What are drag loads?
Drag loads are due to lateral (horizontal) loads generated in high-wind or seismic events. These loads are generated within the structure and transferred into load carrying elements (like drag strut trusses, shear walls or roof diaphragms) which then transfer the loads to the foundation and then safely into the ground. Therefore the loads must be calculated by the building designer (usually required to be a structural engineer in seismic areas on the West coast) based on the expected environmental loads and the configuration of the structural elements. WTCA does not have any information on calculating drag loads, but the location, magnitude, and direction of these loads should be provided by the building designer. Another point to consider, load transfer from the structure to the drag truss is only as good as the connector used. Proper connector detailing and installation is required for the drag truss to perform as expected.
