TENANT SHELL SPACE HVAC-MECH

TENANT SHELL SPACE

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CORRIDOR

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SEISMICJOINT

REMAININGEXISTING STRUCTURE

NEW 2-STORYBUILD BACKSTRUCTURE

DEMOLISHEDPORTION OFATCT & T2

NEWMECHANICALFLOOR & ROOF

ONGOING TSAOPERATIONS

SFO TERMINAL 2 BUILD BACK AND RETROFIT

SEAONC/SEAOC 2020 EXCELLENCE IN STRUCTURAL ENGINEERING AWARDS

The San Francisco International Airport (SFO) Central TerminalBuilding (CTB) was dedicated in 1954 as the airport’s main terminal. Theupper floors of the CTB were transformed into an administrative officebuilding in 2000. In 2010, the flight operations portion of the CTB wasseismically retrofitted and remodeled into the current Terminal 2 (T2),recognized as the country’s first LEED Gold certified airport terminal. The CTB’s six-story concrete structure housed over 600,000 squarefeet, including the airport's original Air Traffic Control Tower (ATCT).Following completion of the new ATCT in 2016, SFO hired TurnerConstruction, AE3 Partners/Woods Bagot Joint Venture, and SimpsonGumpertz & Heger (SGH) to execute a $45 million design-build projectthat included demolition of the original control tower and upper fourstories of T2 and the “build back” of two stories above the existingstructure. The new two-story structure is programmed to accommodateairline lounges, office space, café, and exterior observation decks ateach end of the building. TSA screening for T2 is located directly belowthe “build back” at the 2nd level, which presented a major designchallenge as TSA could not be affected during construction. Advancedanalysis techniques and innovative connection detailing were necessaryto prove that the existing building and foundations could meet currentbuilding code requirements considering changes in design loads andminimal existing structure capacities. The new space was designed withsteel special moment frames (SMF) using SidePlate connections thatresulted in lighter beam and column member sizes and minimizedoverturning forces resulting from seismic loads. T2 now stands as a harmonious union between old and new at thegeographic center of SFO, prepared to serve the 5.5 million passengersthat will pass through its doors annually.

OVERVIEW SMF COLUMN BASE DETAIL

The SMF column bases are designed to emulate a pinnedconnection, minimizing moment demands on existing steelcolumns originally designed to resist gravity loads. Theintricate connection transfers shear forces through lug plateassemblies at the column flanges, compression forcesthrough bearing plates/grout, and tension forces through asplice connection between new and existing columnelements.

SHEAR TENSION COMPRESSION

δuplift

δ2%Drift

ROCKING FOUNDATION ANALYSIS

Higher level analysis included a rockingevaluation that avoided foundationretrofit. We performed a nonlinearpushover analysis to demonstrateequivalent Life Safe performance ofthe foundations supporting the newmoment frame columns. We modeledthe existing pile foundations withcompression-only gap elements thatsimulate lift-off of the cap from thesocketed piles. We demonstrate that ata design drift of 2% in the new addition,uplift in the foundation is less than the3 inch pile embedment into the pilecap.

POST-INSTALLED WELDED HEADED STUDS TO (E) BEAM FLANGE

(E) CONCRETE COLLECTOR RETROFIT

FRP DIAPHRAGM STRENGTHENING

EXISTING COLUMN COVER PLATE STRENGTHENING

FRP COLLECTORSEXISTING STRUCTURE RETROFIT

LFRS: SMF WITH SIDEPLATE CONNECTIONSSMF COLUMN SHEAR-AXIAL BASE CONNECTION

NEW TWO-STORY BUILD BACK STRUCTURE

NEW DESIGN + RETROFIT

BASE SHEAR VS ROOF DRIFT

FOUNDATION UPLIFT VS ROOF DRIFT

ROOF DRIFT (IN)

ROOF DRIFT (IN)

BASE

SH

EAR

(KIP

S)UP

LIFT

(IN

)

Vp

PROJECT TEAM

CONTRACTOR TURNER CONSTRUCTION

STRUCTURAL SIMPSON GUMPERTZ & HEGER

ARCHITECT AE3/WOODS BAGOT JOINT VENTURE

OWNER SFO INTERNATIONAL AIRPORT