SGER: Critical Appraisal of Research Needs for SMF Connections in Steel Buildings

SGER: Critical Appraisal of Research Needs for SMF Connections in Steel Buildings; CMS proposal 0335718 PI: Linda Hanagan, Penn State University

Following the 1994 Northridge earthquake, unexpected damage was discovered in steel moment connections. To address this substantial safety issue, the Federal Emergency Management Agency (FEMA) funded the SAC Joint Venture, which produced the FEMA 350-series guideline documents, state of the art reports and other publications. Subsequently, theses findings have been incorporated into the building code requirements for new buildings. Since the publication of these guideline documents, the American Institute of Steel Construction (AISC) has formalized as requirements many of the recommendations made for steel building design and construction through the ongoing development of the consensus standard Seismic Provisions for Structural Steel Buildings (AISC, 2002). In this way, work is ongoing to incorporate the lessons learned from the Northridge earthquake into the building code requirements for new buildings.

Because the FEMA 350-series documents are not consensus standards, the recommendations contained therein must undergo an adoption process. Presently, the Seismic Provisions for Structural Steel Buildings (AISC, 2002) define the beam-to-column connection requirements for classification as a special moment frame. The essence of these requirements is to provide not only adequate strength, but also adequate ductility. Conformance with this requirement can be satisfied in one of two ways: by testing or by using a connection 'prequalified' in accordance with Appendix P of the Seismic Provisions. To alleviate the need for project based testing, AISC, through its Connections Prequalification Review Panel (CPRP), is in the process of developing a consensus standard. This standard is expected to be modeled after FEMA 350 in that it will outline design, detailing, and fabrication procedures for several connections that are considered prequalified without further testing. The premise is that adequate testing and evaluation has been conducted for a range of typical connections such that they can be included in the consensus standard. In fact, the hope was that the recommendations of FEMA 350 could be adopted in their entirety with some minor modification. Since the publication of FEMA 350, many of the recommendations contained therein have been brought into question by the Structural Engineers Association of California (SEAOC) and others. With the exception of RBS connection, every other connection (WUF-W, FF, WFP, BFP) have received an unfavorable rating in the SEAOC Commentary. The CPRP will seriously consider the concerns raised by SEAOC and others. Currently, task groups within the CPRP are reviewing the FEMA 350 recommendations and the supporting data for conformance with prequalification requirements set forth in the Seismic Provisions (AISC 2002). Without immediate investigation into some of the critical concerns, it is very possible that the first edition of the prequalified connections standard, which will effectively govern all steel moment frame construction in seismic areas, will contain only the RBS connection. After so many resources were dedicated to this topic, this would be a very unfortunate and unnecessary result for the building industry.

PROPOSED RESEARCH

Because most of the SAC Joint Venture research was done in parallel, the research on individual connections did not have the benefit of retrospective analysis. With some exploratory funding the PI's role as a CPRP member can be extended to accomplish three additional objectives: 1) Review existing literature and test data for the possibility of extrapolating connection specific results to other connections. Accomplishing this objective may have the result of more connections being included in the AISC connection prequalification standard. 2) Develop a set of current research needs as identified through the work of the CPRP and the PI. As one of the members of the CPRP, the PI is in a somewhat unique position to identify research required to expand the AISC standard to include more of the FEMA 350 recommended connections. 3) Formulate a research proposal, to be submitted under the NEES Consortium program, to address some of the critical research needs identified under goal #2.

SGER JUSTIFICATION

This research can be characterized as having 'severe urgency' in that accomplishing the objectives is dependant on the deliberations of the CPRP, which have already begun. It is expected that the work conducted under the proposed research initiative will have a nearly immediate impact on the development of the AISC prequalification standard. Without the tangential focus afforded by the proposed research, it is possible that much of the work on conections other than the RBS will be rendered useless by the CPRP until further investigation is conducted.