This is a task order in the general research indefinite delivery, indefinite quantity (IDIQ): technical support services for the Hazard Mitigation team. Enabling a steel truss structure to use alternate load paths during an attack, as with many seismic design or retrofit details, is intended to prevent total or, at least, immediate collapse. Although the physical functions are different, the objectives of both seismic and counterterror designs are to limit the damage and to allow rapid repair, if possible, rather than total replacement. The focus of this Task Order will be methods to provide or improve the alternate load path (ALP) function in surviving members, specifically on steel truss bridges (which often lack redundancy). Providing an alternate load path is one of four countermeasure types used to meet this general objective. The others are inertial resistance, strain energy absorption, and momentum transfer. For any ALP being developed in this task order, the other types of countermeasure may be present as secondary effects.
- Assessment of steel truss bridge existing members' ability to provide full or partial Redundancy/Alternate Load Paths (ALPs) to prevent progressive collapse from blast loads or member cutting.
- Assessment of currently used seismic retrofit designs' ability to provide ALPs to prevent progressive collapse of Steel Truss bridges from blast loads or member cutting.
- Initiate development of bridge retrofit components to provide full or partial redundancy/alternate load paths to prevent progressive collapse of steel truss bridges caused by local blast failure or by cutting of individual members.