Timber frame racking loads (BS6399) - Calculation of timber racking loads
Environment
British Standard
Wind hits wall panels at 90 degrees, at ground floor it assumes half the load transfers directly to the foundations via shear in fixings (nails and straps), so ground floor panels carry half ground floor load and all of the load from the upper floors. At first floor we are clear of the ground floor load and it assumes half the first floor load transfers directly to the first floor diaphragm via shear in fixings (nails and straps again), so first floor panels carry half of the first floor load and none of the ground floor load.
The calculation is about carrying the wind shear to foundations so the applied load at the lower floors exceeds the applied load at upper floors.
You can refer to ‘Timber Frame Housing - Structural Recommendations’, published by TRADA, for a full explanation and example.