Seismic Behavior of Balloon Frame CLT Shear Walls with Different Ledgers

Abstract

This paper presents experimental investigations on the seismic behavior of cross laminated timber (CLT) shear walls in a balloon frame configuration with various ledger assemblies attached at midheight. The tested system consisted of two seven-ply 191-mm-thick CLT panels with generic hold-downs, steel angle brackets, plywood surface splines, and nails as fasteners. A 2-story system was tested with a panel aspect ratio of 3∶1 with different steel and wood ledgers under monotonic and quasistatic reversed cyclic loading. Three ledgers were subsequently tested under vertical quasistatic monotonic loading to determine their remaining load-carrying capacity. The tests showed that the shear wall displacement was due to the rocking of the wall panels, which themselves behaved as rigid bodies with negligible in-plane deformations. When compared to the monotonic tests, the strength in reversed cyclic tests was up to 21% lower. The ledger did not impede the desired rocking behavior of the wall, nor did the rocking of the wall reduce the remaining gravity load-carrying capacity of the ledgers by more than 7%. Balloon-framed CLT shear walls can be detailed and designed using the Canadian standard specifications for platform-type construction.