High-speed repairs

The Bay Area around San Francisco and Oakland in California, US is famous for its earthquakes, and buildings, utilities and infrastructure alike are designed to withstand the full force of these violent shakes. But even with these standards of construction, not every type of problem can be designed for. On April 29 this year a disaster of a different kind took place on an Oakland freeway when a tanker truck hauling 32500 litres of petrol overturned and burst into flames.

According to news reports, the 15 m high ramp connecting westbound Interstate 80 to southbound Interstate 880 was destroyed by intense flames, which topped 1500° C-enough to melt the steel beams that supported the overpass. This led to the collapse of a 50 m section of road, which fell onto the lanes below, closing both routes.

Traffic congestion was a huge concern so repairing the roadway was an immediate priority. California Governor Arnold Schwarzenegger issued an emergency declaration to fast-track the tender process for the repairs as well as to provide emergency funding to the job.

The state went as far as to offer an incentive of US$ 0.2 million a day for each day the project was finished before its June 29 deadline. As a result, contractor C.C. Meyers earned US$ 5 million in incentive pay, finishing the work a full month ahead of the 50-day schedule originally envisaged by state planners.

Clean up

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 the Southbound 880. Bigge Crane and Rigging moved in a 90 ton (82 tonne) 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,” said Andrew Wierda, marketing coordinator at Bigge.“[the crane was] setting girders and shoring the elevated roadway for support.”

The clean-up work took just over a week, allowing the southbound section of the 880 to reopen on May 7.

Re-building

Crews from C.C. Meyers arrived on site 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 replacement beams needed for the repair work was a 17 m concrete span that weighed 90 tonnes. Known as the bent cap, which spans two columns and holds the bridge deck, the beam measured 1.2 m by 1.5 m in cross-section.

A night-time job, the California transport authority (CalTrans) closed the ramp on the lower road underneath the section being repaired, allowing haulage company Reeve Trucking to position the trailer carrying the beam. “they had the cranes sitting on either side of the bridge on the ground,” explained owner and driver for the project Donald Reeve. “I was parked on the bridge about 30 feet (9 m) 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 (152mm) 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 (273 tonne) capacity Grove GMK6300B hydraulic wheeled mobile crane and a 210 ton (191 tonne) capacity Grove GMK5210 telescopic wheeled mobile crane.

Completion

With this challenging tandem lift out of the way, work progressed quickly to replace the steel beams and bridge deck, and surface the road. In fact there was less than a month between the accident and the overpass being re-opened.   IC