Sixth Street Viaduct Replacement

 

Client
City of Los Angeles

Project Overview

The Sixth Street Viaduct (also known as the Sixth Street Bridge) is a 3,500-foot bridge in Los Angeles that connects historic Boyle Heights on the east side with the Downtown Arts District on the west. The bridge spans the LA River and the 101 Freeway, local surface roads as well as 18 railroad tracks operated by five different railroad agencies including Union Pacific and Metrolink. The earlier viaduct on this site, built in 1932, was closed for demolition in January 2016.

The new Sixth Street Viaduct was designed by the HNTB-led team that won an international design competition decided by public vote. The viaduct accommodates vehicles and pedestrians, as did the original, and provides dedicated lanes for bikes.

A new 12-acre public park running below the bridge, accessible by multiple stairways and a monumental helical bike ramp, will provide access to much-needed recreational fields with restrooms and café, the LA River, public art, and a programmed arts plaza. The new bridge will become a destination in Los Angeles as much as a thoroughfare.

The new viaduct, a tied arch bridge referred to as the “Ribbon of Light,” pays homage in its design to the 1932 bridge, which had two pairs of iconic arches over the LA River section of the structure and appeared in countless films, television shows, music videos, and commercials. The new bridge employs a series of 10 pairs of sculptural arches with the tallest pairs placed adjacent to and framing the LA River where the original arches stood and another taller pair span US101 as a gateway on the east. The canted arches, which allow the bridge to embrace its deck and open to the sky above, recall the iconic beauty of the original bridge and create a new cinematic choreography through sequential views framing the city for travelers moving along the bridge. The new viaduct is the largest bridge project in the history of Los Angeles, with a cost of $588 million.

Sixth Street Viaduct Facts

  • The Rams new SoFi Stadium’s seismically isolated roof uses the “stiffening isolation bearing” developed for the Sixth Street Viaduct.
  • Columns fitted with triple friction pendulum bearings allow for a 36-inch sway in any lateral direction before stiffening. Ultimate bearing displacement capacity is over 50 inches.
  • The new span boasts an additional 40 feet width over the original bridge, totaling 100 feet wide, with dedicated lanes for pedestrians, bicycles and vehicles.
  • 110,000 tons of concrete and 8,250 tons of steel were used to build the new viaduct connecting historic Boyle Heights to the downtown Arts District over the last decade.
  • Each viaduct piling extends up to 150 feet underground, equivalent to a 15-story building.
  • Each of the 10 pairs of arches required 260 cubic yards of concrete, that’s more than 65 concrete truck loads per arch.
  • To reduce potential for cracking, liquid nitrogen was injected into the concrete as it was poured to cool it down to ambient temperature. At a rate of four vertical feet per hour, it took 12 to 14 hours of continuous concrete pouring for each arch.
  • The substructure features concrete “Y-Bents” that flow seamlessly into the arches and uses grade 80 reinforcement instead of grade 60 — a first for a California bridge.
  • This is the first HNTB design to use the Envision Infrastructure Rating System for sustainability and resource efficiency, giving the span a 100-year service life.