Delay Analysis Methods
Collapsed As-Built
Collapsed As-Built (CAB) removes a specific delay event from the real as-built schedule record and re-links the network around the gap, comparing the resulting hypothetical finish date to what actually happened.
Definition
CAB is a retrospective technique built entirely from as-built data -- the real dates things actually happened, not a projected model. To isolate one event's impact, the analyst removes that event's duration from the as-built record and re-links the activities around it as if the event never occurred, producing a hypothetical earlier completion date. The difference between that hypothetical date and the true as-built completion is the delay attributable to the removed event. Because it works from real historical dates rather than a forward-looking simulation, it avoids some of the criticisms leveled at prospective, model-based methods -- at the cost of depending entirely on how accurately the as-built record itself was kept.
Example
A 21-day rebar re-fabrication suspension is removed from the as-built foundation activity, and the network is re-linked around the gap -- shifting the hypothetical completion 21 days earlier than the true as-built finish, isolating that one event's impact.