing factors comprehensively. Furthermore, designing multiple dowel connections based on the behavior of individual dowels impedes optimization and limits the applicability of design rules. To systematically investigate the failure modes and mechanical characteristics of Multi-bolted Glulam Connection with Slotted-in Steel Plates (MGCSSP), specimens from 12 groups (6 specimens per group) were subjected to parallel grain tensile tests, considering four key influencing factors: bolt quantity, bolt arrangement, bolt diameter, and base material thickness. The experimental results indicate that as the number of bolts increases, the failure transitions from double-hinge failure to single-hinge failure. Additionally, there is an observable upward trend in both initial stiffness and peak load for the same type of specimen as the quantity of bolts increases, accompanied by a decreasing trend in the ductility coefficient. The analysis of experimental results reveals that both the quantity and diameter of bolts impact the initial stiffness and peak load of MGCSSP specimens. Based on experimental observations, dual-parameter calculation models for the initial stiffness and peak load of MGCSSP are proposed. The calculated results of the models align well with experimental data, providing references and convenience for the design of MGCSSP.

Review of Studies on Performance of Dowel Connections Loaded Perpendicular to Grain

Wood as a sustainable building material demonstrates significant advantages in terms of environmental protection, economy and functionality. Studies showed that adding 1.0m3 of wood could absorb 1.0kg of carbon dioxide, produce 730kg of oxygen, and fix 270kg of carbon, which plays an important role in ecological environment protection. In addition, in addition, wood has good thermal insulation performance, can adjust indoor humidity, beneficial to human health.China's wooden structure architecture has a long history. As an important technology in China's traditional architecture, mortise and tenon connection technology constitutes an important part of Chinese traditional architectural heritage through the insertion of wood components. As a prefabricated building form, modern wood structure has a history of more than 100 years in developed countries. The main forms include heavy wood structure, light wood structure, square wood wood structure and wood mixed structure. In recent years, wood structure architecture has attracted wide attention in scientific research and application in China. Whether for new construction or large-scale reconstruction projects, wood structure buildings are widely adopted because of their design flexibility, high strength and aesthetics, as shown in Figure 1.1. Modern wood structure buildings show the advantages of energy conservation and environmental protection, good earthquake resistance, convenient construction and safety and comfort, and its development is fully in line with the national sustainable development strategy.

Numerical simulation and design method of dowel-type timber joints connecting laminated veneer lumber

Dowel laminated timber (DLT) is a structural engineering wood product composed of laminates connected by wood dowels. It has the characteristics of green, low-carbon, and a high degree of prefabrication. Wood dowel connection is the forming method of DLT, and its joint design is the key to DLT. The properties of laminates affect the mechanical properties of both DLT and dowel-type timber joints. Laminated Veneer Lumber (LVL) is an engineering wood product made by gluing veneers along a fixed grain direction, with excellent physical and mechanical properties. Utilizing small-thickness LVL as the laminates of DLT, a design method of dowel-type timber joints connecting LVL was explored through numerical simulation and theoretical calculation. A three-dimensional finite element model of dowel-type timber joints connecting LVL was presented, and experimental calibration were carried out. The parametric study was adopted to explore the influence of main variables on the shear performance of joints. The calculation formula for the shear capacity of joints was proposed and optimized, and the design method of joints was summarized. The results indicated that the failure mode and shear capacity of joints were dramatically influenced by two variables: the ratio of side laminate thickness to dowel diameter (n) and the thickness ratio of middle-to-side laminate (m). The two variables affected the shear capacity of joints by affecting the failure mode of joints. When the ratio of side laminate thickness to dowel diameter was 1 < n ≤ 3.75, the optimized Johansen theoretical formula could effectively predict the shear capacity of dowel-type timber joints connecting LVL.

