Brad Weber–Staff Writer
A bridge on the Florida International University (FIU) campus collapsed onto the highway killing six people on March 15. The bridge utilized accelerated bridge construction (ABC) techniques and technology to minimize traffic delays and improve construction speed.
A full investigation is in progress, and Justin Vander Werff, a Dordt engineering professor, believes that it will uncover the root cause of the collapse.
Vander Werff noticed that the failure occurred near the end of the bridge, not the middle, indicating that the bridge failed in shear, as opposed to bending. The bridge was in place, the supports removed and crews were working on post-tensioning. Post tensioning is a standard process in which steel cables running through the concrete bridge sections are tensioned after the bridge is in place. Because it failed during this step, it’s possible that a mistake was made in the post-tensioning process that led to the catastrophic failure.
FIU is home to the ABC University Transportation Center, a leading research organization in the field of ABC. Vander Werff has met Atorod Azizinamini, the civil engineering chair at FIU, and identifies him as one of the leading figures in the field of ABC. FIU also collaborated with FIGG, a well reputed bridge design firm, to design the bridge. They, in turn, contracted Munilla Construction Management (MCM) to construct the bridge.
Vander Werff explained that no single person or company oversees all aspects of the bridge construction. Usually the design firm is responsible for the final bridge construction, and the construction company is responsible for the intermediate steps during construction. Regardless, certified engineers must approve of each step of the process.
ABC is a method of bridge construction that involves prefabrication of bridge sections offsite, and rapid instillation of the bridge. Sections of the bridge are built offsite, assembled near the bridge location, and then lifted and moved into place. This method has several benefits. Firstly, the bridge sections are usually produced in a dedicated offsite facility that can ensure that each section is built to specifications. Secondly, because of the rapid instillation, ABC reduces the time roads must be closed. Thirdly, the overall construction time and cost is reduced because less onsite work is required.
A recent success of ABC in Iowa is the Keg Creek bridge that was recently installed near Council Bluffs. According to the Iowa DOT, the bridge was installed in two weeks, a much shorter time than the several months that would have been required for conventional bridge construction.
The engineering community takes note of precious failures, and is careful to avoid the same mistakes. Vander Werff has already included the collapse as a potential topic of study in ENG 212.
But the damage has already been done. Vander Werff called it a “double tragedy,” referring to both the fatalities, and the fact that the collapse has harmed the reputation of the ABC University Transportation Center.
The benefits of ABC are high according to Vander Werff, but bad publicity of the collapse will be a major setback