Bridge inspections get under way

DelDOT engineers (from left) Jason Arndt, Glen Miller and Matthew Mortensen are suspended in a bucket truck Tuesday as they lead a full-scale inspection of the Augustine Cut-off bridge in Wilmington, which is similar to the one that collapsed in Minnesota. (Buy photo) The News Journal/CARLA VARISCO

A man walking a dog crosses the Swinging Bridge over the Brandywine. The Augustine Cut-off bridge is at far left, beside the arched Conrail bridge.(Buy photo) The News Journal/SUCHAT PEDERSON

Keith Gray (left), a Federal Highway Administration engineer, and DelDOT engineer Darren Sobota check trusses on the Augustine Cut-off bridge.(Buy photo) The News Journal/CARLA VARISCO

Four of Delaware's most vulnerable bridges will be inspected every six months instead of every year as a precaution in the wake of last week's bridge collapse in Minneapolis.

Sixteen other Delaware bridges with outdated "fracture critical" designs like the bridge in Minnesota will be examined more frequently, state Department of Transportation Secretary Carolann Wicks said Tuesday. Fracture critical means that the failure of a single beam or pin could cause the entire bridge to collapse.

A team of engineers got started Tuesday.

In sweltering heat, a seven-man inspection crew gathered at the Augustine Cut-off bridge over the Brandywine -- which has a steel deck truss design, the same as the I-35W bridge in Minneapolis.

At least eight people are presumed dead after the eight-lane bridge collapsed during rush hour Aug. 1. The bridge had passed regular inspections but was listed as "structurally deficient," meaning at least one component needed attention.

"We don't have enough information to know what happened in Minneapolis," said Michael Chajes, chairman of the Department of Civil and Environmental Engineering at the University of Delaware, which has partnered with DelDOT on more than a dozen bridge monitoring projects.

"There are some things that are very difficult or impossible to monitor. Some failures are so localized. ... I think it will turn out to be something unique to the bridge in Minneapolis, and I think it will be related to construction activity."

The U.S. Department of Transportation directed all states to immediately inspect steel deck truss bridges, or at least review reports, the day after the Minneapolis bridge collapsed.

With a daily traffic count of about 8,000 vehicles, the two-lane Augustine Cut-off bridge isn't nearly as busy as an interstate. It was built in 1920, and all but the foundation was rebuilt in 1980. The bridge was in good condition when last inspected in May 2006 and wasn't due for another inspection until 2008, said Ed Finney, DelDOT's bridge management engineer.

"It's a similar type construction to the one that failed, but it is a lot newer," said Finney, who stood on a steep ledge at the foot of the bridge, gazing upward.

Above him, inspectors straddled steel beams or stood on a catwalk. Three men stood inside the bucket of a bucket truck, preparing to move to the second of six 100-foot-long spans.

Later, inspectors will enter the Brandywine to measure the water's depth and monitor foundation corrosion. On Friday, the final day of the three-day inspection, a consultant will use ultrasound to check beams and pins.

New technology to monitor bridges, such as X-ray machines and computerized monitors, is constantly being developed, though few states have invested in it because of the expense, Chajes said. It costs about $250,000 to install a monitoring system on a large bridge.

DelDOT, which spends about $30 million a year to maintain its bridges, has been progressive in its use of evolving technology, Chajes said. In the next 18 months, DelDOT and UD will partner to install two new types of sensors at the Indian River Inlet Bridge, at a cost of about $500,000.

"They have pretty aggressively looked at their bridges that are problematic," said the university's Chajes. "They are one of the states that have made a lot of progress."

Of the state's 1,426 bridges, 38 are categorized as structurally deficient, or 2.7 percent. The four bridges that are both structurally deficient and fracture critical are considered to be the most vulnerable. They are Rising Sun Lane over the Brandywine, James Street over the Christina River, Walnut Street over the Christina and St. Annes Church Road over railroad tracks near Middletown.

None is considered to be unsafe, Wicks stressed.

Several Delaware bridges, such as the Delaware Memorial Bridge, aren't maintained by DelDOT. Last inspected in October, it is rated in good condition with no structural deficiencies, said Jim Salmon, spokesman for the Delaware River & Bay Authority, which maintains the bridge. Its annual inspection is scheduled for September and will take eight to 10 weeks.

The bridge is part suspension, part deck-truss and part deck-girder.

The Army Corps of Engineers doesn't plan to conduct immediate inspections of any of its bridges in Delaware. None of the corps' three Delaware bridges falls into the category of steel deck truss, said spokesman Ed Voight.

The Reedy Point and Summit bridges were inspected last summer and are scheduled for inspection again next summer. An inspection of the St. Georges Bridge was completed in June.

Post a Comment   View All Comments

Posted by: delawareisfullofidiots- Thu Aug 09, 2007 12:58 am

First picture: "See guys...just tap this little hammer here and that will make everything better." Other two guys..."Ohhh...okay, yeah, I can see that." Plus...ya gotta love the cool sunglasses!!!!

Second one: The train bridge isn't going anywhere soon.

third picture: "Can I get a drink of that?" "Sure."

Posted by: Rhinobo- Wed Aug 08, 2007 8:43 pm

The steel structure associated with the MN failure was pigeon infested that makes ordinary visual inspection difficult at best.

Also, for us non structural types, "fracture critical" means when once part of structure fails so does the rest. Now that seems a bit foolish even if you do use a 4:1 SF.

Just an HVAC guy.

Posted by: dennisden- Wed Aug 08, 2007 7:51 pm

Just another reactinary dog and pony show paid by the taxpayer. One thing that structural engineers are good at is learning from thier mistakes.

Posted by: willie- Wed Aug 08, 2007 2:50 pm

Deldot post BS summed up!

Paragraph 1+2 We are doing an excellent job for Delaware!

Paragraph 3 we need more money!

The rest just filler pr BS!

Posted for those with ADD and want the short version!

Posted by: kim- Wed Aug 08, 2007 2:08 pm

How old are the trusses supporting the Augustine bridge? I'll bet they will last a lot longer than anything more in the last 40 years.

Post a Comment   View All Comments