Do wind tower anchor bolts always carry all horizontal base shear?

The short answer

No. Horizontal base shear can be transferred through designed friction, a shear key, anchor action or an assessed combination. The correct mechanism depends on the connection geometry, contact force and detailing. Assuming that anchors carry all shear can misrepresent their demand, while assuming friction alone can overlook uplift or loss of contact.

Identify the shear path on the drawing

Follow the horizontal action from tower steel to plate, grout or key, then into concrete and ground. A shear key needs its own bearing and concrete load path; it is not merely a positioning feature if structural resistance is credited.

For anchors, hole clearance and the way load reaches the rod influence engagement. A loose fit does not necessarily distribute shear equally among all anchors at the first movement.

Check the concurrent compression and tension

Friction depends on the applicable normal contact force and interface assessment. Overturning or uplift can reduce contact, so a dry dead-weight friction estimate may not represent the governing case.

Where anchors carry shear and tension together, both actions need the relevant interaction assessment. Adding separate maximum resistances from different mechanisms can be misleading if they require different displacements or rely on the same limited concrete region.

Coordinate the selected mechanism with construction

Request an explicit statement of which components resist shear and how installation tolerances are accommodated. The detail should remain buildable without field welding, hole alterations or unassessed shims.

If the intended key or contact detail is omitted, the load cannot simply be assigned to the anchors after construction without redesign. Primary base-connection tests demonstrate several possible mechanisms; they do not identify which one is used by a particular MARSTON tower or supply a universal friction coefficient for its foundation.