However, FEMA has made an exception to that policy in recognizing the unique situation presented by the inspection of welded steel moment frame connections that potentially can have brittle fractures. These connections typically are covered with architectural finishes and occasionally are protected with asbestos or other fire retardants. These coverings add complexity to an inspection of such connections. Because of the numerous incidents of structural damage to welded steel moment frames (WSMF) caused by the Northridge Earthquake, it was necessary to establish a policy by which FEMA would determine the eligibility of funding for inspection, evaluation and repair of this damage.
A multi-year study of the welded steel moment frame fracture issue has resulted in recommended criteria to the technical community for (a) evaluation of steel moment frame buildings affected by strong earthquake ground shaking to determine if they have been damaged, and to what extent; (b) identification of those buildings that have been so severely damaged that they constitute a significant safety hazard; and (c) repair of damaged structures such that they may safely be restored to long term occupancy. These results are published in Recommended Post-earthquake Evaluation and Repair Criteria for Welded Steel Moment-Frame Buildings, Federal Emergency Management Agency, FEMA 352, July 2000. FEMA 352 provides the technical base for this policy.
The revision of RR #9524.1, Welded Steel Moment Frame Policy, August 17, 1999, will be made following FEMA's normal coordination procedure. That policy was based on FEMA 267, Interim Guidelines: Evaluation, Repair, Modification and Design of Welded Moment Frame Structures, August 1995, which is now out-of-date. The revision of RR #9524.1 will replace the recommendations of FEMA 267 with those of FEMA 352.
This Interim Policy is being issued at this time because the revision of RR Policy #9524.1 will take too long to be responsive to the Nisqually Earthquake recovery and because FEMA 352 provides the best current technical information.
FEMA has identified two potential cost impacts caused by the publication of FEMA 352. These impacts are a consequence of the changes between FEMA 267 and FEMA 352 and do not reflect changes in policy. The potential cost impacts are assessed below:
First. Physical indications that require the search for damaged welded moment frame connections are similar in FEMA 267 and FEMA 352 but not identical.
Second. In the selection of the number of connections to be inspected in the search for damaged connections, the minimum number of connections has been increased slightly. However, whenever significantly damaged connections are found, FEMA 352 recommends that, for an exterior moment frame, 9 additional connections rather than 4 additional connections be inspected, and, for an interior moment frame, 13 additional connections rather than 12 additional connections be inspected. For a severely damaged building the change in cost will be small, but for a minimally damaged building the cost increase may be significant.
The currently published national policy on welded steel moment frame buildings (RR #9524.1) included a discussion of the use of mitigation measures under Section 406 of the Stafford Act. That topic is not being addressed in either the planned revision to RR #9425.1 or in this interim policy for the Nisqually Earthquake recovery. Instead, proposed mitigation measures for welded steel moment frame buildings, as all other public assistance grant program mitigation measures, will be evaluated under the provisions of RR #9526.1, Hazard Mitigation Funding Under Section 406 (Stafford Act).
Visual inspection of additional connections (at locations recommended by FEMA 352, following the discovery of damaged connections) will also be eligible for reimbursement, but only after FEMA has been informed of the frame damage already discovered, and a PW for the follow-on inspection has been approved. The PW may also authorize non-destructive testing if the visual inspections indicate a significant potential for concealed damage.
Last Modified: Friday, 28-Apr-2006 11:34:00 EDT