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Rolling shear properties of cross laminated timber are important mechanical properties for its structural application. To evaluate the influence of technical characteristics such as edge-gluing and gap size in the cross layers, on the measurement of rolling shear modulus and strength of cross laminated timber, three-layer spruce-pine-fire cross laminated timber shear block specimens with and without edge-gluing, with gaps of 2 mm, 4 mm and 6 mm, were tested by a modified planar shear test method. The mean values of rolling shear strength and modulus of No. 2 visual grade spruce-pine-fire cross laminated timber were 1,32 MPa and 111 MPa with coefficients of variance of 20% and 28%, respectively, regardless of technical characteristics. The characteristic rolling shear strength of all groups of three-layer cross laminated timber specimens was determined to be 0.88 MPa. The results indicated that the rolling shear strength and modulus values used in current design practice of spruce-pine-fire cross laminated timber were conservative. It was found that edge-gluing and gap size had a significant influence on measuring rolling shear strength rather than apparent rolling shear modulus by the modified planar shear test method. With the gap size larger than 2 mm, its influence on measuring rolling shear strength became negligible. The three major initial failure modes identified for the cross layer regardless of technical characteristics were rolling shear failure along the growth ring, tension perpendicular to grain failure in wood pith and tension perpendicular to grain failure along the wood ray.

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.

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