| Design and construction team: Owner: U.S. Army Corps of Engineers Architect: Joint Venture Team Comprised of HDR, Inc. and Dewberry Structural engineer: HDR, Inc. Connection technology Consultant: SidePlate Systems, Inc. General contractor: Joint Venture Team Comprised of Turner Construction and Gilbane Building Co. Fabricator: Banker Steel Company Erector: L.R. Wilson & Sons, Inc. |
HDR, Inc. and Dewberry teamed together to design this new 9-story environmentally friendly Community Hospital complex that will be a signature landmark for the area, thanks to the latest in steel frame connection technology. A structural steel frame structure was selected over reinforced concrete because of its faster construction schedule, greater cost efficiency, reduced foundation costs, and because of its easier accommodation of complex building forms. When completed in the spring of 2011, this state-of-the-art 120-bed healthcare facility will provide primary and secondary-level care in more than 1.2 million square feet of floor space.
HDR, Inc. performed the structural engineering for this new Hospital. The structural engineering team faced two major challenges—the two extending wings on the main body of the hospital with very limited room for any lateral load resisting elements, and compliance with vertical tie force requirements for progressive collapse mitigation per the USACE’s Unified Facilities Criteria (UFC) Design of Buildings to Resist Progressive Collapse, UFC 4-023-03. While these building configuration challenges would clearly not be a ’piece of cake’ when designing to typical building code criteria for natural hazards such as earthquake and extreme wind, they in fact would introduce even greater and unique complications to the design of a federal healthcare facility which must also address malevolent threats; in particular direct bomb blast attacks and subsequent progressive collapse load conditions.
The architects developed a column grid layout to optimize the functional design and future flexibility of the hospital. As such, it was determined early on that the lateral load resisting system would consist of a steel moment frame, as is commonly used in healthcare facilities. Because of the limited quantity of columns available in the extended wings of the main hospital, it became extremely difficult to provide enough lateral stiffness in the steel moment frame system using traditional steel beam-to-column welded moment connections to control the lateral story displacements induced by the IBC/ASCE 7 building code prescribed wind forces.
In addition, there were several locations throughout the building where it physically was not possible to satisfy the vertical tie force requirements as prescribed by the UFC due to the presence of several transfer girders precluding the columns from going all the way to the ground level. In order to satisfy the progressive collapse design criteria at these locations, the UFC allows the use of the Alternate Path (AP) method "to prove that the structure is capable of bridging over the deficient element." AP typically requires the use of moment connections and can result in deeper and heavier frame beams in order to minimize the large beam and column rotations. Upon recognizing these impediments, a decision was made by HDR’s Structural Engineer to change design direction by investigating the latest advances in steel frame connection technologies capable of multi-hazard mitigation, in order to retain the advances achieved by the building’s architectural design.
SidePlate Systems was contacted to see if they could help. The wide range of design freedoms and connection stiffness provided by SidePlate steel frame connection technology, as well as the extremely high joint rotational capacities demonstrated in the recently completed GSA full-scale blast and progressive collapse testing, would prove to be ideally suited for resolving all of the project’s steel frame design challenges, while still allowing the use of smaller/lighter beams and columns compared to the those required with a traditional moment connection. Even more surprising, the design of the building using this proprietary connection technology would prove to be more economical than the design with traditional moment connections. Collectively, the technical and cost efficiencies of the SidePlate system would ultimately become the winning combination to rescue and fulfill the project’s architectural design excellence and provide the client with a higher level of protection.
The joint venture construction team comprised of Turner Construction and Gilbane Building Co. awarded the structural steel contract for the project to Banker Steel Company of Lynchburg, Va. Banker developed unique rotating fixtures in its shop for mass production of the column trees, capable of allowing each of the fillet welds in the SidePlate connection to be easily accessed and deposited in the flat or horizontal position for both speed and weld integrity.
The construction of the SidePlate connection system uses all shop fillet-welded fabrication, configured with simple unrestrained fillet welds for increased reliability and robustness of all critical connection welds affecting connection performance. Fillet welds require only visual inspection. All fillet welds are made in either the flat or horizontal position using column tree construction for maximum quality control. Shop fabricated column trees and link beams are then erected and joined in the field using standard AISC/AWS erection tolerances with CJP welded flanges and a bolted web to complete the moment-resisting frame. It should be noted that during construction of the fifth and final building of this project, SidePlate Systems introduced their latest innovation to the marketplace called SidePlate FRAME. This resulted in the elimination of the field beam-to-beam CJP welding because the frame beams are now full-length, and joined to the side plates with six bolts and four horizontal fillet welds. According to Banker Steel, using SidePlate FRAME on the final building would have resulted in a 33 percent reduction in shop labor and an even faster completed steel erected time. Though the fast-track nature of this project precluded the implementation of SidePlate FRAME on the final building, it is now being implemented on numerous government and non-government projects throughout the country.
Throughout this project, the SidePlate Connection Technology has been able to accommodate multiple architectural and mechanical challenges. SidePlate is very beneficial to the dynamically changing design which continues even during the construction phase of the project.
Michael G. Paczak, P.E., is with SidePlate Systems, Inc., in Laguna Hills, Calif. He can be reached at 800-475-2077. Learn more at www.sideplate.com.
