Glossary

Ultimate design load is the maximum load a joint, fastener, anchor, or connection is required to resist at the “ultimate” (strength) limit state, after applying the applicable load factors to the expected service loads. In other words, it’s the factored demand used to check that the connection will not fail by yielding, fracture, pullout, shear, prying, tear-out, or other strength-controlled modes.

In practice, the ultimate design load is calculated from load combinations (dead load, live load, wind, seismic, pressure, etc.) using a design method such as LRFD/limit-state design, where service loads are multiplied by factors (e.g., 1.2D + 1.6L type combinations). That factored load is then compared against the connection’s factored resistance (capacity reduced by a resistance factor, or otherwise adjusted per the governing code/standard). The connection is acceptable when the available strength ≥ ultimate design load.

This is different from working load / allowable load, which is typically based on service-level loads and includes safety through safety factors rather than load factors. You’ll often see all three ideas in fastener/anchoring language: service load (working load) → ultimate design load (factored) → ultimate capacity/strength (tested or calculated failure load).