Numerical investigation on the behaviour of the high-strength ring strengthened dowel connection under vertical load

ABSTRACT To improve the bearing resistance of individual pavement connections at joint surface, an innovative high-strength ring strengthened dowel connection was developed. A comprehensive finite element analysis (FEA) was then conducted to investigate the ultimate load of this novel connection and the compressive stress development of concrete. Parameters including the compressive strength of high-strength concrete (HSC), the thickness and the length of the high-strength ring were analysed. The FEA results indicated that the ultimate load of the dowel connection was enhanced as the thickness and compressive strength of the high-strength ring increased. Due to the expanded contact area created by the high-strength ring, compressive stress created in normal-strength concrete was reduced, thereby delaying the initiation of localised concrete crushing. Furthermore, since the crushing failure primarily concentrated at the joint surface, the length of the high-strength rings was optimised to 25 mm to fully utilise the excellent compressive behaviour of HSC. Finally, based on the obtained FEA data, analytical models were derived to predict the maximum compressive stress of concrete under the service limit state and the ultimate load of the dowel connection embedded into concrete under the ultimate limit state.

FEATURES OF BEHAVIOR AND CALCULATION OF DOWEL TIMBER JOINTS WITH SLOTTED-IN PLATES ACCORDING TO EC5

The paper presents an overview of theoretical and experimental studies of connections of timber structures with steel dowel with steel slitted-in plates. The correct choice of the type of connections allows you to significantly influence the total cost of the structure due to the formation of thestructural and assembly scheme of the structure (minimization of the number of nodal and assembly connections), optimal unification of connections isan additional argument for creating an economical and competitive solution. For the analysis of the dowel connection, it is taken into account that theforce is transmitted due to the bending and shear resistance of the fastening element, as well as crumpling in the connected timber elements. The limitstates of the dowel joint are considered loss of strength due to crumpling and splitting of the wood of the hole wall, as well as due to bending of the nailin the nail socket. The works considered in the review provide extensive factual material on the strength of connections depending on the geometricand physical parameters of its components, as well as the stiffness of the connection, which is currently the subject of active attention of researchers. Attention is paid to the need to study the operation of nodes under the action of a moment during group operation of the connection. The analysis of numerous experiments makes it possible to check the reliability of the current design rules and norms of EC5 and the design norms of DBN В.2.6-161:2017 implemented to them, and also revealed the shortcomings and limits of the application of the design rules for this type. connections The results of numerical and experimental studies are the basis for improvingthe structural solutions of the joints of wooden elements and allowed to accumulate significant factual material for the verification of numerical simulation models.

Study on Vertical Dowel Connections in Precast Walls

Precast concrete wall connections using dowels are becoming more popular and effective these days due to their ease of installation and cost. In this study, one-third scale models of slender and intermediate precast walls with dowel connections and monolithic concrete walls were tested experimentally and numerically under lateral cyclic loads. The experiments on precast walls and monolithic walls were conducted on a loading frame of capacity 20 T and the cyclic loads were applied until the failure of the wall specimens. The numerical studies on walls were carried out using Abaqus.cae software, and the same cyclic loads were applied. The responses such as ultimate load, displacement, cracking pattern, ductility, and energy dissipation capacity of precast walls were compared. The results obtained from the numerical investigation proved to be effective in simulating the actual behavior of the studied precast and monolithic walls, thereby reducing the burden of doing physical tests on a huge number of precast wall specimens.

Load transfer of circular reinforced composite dowel connector: a comparison of existing analytical equations

AbstractThe effectiveness of headed studs for shear transfer in the steel‐concrete interface of composite columns is questionable when important load needs to be transferred. Circular reinforced composite dowel (CRCD) connectors are known for their high initial stiffness and significant load‐bearing capacity. This paper presents the different types of CRCD connectors and the available analytical equations to determine their shear resistance, as well as a database of 52 experimental specimens to study their performance. The results show that the equations developed by Wang et al. 2014, He et al. 2016 and Zhao et al. 2016 provided the best performance, with 76% of the predictions falling within the error bounds of +/−15%. Further research is recommended to understand the behaviour of CRCD connectors on H‐shaped steel profiles and to develop analytical equations to calculate their resistance.

