Akihisa Kitamori

Evaluation on structural performance of compressed wood as shear dowel

Abstract This study addresses the application of compressed wood (CW) made of Japanese cedar, as a substitute for high-density hardwood, to shear dowel. A double wood-to-wood shear test was performed to evaluate the mechanical shear properties of CW perpendicular to the grain, and the results were compared with those of several types of dowel material. CW with its annual ring radial to loading direction (0°) had a unique double shear performance characteristic, and showed good properties as a dowel material by virtue of its strength and rich ductility. In contrast, CW with its annual ring tangential to loading direction (90°) and maple exhibited brittle failure. While thickness of the base member was varied, the ductility of the joint became stable for diameter over 36 mm and 24 mm thickness for the main and side members, respectively. When the density of the base member increased, its stiffness, yield load, and maximum load exhibited proportional improvement with different inclinations; however, in the case of a maple dowel, the increases were small. When the density of the base member was increased, the ultimate load had positive linear tendency, whereas plastic modulus decreased. Consequently, almost constant energy absorption was observed in spite of the increased density. The optimum load-carrying capacity and ductility of a compressed wooden dowel joint could be designed by introducing an appropriate base member.

Traditional Javanese Wooden Houses (Joglo) Damaged By May 2006 Yogyakarta Earthquake, Indonesia

A post-earthquake survey was performed on Joglo Javanese wooden houses, seriously affected by the May 27, 2006, Yogyakarta earthquake in Java, Indonesia. Investigations on 20 damaged Joglo buildings reveal that the structures damage can be classified into three categories: slip between columns and stone foundation, broken joints between outer ring beam and column, and collapse of core structure. Four damage levels were defined: I) damage on the base joint of side structure, II) fatal damage on the side-structure, III) destroyed core structure, and IV) totally collapsed core structure. The side structure turns out to be relatively weak, while the core structure is able to secure the structural performance of Joglo buildings. A distinct relationship was identified between the levels of structural damage and the area ratio of core structure and the main column projection. It was verified that structural proportion significantly contributes to the assessment of damage. The joint failure represents a significant point in terms of maximum retention for conservation. Based on a damage level approach, an assessment methodology to optimize reinforcing strategies. This study gives recommendations for the preservation of such precious structures from future earthquakes, while avoiding inappropriate interventions.

Development of a joint system using a compressed wooden fastener I: evaluation of pull-out and rotation performance for a column—sill joint

Compressed wooden plates and dowels were used to connect members in post-and-beam structures as a substitute for a steel fastener. In order to take advantage of the characteristic properties of compressed wood and to achieve optimum joint performance, two compressed wooden plates were used in each joint to give multiple shear planes for each compressed wooden dowel. Consequently, this type of joint showed very good properties in pull-out and momen-trotation performance, and its engineering design could be further optimized. This joint is expected to be introduced to many kinds of structural systems, including long-span frame structures made of domestic timber found in Japanese residential houses.

Development of a joint system using a compressed wooden fastener II: evaluation of rotation performance for a column-beam joint

In the present study, a plate and a doweled fastener made of compressed wood (CW) were newly introduced into a moment resisting column-beam joint system for a small portal frame structure. A mechanical model that contains not only an axial spring, but also a rotational spring, considered resistant factors to verify how each element resists rotation. Theoretical performance was compared with experimental data. Consequently, the mechanical model was shown to be suitable and the combination of resisting factors was found to be very effective; i.e., the rotational spring provides more influence on the stiffness and moment compared with the axial spring. Large moment and ductility can be achieved by virtue of the high embedding performance of the CW plate in the rotational spring, accompanied with the high shearing performance of the CW dowel in the axial spring.

Performance of Shear Wall Composed of LVL and Cement Fiber Board Sheathing

Abstract In this study, an experiment on shear walls has been carried out to determine structural reliability; this is necessary information for practitioners when constructing non-engineered houses or earthquake-resistant residential buildings. Analytical and numerical analyses have also been conducted, to establish an appropriate method to estimate the performance of this kind of structure that can be used in the future. A 3D specimen made of a Laminated Veneer Lumber (LVL) structural frame sheathed by Fiber Cement Board (CFB) with shear wall elements embedded in the wall without openings, termed Type 36 hereafter, was tested in the study. Static push and pull cyclic load was applied at the top of the specimen to simulate the seismic load. The study found that the Non-Engineered earthquake resistant Type 36 house needs two shear wall panels without openings; these walls act as structural elements, to resist seismic force, at the zone with the highest risk of earthquake in Indonesia. The structural system consisting of wood and cement-based building materials, shows sufficient resistance to earthquake, and so the shear wall panel can be used as a structural element in houses and earthquake-resistant residential buildings.

Relationship between clamp force and pull-out strength in lag screw timber joints

This study empirically examines the relationship between clamp force and pull-out strength in lag screw joints of timber members, using data obtained in tightening tests and pull-out tests. Maximum clamp force per unit screw length as determined from the tightening tests was lower than the lower bound for the 95% tolerance range for pull-out strength per unit screw length as determined from the pull-out tests. Moreover, X-ray CT (computed tomography) observations of anchor members from both tests revealed that failure behavior clearly differed between the tightening test and the pull-out test: tightening caused damage to the wooden, female thread in addition to major splitting damage in the wood perpendicular to the grain near the tip of the lag screw.

Propose Alternative Design Criteria for Dowel Type Joint with CLT

The load carrying capacity of dowel type joint in Cross Laminated Timber (CLT) was derived based on the Johansen’s yield model. The steel plate inserted drift pin joint with CLT (5 layered; thickness of laminae were same in one CLT, all of laminae were orthogonally arranged) was chosen as the specimen. Stiffness and nonlinear load - deformation relationships were calculated by numerical analysis using Rigid Body Spring Model (RBSM). Estimation showed the good agreement with the tensile test results on the joints.

EVALUATION FOR LATERAL SHEAR PERFORMANCE OF PREFABRICATED MUD SHEAR WALL (PMSW)

This research was performed to evaluate the shear performance of prefabricated mud shear wall (PMSW) which was developed to introduce more vigorously into the modern timber house with appropriate modification. In order to precisely investigate the performance of PMSW, relative relationship between rotational and shear behavior of mud in side of frame was considered with the parameter of number of screw. Consequently, PMSW-2 and PMSW-3 which are fixed by 16 and 24 pieces of screws for one PMSW unit showed high performance compared to the CMSW. On the behavior of mud unit for shear deformation of timber frame, rotation of mud was dominant until yielding of wall at both CMSW and PMSW, then yielding of whole was occurred along with shear yielding and failure of mud.