Alternate Load Path
Definition
A route by which loads can be redistributed around a failed element without causing progressive collapse. Its presence or absence is central to the ASCE 7 robustness assessment.
- Concept
- Load redistribution after element failure
- Governing standard
- ASCE 7 structural integrity provisions
- Absence leads to
- Progressive collapse
- Field
- Structural failure investigation
Common questions
What is progressive collapse and how does load path relate to it?+
Progressive collapse is a chain reaction where the failure of one structural element overloads and fails adjacent elements in sequence, and a structure with a viable alternate load path can shed the lost element's load onto neighboring members instead of triggering that chain.
How does an investigator use this concept after a partial collapse has occurred?+
The investigator traces which members carried load before failure, identifies whether a redundant path existed to redistribute that load, and evaluates whether its absence, or a connection detail that could not develop it, explains why the collapse spread rather than stopping at the initiating failure.
Related terms
- 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...
- Tie-Force Method
- A prescriptive design approach requiring minimum tensile continuity across connections so that elements can hang or span around a failed support rather...