Dowel-bearing Strength Research Articles

Experimental Study on the Dowel-Bearing Strength of Bambusa blumeana Bamboo Used for Sustainable Housing Construction

This study addresses the critical issue of dowel-bearing strength in Bambusa blumeana, a key sustainable construction material crucial for climate change mitigation. Given the lack of bamboo connection standards, this research focuses on determining the dowel-bearing strength of Bambusa blumeana, emphasizing factors such as dowel diameter, node placements, and the physical properties of bamboo. A predictive equation is derived, enhancing the practicality of bamboo in structural design. The results underscore a notable correlation between dowel diameter and characteristic strength, with implications for engineering practices. Node placements significantly affect dowel-bearing capacity, while bamboo’s physical attributes, including thickness, culm diameter, and moisture content, exhibit modest correlations with strength. The derived equation aims to assist in structural design, mitigating splitting and bearing failures in bamboo structures. This research establishes a foundation for optimizing the use of Bambusa blumeana in sustainable construction, advancing the understanding of its dowel-bearing strength for improved sustainability and resilience in the construction industry. Future research suggestions include exploring bamboo–mortar composites, additional node placements, and employing more comprehensive empirical equations and curve-fitting techniques. The study advocates for further investigations with more diverse and larger bamboo samples to bolster robustness. Additionally, delving into bamboo ductility may offer valuable insights.

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.

Dowel–bearing behavior of bamboo scrimber for bolted–type joint

Dowel-bearing behavior is one of the key material characteristics in the design of laterally loaded joints with dowel-type fasteners and provides its strength and stability of structures. In this study, the dowel-bearing behavior of bolted joints on bamboo scrimber were investigated by analyzing the effect of specimen size, bolt diameter and loading direction on the dowel-bearing behavior. The estimation formulas of dowel-bearing strengths of bamboo scrimber for engineering utilization were developed based on conducting on 16-group experiments comprising a total of 80 half-hole samples. The results indicate that the initial stiffness was affected by the bolt diameter, sample thickness and loading direction. Dowel-bearing strength was only affected by bolt diameter and it decreased gradually with the increase in bolt diameter, irrespective of specimen sizes and loading direction. The failure mechanisms of the samples loaded in parallel- and perpendicular-to-grain were completely different. The existing empirical expressions was suitable for bamboo scrimber loaded in parallel-to-grain when larger bolts were used, but can under-estimate the dowel-bearing strengths in perpendicular-to-grain direction. Finally, semi-empirical regression-based formulas as functions of compressive strength and bolt diameter were proposed, which exhibited good agreement with the experimental dowel-bearing strength. The findings will be useful for designing safe and efficient bolted joints to promote more widespread use of bamboo scrimber in construction, as well as supplying basic data for systematic development of test and design standards for bamboo structures.

Perpendicular-to-grain dowel-bearing strength behavior of side pressure laminated bamboo lumber

Research on dowel-bearing strength is an indispensable part of bolt connections. The size effect (length, width, and thickness), bolt diameter, and the arrangement of bamboo units are examined in this research, to study their influence on the dowel-bearing behavior of side pressure laminated bamboo lumber (LBL). The test results show that when the specimen length and width are 5 times larger than the bolt diameter, and the thickness is 3 times larger than the bolt diameter, the dowel-bearing strength of the specimen tends to be stable. The stiffness of the standard size specimen (80 mm × 80 mm × 40 mm) reaches the minimum at 16 mm of bolt diameter, and the dowel-bearing strength remains stable after 16 mm of the bolt diameter. The increase in the specimen thickness can enhance the ability of the specimen to oppose deformation. Comparing the two different arrangements of bamboo units, it is found that the strength and stiffness of the specimen with a horizontal arrangement (ZRT) are lower than those with a vertical arrangement (ZTR). Finally, a new formula to predict the perpendicular-to-grain dowel-bearing strength of side pressure LBL is reconstructed based on existing specifications.

