A Way out of Isolation: The new Angeles Crest Bridge

The Angeles Crest Highway, a section of Highway 2 linking Los Angeles with San Bernardino, had to be closed after two severe winter storms in 2005 and 2006 because a road section had been washed out. Finding a solution for the re-opening of the mountain pass proved to be very difficult because the local rock mass could not be stabilized and the slide area remained active.

In May 2009, the new Angeles Crest Bridge was re-opened to traffic. After a long break, the pass section once again brought tourists and business to the mountain village of Wrightwood and spares travelers the inconvenience of long detours.

The construction of a cast-in-place bridge was impossible due to the fact that falsework could not be erected on the unstable ground. The decision was made to construct a 63m (208ft) long precast concrete girder bridge instead.

The precast, post-tensioned spliced girder bridge had to be longer than usual because the abutments had to be erected on stable ground both right and left of the active slide area.

Due to space limitations, the precast elements had to be produced off site in individual segments. The precast segments had to be short enough to be transported on the narrow and winding mountain road to the job site. To this end, the 63m (208ft) long girders were divided into three parts: a 28m (92ft) long middle section and two 17m (56ft) long end sections that accommodate the posttensioning anchorages.

The girder segments were assembled on temporary supports, and closure concrete was placed at the segment joints. Afterwards, approximately 50% of the post-tensioning was applied. Once the girders were set on their abutments, concrete was placed and the final post-tensioning and grouting was completed. For post-tensioning the segments, DSI USA supplied a total of 32,309m (106,000lf) of Type 0.6" DYWIDAG Strand Post-Tensioning Tendons with Type 12x0.6" and 15x0.6" MA Anchorages.

Thanks to the new bridge, snow run-off, debris and eventual future rock slides can now slide off the 75% mountain slope and pass underneath the road without endangering traffic. As the third largest bridge of its kind worldwide, the Angeles Crest Bridge was awarded the American Precast/Prestressed Concrete Institute (PCI) prize in the Best Bridge with Spans More than 47.7m (150ft) category.