Tennessee highway officials believe an impact from a vehicle’s oversized load is likely to blame for the April 1 partial collapse of a ramp structure at the I-75/I-24 interchange in Chattanooga. The impact caused the outer box beam and railing of the 148-ft-long bridge’s nearly 51-ft main span to fall onto an access ramp, injuring a motorist whose vehicle collided with the debris.
A forensic investigation conducted by the Tennessee Dept. of Transportation suggests a hardened piece of steel or similar material sliced through five 3⁄8-in.-dia reinforcing strands in the beam, which had a vertical clearance of 16 ft, 10 in.