Analytical framework for the design of multi-storey platform-type CLT shear walls incorporating floor-wall interaction

The lateral design provisions implemented in CSA O86-24 for cross-laminated timber (CLT) shear walls are derived for a single storey. Applied storey by storey to multi-storey platform-type walls, they omit the inter-storey coupling through tension straps or hold-downs, the contribution of the shear brackets at the wall top, and the rotation of the floor and its interaction with the wall segments. In this paper, a storey-level design procedure is presented that accounts for these mechanisms while preserving the format of the code expressions. The rocking stiffness of each storey is extended by two modified connection stiffness terms, and the interactions are embedded through two rotation ratios, floor-to-wall and wall-to-wall, for which representative design values are tabulated by panel count and storey position. The procedure, verified against finite element models of four-storey walls with two to four panels under two gravity load levels, predicts the storey rotations within 8%. Comparison with the CSA O86-24 procedure on the same configurations shows that the code overestimates the wall rotation at the intermediate storeys, increasingly with panel count and gravity load, with the dominant share of the discrepancy stemming from the floor-wall interaction and inter-storey coupling that a single-storey procedure cannot represent. The proposed procedure closes this gap with the same inputs as the code expression plus the two tabulated ratios.