STATIC HORIZONTAL LOADING TEST OF TRADITIONAL WOODEN FRAME BY DEFORMATION DISTRIBUTION CONTROL

Abstract

 In the design and seismic diagnosis / reinforcement of traditional wooden buildings in Japan, it has become mainstream to use the limit strength calculation for the evaluation of seismic resistance. In the limit strength calculation of a traditional wooden building with multiple stories, a method is often used in which the restoring force characteristics of the seismic elements of each story are evaluated as independent for each story, and the deformation angle of each story by earthquake is calculated. In the past studies, authors showed that hysteresis characteristics and failure modes are different by rigidity and deformation distribution of each story of 2 storied frames, and suggested that it is necessary to set the restoring force characteristics that appropriately reflect the rigidity and displacement distribution of each story for each building in the limit strength calculation.

 In this paper, authors have developed a loading system capable of giving an arbitrary deformation distribution to the top and the middle story of a 2 story framed structure, and report the results of a loading experiment using the system. The experiment was conducted on a framed structure with 1 span and 2 stories with Toushi-bashiras (continuous columns through 2 stories), with multiple deformation distributions set. In addition, two different types of connections, Hanasen and Komisen, were set for the connections between the columns and Sashigamoi (middle beam), and experiments were performed.

 The findings obtained as a result of this experiments are shown below.

 1 ) The result was obtained that even if the deformation angle of the 1st story was the same, the shear force of each story changed by the difference of the deformation angle between the two stories. The smaller the ratio of deformation angle of the 2nd-story to that of the 1st story is, the greater the reverse shear force generated in the Toushi-bashiras.

 2 ) The magnitude of shear force that column bears changes depending on the position of the column against to the loading direction.

 3 ) At the beam-column connections, it was confirmed that the moment of the connections and the axial force of the Sashigaoi differed depending on the deformation distribution of each story.

 4 ) It was confirmed that the type of collapse of the frame was different depending on the difference of connection type of the Hanasen and the Komisen. In particular, in the case of the Komisen type test specimen, a fracture mode due to the splitting of the column was observed. The failure mode of the Komisen type test specimen can be explained by assuming that the column fiber was cut into a notched state by the force just before the fracture, and the splitting was caused by bending fracture starting from the notch.

 From the above, it was confirmed in addition to the previous research that the failure mode and the restoring force characteristics of each story differed due to differences in the rigidity, displacement distribution and connection specifications of each story of the two- storied framed structure. In particular, it was confirmed that it is necessary to consider the differences in rigidity / displacement distribution and connection specifications of each story when setting the restoring force characteristics of each story in the limit strength calculation of a two- storied building with Toushi-bashiras.