Journal of Structural and Construction Engineering: Transactions of AIJ
In this paper, the new type of seismic retrofit method using CLT panels as shear walls is proposed. In this method, setting small CLT panels in RC frame and bonding each panel and panel to RC frame with epoxy resin, panels compose shear walls. The advantages of this technique are: There are less dust, noise, and vibration during construction; Light weight panels enable easy construction and short construction period; Light weight panels also cause small seismic force.
In this research, cyclic loading tests for 5 types of reinforced specimens and 2 types of plain RC frames as control were conducted. The stress analysis showed that the bond strength between CLT and RC and shear modulus of CLT in these specimens match the result of element tests. So the specimen strength could be divided into the RC frame strength and the CLT strength until the initial deformation. As the bond strength between CLT and RC was smaller than the shear strength of CLT, the specimens can be stronger by increasing the adhesive area.
A reduction coefficient is applied in usual design of multiple dowels type connections. The numbers of stiffeners in row is one of important factor to decide this coefficient. CLT drift pinned joint showed small orthotropy against in plane tensile load. Tensile tests of multiple drift pins joints were performed to evaluate the effect of array. Numbers of drift pins n in each specimen were same (n=12), but the arrangements were different (2 x 6, 3 x 4, 4 x 3, 6 x 2). Also the grain directions were parameters (0, 90 degrees). The reduction of initial stiffness and proportional limit load showed good agreement between theoretical prediction and experimental results.
Various kind of in-plane bending tests of cross laminated timber (CLT) with different shapes have been previously carried out. The results indicate that the bending strength of CLT loaded in plane reduces as the number of layer increases. To evaluate this lamination effect on in-plane bending strength of CLT, a computational model based on Monte Carlo method was developed. The estimated bending strength showed the same tendency.
Earthquake-resisting performance of glulam frame structure was evaluated by shaking table tests on a specially designed glulam “double cross shape” specimen composed of slotted bolted connection (SBC) system. By the first vibration test using sinusoidal wave, the specimen survived until 80% level of input waves without damage. After renewing SBC system, the second vibration test was done on a same specimen using the JMA-Kobe NS waves having a maximum acceleration of 816gal. The specimen survived until 100% level of input without damage but failed by the panel-shear when 120% level was inputted. Earthquake-resisting performance of glulam moment-resisting joints composed of SBC system was considered as satisfactory enough for ductile joint system, but improvement of panelshear of glulam member itself was recognized as a future research need.
The connectors for the CLT shear wall with drift pin joint were suggested. The wall composed of five layers Japanese cedar CLT, steel connectors and drift pins (diameter d = 16mm). The horizontal shear performances of the walls were evaluated by static experiment and 2D frame analysis. The experimental parameter was number and position of drift pins. Characteristic failure was shear failure on the border of the laminae. There were good agreement on initial stiffness, yield load and second stiffness between experiment and calculation.
The purpose of this study is to develop a high strength leg joint for shear wall made of small size cross laminated timber panel in a simple system. The joint of CLT in which steel plate was inserted in the central slit and fixed by high strength bolt at inside of short steel pipes was proposed. In order to grasp the failure mode and strength of CLT member, material tests on embedment and shear were carried out using small CLT blocks. The test results indicated that there is few reinforce effect by cross bonding of each lamina. It was concluded that the precise estimation of the strength of CLT member is important in order to develop the joint proposed in this paper.
In this study, glulam beams were strengthened by inserting compressed wood (CW) blocks into the precut rectangular holes with one-thirds of the beam depth from the top of the beams. This practice was to make use of moisture-dependent swelling nature of the compressed wood which was conditioned with the moisture content significantly lower than the ambient one. The test results showed that a pre-camber was produced in the mid-span of the beam reinforced due to expansion of the compressed wood blocks on the top part of the beam. As a result, significant initial tensile and compressive stresses were generated on both the top and the bottom extreme fibres of the beam, respectively. Subsequent bending tests revealed that the initial stiffness and load carrying capacity of the pre-stressed beams were increased significantly in comparison to the beam without pre-stressing.