Experimental evaluation of the dowel-bearing strength of laminated flattened-bamboo lumber perpendicular to grain

• The dowel-bearing characteristics of laminated flattened-bamboo lumber (LFBL) were tested. • The effecte of diameter, length, width, thickness and four kinds of arrangement method of flattened-bamboo panels was considered. • The applicability of different prediction formulas was evaluated, and the new formulas were proposed for predicting the dowel-bearing strength of LFBL. This paper examines the dowel-bearing strength of laminated flattened-bamboo lumber (LFBL) perpendicular to grain under the influence of the flattened-bamboo arrangement method, the bolt diameter, and specimen size in accordance with ASTM D5764-97a. There were 360 specimens tested in total. As a result of the test results, it was demonstrated that the arrangement method of flattened bamboo panels significantly affected the dowel-bearing strength of the LFBL. In two of the groups (bolt direction perpendicular to the grain), the dowel-bearing strength was significantly greater than in the other two groups (bolt direction parallel to the grain). According to the arrangement method of the bamboo panels, the size effect on dowel-bearing strength varies. However, the dowel-bearing strength always decreased as the diameter of the bolt increased. Four typical failure modes and load–displacement curves were classified. Results of the tests were compared with those calculated by predicting formulas from other studies, allowing empirical equations for predicting the dowel-bearing strength of LFBL specimens to be developed.

Performance evaluation of a wood treatment for connections with dowel-type bolts

Recent studies have shown the advantage of wood impregnation on increasing the dowel-bearing strength of black spruce wood by almost 50%. The aim of the present study was to improve the mechanical performance of a dowel-type connection through an impregnation method for black spruce wood. The results showed that wood treatments improved the mechanical performance of dowel-type connections. The dowel-bearing strength increased up to 25%, while the stiffness increased up to 52%. The increase obtained was lower in comparison with the previous studies, however. A lower polymer quantity, resulted in a shorter vacuum time, and a lower temperature polymerization used in wood treatment brought the process closer to an industrial application.

Dowel-Bearing Strength of Southern Pine Cross-Laminated Timber

AbstractThe current method for estimating parallel-to-grain dowel bearing strength of cross-laminated timber (CLT) fasteners applied perpendicular to the face in the US adjusts the length of the fa...

Effect of Exposure to Elevated Tempeture on Dowel Bearing Strength of Mass Plywood Panels

Design of connections in mass timber are critical. Mass plywood panels (MPP) are a relatively new mass timber product, therefore, only a few studies characterizing their mechanical and connection properties exist. Dowel bearing strength is a critical parameter required in connection design regardless of the complexity of the connection. This study investigated the dowel bearing strength of MPP under the effect of exposure to elevated temperature. Thirty-two exposure duration-temperature combination was tested along with control group. Two analytical models are developed to explain the thermal degradation, one assuming a mechanism based on first-order kinetics and the second using a statistical regression. The degradation in the dowel bearing strength with respect to the increase in time and temperature exposure was characterized. In general, the kinetics model seemed to explain the data better than MLR using one less parameter.

Bearing capacity of bolted-mortar infill connections in bamboo and yield model formulation

Bolted-mortar infill connections in bamboo structures are one of the most challenging aspects of the design and construction of these structures, due to the uncertainty in the evaluation of the connection strength. The shape of bamboo cross-sections (round, hollow and tapered) and the interaction between bamboo, mortar infill, and steel bolts or dowels are not clearly understood. Therefore, the main objective of this research was to develop an analytical method to estimate the strength of Bolted mortar infill (BMI) bamboo connections, based on the modified yield model theory (EYM). The proposed model consists of 5 controlling yield modes used to predict a BMI bamboo connection behaviour under load applied parallel and perpendicular to the fiber direction, based on the strength and geometry of materials. To validate the proposed model, a comprehensive experimental program that consisted of 112 tests for evaluating dowel-bearing strength on the Guadua bamboo, 126 test for determining bearing strength of the mortar filling, 61 test for evaluating bolt bending yield strength and 70 BMI connections were performed for 10 different configurations of dowel diameter and load angle direction. After calibration procedures, the model adequately predicted the connection strength for the different connection configurations with an average difference between the predicted and tested and Colombian National Code (NSR-10) values of 15.7% and 11.6%, respectively. In general, the predicted values of the proposed model, underestimate the connections capacity. This research aims to improve the design procedures and national regulations for BMI connections of Guadua Angustifolia Kunth and other bamboo species.

