In this study, DOL of structural timber and the clear wood and DOL of modulus of elasticity of wood were investigated. The dimension lumber of Spruce-Pine-Fir of Grade No. 2 and Grade No. 3 and the small clear specimens of the same species of the dimension lumber were used to conduct the short-term and the long-term bending test. The short-term strength distributions of the dimension lumber and the small clear specimens were obtained. The long-term tests were conducted under constant environmental conditions for 18 months. The sample matching technique was used to estimate the short-term strength of the specimens that underwent long-term tests. It was found out that there is virtually no difference in DOL between different grades or quality of lumber and no difference between structural timber and clear wood, and DOL obtained from the test of this study is more in agreement with Wood’s curve. A threshold stress ratio of about 0.55, loaded above which the wood began to experience strength loss, was revealed from the test. Making use of the threshold ratio concept, the DOL of wood can be obtained not only from failed specimens under load in the process of the long-term loading, but also from the ramp loading test of the specimens that survived the long-term test. Sustained load also poses DOL on the modulus of elasticity of wood, though to less degree than DOL of strength of wood.

The lateral resistance of dowel-type connections with CLT is related to its lay-up, species of the laminations and even the manufacture method. Treating the CLT as homogeneous material, current methods develop new equations through test results or make use of the existing equations for the embedment strength already used in design codes; thus, the lateral resistance of dowel-type connections of CLT can be calculated. This kind of approach does not take the embedment stress distribution into account, which may lead to inaccuracy in predicting the lateral resistance and yield mode of the dowel-type connections in CLT. In this study, tests of the bolted connections and the screwed connections of CLT were conducted by considering the effects of the orientation of the laminations, the thickness of the connected members, the fastener diameter and strength of the materials. The material properties including yield strength of the fasteners and embedment strength of the CLT laminations were also tested. Using analysis of the dowel-type connections of CLT by introducing the equivalent embedment stress distribution, equations for the lateral resistance of the connections based on the European Yield Model were developed. The predicted lateral resistance and yield modes were in good agreement with the test results; the correctness and the feasibility of the equations were thus validated.

The calculation method for buckling capacity of cross-laminated timber (CLT) under axial load with one-way members has been investigated and incorporated into design codes worldwide. However, the load may only be applied to a part of the CLT members. In this case, the available calculation method for buckling capacity is not applicable. To solve this problem, a 3D numerical model was developed to study the buckling behavior of axially loaded CLT members. After being validated by comparison with experimental results, the model was used to investigate the buckling capacity of axially loaded CLT members with different aspect ratios and bearing length ratios. The CLT members all consisted of three layers. The thickness of the CLT members was 105 mm, the width ranged from 300 mm to 2100 mm, and the height ranged from 1400 mm to 3500 mm. It was found that the unloaded part of CLT served as constraints to the loaded part. The longer the unloaded part, the stronger the constraint was. The buckling capacity increased with the increase in bearing length ratios. An equivalent width method (EWM) was proposed; i.e., the partially loaded CLT member was replaced by a fully loaded member with an equivalent width, which can be determined by the proposed formulas. It was found that the proposed calculation method is reliable and simple to apply. This study supplies the missing calculation method for the buckling behavior of partially loaded CLT members and helps to promote the engineering application of CLT members.