Evaluation of effects of fire on the I-465 mainlines bridges.

摘要

On October 22, 2009 in Indianapolis, IN a semi tanker carrying liquefied propane lost control on the underpass from I-69 southbound to I-465 eastbound, crashing beneath the east and westbound bridges carrying mainline I-465 traffic. The tanker rolled, causing the tractor to catch fire and the propane tanker to explode. There were concerns the steel superstructure and the high-strength (HS) bolts used in the beam splices were affected by the fire. Also, since the bridge deck was built composite with the steel superstructure, there were concerns the composite action might have been lost or diminished causing the bridge to not behave as it was originally designed. Therefore, the study was focused on identifying any short-term or long-term effects the bridge may have sustained due to the fire exposure. To address the short-term effects, immediately after the accident, several core samples and HS bolts were removed and sent to independent testing laboratories. To establish any long-term effects, field testing was performed over a period of approximately four (4) months. Weldable resistance strain gages were installed at key locations to understand the behavior of the bridge under load and to develop the stress-range histograms. Both controlled load tests, using test trucks of known weight and geometry, and long-term monitoring of random traffic were performed as part of the study.;The results presented in this report show the following: · The explosion and subsequent fire did not negatively impact the properties of the steel in the main girders, nor the properties of the HS bolts. · The explosion and subsequent fire did not negatively impact the overall load distribution nor adversely alter the behavior of the bridge. · Controlled load testing and long-term monitoring confirmed the steel girders are acting compositely with the concrete deck. · Based on the results of the long-term monitoring, infinite fatigue life is expected at all the monitored locations.