6th Street Viaduct, Los Angeles, USA

A celebrity bridge built to withstand seismic activity

About

Challenge

Replacing the existing viaduct, which had become seismically vulnerable. The project required designing and installing a complex bridge structure while ensuring the safety of the public and construction crew.

Solution

Developing a constructible erection sequence that included step-by-step camber and stress analyses, as well as the installation and stressing procedure of the bridge hangers. Customised lock-up devices were designed to stabilise the seismic pendulum bearings of the bridge during construction to ensure safety.

Value

In combination with accessible ramps and stairways, the bridge’s walkways and bicycle lanes allow people to both cross the bridge more easily and access planned recreational areas. Shielding visitors from the Southern Californian sun, the structure accommodates parks, soccer fields, exhibition spaces and an amphitheatre within its shaded expanse. The bridge construction also achieved its sustainability and environmental impact targets and received a high rating.

Specifications

Facts

The 3,060-foot (933 metre) jointless cast-in-place concrete bridge comprises ten continuous arch spans with a 100-foot-wide (30-metre) cast-in-place deck. The bridge spans over Freeway 101, several railroads and the Los Angeles (LA) River in California.
The 3,060-foot-long and 100-foot-wide bridge includes ten network arch spans, with a total of 388 hangers supporting the bridge deck.

Location

Connecting downtown LA’s Arts District with Boyle Heights over the LA River in California.

Period

2015–2022

Country

USA

Partners

Client: Skanska-Stacy & Witbeck

Services

Erection engineer; development of a constructible erection sequence.

Safety first while keeping traffic flowing

The iconic 6th Street Viaduct in Los Angeles, known for its starring role in the movie-musical Grease - as well as other movies such as Point Blank, Terminator 2 and The Mask to name but a few - was closed in 2016 for demolition and replacement due to concerns over its seismic vulnerability.

The bridge provided a vital connection between the Boyle Heights neighbourhood and Los Angeles’ Art District, making its timely replacement an important project for the city.

Appointed erection engineer on the project with extensive complex structure expertise, we worked closely with Skanska Stacy and Witbeck (SSW) to develop a constructable erection sequence, which includes step-by-step camber and stress analyses, hanger installation and stressing procedure of the bridge.

COWI took 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 customised lock-up devices to stabilise the seismic pendulum bearings of the bridge during construction.

“This is an 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.”

Tobias Petschke, Associate Technical Director, Canada

Together with SSW, we 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.

The completion of the bridge and inauguration ceremony with 900 invited guests took place in 2022.

In 2021, the 6th Street Bridge was showcased at the prestigious Biennale for Architecture in Venice.

What we do in North America

COWI in North America works primarily within transportation, water, climate resiliency, renewable energy and federal infrastructure. We draw on nearly a century of expertise, and with our 7,500 experts worldwide, we can work around the clock to deliver projects for our customers.