Los Angeles, US: COWI, a leading international engineering consulting group, celebrates an engineering milestone on the new 6th Street Viaduct construction in Los Angeles (LA), following the successful hanger installation of the first span out of 10 spans of the new viaduct.

Spanning across Freeway 101, several rail roads and the LA river, the 6th Street Viaduct replacement project is one of the largest bridge projects currently underway in the City of LA. Originally built in 1932, the iconic bridge – commonly recognized for its appearance in the hit movie-musical ‘Grease’ – provides a vital connection between Boyle Heights and Downtown LA’s Art District. In 2016, the bridge was demolished following the decision to replace the existing 6th Street Viaduct due to the structure becoming seismically vulnerable.

At 3,060-ft-long and 100-ft-wide, the redevelopment of the bridge – designed by Michael Maltzan, Architect, and HNTB, Structural Engineer – includes 10 network arch spans, with a total of 388 hangers supporting the bridge deck. Appointed as the Erection Engineer on the project with an extensive complex structure expertise, COWI worked closely with Skanska Stacy and Witbeck (SSW) to develop a constructable erection sequence, which includes step by step camber and stress analyses, and hanger installation and stressing procedure of the bridge.

The current construction stage concludes the hanger installation of the first span as well as the removal of the falsework underneath.

“If you consider each arch span as an individual bridge, then this essentially marks the completion of the first of ten bridges – making this such an exciting milestone for the project.” Tobias Petschke, Senior Project Manager at COWI North America explains.

COWI has taken a multitude of considerations to ensure the safety of both the public and the construction crew during this complex bridge erection. This included the design of customized lock-up devices to stabilize the seismic pendulum bearings of the bridge during construction.

Petschke adds “This is a really exciting time to be an engineer. Having the opportunity to apply our expertise to projects of this kind reminds you just how important our work is. By exploiting some of the most advanced techniques we can ensure the safe and sound erection of complex infrastructure projects. We are proud to be working with an amazing construction joint venture such as Skanska Stacy and Witbeck, who are providing exceptional services and are going above and beyond to build this viaduct.”

For this project milestone to happen, SSW and COWI carefully monitored the falsework supporting the deck and the hanger forces during installation to ensure that everything went according to plan. Performing such a procedure over highway 101 and maintaining uninterrupted traffic required the highest consideration of public safety from the team.

Geraldo Iniguez, Project Executive at Skanska Stacy and Witbeck comments “Having COWI as our Erection Engineer has proven to be invaluable. The complexity of the 6th Street Viaduct requires constant engineering analysis, in which Skanska Stacy and Witbeck has relied upon. We thank COWI for its competency and dedication to our project.”

The next step of the project is the closure of the superstructure continuity followed by the hanger installation in the second span with completion of the bridge planned for mid-2022.

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