A 69-ft. (21 m) by 3-in. (7.62 cm) section of sidewalk on the Delor Street Bridge over Interstate 55 in St. Louis fell on the highway below, blocking the northbound lanes for several hours on March 1 at approximately 8 p.m. The debris was immediately cleared and analyzed by Missouri Department of Transportation (MODOT) inspectors and engineers.
Built in 1963, the Delor Street overpass has reinforced steel rods holding sidewalks in place on both sides of the street. Such bridges are inspected every two years. The Delor Street overpass passed its 2005 inspection, said MODOT Director Pete Rahn.
As a result of the incident, MODOT ordered immediate reinspections of all bridges of similar design throughout the state to determine the extent of deterioration. It was eventually found of the 119 bridges inspected, 60 will require emergency procedures to secure them.
This process began when MODOT solicited bids on March 9 and March 14 to repair the bridges. Contracts were awarded to Wales Contracting Inc. of St. Joseph, Mo.; Progressive Contractors Inc. of St. Michael, Minn.; and Gershen Construction Co. Inc. of Eureka, Mo., to institute repairs.
“We’ve determined that water leaking through cracks has corroded pins that held the walkway overhang in place,” said Rahn. “An emergency contract will be in place to put secure bolts on all the overpasses found to have similar problems.”
MODOT also notified the Federal Highway Administration regarding this matter.
“To our knowledge this has never happened before nationwide,” said Rahn, “and we want the FHWA to notify other states.”
According to David Scrivens, engineer of MODOT, “The sidewalks in question will be pinned to the underlying bridge deck by drilling holes and fitting them with No. 5, epoxy-coated steels pins.
These pins will then by epoxied in place. As a preventive measure a silicone joint sealant was placed between the sidewalk curb and the bridge slab to inhibit drainage and seepage beneath the sidewalk.”
Scrivens also stated that any deteriorated and defective surface concrete will be removed as directed and replaced with a rapid set concrete patching material. This material will have a 4,000 psi (276 bar) comprehensive strength after seven days and a bond strength of 1,000 psi (69 bar) bond strength after seven days.
On March 14, MODOT awarded emergency contracts to seven contractors to implement immediate repairs on 45 bridges in the St. Louis area, 12 in the Kansas City area and three in St. Joseph, Mo. The cumulative bids totaled $691,422. Work on the bridges was completed in May. CEG