Tie-Force Method
Definition
A prescriptive design approach requiring minimum tensile continuity across connections so that elements can hang or span around a failed support rather than triggering progressive collapse.
- Type
- Prescriptive structural design approach
- Requirement
- Minimum tensile continuity across connections
- Purpose
- Let elements span or hang around a failed support
- Prevents
- Progressive collapse spreading beyond the initial failure
Common questions
How does a failure investigator use the tie-force method after a collapse?+
The investigator checks whether the as-built connections actually provided the code-required tie forces, since a collapse that spreads far beyond its initiating failure often traces back to a tie or connection that was undersized, omitted, or degraded before the event.
How does tie-force design differ from an alternate-load-path analysis?+
Tie-force design is prescriptive: it specifies minimum connection strengths without modelling the full structure. Alternate-load-path analysis instead removes a specific element in a model and checks whether the remaining structure can carry the load, a more direct but more computationally demanding check.
Related terms
- Alternate Load Path
- A route by which loads can be redistributed around a failed element without causing progressive collapse. Its presence or absence is central...
- As-Built Drawing
- A drawing that records what was actually constructed, as opposed to the approved design drawing. Discrepancies between the two are a common...
- Collapse Mechanism
- The kinematic sequence of element failures that produced the observed final geometry of the collapse, reconstructed by investigators from wreckage patterns and...
- Load Path
- The route forces travel through a structure from their point of application to the ground. When one element fails, loads redistribute onto...
- Progressive Collapse
- A failure mode in which local structural failure triggers a sequence of failures in adjacent members, resulting in collapse disproportionate to the...