PREDICTION METHOD OF SHEAR BUCKLING OF SHEATHED SHEAR WALLS WITH VARIOUS NAIL ARRANGEMENTS

Abstract

 The formula for calculating the maximum bearing capacity of sheathed shear walls is derived assuming that the yield strength of the nails determines their maximum bearing capacity. When sheathed shear walls have high bearing capacity, the maximum bearing capacity may be often determined by shear buckling or shear failure of sheets. The formula to calculate the critical shear buckling stress of sheathed shear walls with nailing along all edges of sheets by using regression analysis based from the calculation chart has been already proposed by one of the authors.

 

 It is danger when sheathed walls with high bearing capacity which are not satisfied with the specification of nail arrangement of shear walls are structurally designed, because there is no formula to predict the critical shear buckling stress of sheets which are nailed along two parallel edges or three edges for e.g. hanging walls, spandrel walls, inner walls, and floors.

 

 The formula for the shear buckling of walls whose all edges are not nailed was made, and its validity was confirmed by experiments in this paper.

 

 In the past studies, since there is only a calculation chart for the theoretical values of pined support along all edges, the formula for critical shear buckling stress of sheets with pined support along two parallel edges was derived by regression using the results of FEM eigenvalue analysis as the correct values. Regarding the shear buckling of pined support along all edges of sheets, the error between the FEM eigenvalue analysis results and the values obtained by the calculation chart are about 20%. Therefore, the FEM eigenvalue analysis results were used as the correct values when the formula of the critical shear buckling stress with pined support along all edges was derived by regression.

 

 When only one edge of sheets is not nailed, the theoretical value of the critical shear buckling stress can be estimated by the model for two parallel edges. Because the critical shear buckling stress for walls with only one free edge is much closer to that with pined support along two parallel edges than that with pined support along all edges.

 

 In the experiments, split failure along nailing on frames and shear failure of sheets were often observed at the shear stress much lower than the critical shear buckling stress calculated with the size of sheets divided by stiffing members. The current study empirically confirmed that the critical shear buckling stress of sheets with stiffing members which is influenced by split failure is twice higher than that without stiffing members.

 

 At present, it is not possible to estimate the strength of split failure of wood, so the specification of minimum nail spacing must be satisfied.