Need a book? Engineering books recommendations...

Return to index: [Subject] [Thread] [Date] [Author]

[SEAOC] LA Position on SMRF

[Subject Prev][Subject Next][Thread Prev][Thread Next]
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.WPDATTACHMENT


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

  

...