Atlanta Botanical Garden Walkway Collapse Investigation
On 19 December 2008, a large portion of the S-shaped, steel-framed walkway under construction at the Atlanta Botanical Garden suddenly collapsed during concrete placement operations. The approximately 575 ft long, cable-stayed canopy bridge was designed to be supported by four masts along the curved spline segments and two opposing inclined columns at the transitional straight spline segments. At the time of collapse, the walkway structure was supported on temporary shoring tower frames and helical piles. SGH investigated the cause of the collapse.
SGH performed a detailed study of movement and structural behavior to help identify the failure initiation location and probable cause of collapse. Our work included a site investigation, project document review, and an iterative structural analysis. Highlights of our investigation include the following:
- Reviewed construction photos to compare the erected locations of shoring tower frames and grillage members with their post-collapse locations and stacked configurations
- Studied spline impact marks on the ground and shoring members below, which showed varying degrees of post-impact translation at points along the length of the collapsed walkway structure
- Evaluated type and directionality of bolt failures at spline beam splices and abutments, bends of steel grillage members, and angles of inclination of shoring tower support piles above the ground surface
We narrowed the collapse initiation to one of two adjacent shoring towers, just within the extent of concrete placement operations at the time of collapse. Our investigation techniques brought clarity to the scattered collapse debris and the project as a whole.
This project was completed in collaboration with Wasson, Sours, & Harris, P.C. and Freeman Mathis & Gary, LLP (attorneys) and GeoSurvey, Ltd. (surveyor).