Seattle Seahawks Stadium.pdf by wangnuanzg


									                                                                                                            $100M or greater

                                                                                                                                                        Merit Award

                                                      Seattle Seahawks Stadium                                                                                     Seattle

                                                                                                                             Photo courtesy Michael Dickter, Magnusson Klemencic.

                                                                                                                                             Juror Comment
                                                                                                                               “The idea of isolating the
                                                                                                                                mass of the roof structure to
Photo courtesy Timothy Hursley.

                                                                                                                                resist lateral transfer loads in
                                                                                                                                seismic events reflects a real
                                                                                                                                sense of ingenuity by the
                                                                                                                                engineering team.”

                                            he Seattle Seahawks Stadium         Steel Innovations                            pylons and foundations. This also saved

                                  T         and Exhibition Center is a $430-
                                            million public-private develop-
                                            ment project. It incorporates a
                                            67,000-seat football/soccer sta-
                                  dium, a 201,800-sq.-ft exhibition hall, and
                                  a parking structure on a small site just
                                  south of downtown Seattle
                                                                                    First-Ever Seismically Isolated Sta-
                                                                                dium Roof. The stadium sits on liquifi-
                                                                                able soils in a high seismic zone. In the
                                                                                event of an earthquake, the site’s north
                                                                                end could move a foot to the north while
                                                                                the south end moves a foot to the south,
                                                                                potentially stretching or compressing the
                                                                                                                             more than $3 million in the construction
                                                                                                                                Special Hinged Columns Take Up
                                                                                                                             the Slack. With the potential for the roof
                                                                                                                             to move up to 2’ atop the dampers in the
                                                                                                                             pylons, “hinged columns” support the
                                                                                                                             roof around the back of the bowl to ac-
                                     The new stadium is located within the      roof up to 2’. Expansion/contraction due     commodate this movement.
                                  space envelope of the old Kingdome, but       to temperature could be 8” in the roof.         New “Slipped Nickel” Approach. A
                                  offers a new experience for spectators:       Special bearings known as “friction pen-     “slipped nickel,” approach to the roof
                                  two signature 720’ tied structural steel      dulum dampers,” allow the ground/            geometry was developed to simplify the
                                  arches support the stadium roof, and no       seating bowl to move independently           roof framing and connections. A uni-
                                  columns block views of the field, down-       from the roof during an earthquake, iso-     formly skewed stack of circular, parallel
                                  town Seattle, the water, or the mountains.    lating the roof from movement and po-        planes (the nickels) became the template
                                     The project was finished one month         tential damage. The ends of each 720’        for roof geometry, yielding a condition
                                  ahead of schedule and on budget. Even         roof arch rest on these dampers, located     where all roof beams are parallel and
                                  though the stadium has large roof sec-        within the roof support pylons. Each         equal length, and the roof deck is flat and
                                  tions and is located in a high seismic zone   damper supports 3 million lb of vertical     parallel. This simplified construction,
                                  on liquifiable soils, it cost 7% less on a    load. By decoupling the mass of the roof     shortened the schedule, and cut costs.
                                  per-seat basis than the last 13 NFL stadi-    from the rest of the building, it was pos-      Advanced Shaping Exercise Opti-
                                  ums constructed.                              sible to reduce the design forces on the     mizes Arch Curvature. A sophisticated

                                                                                                                              April 2004 • Modern Steel Construction
Photo courtesy Michael Dickter, Magnusson Klemencic.   Photo courtesy Corky Trewin, Puget Sound Digital.

   shaping exercise helped determine the               forms. Next, the dramatic steel arch was
   optimum funicular shape of the roof                 erected with 16 A-frame components.                 Owner
   arch. Funicular—or “rope-like”—refers                   Precision Post-Tensioning Controls              Washington State Public Stadium
   to the concept that between any two                 Roof Arch Deflection. Each tri-chord                Authority, Seattle
   points, a rope suspended will hang in a             truss is post-tensioned with 4.5 million lb         Paul Allen, Seahawks owner, Seattle
   naturally perfect shape under a given set           in 130 strands. This post-tensioned ap-
   of loads. This translates into an opti-             proach allowed the arches to lift off the           Architect
   mized stadium roof arch representing the            erection towers, and final vertical deflec-         Ellerbe Becket Architects & Engi-
   most economically efficient shape.                  tions to be precisely controlled.                   neer, Kansas City, MO
       Extensive Integration of Steel Detail-              Dramatic Seating Cantilever. To                 LMN Architects, Seattle
   ing into the Engineering Design Process.            bring fans as close as possible to the field,
   The structural steel detailer was incorpo-          the upper deck was cantilevered over the            Engineer
   rated as a part of the design team, which           lower deck seating. This creates the                Magnusson Klemencic Associates,
   allowed all the structural details to be in-        longest interior cantilever seating over-           Seattle
   dustrially “tested” (using 3-D CAD tools)           lap (56’) and the most intimate sightlines
   and included on the structural drawings.            in the NFL.                                         General Contractor
   This provided bidders more precise infor-               Advanced Vibration Analysis. Spe-               Turner Construction, Seattle
   mation than would normally be available.            cialized wind and vibration analyses
       New “Erection Structure as Final                were performed on specific elements of              Engineering Software
   Structure” Technique. The dramatic                  the stadium to meet performance objec-              SAP Non-Linear
   tied-arch roof comprises two separately             tives. The structural steel tower for the
   erected elements that work compositely              scoreboard—the first portrait-oriented              Detailing Software
   as one. The lower tri-chord truss was               board in an NFL stadium—was subjected               Tekla Xsteel
   built on the ground in seven pieces and             to a special vibration analysis for wind.
   lifted on three erection towers. It was             Vibration analyses also were performed
   then used as a staging platform for the             for the cantilevered seating deck to avoid
   remainder of the roof erection, eliminat-           the need for any costly supplemental vi-
   ing the need for additional erection plat-          bration-reduction technology.5

                                                                                                           April 2004 • Modern Steel Construction

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