木造軸組の初期傾斜が土塗り壁のせん断耐力と建物耐力に及ぼす影響

The damaged mud walls and inclined columns are found commonly in very old houses such as traditional wooden houses. In case of the seismic strengthening works of these houses, however, the inclined columns are often not restored because of a higher cost and wall clay are applied to the damaged mud wall with inclined columns. In such cases, it is not clear about the failure mode and P-Δ effect on the strength. In the present study, in-plane shear tests were performed on mud walls with inclined columns, and the failure mode and P-Δ effect on the strength are verified. In addition, numerical computation with 3D frame model of the houses was conducted in order to verify the effect of the inclined columns on the seismic strength of the houses in the large deformation area.The configuration of the specimen is shown in Fig. 1, and the parameter of specimens are given in Table2. Specimens 1-1 and 1-2 are the standard specimens with normal frame and Specimens 2 and 3 are the specimens with inclined columns. The ultimate deformation states of Specimens 1-2 and 3 are shown in Photo3 and Fig. 3. In all specimens, the cracks were observed along the penetrating beams called Nuki in 1/100 rad and a part of wall clay was taken off in 1/50 rad. As the results, there was no significant differences in failure mode among the specimens. The relationship between the load and drift angle is shown in Figures 4 and 5. In Specimens 2 and 3 with inclined columns, the load decreased rapidly as the drift angle increased because of the negative shear force due to the P-Δ effect. In addition, the inclined columns were found to be sunk into the base by cyclic loading (see Fig. 7) because of the stress concentration, verified by 3D FEM Analysis using LS-DYNA, a general-purpose FEM analysis program (see Fig. 10).The analytical model of a one-story house is shown in Fig. 19. A total of 2 models, Model -1 is the house with no inclined columns and Model -2 is the house with inclined columns, are constructed. The detail of the analytical model of seismic walls is shown in Fig. 15. The model is separated into 2 parts, one is the column-beam frame with mud walls which is taking account of the shear force and the bending deformation of the joint between column and beam, and the other is the rigid frame which is taking account of the P-Δ effect. Wallstat, which is the collapsing simulation program for wooden structures based on the Distinct Element Method, is used for the analysis because the P-Δ