The United States General Services Administration (GSA) has officially released a new update to their progressive collapse criteria titled, General Services Administration Alternate Path Analysis & Design Guidelines For Progressive Collapse Resistance, dated October 24, 2013. This document has been modified from previous versions to more effectively address leased as well as owned facilities.

Applicability
These Guidelines have been written specifically for professionals working on projects related to the planning and design of new facilities or major modernization projects. Applicability of the progressive collapse requirements are based on the Interagency Security Criteria (ISC) Physical Security Criteria’s Facility Security Level (FSL) of the building and the number of stories. These Guidelines are not applicable for facilities already designed for progressive collapse under previous GSA or UFC criteria.

For lower FSLs, no progressive collapse design is required, regardless of number of floors. The higher FSLs do require progressive collapse assessments for buildings that are 4 stories or taller. For the highest FSL, progressive collapse analysis is required regardless of the number of floors.

Two key features in the new document include:

• Changing from a threat-independent approach (as is utilized by the UFC 4-023-03 and the previous GSA progressive collapse documents) to a threat-dependent approach, and
• Removal of both tie forces and enhanced local resistance requirements.

Threat Dependent
Instead of a threat-independent approach, the new document takes “a flexible risk-based approach where requirements are driven by the security needs of the Federal tenant (s).” This approach focuses on reducing progressive collapse potential through two methods. The first is stopping failure of load-carrying elements through structural hardening for a given threat and the second is to reduce propagation of the damage without consideration of the cause of the event. In some cases, as approved by GSA Technical Representatives, hardening a structure can be utilized instead of the GSA’s Guidelines for certain FSL facilities.
Removal of Tie Forces and Enhanced Local Resistance
The GSA’s new guidelines do not include Tie Force methodology or Enhanced Local Resistance, rather an Alternate Path approach requiring the structure to bridge over loss location elements is required for higher FSL facilities.
To learn more about the new document, Click here to download the GSA PC Guidelines.