Embedment Strength of Cross-Laminated Timber for Smooth Dowel-type Fasteners

Abstract

Embedment strength is a significant property in the dowel type connection in timber structure, i.e. cross-laminated timber (CLT). The CLT design properties are different from those of sawn timber (ST) and glued-laminated timber (GLT) because of the orthogonal structure, which may particularly have influence on the design of connections. The layup feature, i.e. the thickness ratio of transverse layer (TRTL) was considered as an effective factor on CLT embedment strength in this study, except for other factors, i.e. wood density, smooth dowel diameter, and loading angle. Approximate 660 embedment tests were performed according to ASTM D5764 half-hole test method. A few of existing design models for CLT embedment strength were evaluated using experimental data. It was found that different factors had different effect tendency and each factor had statistically significant impact on CLT embedment strength. The embedment strength and failure modes of CLT were obviously different from those of GLT due to the existence of transverse layer in CLT. The existing design equations should be improved. Based on the test results, a new design equation was proposed which had better prediction.

Embedding strength of fully-threaded dowel-type fasteners in cross-laminated timber: an experimental study

“…When analyzing the trend lines, a decrease in the embedding strength was observed as the dowel diameter increases in both directions. The same pattern was observed by DONG et al [14,32]. Figure 5 shows the relations between the solid timber embedding strength and the dowel diameter, in direction 1 (Figure 5a) and direction 2 (Figure 5b).…”

“…Results calculated according to the equation proposed by KENNEDY et al [31] show significant agreement with the embedding strength in direction 1, being the biggest difference observed for diameter of 6 mm, when the calculated value was 7.0% lower than the mean value of the test. [32] considers a decrease of embedding strength as the dowel diameter increases, however this is greater than decrease observed in the tests and that from BLASS and UIBEL [28] method. The embedding strength in direction 1 calculated according to DONG et al [32], showed in Table 5, was conservative only for diameter of 16 mm.…”

“…Initial research on the CLT embedding strength was conducted in Germany by BLASS and UIBEL [28] and Uibel and Blass [29,30].After, KENNEDY et al [31], in Canada, and DONG et al [14,32,33], in China/Canada, also researched the topic. Several embedment tests on CLT specimens were accomplished in these research projects, and based on the experimental results, the authors developed empirical equations to determine the embedment strength.…”

“…Recently DONG et al [14,32,33] also investigated the embedment behavior of dowel-type fasteners positioned perpendicular to CLT panel. Experimental tests were carried out in accordance to ASTM D5764-97a [35] half-hole test method, using smooth dowels with diameters of 10 mm, 12 mm and 14 mm, loaded 0º, 45º and 90º to the grain of outer layers.…”

“…4) for the embedment strength derived by a nonlinear regression analysis. According to DONG et al [32], the thickness ratio of transverse layer statistically influences the embedment strength and cannot be neglected. (4) Where: d = dowel diameter, in mm; ρ 12 = density at 12% moisture content, in kg/m³; tt = thickness ratio of CLT layers loaded perpendicular to the grain; α = loading angle relative to the grain of the outer layers, in degrees.…”