In the past study, we conducted compression tests with laminated veneer lumber of Japanese Larch. We observed the deflection and strain behaviour. As a result we could evaluate the bucking strength with Euler’s equation and Tetmajer’s method. For structural design we should expand the versatility of that method. Three wood species for structural members would be selected for these tests. Those were Japanese larch, Japanese cypress and Japanese cedar. For the test parameter, we set the 8types of slenderness ratio for the compression test and we conducted monotonic compression tests with pin-supported on both edges. For the mechanical properties we conducted compression tests with short column members and got yield compression for those materials. In the compression tests, we could see the bending deflection. We would get the ratio the maximum strength and yield strength for distinguish the limited slenderness ratio. As a result it was cleared that the limit slenderness ratio of these wood species was 100. And we could confirm that the Tetmajer’s method is useful for evaluation the yield strength.
In this paper, bending behaviours in hybrid composite glulam timbers reinforced using deformed steel bars and epoxy resin adhesives (RGTSB) are presented. The technique RGTSB was developed in order to improve flexural stiffness and strength in glulam timbers...
We developed a one-hour fire-proof glulam made of Japanese cedar and got the authorization as abuilding material from the Minister of Land, Infrastructure and Transportation. We also succeeded to give one-hour fire performance to cross laminated timber (CLT) using the same concept. The both structures consist of three parts which are load-bearing part, fire-die-out part and surface part. Therefore, we challenged two-hours fire-resistive glulam using the same concept. We used not only drill but also CO2 laser as an incising for lamina of fire-die-out parts and impregnated the fire retardant evenly for diffusion. The main reason to use drill is that the handling of CO2 laser is not so easy for glulam manufacturer. Comparisons of fire-performance between fire-die-out parts whose lamina were incised by drill and CO2 laser, and finger jointed load-bearing part made of Japanese cedar and larch were also achieved using the same glulam whose fire-die-out part is 90 mm in total thickness. The fire test was achieved in a furnace in accordance with a standard heating curve by ISO 834-1. Though this glulam failed two-hours fire performance by a little char and discoloration, we could know the difference in incising method and density of load-bearing part.
For a cross-laminated timber (CLT) manufactured using Sugi, a digging test was performed by changing the number of layers, the laminar configuration, the direction of the outer layer laminar with respect to the direction of the pressure plate, and the arrangement of the test piece with respect to the load direction, and each combination was performed. In addition to clarifying the sunk strength performance of CLT, a method for easily evaluating the sunk strength performance was examined. As a result of the sinking test, it was found that the parameters that determine the sinking strength performance are the direction of the outer layer laminar and the arrangement of the test piece, and the number of layers and the laminar configuration do not contribute much to the sinking strength performance. When the proportional limit stress of CLT was estimated using the proportional limit stress of each laminar, the estimated value and the measured value were in relatively good agreement.
Creep and duration of load characteristics of cross laminated timber (CLT) were evaluated from the test results of creep and duration of tests. Japanese Ceder (Cryptomeria japonica) was chosen for the specie for the laminations of the test specimens and API was chosen for the adhesive. The results are summarized as follows: (1) The creep factor [i.e. (Initial deflection + Creep deflection) / Initial deflection] for CLT was evaluated to be 2.0 and was almost equivalent to the creep factor commonly known for solid lumber. (2) The duration of load factor [i.e. Strength for 50 years duration of load / Strength for 10 minutes duration of load] of CLT was evaluated to be 0.66 and was almost equivalent to the duration of load factor measured for solid lumbers.
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.
Field tests of untreated and preservative-treated glulam beams in outdoor exposure, in ground contact and above ground, were inspected for decay after five years. Copper azole and ACQ-D-treated material was in excellent condition, while moderate to severe decay was present in untreated non-durable material. Early stages of decay were also noted in yellow cedar glulam in the above-ground test. Using galvanized rather than stainless steel fasteners appeared to have a protective effect against decay in untreated material, supporting the hypothesis that zinc from the sacrificial coating on galvanized bolts inhibits germination of basidiospores.
Hybrid composite glulam timber reinforced using deformed steel bars and epoxy resin adhesive (RGTSB), was significantly developed in Kagoshima University. In this paper, new experimental data on structural behaviour of CLT-to-the RGTSB composite beams is presented. Two full-scale simply-supported beams were tested under four-point flexural bending in elastic or until destructive. The beam composite sections were built up of a top flange part made of CLT slab and a web part made of RGTSB rectangular section. The CLT slab and the web part were mechanically fastened using thread self-tapping screws. Experimental parameters of the specimens are the arrangement of the steel bars in RGTSB beams, the thickness of the slab, and the spacing pitch of the screws.
Glulam members which are manufactured with Japanese cedar plantation timber are constructed into a box type of portal frames to investigate the moment-resisting performance when subjected to a lateral load. The joints of the frame are connected using aluminium connectors and self-tapping screw fasteners, and the placement of fasteners on the connection are arranged into three patterns. The loading protocol is applied laterally in seven cyclic stages for the racking test. The maximum lateral load of 51.4 kN is attained for the portal frame fastened using self-tapping screws arranged in square pattern, followed by single circular pattern and double circular pattern. Resulted dissipated energy obtained from the portal frame with square pattern placement is 1224.2 kNmm during the cyclic loading stages, higher than the other fastener arrangement by 20%. The allowable shear strength of the box-type portal frame is decided by the load corresponding to the shear deformation of 1/120 radian.