FEATURE STORY

AVIATION

is SOARING

T.Y. Lin International’s (TYLI) worldclass Aviation sector has a long history of providing professional services for airport projects in the United States and worldwide. This includes the Aviation team’s successful relationship with Los Angeles World Airports (LAWA) and their main international hub in Southern California, Los Angeles International Airport (LAX).

One of TYLI’s recent LAX projects was the new West Gates at Tom Bradley International Terminal (TBIT). Located just west of TBIT, the five-level, 15-gate, 750,000-square-foot facility is part of LAWA’s USD 14.5 billion modernization plan to improve connections to Los Angeles’ regional transportation system and promote economic growth for the city and its environs.

The West Gates at TBIT facility functions mainly as an international departure and arrival concourse able to accommodate both wide and narrow body aircraft. What travelers experience is a modern “guest experience” in a cutting-edge environment, with all the latest digitally-based technologies and amenities at their fingertips.

TYLI was a critical member of the design-build team for the project, which was led by Turner/ PCL Joint Venture and Corgan Associates, Inc. The firm served as the primary structural design consultant and Engineer of Record for three cutand-cover tunnels connecting TBIT to the West Gates and a new north-south taxiway.

View of the completed Passenger Tunnel connecting TBIT to the West Gates facility.

TUNNEL DESIGN

The tunnels portion of the project included three tunnels connecting TBIT to the West Gates and their extensions, including associated structures, grading, utilities, drainage, and other key design aspects.

The Passenger Tunnel (PAX) measures 921 feet long with typical clear dimensions of 50 feet wide by 19 feet tall. The design includes 3-foot-diameter concrete columns spaced at 20 feet along the center of the tunnel to separate arriving and departing passengers.

The other two tunnels are for baggage and utilities and include the 1,235-foot-long, 30-foot-wide West Utilidor Tunnel and the 500-foot-long, 40-foot-wide East Utilidor Tunnel (TUTL-E). The clear height for both is 14 feet. A portion of the TUTL-E uses a grid of steel columns spaced at 20 feet.

Design challenges included constructing the tunnels under an active taxiway - and with no interruptions to airport operations. TYLI’s solution was a phasing plan that allowed construction to take place in two distinct stages. The Aviation team also had to fast-track the tunnel design, which required close coordination with the contractor to meet tight schedule demands.

EXCELLING AT COLLABORATION

The location of the new tunnels in a high seismic area constituted another major design challenge. Reflecting TYLI’s spirit of collaboration, the firm’s Aviation and Bridge sectors joined forces on the tunnel designs. Although bridges were not part of the project, the required large dimensions, the use of concrete columns, and the unique seismic evaluation for the tunnels matched with the Bridge sector’s expertise.

TYLI’s Bridge team took the lead here, performing soilstructure analysis to evaluate the seismic demands on the tunnels. This intensive raking analysis considered two seismic hazard levels, the 475-year return period and the 2,475-year return period. TYLI also designed the tunnels to support the immense weight of an Airbus 380-900 or its equivalent, in addition to the self-weight, backfilled soil, and taxiway slab loading.

New PAX with 3-ft.-diameter concrete columns.

TYLI provided engineering design for the construction of a new taxiway east of the new West Gates facility.

TAXIWAY DESIGN

As a separate contract, TYLI also provided engineering design for the construction of a new north-south taxiway west of the existing Taxiway S and east of the West Gates facility. Since it was imperative to avoid interruption to airport services or ongoing tunnel construction, the design plan designated phased taxiway construction.

TYLI’s taxiway design included a new taxiway alignment and new concrete and asphalt pavements. Ultimately, the pavement design called for 30,556 square yards of 12-inch lean concrete base course, 19-inch-thick unreinforced Portland Cement Concrete (PCC) pavement, and the construction of 300 square yards of 19-inch-thick reinforced PCC pavement.

The taxiway design also included a new service road, new underground utilities; grading; new airfield electrical (in-pavement taxiway edge and centerline lights), new airfield pavement markings, security fencing, and new and modified storm drain systems.

AWARD-WORTHY RESULTS

The West Gates at TBIT project demonstrates TYLI’s ability to provide multi-disciplinary experts, experience, and expertise on challenging projects in complex airport environments. The project also showcases the firm’s ability to work closely with its design-build partners to deliver difficult alternative projects successfully.