Effects of moisture content and load orientation on dowel-bearing behavior of bamboo scrimber

The influences of moisture content and load orientation on dowel-bearing behavior were investigated in order to understand the dowel-bearing behavior of dowel-typed fastener on bamboo scrimber. The half-hole embedment tests in compression were conducted with samples of equal characteristics with the same thickness, length and width, only with changes in the investigated factors. The result indicates that the effect of moisture content (MC) on initial stiffness is not significant. There is significant effect of MC on the dowel-bearing strength. The initial stiffness and dowel-bearing strength decreased first, then remained a constant value of 33.4 kN/mm for initial stiffness (with an average MC of 14.0%), 63.7 MPa for dowel-bearing strength (with an average MC of 21.2%), respectively. A linear regression for determining the relationship between the dowel-bearing strength and various MCs was proposed. The dowel-bearing behavior was affected by load orientation significantly. Hankinson’s formula could commendably predict the initial stiffness of arbitrary load orientations to the grain, but segmental Hankinson’s formula was satisfactory for estimation of dowel-bearing strength. The failure modes at various load orientations was complex because of the interaction between brittle and ductile failures. They changed from splitting to crushing when the load orientation changed from 0° to 90°. The study contributes to a safe and efficient design of dowel-typed joints in bamboo scrimber.

Determination of dowel-bearing strength of laminated bamboo at elevated temperatures

The Eurocode Yield Model to calculate the load capacity of dowel-type fastener connections is commonly adopted at normal temperature and in fire. The dowel-bearing strength of bamboo and timbers are required for the use of the calculation method. A total of 100 laminated bamboo specimens are employed to study the effect of temperature and grain direction on the dowel-bearing strength by the steady-state test method. With the temperature increasing from 20 °C to 250 °C, the embedding strength decreases gradually for both grain directions. But due to the evaporation of inherent water and glass transition of hemicellulose and lignin, the load-displacement curves of laminated bamboo have a turning point at 100 °C and 150 °C. For laminated bamboo perpendicular to grain, the embedding load rises linearly with the displacement, and a continuous increase is witnessed after yielding. And it shows obvious brittleness regardless of the increase in temperature. Four different typical failure modes have been observed, each two for one kind of grain directions. The yielding load of laminated bamboo is determined by the 5% diameter off-set method in different temperature ranges. By comparing different national standards and literature, the formula for embedding strength and the reduction factor with temperature are established at normal and elevated temperatures. This paper gives a valuable reference to calculate the bearing capacity of a dowel-type connection and predict structural performance under fire exposure.

Connection Performance of Mass Plywood Panels

Abstract Tall wood buildings have become more prevalent in North America in the past 10 years. Tall wood-frame buildings implement both mass timber construction and products. Mass timber products are wood-based products that can withstand and hold large loads for long durations of time. Mass timber has allowed for large buildings, which consist mainly of wood, to be erected comprising multiple stories. One new mass timber product that has been fashioned is Mass Plywood Panels (MPP). MPP is a veneer-based engineered wood product, which is a massive, large-scale, structural composite lumber–based panel designed for use in building applications as both a vertical and horizontal element. For any new product to be used in the industry with confidence, a thorough investigation of its physical, mechanical, and connection properties is needed. A series of connection tests, such as fastener withdrawal resistance, dowel-bearing strength, lateral resistance, and a component test on a wall-to-floor system were conducted. The lateral resistance test indicated that the current European Yield Models can be used to calculate the yield loads and yield mode of the MPP by using the dowel-bearing strength of plywood. Three different connection configurations were tested in two distinct loading directions—shear and withdrawal. Their performances are evaluated and compared using two existing engineering models—namely, the American Society of Civil Engineers 41-13 tri-linear model and the seismic analysis of wood-frame structures 10-parameter connection model.

