ESTIMATION METHOD OF SHEAR STRENGTH FOR A SEMI-RIGID TIMBER FRAME WITH PLYWOOD WALL

Abstract

 Herein, the stress of a wooden semi-rigid frame containing structural plywood that is used to secure rigidity has been elucidated via static racking tests and numerical simulations. The assumed semi-rigid frame composed of structural plywood is 4–6 m wide, and a lag-screw-bolt is used at the joint. When structural plywood is combined with a semi-rigid frame, the behavior of the plywood due to pull-out affects the behavior of the semi-rigid frame at the column. In our previous report, the stress in such a case was determined. The contents of the report are as follows.

 1) The temporary allowable shear force of a wooden semi-rigid frame composed of structural plywood was calculated by adding the reduction coefficient to each temporary allowable shear force of the wooden semi-frame and the structural plywood.

 2) When the structural plywood was nailed directly, nailing it on the inside of the wooden column instead of the outside is more advantageous.

 

 Herein, our previous research was extended. The target was a gate-type wooden semi-rigid frame and column details adopted in real houses. Tests were conducted on a sample in which the nail was directly attached to the inside of the wooden column and on a sample in which plywood was installed on a wooden semi-rigid frame. Moreover, several numerical analysis simulations were performed and statistically analyzed.

 The following conclusions were obtained.

 1) If a plywood wall is nailed directly on a wooden column, the column is restrained by nails. As a result, the applied shear force at the same deformation angle is larger than the shear force of the un-nailed column.

 2) The shear force of the wooden semi-rigid frame composed of structural plywood can be calculated by combining the single wooden semi-rigid frame and the single plywood by multiplying the coefficients.

 3) If the wooden semi-rigid frame is directly nailed, the axial force of the plywood directly affects the wooden semi-rigid frame column. The yield of the Lag-screw-bolt accelerates at the same deformation angle. Therefore, limiting the deformation angle at the Lag-screw-bolt yield point is necessary.

 4) By securing the elongation of the Lag-screw-bolt and increasing the plastic region after the yield point, the limitation of the deformation angle can be eliminated.