The Design-Build Institute of America (DBIA) recently honored the West Gates at TBIT with a 2021 National Award of Merit (Aviation category). As a National Merit Award Winner, the project now competes to be named an Excellence Winner (top project in its category) and DBIA’s Project of the Year. Winners will be announced in November 2021 at the annual DesignBuild Conference & Expo. >>>

FEATURE ARTICLE

TYLI Provides Design for Grist Mill Bridge Using New FRP Girder Technology

Image Courtesy of Wilfong Work

Aerial view of load testing for the Grist Mill Bridge. (Image Courtesy of Wilfong Work)

Located in Hampden, Maine, the original Grist Mill Bridge was a buried T-beam structure built in 1924 and widened in 1948 to the current alignment. When the Maine Department of Transportation (MaineDOT) was looking to rehabilitate or replace the aging bridge in 2016, TYLI’s Falmouth office conducted a preliminary engineering analysis on the project site to determine the project scope and direction. The study indicated that a replacement bridge was the more cost-effective option.

A major design consideration for the replacement bridge was longevity, with a target useful life in excess of 100 years while minimizing required maintenance. To that end, MaineDOT decided to use the project site as a trial for an experimental lightweight, durable Fiber Reinforced Polymer (FRP) girder technology developed and tested by AIT Bridges and the University of Maine’s Advanced Structures & Composites Center.

Overcoming Project Challenges

Along with the demands of designing and constructing a bridge using composite girders instead of precast concrete or steel girder construction, the site also had considerable challenges and constraints. These included a complex geometry, multiple utility crossings, tidal influences, a highly variable ledge, and the presence of endangered Atlantic salmon.

The complex geometry and utility crossings required constant communication and coordination between TYLI, AIT Bridges, MaineDOT, and the consultant hired by the town to design the utilities (Woodard & Curran). The utilities also required careful consideration of construction phasing, as the sewer and water lines crossing the structure serve as the critical arteries for a large segment of the town and are essential for transporting sewage to the treatment facility in Bangor.

The tidal influences, variable ledge, and Atlantic Salmon presence were mitigated through careful construction phasing consideration and detailing, allowing the contractor to quickly bring the work to an elevation above the tidal influences and out of the stream.

Success through Teamwork

Along with providing engineering guidance throughout the project duration, TYLI coordinated its preliminary and final design efforts with the surrounding highway replacement project, the utility upgrade designer, and the beam designer. AIT Bridges provided the design, detailing, specifications, and fabrication for the composite girders used in the replacement structure.

Scope of work for TYLI’s Falmouth team included the final design calculations, complete combined planset, engineering estimate for construction, and construction support during project construction.

The project was completed on schedule, despite numerous and significant design change requests made by Maine DOT in the late stages of the project.

The Grist Mill Bridge is the first bridge in the U.S. to use a hybrid composite FRP girder as the main structural element.

TYLI’s Falmouth team for the project included Ben Toothaker, P.E., as the lead structural engineer and bridge project manager. Daniel Myers, P.E., Chris Taylor, P.E., Rick Hebert, P.E., Norm Baker, P.E., Jeffery Legere, and Roman Kravchuk all provided critical design assistance and review for the bridge project throughout the design process.

TYLI’s Shawn Davis, P.E. was the project manager and lead highway engineer for the surrounding highway reconstruction, with critical design assistance provided by Tim Kelley.

Industry Firsts

Among its industry firsts, the Grist Mill Bridge represents the first use of the Composite Tub Girder technology developed at the University of Maine’s Advanced Structures and Composites Center. It is also the longest span FRP girder vehicular bridge in the U.S. and the first bridge in the U.S. to utilize a hybrid composite FRP girder as the main structural element.

In June 2021, the Maine Section of the American Society of Civil Engineers honored the Grist Mill Bridge project with the Kitty Breskin Award, which recognizes innovative practices in civil infrastructure projects built each year in Maine.

A recent issue of Transportation Builder from the American Road & Transportation Builders Association (ARTBA) also featured the Grist Mill Bridge on its cover and in an article by Ken Sweeney, president of AIT Bridges. >>>