Evaluation of ASTM D5764 Dowel Connection Tests for Laminated Veneer Bamboo (LVB)

Abstract The ASTM D5764 standard, Standard Test Method for Evaluating Dowel-Bearing Strength of Wood and Wood-Based Products, for testing dowel connections provides a procedure for measuring the dowel bearing strength of wood and wood-based products. Laminated veneer bamboo (LVB) is a new building product that is employed in similar sizes and applications as dimensional lumber. Being new, more research is needed to understand the key factors and fundamental failure mechanisms that occur in LVB dowel connections to help ensure safe standards for further LVB product adoption and design. This study develops three-dimensional bilinear finite element models for half- and full-hole specimens in accordance with ASTM D5764 when loaded in compression parallel to the grain. The models simulate LVB fracture initiation due to shear stresses in the dowel joint by incorporating frictional stresses in the contact region between a steel bolt and LVB. The model also predicts displacement at failure, which is validated through comparison with experimental results: the material fails at 1 and 1.18 mm displacement loading parallel to the grain for half- and full-hole specimens, respectively. It is found that, despite the higher load-bearing capacity (strength) of the half-hole specimen, both specimens fail at approximately the same displacement because of in-plane shear stresses. This article clarifies the complex interactive state of in-plane shear, tension perpendicular to the grain, and compression parallel-to-grain stresses using the Tsai–Wu failure criterion in the critical zone beneath the bolt hole for half- and full-hole specimens. These findings suggest that care should be taken to select a test method that captures the performance of LVB dowel joints because of different failure mechanisms that occur for full- and half-hole specimens.

Comparison of Parallel Dowel-Bearing Strength of Mengkulang, Kempas and Pine Glulam between ASTM D 5764-97a and BS EN 383: 2007

Dowel-bearing strength is a significant parameter for designing wood connection. The strength of timber connection can be influenced by the bolt diameter, wood grain direction either parallel or perpendicular, thickness of wood, moisture content and other parameters. The dowel-bearing strength test was conducted with a 12 mm bolt diameter dowel, for three different types of timber species, which were mengkulang (Heritiera sp.), kempas (Koompassia malaccensis) and pine (Pinus sp.) glulam. The dowel was placed parallel to the timber grain direction with a glue line at the center of the half-hole test. The 5% diameter offset load (F5%) for dowel-bearing strength (Fy) was determined by using the ASTM D 5764-97a whereas the dowel-bearing strength (Fh) was determined based on BS EN 383: 2007. The results of the three different types of wood showed that the Malaysian timber kempas and mengkulang were 51.740% and 32.966%, respectively, which were higher than the European timber pine. The results of the dowel-bearing strengths (Fh), which were based on the BS EN 383: 2007 gave higher values compared to ASTM D 5764-97a.

The Influence of Dowel-Bearing Strength in Designing Timber Pegged Timber Joints

ABSTRACTThe employment of timber pegs in timber structure joints is a widespread technology in the field of timber frame building in the United States, where the Timber Frame Engineering Council has published a special Standard to supplement the National Design Specification for Wood Construction. The authors have been studying the possibility of supplementing the Eurocode 5 design formulas, thought for timber joints with metal connectors, with specifications needed for a reliable design when employing timber pegs. The field of application envisaged is that of restoring timber structures and results obtained until now are quite encouraging. In this step of the research, more attention has been paid to deformation process: fir and chestnut samples have been tested to determine their dowel-bearing behavior with steel and ash timber peg while double-shear plane joints made of the same wood species, and fastened with steel as well as timber pegs, have been analyzed.

Restoring of timber structures: connections with timber pegs

A quite widespread methodology of restoration of ancient timber structures envisages the introduction of new timber elements, connected to the standing structure by a timber-to-timber joint. An efficient alternative to the most used jointing technologies, which employ metallic bolted plates, steel pins, or epoxy resin adhesives, could be the use of timber pegs, if reliable design formulas could be found in codes devoted to timber structures. The design rules currently available for pinned joints contemplate only steel connectors, involve mechanical characteristics of the dowel as well as of the timber elements constituting the joint and are based on Johansen’s theory. The present research has the target of verifying the applicability of this theoretical model, and of the derived design formulas, to the case of timber pegs. At this aim, an experimental research has been performed, devoting special attention to the description of timber peg behavior inside the double shear plane joint and of dowel-bearing strength of the base timber, when a timber peg substitutes the envisaged steel bolt. Obtained results were compared with theoretical ones, showing that the different nature of the material employed for the pins needs more specific evaluation of the mechanical properties to be inserted in design formulas. Moreover, as in the field of new building timber joints fastened by timber pegs are widely employed in prefabricated timber frame industry, contents of the design standard for those structures are also taken into account, especially with reference to the “effective shear” failure mode of the timber peg.

