Bracing with steel straps

How it works

Steel strap works in tension: in compression it buckles immediately and carries nothing. So it always goes in crossed pairs — one diagonal takes the wind from one direction, the other takes it from the opposite.

The bracing forms a truss inside the wall: the studs and tracks give the frame, the diagonals give the stiffness.

The critical points

The end connection

The capacity of the strap is almost never limited by the material of the strap but by the connection: the number of screws, tear-out of the sheet, the edge distance.

That connection is a design task — it cannot be solved with “a few screws”.

Tightness

A slack strap only starts working once the structure has already moved. That brings two problems: larger displacement, and dynamic loading on the connection. The strap has to go in taut.

Continuity

The strap has to run right across the braced bay and arrive at real restraint at both ends — at the anchorage point.

Anchorage

The bracing takes the force down into the foundation. Strong bracing is wasted on weak anchorage. Hold-down anchorage.

Advantages and limits

Advantage

Cheap, little material, takes up no room in the build-up and does not disturb the insulation.

Limit

It only works where there is enough continuous wall length for the diagonal. On a façade broken up by many openings it is hard to find room for it.

That is where sheathing bracing comes in, using the whole wall surface. Sheathing diaphragm.

What this pushes back onto the design

The position of the bracing bays is a floor-plan question. If the plan does not offer enough continuous wall length in both directions, the bracing has to be solved more expensively. So bring the structural engineer in at concept design. Concept design.

The point

Steel strap is the cheapest bracing, but it only works taut, in pairs, and with both ends genuinely held. The fault is always at the ends.