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SSDA Files Patent Infringement Suit Over Unauthorized Use of Structural Steel Seismic Connections in Building of Constellation Place

Construction engineering firm Seismic Structural Design Associates, Inc. (SSDA) has filed a patent infringement lawsuit alleging that a structural engineering firm has used its patented award-nominated SlottedWeb(TM) structural steel seismic connection in building construction without authorization.

The SlottedWeb connection is a cost-effective, structurally important design that has become the standard for earthquake resistant construction. Washington, DC-based law firm Venable LLP will represent SSDA in the patent action. The suit, filed yesterday in Los Angeles federal district court, charges that WHL Consulting Engineers, Inc. and its Principal, Lauren D. Carpenter, Ph.D. have engaged in various infringements of SSDA's patented designs, including at Constellation Place, a high-rise property designed by architect Johnson Fain Partners, developed by JMB Realty Investment Partners, and built by Hathaway-Dinwiddie Construction with steel subcontractor Herrick Corporation.

The suit seeks actual and enhanced money damages, and a preliminary and permanent injunction prohibiting WHL and Dr. Carpenter from using SSDA's patented designs. The SlottedWeb connection, which was nominated for a 2002 NOVA Award for innovation in the construction industry, works to improve the popular but fundamentally flawed pre-Northridge earthquake field-welded, field-bolted beam-to-column moment frame connection. Longitudinal slots are cut to separate beam flanges from the beam web in the region of the connection, and the beam web is welded to the column flange. These changes dramatically alter the force, stress, and strain distributions to make the connection cost effective for both new and retrofit construction.

There are two other designs that also fix the pre-Northridge flaw, but both are significantly more expensive than the SlottedWeb.

The SlottedWeb connection has been approved for general use as a pre-qualified connection in Special Moment Frames (SMF) by the International Code Council (ICC). It also satisfies the April 15, 1997 Seismic Provisions for Structural Steel Buildings of the American Institute for Steel Construction (, as well as its Supplements No. 1 dated February 15, 1999 and No. 2 dated November 10, 2000. A description of the SlottedWeb connection is also shown in widely disseminated publications of the Federal Emergency Management Agency (, such as 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."

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