Behaviour of small-scale glulam timber connections with slotted-in steel plates and dowel-type fasteners reinforced with self-tapping screws

Braced frames are a common lateral force-resisting system in mass timber structures. In timber braced frames, timber-steel dowel connections are relied upon to provide ductility and energy dissipation capacity under earthquake loads. However, the ductility and energy dissipation capacity of these connections can be limited by the onset of a brittle failure mechanism (e.g., row-shear or group tear-out) prior to significant dowel yielding. This paper presents an experimental campaign investigating the structural performance of timber-steel dowelled connections reinforced with self-tapping screws. Twelve connections were tested; with 8 tested under monotonic loading and 4 tested under a cyclic loading regime. The tested connections included two different fastener diameters of 11 mm and 16 mm, with one or two internal steel plates, both with and without reinforcing screws designed to prevent brittle shear failure. The results demonstrate that the reinforcing screws are most effective for improving the ductility and energy dissipation for connections with similar design values of dowel yield and row shear capacities. In addition, the increases in ductility and energy dissipation with reinforcement were greatest for connections with high slenderness (defined as the ratio of dowel diameter to timber thickness) dowels. There was little improvement in the ductility of connections whose design capacity was dominated by row shear, although there was improvement in the energy dissipation of the connections. Overall, results of this study demonstrate the potential for using self-tapping screws to reinforce steel dowel connections and improve the seismic performance of mass timber braced frames.

Behaviour of bonded-in dowel shear connections in timber lightweight concrete composite beams including effect of an interlayer

With the need of renovation in the current timber structures, use of a cement based layer is a popular solution, which improves the structural integrity and increases the structural mass. In this paper, the use of a lightweight concrete with dowel type connections is investigated since such a combination can serve for both new and existing structures. Two types of dowel connections are experimentally tested, screws and bonded-in rods, to observe their limits and the contribution of an adhesive. To extend the application to an existing structure where a wood-based flooring may be present (such as OSB), which acts as an interlayer in the composite solution, the connections are tested with an interlayer as well. To overcome this challenge, in this paper, the predrilled hole at the wood based material (timber and interlayer) is filled with an adhesive to form a bond to the connection. The experimental results indicate that the addition of an adhesive lead to a positive contribution in mechanical properties. The experimental results are compared with the analytical approaches given in the current codes. The difference in comparisons are justified and further supported with the literature.

Experimental investigation on the structural performance of the high-strength ring strengthened dowel connection under monotonic load

Traditional dowel connections embedded into concrete are susceptible to localised concrete crushing under heavy wheel loads. To address this issue, this paper introduces an innovative high-strength ring strengthened dowel connection to improve the bearing resistance of concrete at the joint surface. Monotonic load tests were conducted to investigate the effects of the high-strength ring concrete compressive strength, the high-strength ring thickness and length on improving ultimate load and mitigating localised concrete crushing. Test results indicated that the ultimate load and the initial stiffness of the specimen were greatly improved after applying the high-strength rings. Because of the excellent compressive resistance of the ring concrete, the initiation of the crushing zone was delayed, and the maximum compressive stress in normal strength concrete was reduced with the increase of the ring thickness. In addition, the deflection response of the dowel connection embedded into concrete could be predicted by the beam on elastic foundation (BEF) and the beam on inelastic foundation (BIF) theories. Based on the deformation of the dowel connection and surrounding concrete, the analytical solution was derived to predict the ultimate load of the high-strength ring strengthened dowel connection embedded into concrete.

Kath-Kuni architecture: field investigations and material characterisation

An extensive investigation was carried out to gain better understanding of the seismic-resilient features of Kath-Kuni structures (mainly timber-laced dry masonry construction) prevalent in the Himachal Pradesh region of India. The research involved field reconnaissance surveys through rapid visual screening to understand the structural configuration. Laboratory testing was then conducted to evaluate the mechanical properties, joint characteristics and interfacial resistance of timber and stones. The results from the field survey indicted that the symmetrical geometry, the use of lintels above openings and corner interlocking were the major contributors to the seismic resilience of the buildings. Laboratory tests on the timber joints present in the walls – namely dowel connections and double-dovetail joints – revealed the importance of connection conditions in increasing the shearing capacity. The shearing capacity was also found to be dependent on the overburden pressure, with the smallest capacity of the connections in the top portion of the wall and the highest capacity at the bottom portion of the wall. The interface of timber and stones contributed to a further increase in the shearing capacity of the walls. This research provides the first insights into the mechanical behaviour of joints of Kath-Kuni structures.