Impact of a reinforcement treatment with acrylate impregnation on the mechanical behavior of black spruce as connector member

As a previous study has shown, it is possible to increase by 50% the dowel bearing strength of black spruce with an acrylate formulation applied by impregnation. Three diameters of bolts and two orientations of loading were included in this study. The effect of treatment on the dowel-bearing strength appeared to increase while the diameter of bolt decreased. The orientation of loading was significant as the treatment had a major impact in the parallel to grain direction and no impact in the perpendicular direction. With the digital image correlation analysis, an expanded strain field perpendicular to the load direction was observed. The superior embedding capacity would help to reduce the dimensions of the timbers as well as the number of connections required in the building design. With an increase of ductility, wood connections show a safer yielding behavior.

Dowel-Bearing Strength Behavior of Glued Laminated Guadua Bamboo

AbstractBamboo is an excellent eco-friendly construction material because of its high renewable rate, embodied energy, reduction of pollution, high strength-to-weight ratio, and low cost. However, the use of round bamboo is limited because of its variations in dimensions, properties, and composition and the difficulty of making connections. Laminated bamboo has the potential to overcome these difficulties. Therefore, its mechanical properties and the behavior of the connections need to be established. In this research, the dowel-bearing strength of glued laminated Guadua angustifolia Kunth bamboo is experimentally determined under nail and threaded bar fasteners with different diameters and in different loading directions. A three-dimensional FEM computational model is developed with excellent agreement with experimental results. It was found that, similar to wood, the bearing strength depends on both the diameter and the specimen width-to-diameter ratio. The local behavior of the zone under the fastener ...

Studies on the Evaluation of Dowel-Bearing Strength for the Manufacture of Skin Timber

A skin timber is a type of wooden structural member that is circular or square in cross section and that has an inner hole that is approximately 90% the width of the external measurement. It can be the best choice for building large–scale wooden structures of the sort that have been in increasing demand in Korea recently. In the United States and Canada, single–family houses and some apartment houses are generally of a wood– frame construction. According to a survey (KFRI, 2007), however, Korean people tend to prefer the post–and– beam type of house with exposed structural members because of the sentimental appeal of traditional Korean– style houses. According to the report, ‘The research on the future of Korean–style wooden building,’ conducted by the Korea Forest Research Institute (2007), both suppliers and consumers (63.3% of suppliers and 98.3% of consumers) prefer the post–and–beam construction with exposed very large–scale structural members to building with light wood frames, as with the 2–by–4 method of construction and pre–fabricated methods. One potential solution is the use of skin timbers. The structural members used in the post–and–beam method of construction are required to have high structural performance of connection. It is the bearing strength of the members that determines the structural performance of connection. Therefore, in this study, we performed experiments on with non–bored and bored small clear samples in order to determine the bearing strength of the bored specimens compared with the non–bored specimens and to determine the difference in performance between them as a function of the load direction. Once large–scale skin timber is made, a similar evaluation of bearing strength should be carried out on the full–size samples. We are developing the skin timber such as Fig. 1.

Effect of Interlocked Laminates on Fracture of Laminated Veneer Lumber in Dowel-Bearing Strength Test

Using the longitudinal and flexural vibration method, the Young's modulus and shear modulus of the interlocked laminated veneer lumber (LVL) with symmetric angle-ply laminates were measured by tapping ; in addition, the connection strength was tested with a drift pin. The measured mechanical properties of the interlocked LVL were consistent with those predicted by the so-called classical lamination theory ; further, it was found that the properties change to a great extent with the interlock angle (orientation angle of veneer) but do not vary with small changes in the interlock angle. The connection strength of the interlocked LVL was determined by a dowel bearing strength test (embedment strength test). The dowel bearing strength tended to decrease to a small extent with an increase in the interlock angle. While the Young's modulus decreased to a great extent for changes in the interlock angle exceeding 10 degrees, the initial stiffness obtained from the embedment stress-displacement curve decreased to a small extent with the interlock angle. The analysis of the curve after the yield point revealed that the stress increased (strain hardening) when the interlock angle was greater than 10 degrees. The connection properties tested with a drift pin depend on not only the Young's modulus of the main member but also its shear modulus ; further, the angle-ply laminates prevent the member from cracking due to its expansion after yielding.