The SlottedWeb Steel Moment Connection

Transcription

1 The SlottedWeb Steel Moment Connection Seismic Structural Design Associates Jay Allen, S.E. Jay Allen President (602)President Jim Partridge, C.E. Jim Partridge Secretary & CFO Secretary & CFO (213)

2 What Is SlottedWeb Technology? The SlottedWeb structural steel seismic connection developed by Seismic Structural Design Associates Inc. (SSDA) has been approved for general use as a pre-qualified connection in Special Moment Frames (SMF) by the International Code council (ICC). The design, fabrication, and field inspection requirements for this connection is given in ER-5861, which may be down loaded from the ICC website ( This connection also satisfies the April 15, 1997 AISC Seismic Provisions for Structural Steel Buildings and its Supplements No.1 dated February 15, 1999 and No.2 dated November 10, A description of this proprietary connection is also shown in FEMA-350 "Recommended Seismic Design Criteria for New Steel Moment-Frame Buildings" and in FEMA-351 "Recommended Seismic Evaluation and Upgrade Criteria for Existing Steel Moment-Frame Buildings". The ICC approval includes seismic moment frame designs using either deep or standard columns without lateral column bracing. Moreover, no bracing of the beam at the connection is required. These exclusive assets derive from the SlottedWeb technology, which eliminates both the lateral torsional buckling mode and virtually all of shear in the beam flanges. The SlottedWeb connection technology and designs were developed by SSDA through an extensive privately funded research and development effort. These cost effective connections have gained widespread acceptance by structural engineers as demonstrated by their use in over 220 buildings including commercial office buildings, hospitals, schools, hotels, and residential structures. Approved for Use by: ICC, AISC, OSHPD to W36 x 393 #/Ft 1

3 Detail Notes Example 2

4 How Much Does the SlottedWeb Save? SlottedWeb (SW) vs. Dogbone (RBS) Connection 1. RBS moment frame beams are heavier than SW beams. This is because seismic lateral story drift controls the design of Special Moment Frames so that RBS beams, due to their reduction in stiffness, are typically one to two sizes heavier than SW moment frame beams. For example, in Reference (1) parametric studies were conducted on six-story two- and three-bay moment frames subjected to seismic base shears. Lateral story drift coefficients of the frames with and without RBS beams were compared. The frames with RBS beams were designed with a 40% reduction in their flange areas. When compared to frames without the RBS cuts, these flange reductions showed a 10.6% increase in story drift for the two-bay frame and a 10.3% increase in the story drift for the three-bay frame. 2. Fabrication of SW beams is more economical than for RBS beams. Only two web cuts are required for the SW beams whereas four flange cuts are required for the RBS beams. Moreover, web cuts involve the thinner web material than the thicker flange material. Additionally, no special surface preparation is required for the SW weld access holes, which may be flame-cut. 3. Field inspection of the connection weldments is significantly reduced. For the SW moment frame connections, the nondestructive testing rate for an individual welder or welding operator may be reduced from 100% to 25%, provided the reject rate is demonstrated to be 5% or less for the welds tested for the welder or weld operator. A sampling of at least 40 completed welds for a job shall be made for such reduced evaluation. (See Reference 2, Section 2) 1. Chambers, J.J., et al., "Effect of Reduced Beam Section Frame Elements on the Stiffnes s of Moment Frames", Journal of Structural Engineering, ASCE, March 2003, pp Engineering Report 5861, ICBO Evaluation Service, Inc., Whittier, CA, May 1,

5 Real-World Savings Estimates Below are steel bids from four independent steel fabricators for a project in Irvine, CA. Each fabricator priced the SSDA SlottedWeb TM moment connection as well as the Reduced Beam Section (RBS - a.k.a. Dogbone) and the ICF/Kaiser Moment Connection Detail. Building Size Location # Moment Frame Connections Office Tower 280,000 sq. ft. Irvine, CA 750 SSDA SlottedWeb Detail Contractor #1 Contractor #2 Contractor #3 Contractor #4 AVERAGE Cost per Connection $1, $1, $1, $3, $1, Design Fee $40, $40, $40, $40, $40, Connections Cost + Fee $793, $1,144, $1,153, $2,587, $1,419, Dogbone Detail Cost per Connection $1, $2, $1, $4, $2, Total Cost of Connections $1,161, $1,608, $1,315, $3,000, $1,771, Cost INCREASE over SlottedWeb $368, $463, $162, $412, $351, ICF/Kaiser Detail Cost per Connection $1, $2, $1, $4, $2, Total Cost of Connections $903, $1,617, $1,335, $3,183, $1,759, Cost INCREASE over SlottedWeb $110, $473, $182, $595, $340,

6 Completed SSDA Projects Yerba Buena Tower San Francisco 37 Stories 1.3 million Sq. Ft. 5

7 Completed SSDA Projects GAP Embarcadero San Francisco 15 Stories 400,000 Sq. Ft. 6

8 Completed SSDA Projects Hyatt San Diego San Diego 32 Stories 450,000 Sq. Ft. 7

9 Recent Testing for El Camino Hospital The following test results include A very significant factor of safety against failure Rotations to 5 and 6 radians Proof of very high shear carrying capacity of 970K for a W36 x 393 beam The attached OSHPD approval includes Deep Column use (>W14 columns) Beam size to W36 x 393 Beam span minimum at