Melt-down

The California Bay Area has perhaps the most studied urban infrastructure in the world, with engineering and seismic experts constantly assessing how to shore up the infrastructure of San Francisco, Oakland and surrounding areas to withstand the wrath of frequent earthquakes.

Buildings are built to withstand catastrophic earthquakes, as are sewer and utility lines and, of course, the expansive freeway system. Despite all this engineering, retrofitting and rebuilding to make the infrastructure seismic sensitive, planners don't always anticipate the damage that a fire could cause. On April 29, 2007, a disaster of a diffierent kind took place on an Oakland freeway: a tanker truck hauling 8,600 gallons of gasoline overturned and burst into flames.

According to news reports, the 50-foot-high ramp connecting westbound Interstate 580 to southbound Interstate 880 was destroyed by intense flames, which topped 2,750 degrees F, and melted the steel beams that supported the overpass. When the steel beams were compromised, a 165 foot section of the freeway collapsed onto the roadway below, closing two major arterials in the interchange.

Traffic congestion was a huge concern so repairing the roadway was an immediate priority. California Governor Arnold Schwarzenegger issued an emergency declaration to streamline public contracting and permitting codes and provide emergency funding to allow repair operations to begin immediately. The state went as far as to offer the low bidder that landed the job an incentive of $200,000 a day for each day the project was finished before a June 29, 2007 deadline. CC Meyers earned $5 million in incentive pay, finishing the work a full month ahead of schedule on May 25, 2007. The state originally estimated the job would take 50 days.

The first task was to remove the demolished asphalt and allow the reopening of Interstate 880. Cleveland Wrecking Company was called in to demolish and remove the damaged section of freeway to reopen Southbound 880. Bigge Crane and Rigging moved in a 90 ton capacity Link-Belt HTC8090 hydraulic truck crane to lift girders and do shoring work on the elevated roadway below.

“We mainly did the preliminary structure support work,” says Andrew Wierda, marketing coordinator at Bigge. “[The crane was] setting girders and shoring the elevated roadway for support.”

Crews from C.C. Meyers showed up the day the contract was awarded, coordinating the engineering and repair work that would be an around the clock effort the next three weeks. Steel was supplied from Pennsylvania and Texas and fabricators from Arizona and California worked on the project.

Among the beams needed for the repair was a 57 foot concrete beam that weighed 100 tons. Known as the bent cap, which spans two columns and holds the bridge deck, the beam measured four feet wide and five feet tall.

Reeve Trucking of Stockton, CA hauled the beam to the site with Donald Reeve, owner and president of the company, driving the truck himself from the steel fabricator ConFab California Corp. in Lathrop, CA.

“The bent cap is the piece of concrete that spans between the columns and holds up the girders,” says Reeve. “It is concrete, which is interesting because the original bridge is steel. But for whatever reason, this bent cap was concrete, maybe the reason being how fast they could get it fabricated. They had to get it custom designed and engineered and get approvals and build it with the bracketry on each side to bolt the concrete to the steel in just a matter of weeks.”

Reeve and his son Don Reeve, Jr. drove the truck and made the trip in about three hours. The beam was hauled on an 11 axle unit comprising a tractor, two jeeps and a steerable dolly. They delivered the beam right up to the ramp area near where the tanker crashed and burned back in April. Reeve placed the beam so that its end would pivot perpendicular to the I-880 ramp allowing the two cranes easy access.

A nighttime job, CalTrans closed the ramp on the freeway underneath the freeway to be repaired for Reeve to position the trailer in the precise place. “They had the cranes sitting on either side of the bridge on the ground,” explains Reeve. “I was parked on the bridge about 30 feet below the bridge being repaired. There were cranes on the ground and they had enough boom to extend up beyond the bridge I was on up to the bridge being repaired. We steered the dolly sideways so the bent cap could be picked and put in place close to each column.”

The setting of the beam attracted the media and onlookers. A laser measuring system was used to ensure the exact placement of the beam on the columns. Cores had been drilled in the columns, and after the laser measuring system determined exact placement, the riggers dropped long pins, six inches in diameter, into the holes to secure the beam in place. The holes were then grouted and the entire bent cap was installed the night it arrived onsite.

The Sacramento branch of Maxim Crane Works provided the two cranes that worked on the reconstruction project, according to Maxim's Mark Swaney. Two cranes were used for the project, a 300 ton capacity Grove GMK6300B hydraulic wheeled mobile crane and a 210 ton capacity Grove GMK5210 telescopic wheeled mobile crane.

“We had both cranes for installation of the bent cap and one crane stayed for installation of steel beams and miscellaneous materials,” says Swaney.