Experimental Analysis of the Performance of Doweled Connections Reinforced with Glass-Fiber-Reinforced Polymer (GFRP) in Wood Pinus spp.

In line with technological advancements, the construction industry worldwide has sought more efficient building systems in relation to aspects such as increased productivity, reduced material waste and meeting the growing demand. The objective of this research was to use structural joints composed of composite dowels in laminated wood beams as an alternative to connect pieces of wood. Composite materials are composed of a matrix phase and a reinforcement phase and, in civil engineering, are generally applied as reinforcements in concrete structures. This article presents the structural performance of laminated pine timber with composite dowels made of fiber-reinforced polymeric resin (epoxy resin, hardener and glass fiber) (glass-fiber-reinforced polymer, GFRP) with a diameter of 12.5 mm, which was subjected to tensile force in the direction of the connection. For this, an experimental program was carried out that included characterization of the GFRP dowel, characterization of the woods used to make the connection and a tensile test of the connections with the dowels reinforced with fiberglass through a prototype designed specifically for the test. Subsequently, the results were compared with those observed in the literature. In the comparisons, it was possible to conclude that the joints with FRP pins exhibited better performance in terms of shear strength per section than those such as common nails, helical nails (Ardox) and composite structural pins (half-lap, 90°), which were 3.8 mm, 3.4 mm and 6 mm in diameter, respectively. This indicates that this composite material has potential for application in these types of connections. As an original contribution, it proves the feasibility of using this material in dowel joints for wooden structures.

Embedment behavior of dowel-type fasteners in birch plywood: Influence of load-to-face grain angle, test set-up, fastener diameter, and acetylation

Birch plywood has superior mechanical properties compared with plywood made from most softwood species, which makes it suitable for structural application. Plywood is also more environmentally friendly, cost-efficient, and less prefabrication demanding than steel plates. For a proper design of birch plywood as joint plates in timber-timber connections, the embedment behavior of mechanical connectors into plywood needs to be properly investigated. In this study, the authors performed embedment tests of dowel connectors into birch plywood specimens under five different angles from parallel to perpendicular to the face grain with a step size of 22.5°. Dowel connectors with three different diameters were utilized to study the influence of dowel diameter on embedment strength and stiffness. Besides, test series using self-drilling screws and acetylated birch plywood specimens were conducted to study the effect of both fastener type and acetylation. Moreover, full-hole and half-hole test results were compared. The embedment strengths were calculated analytically according to different term definitions. The test results were then compared with the analytical results based on formulas reported in the literature, e.g., Eurocode 5 and other design standards.

Experimental investigations on the load-bearing properties of dowel connection joints of bamboo scrimber

The joints in bamboo structures are critical, and dowel connections are the most convenient form of joint. Research on dowel-bearing behaviour is important to develop the theory of joints for bamboo structures. One hundred fifteen half-hole dowel-compression specimens were tested in this study to explore the effects of specimen length, dowel diameter and fibre direction on the dowel-bearing behaviour of bamboo scrimber. Results showed that length had little effect on the stiffness and dowel-bearing strength of bamboo scrimber. When the dowel diameter increased from 8 to 20 mm, the stiffnesses of parallel to grain and perpendicular to grain specimens both increased by more than 43%, while the dowel-bearing strength of parallel to grain specimens decreased linearly from 177.11 MPa to 126.74 MPa, and the variation law of the perpendicular to grain specimens conformed to the trend of the quadratic function. When the angle between the direction of the bamboo fibre and the horizontal direction changed from 90° to 0°, the stiffness decreased from 63.55 kN/mm to 32.62 kN/mm, and the dowel-bearing strength decreased from 167.22 MPa to 138.43 MPa and exhibited different downwards trends with 45° as a boundary. Based on the calculation concept in Code for the design of timber structures in China, the calculation formula of dowel-bearing strength of bamboo scrimber was proposed by considering the influence of dowel diameter and fibre direction. The predicted results are in good agreement with the test results, which have good applicability to bamboo scrimber and can effectively provide a design method for dowel connection joints of bamboo structures.

