Pedestrian Bridge Collapse Over SW 8th Street HWY18MH009

This animation depicts the sequence of events leading to the collapse of the reinforced concrete pedestrian bridge over SW 8th Street just north of Florida International University in Miami, Florida at March 15, 2018. The animation begins with an overall area view showing the location of the pedestrian bridge relative to the center of the city of Miami, Florida. A satellite picture shows where the pedestrian bridge was to be located on the west side of the intersection of SW 8th Street and 109th Avenue. The bridge was intended to connect Florida International University with the City of Sweetwater by extending over SW 8th Street and the parallel running Tamiami Canal. The first section of the bridge that was built was the section over SW 8th Street, and that is the section that collapsed. Security video shows the construction site where the bridge section was built on the ground adjacent to the roadway. The bridge section was moved from the construction location onto its support piers using two self-propelled modular transporters. An artist’s rendition of the overall conceptual design, and a photo of the constructed bridge section as placed on the piers are used to display elements of the bridge structure, including the deck, the single row of non-redundant truss elements, and the canopy. Truss elements were numbered 1 through 12 beginning from the south. The 174-foot length and 950-ton weight of the bridge section over SW 8th Street are indicated. A three-dimensional computer model of the bridge section is used to describe the pouring of the concrete in three stages: first the deck, then the truss members, and finally the canopy. The model is also used to show the locations of cold joints between elements, and to show the steel reinforcing bars and larger diameter steel post-tensioning rods within the concrete. The model is also used to explain that truss members 2 and 11 were post-tensioned to counteract the tensile forces developed while the ends of the bridge hung over the transporters when the span was moved. Truss members 2 and 11 were de-tensioned after the bridge section was placed on the piers. A series of photographs show growing cracks in the structure at and adjacent to the cold joint between the deck and the bottom ends of truss members 11 and 12 (the north end of the bridge section). The photographs show increasing damage accumulating over the five days the bridge was in place, from March 10, 2018 through March 15, 2018.A photograph from March 15, 2018 shows workers on top of the bridge to re-tension member 11 in an effort to stop the cracking. The collapse of the bridge is shown in a video captured by a dashboard-mounted camera from a truck driving on SW 8th Street. The animation ends with a picture of the collapsed bridge, with inset photographs showing closer views of truss members 11 and 12, the canopy, and the north or pylon pier where the collapse initiated.