Abstract
Diaphragm need to have high in-plane strength and stiffness of shear walls to perform in structure. However, it is difficult to regard timber diaphragm as rigid due to characteristics of timber structures. Considering this background, there are a lot of studies about in-plane performance for timber diaphragm. However, few studies have focused on the in-plane performance of CLT diaphragm, which has become popular in recent years. There are generally two types of CLT diaphragm. One is the diaphragm sheathed with CLT panels on floor frame. The other is the diaphragm constructed by only CLT panels jointed without floor frame. There are some data about the former diaphragm; some studies showed the in-plane performance obtained by experiments and analysis. On the other hand, the study about the latter is not found. Thus, it is necessary to clear in-plane performance of the CLT diaphragm without floor frame. In the present study, we discussed about in-plane performance of the CLT diaphragm without floor frame, modeling method to predict in-plane performance and the effect of joints performance on the in-plane performance.
Chapter 2 showed the experimental outline and the results about the lateral loading test of the full scale CLT diaphragm to clear in-plane performance. It is shown that in-plane performance of CLT diaphragm is higher than timber diaphragm nailed thick plywood considered to have high performance. The effect of the shear behavior on the rotational behavior was observed at the boundary position of each CLT panel.
Chapter 3 showed the experimental outlines and the results about the joint tests to get their seismic performance of joints were used on CLT floor. In this chapter, it was focused on the shear performance of spline joint, the tensile performance of metal plate, in particular metal joint STF (χ mark), and the compression performance of CLT-to-CLT.
In Chapter 4, mechanical model based on mechanism to resist lateral load of CLT diaphragm was proposed. The model was validated as a predictor of in-plane performance and local behavior.
Finally, in Chapter 5, the effect of the structural performance of joints on the in-plane performance of CLT diaphragm was discussed by parametric study. The shear performance of joint (Asp), the tensile performance of metal joint (Amp) and the pitch of shear joint (Ap) were dealt as parameter in the study. On the whole, the higher Asp and the lower Ap were, the higher in-plane performance was. Focus on the effect Amp. The influence was small even though Amp was higher, in case of shear yield occurring. On the other hand, in case of bending yield occurring, the influence was big. In particular, the influence of Amp on yield force was big. If tensile performance of metal plate was short, yield force of diaphragm decreased and the effect of Asp became less. Therefore, the importance of tensile performance of metal plate was shown. In addition, focus on the stiffness, specification of joint to regard CLT diaphragm as almost rigid was shown. The specification can be obtained by comparing the torsional stiffness with KθUL derived from specification of joint of CLT diaphragm.
