California Department of Transportation


SR-91 is a major east-west freeway located in Southern California, serving several regions of the greater Los Angeles metropolitan area. The SR-91 overpass is a large reinforced concrete box girder bridge that was built in the early 1970s.


Mobilizing members from WJE’s Los Angeles, San Francisco, Austin, and Northbrook offices to respond to the emergency, a team of six engineers was working on site within twelve hours of receiving the request for assistance. WJE engineers performed a variety of physical and nondestructive tests on the overpass, including visual observation, acoustic impact testing, petrographic studies, compressive strength testing of concrete cores, and tensile strength testing of reinforcing steel to assess the damage caused by the fire exposure. Only ten days after receiving the assignment, the team completed all testing and provided Caltrans with conclusions regarding the condition of the concrete and recommendations for the repair or replacement of the concrete where necessary. The team concluded that the accident at the interchange connector caused moderate structural damage to the bridge supporting the westbound lanes of SR-91. The worst damage occurred to the north face and railing of that bridge, which sustained significant spalling and heat damage to the concrete.