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[SEAOC] LA Position on SMRF[Subject Prev][Subject Next][Thread Prev][Thread Next]
- To: "'seaoc(--nospam--at)seaoc.org'" <seaoc(--nospam--at)seaoc.org>
- Subject: [SEAOC] LA Position on SMRF
- From: Shafat Qazi <seaoc-ad(--nospam--at)seaoc.org>
- Date: Tue, 9 Apr 1996 20:12:15 -0700
- Encoding: 156 TEXT
March 26, 1996 CP-2 TO WHOM IT MAY CONCERN: COUNTY OF LOS ANGELES CURRENT POSITION ON THE DESIGN AND CONSTRUCTION OF WELDED MOMENT RESISTING FRAME SYSTEMS GENERAL The publication of SAC Interim Guidelines(FEMA 267) in August 1995 was a major milestone in the SMRF recovery effort. The document provided guidance on engineering procedures for modification and design of SMRF structures to this date. While it is the County's position to continue supporting the SAC effort and the County considers the SAC Guidelines the best document to date on the SMRF issue, clarification of the County's position is necessary for current and future projects. Research into the behavior of these structures is continuing. This memorandum is to provide up-to-date information as the result of the County's continuing and active effort to resolve the SMRF crisis for County projects. A Technical Advisory Panel(TAP) consisting of experts in the design, research, and quality assurance of welded steel construction was invited to assist County engineers in meeting the SMRF challenge. Members of this panel are identified in the attachment. COUNTY'S POSITION ON SMRF Welded special moment resistant frame systems are not allowed unless the connections proposed meet the following three requirements and are submitted to and approved by the County: a. Three full size prototype specimens of the configurations to be used shall have passed full-scale cyclic loading tests and demonstrated plastic rotational capacity equal to or greater than 3.0% radians. b. Inelastic finite element analysis to demonstrate that the behavior of prototype test specimen can be duplicated. c. A clear and complete design methodology for all the components of the joint assembly especially where extrapolation of the test results will be necessary for the design. The County's and TAP's extensive review of any connection systems is required and will consist of examining the submitted documents and test results, meeting with the proposer, and TAP issuing recommendations and reports to the County. The TAP's reports are issued by the Construction Quality and Contracting Division as TAP SMRF-Bulletins. It is recommended that the TAP SMRF-Bulletins be used to compliment the SAC Interim Guidelines. FACTORS CONSIDERED RELEVANT TO THE BEHAVIOR OF SMRF CONNECTIONS The following factors are considered relevant to the performance and/or reliability of a connection system and therefore of the structural system. These factors should be considered when evaluating any connection system: 1. Configurations of Connection: Two-sided Strong-axis Dual-strong-axis Weak-axis and Skewed-axis Effect of Bracing Members Effect of Concrete Slab Effect of Perpendicular Gravity Framing: 2. Major Contributing Factors to the General Behavior of Connections: Through-thickness Strength of Column Flange Column Panel Zone distortion Location of Plastic Hinge Shorter Spans/Amplified Rotation Angle Axial Load on Column Axial Load on Beams Beam Material Strength Column Material Strength Variation of Column Depth b/t Ratio of Column Flange b/t Ratio of Beam Flange Connection Plate Thicknesses Rolling Direction of Connection Plates Weld Sizes, Configurations and Fit-up 3. Extrapolation of Test Results - Methods and Justification 4. Construction and Quality Assurance: Construction Sequence Erection Fit-up Welding Materials and Methods Size of Welds Notch-toughness of Weld Weld Finishing (e.g. Grinding, Removal of Backing etc.) For comments or questions regarding the contents of this memorandum and/or TAP SMRF-Bulletins, please contact Y. Henry Huang, Supervising Civil Engineer III, Construction Quality and Contracting Division at (213)738-2832 or by fax at (213)386-4818. Very truly yours, HARRY W. STONE Director of Public Works THOMAS V. SCHRIBER JOHN B. KELLY Division Chief Superintendent of Building Attach. TVS:YHH cp-2/C:\HH96\TAPSHORT.WPDATTACHMENT TECHNICAL ADVISORY PANEL MEMBERS: Mark Saunders, SE (Chairman) Vice President, Rutherford and Chekene Consulting Engineers, San Francisco, CA. Director, Structural Engineers Association of California, 1993-1995 Vice President, Applied Technology Council Chairman, Technical Sub-committee 6 on steel, "National Earthquake Hazard Reduction Program (NEHRP) Recommended Provisions for the Development of Seismic Regulations for New Buildings" SAC Guidelines writer for new buildings chapter Karl Frank, Ph.D. Secretary/Treasurer, Research Council on Steel Connections Professor of Civil Engineering, University of Texas at Austin Egor Popov, Ph.D. Professor Emeritus of Civil Engineering, University of California, Berkeley Bob Schwein, CE Principal, Schwein/Christensen Laboratories, Inc., Lafayette, CA. SAC Guidelines writer for welding, testing, metallurgy and inspection chapter ...
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