Embedding strength in joints of fast-growing Argentinean Eucalyptus grandis with dowel-type fasteners. Analysis according to the criterion adopted by European standards

Abstract

The present paper reports on the results of an investigation regarding the determination of the embedding strength of sawn timber of Argentinean Eucalyptus grandis with dowel-type fasteners. The importance of accurately knowing this property has increased with the increasing demand for this material for structural purposes. An empirical research project with 294 specimens prepared for testing under the embedding action of rigid fasteners (nail, bolt and dowel) was carried out according to the procedures prescribed in EN 383 (2007). The results showed no significant influence of pre-drilling on the embedding strength for nailed joints, which is not in line with the European experience and the corresponding criterion adopted by the Eurocode 5 (2005). The characteristic values of the embedding strength estimated based on the timber density and by applying the corresponding equation from the Eurocode 5 (2005) for bolted joints were 45% and 176% greater than those obtained in this project for the specimens loaded parallel and perpendicular to the grain, respectively, and similar percentages were found for dowelled joints (45% and 126%). These results showed that the reliability of structural design may be strongly affected if the embedding strength of this timber species is estimated by following the procedures adopted by the Eurocode 5 (2005) for dowel-type connections. Lochleibungsfestigkeit von Vollholz ausEucalyptus grandis aus Argentinien. Analyse nach europäischen Normen Zusammenfassung Dieser Beitrag fasst die Ergebnisse einer Studie zusammen, in der die Lochleibungsfestigkeit von Vollholz aus Eucalyptus grandis aus Argentinien untersucht wurde. Das empirische Versuchsprogramm umfasste 294 Prüfkörper, die mittels steifen Verbindungsmitteln (Nagel, Bolzen und Stabdübel) nach EN 383 (2007) beansprucht wurden. Im Gegensatz zu der europäischen Erfahrung und dem entsprechenden Kriterium des Eurocodes 5 (2005) zeigten die Ergebnisse keinen deutlichen Einfluss der Vorbohrung auf die Lochleibungsfestigkeit von Nagelverbindungen. Die Abschätzung der charakteristischen Lochleibungsfestigkeit in Abhängigkeit der Rohdichte nach Eurocode 5 (2005) ergab Werte die 45 % und 176 % höher sind als die Ergebnisse dieser Untersuchung bei Beanspruchung in Richtung parallel bzw. rechwinklig zur Faser. Ähnliche Abweichungen wurden für die Stabdübelverbindungen gefunden. Diese Ergebnisse zeigten, dass die Zuverlässigkeit der Berechnung von Holzbauwerken stark vermindert werden kann, wenn die charakteristische Lochleibungsfestigkeit dieses Holzes nach dem Kriterium des Eurocodes 5 (2005) abgeschätzt wird.

Bolt-bearing strength parallel and perpendicular to the grain of four Indonesian hardwoods

“…This was different from the parallel-to-grain test where the graph pattern tended to flatten after reaching a certain load. This curve is in line with the curve obtained from the study of the wood-bearing strength perpendicular to the grain of Eucalyptus grandis [6]. The condition of the sample, in this case, experienced compaction at the bottom of the bolt so it gave a tendency to increase strength due to the compaction.…”

“…The condition of the sample in this case experienced compaction at the bottom of the bolt. This pattern was also shown in Eucalyptus grandis [6] and light and heavy red meranti wood where the specific gravity was 0.43 and 0.62 respectively [9]. Determination of the load used to calculate the bearing strength was based on the yield load determined by the 5% offset diameter method from the load-deformation curve of the test results.…”

“…Previous studies have shown that the formula contained in the referenced standard is more suitable for softwood than for hardwood [4,5]. Some studies on the dowel bearing strength using hardwood showed a lower value than the value found in the referenced standard [5][6][7][8][9]. Besides the limited hardwood database in formulating the standard, this is also related to the wood moisture content (MC) in the test, where usually test for tropical hardwood is carried out in air-dried MC conditions which are usually above 12% to 20%.…”

Resistencia al aplastamiento en madera de Populus x canadensis ‘Conti 12’ para uniones tipo clavija, en dirección paralela y en dirección perpendicular a las fibras

“…Existen trabajos de investigación previos sobre madera aserrada de bosques implantados en la República Argentina de álamo Populus deltoides 'Australiano 129/60' (Manavella et al, 2017), y también variedades de pinos (Manavella et al, 2012) y eucaliptus (Sosa Zitto et al, 2012), donde se presentan los valores obtenidos de la resistencia al aplastamiento en direcciones paralela y perpendicular a la fibra, la relación entre la variación de los valores de la tensión de aplastamiento en relación a la densidad y los diámetros de los pasadores y las curvas tensión de aplastamiento vs deformación. Para los casos de la madera de álamo y pino, se han comparado los valores de resistencia al aplastamiento experimentales con los presentados en el CIRSOC 601, observándose que los resultados de ensayo difieren considerablemente de los valores de referencia indicados por el Reglamento.…”

Evaluation of embedding strength on Uruguayan wood to apply the European yield theory for double shear bolted joint

“…On timber structures, the hold down connector [6] with bolted joints is generally used for a column base joint. Since there are few examples of joint experiments using EGH [7], it is necessary to verify the shear capacity of the bolted joint and, whether the calculation of its yield strength based on the European yield theory [8] (EYT) is applicable or not.…”