Image: NTSB via Munilla Construction Management
Cracking that appeared in the Florida International University (FIU) bridge days before it collapsed was more extensive than previously disclosed, according to a preliminary report released this week by the National Transportation Safety Board (NTSB), the Miami Herald has reported.
The images in the document show four large cracks developing in the location of the span that is believed to have failed on March 15, which killed six people. The cracking appears much wider and more severe than smaller cracks found in the structure before it was lifted into place on March 10, as reported by the Herald.
No conclusions were put forward as to the cause of the collapse, but the six-page report from the NTSB did not find problems in the concrete and steel bars used in the bridge. The photographs released by the NTSB were taken a day or two before the collapse.
The report discloses that the Federal Highway Administration (FHWA) has taken part in the investigation, providing resources and expertise to evaluate materials used in the construction of the bridge. FHWA and NTSB investigators have conducted various tests to evaluate multiple concrete core and steel samples taken from the bridge following the collapse. In addition, one one of the steel post-tensioning rods from diagonal member 11 involved in the re-tensioning activity from the day of the collapse and the hydraulic jack used to tension the rods have been evaluated. The NTSB says the initial results from the tests have not indicated any notable material issues.
NTSB investigators have completed the majority of interviews of engineers, contractors, consultants, and Florida DOT officials, and expects to complete any remaining interviews in early August. Experts interviewed by the Herald say investigations such as these can take a year or longer.
Source: Miami Herald / NTSB