MORGANTOWN, W.Va. — As crews clean up the bridge collapse in Pittsburgh today (Jan. 28), West Virginia University infrastructure expert Hota GangaRao says measures can be taken to prevent similar structural failures in other locations at a lower cost than total replacement. GangaRao also outlines possible causes for bridge failures.
QUOTES – Hota GangaRao, WVU Wadsworth Professor and Director of Constructed Facilities Center – Wadsworth Department of Civil and Environmental Engineering:
If a bridge superstructure that is supporting the concrete deck is not corroded excessively or fatigued, then we can use advanced composite materials (as a carpet) over existing concrete decks after desalting (of course) and fuse with polymer composite glass fabric reinforcement with the concrete deck and increase the strength of a bridge. But we still must make sure that deck supporting members are in good shape. If those supporting members are not in good shape (corroding), then we wrap them with glass composite materials. Such methodology of rehabilitation is about 40% of the cost of replacement and much more user-friendly, and also accomplished in a few days as opposed to three months for conventional repairs. We have successfully adopted the above methodology at USACE Loyal Hanna Dam bridge near Pittsburgh.”
“The bridge deck is the first line of defense for a bridge system. Decks are typically rated lower than the stiffening structural parts underneath the deck due to weather and traffic-related distresses.”
“Nationally, on average concrete decks provide a service life of about 30 to 35 years and this bridge deck rated at 4 in 2011 for a bridge built in 1970 is not surprising.”
In general, bridge failure may be caused by:
— Heavy corrosion of members and joints under the concrete deck from salting (necessary in high volume traffic areas). — Fatigue cracking of steel and jointing systems from high travel volume. — High humidity levels around a bridge can create a halo effect. (In this case, the surrounding park may have contributed to accelerated corrosion due to partial degradation of the superstructure with time.)