Clark Construction uses scans, animation to smooth installation of elevated airport walkway

Ruth D. Adamson

The issues dealing with the job staff on the $968 million Worldwide Arrivals Facility job at Seattle-Tacoma Worldwide Airport could barely have been much more extreme. Topping the checklist of challenges on the job was a middle-of-the-night time set up of a 3 million-pound glass and metal walkway through driving rain […]

The issues dealing with the job staff on the $968 million Worldwide Arrivals Facility job at Seattle-Tacoma Worldwide Airport could barely have been much more extreme.

Topping the checklist of challenges on the job was a middle-of-the-night time set up of a 3 million-pound glass and metal walkway through driving rain whilst Boeing 747s landed and taxied nearby.

The 780-foot-extensive walkway, with 85 toes of vertical clearance and a 610-foot-extensive apparent span in between footings —​plenty of place for huge-human body plane to taxi underneath — was developed to connect the airport’s South Satellite making to the new Worldwide Arrivals hall.

Moving and hoisting the walkway’s 320-foot-extensive heart segment into spot was a elaborate undertaking that needed months of organizing, large-tech equipment and coordination between all stakeholders.

In get to enhance safety and reduce the affect to ongoing airport functions, the span was fabricated at a nearby airport cargo space. This method enabled the staff to streamline fabrication initiatives, troubleshoot probable challenges and perform sensitive functions, this sort of as the set up of the walkway’s keep cables, in a managed surroundings, according to Brad McDermott, project government at Clark Building, the project’s style and design-builder. 

When the large construction was comprehensive, Clark used self-propelled modular transport gadgets (SPMTs) operated by hefty transport marketing consultant Mammoet to transfer it on to the tarmac. The specifically developed hydraulic trailers can transfer in any path and element axles that telescope independently of 1 one more to support evenly distribute fat and keep hundreds flat whilst relocating over uneven terrain, McDermott informed Building Dive. Mammoet operating engineers managed the SPMTs by means of remote, going for walks right guiding the transport through the transfer.

Undertaking staff

Structure-Builder  Clark Building Team
Engineer of File / Structural Engineer  KPFF
IAF designer  Skidmore, Owings & Merrill
Walkway erector  The Erection Co. (TEC)
Metal fabricator  Supreme Metal
Large transport engineer  Mammoet
Peer review business  KCE Structural Engineers

Spotters, in a convoy of cars in entrance and back again of the transport, as properly as going for walks on foot, also accompanied the heart span as it navigated the circuitous 3-mile route from the cargo space down the airport’s heart runway to the IAF ​at going for walks speed. The operator and all users of the transfer staff maintained ongoing radio interaction throughout the whole operation, McDermott reported.

The painstaking a few-and-a-fifty percent-hour operation took spot just soon after midnight through intervals of hefty rain and as airplanes taxied, landed, and took off on nearby runways. 

“We realized that any big movement to the metal assembly could result in tension to the construction,” he reported. “We wanted a transport remedy for the walkway’s heart span that delivered a secure, steady journey from starting to stop. The SPMTs helped us attain that aim.”

Tech usually takes off

To clean the way for the transport, the business leveraged what it says is chopping-edge survey technological know-how to review existing situations on the web page, like laser scanning the walkway’s heart and stop span connections and the airport’s heart runway. The scans authorized the staff to detect critical stake points along the runway that presented hefty cross-slopes or elevation adjustments. 

All through the transport, the staff monitored much more than a hundred pressure gauges, which had been hooked up to the heart span metal to measure strains on the span this sort of as bending or stretching. The gauges shipped real-time info that the staff calculated and compared to the threshold restrictions predicted by structural engineers from KPFF.

Self-propelled modular transport gadgets moved the heart span on to the tarmac.

Clark Building


“It was vital for the job staff to detect the variations in elevation and cross-slopes of the runway, specially at the taxiways in between runways, in get to totally understand how the transport path would affect the heart span through its transfer,” McDermott reported. “Next extensive investigation of the survey info, the job staff elected to stiffen the non permanent metal guidance style and design even more, building the heart span much more rigid.”

After the transport was comprehensive, the hoisting operation started. Crews leveraged the walkway’s stop spans to guidance the fat of the lift. Working with 4 strand jacks anchored to every single stop span connection, they hoisted the walkway to its last situation 85 toes higher than the airport’s taxi lane. The strand jacks delivered the steady strength wanted to transfer the large construction upward and delivered higher regulate over the lift. 

With engineering tolerances in between the heart and facet spans as tiny as 1 inch, there was no place for error, McDermott reported. 

“We realized we experienced to get this proper the very first time,” he reported. 

Clark’s digital style and design and design and subject engineering groups relied on laser scanning and animation to support visualize the whole method forward of time, from fabrication and transport to the lift operation. The laser scans made applying Autodesk/Navisworks and Recap Professional delivered what the staff reported ended up remaining precise as-constructed info, which it utilised to verify that the numerous phases of fabrication remained within just the tolerances of the style and design.

Strand jacks anchored to every single stop of the span helped hoist the walkway to its last situation 85 toes in the air. 

Clark Building


Animations applying Bentley Systems’ Synchro software package specific the sequence of operate forward of time. This was essential due to the fact the team’s aim was to limit the affect to airport functions, so there was very restricted laydown space to operate within just, McDermott reported.

“The Synchro animation helped the staff create and test their sequencing logic to make sure they minimized the affect to the airport and airways,” he reported. “The animation also served as a instrument to talk their approach to job stakeholders.”

Other software package utilised on the job integrated Leica Cyclone laser scan registration and Strain Gauges micro-measurements from Vishay Precision Team (VSG). Due to the fact the IAF project and pedestrian walkway are remaining created at an lively airport, drones had been not an solution, he reported. 

Planet record

Thanks to progress organizing, technological know-how and collaboration between all stakeholders, the construction arrived with each other seamlessly without the need to have for more adjustment, McDermott reported. Previous 7 days, the taxi lane beneath the walkway reopened, enabling plane targeted visitors entire obtain beneath the large construction.

Now totally supported, the walkway is the world’s longest pedestrian bridge over an lively airport taxi lane, eclipsing London’s Gatwick Airport’s Pier 6 Connector by one hundred twenty toes. Clark and trade lover The Erection Co. will proceed welding functions on the walkway and start exterior cladding operate this spring with the aim of finishing the walkway construction and Worldwide Arrivals Facility this slide. 

In the stop, technological know-how was an crucial issue in the good results of the job but it did not substitute the collaborative operate of the staff, McDermott observed.

“Technology served to heighten organizing, good quality, and safety, but it was the team’s lifestyle of relentless organizing that in the long run ensured the precise execution of operate,” he reported.

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