An experimental and numerical study of twin dowel type shear connector

The hunger for a better, more effective, more economic, easier for construction, and overall more sustainable bridge design is enormous nowadays. One of the solutions for the problems described is a steel-concrete composite structure with embedded continuous shear connectors. Such structure uses advantages of both materials (concrete in compression and steel in tension) while lowering the overall height of the structure and time of the construction. This paper presents a new design of the connector of twin dowel type, with clothoid dowel, where two dowel connectors are welded longitudinally by flanges to create one twin connector. Its geometrical attributes are closely described and the design origin is explained. The study of the proposed shear connector consists of experimental and numerical part. In experimental study, the experiments performed—four push-out tests—and their setup, instrumentation and material characteristics are described and their results in a form of load-slip curves are presented and analyzed. In numerical study the finite element model developed in ABAQUS software is presented with a detailed description of the modeling process. In results and discussions the results of the numerical study are compared with results from the experimental study and the resistance of the proposed shear connector is briefly compared to shear connectors from chosen studies.

Ductility of Precast Beam-Column with Dowel Connection Due to Cyclic Load

Precast concrete elements have advantages in terms of working time efficiency and quality uniformity. But beyond the benefits, there is something else to consider, namely the connection method. In addition, the ductility value is a measure of the success of precast concrete elements in construction, especially when it comes to absorbing earthquake loads in the form of cyclical loads. This study aims to analyze the ductility value of the precast beam-column with dowel connection under cyclic loading. The sample test was performed with cyclic loading based on the displacement control method. The sample consists of 1 monolith beam-column (BN) and 1 beam column with dowel connection (BG). The results of the investigation revealed that the beam-column with dowel connection (BG) had a higher ductility value than the monolith beam-column (BN). Based on the ductility classification according to ASCE 41-17, both samples were categorized as moderate ductility.

Thermo-mechanical behavior of CLT beam-to-girder assemblies connected with T-shaped dowelled connections before, during and after fire exposure

Purpose3-ply cross-laminated timber (CLT) is used to investigate the thermo-mechanical performance of intermediate-size assemblies comprised of T-shaped welded slotted-in steel doweled connections and CLT beams at ambient temperature (AT), after and during non-standard fire exposure.Design/methodology/approachThe first set of experiments was performed as a benchmark to find the load-carrying capacity of the assembly and investigate the failure modes at AT. The post-fire performance (PFP) test was performed to investigate the residual strength of the assembly after 30-min exposure to a non-standard fire. The fire-performance (FP) test was conducted to investigate the thermo-mechanical behavior of the loaded assembly during non-standard fire exposure. In this case, the assembly was loaded to 67% of AT load-carrying capacity and partially exposed to a non-standard fire for 75 min.FindingsEmbedment failure and plastic deformation of the dowels in the beam were the dominant failure modes at AT. The load-carrying capacity of the assembly was reduced to 45% of the ambient capacity after 30 min of fire exposure. Plastic bending of the dowels was the principal failure mode, with row shear in the mid-layer of the CLT beam and tear-out failure of the header sides also observed. During the FP test, ductile embedment failure of the timber in contact with the dowels was the major failure mode at elevated temperature.Originality/valueThis paper presents for the first time the thermo-mechanical performance of CLT beam-to-girder connections at three different thermal conditions. For this purpose, the outside layers of the CLT beams were aligned horizontally.Highlights Load-carrying capacity and failure modes of CLT beam-to-girder assembly with T-shaped steel doweled connections at ambient temperature presented.Residual strength and failure modes of the assembly after 30-min partially exposure to the non-standard fire provided throughout the post-fire performance test.Fire resistance of the assembly partially exposed to the non-standard fire highlighted.