Evaluation and Repair of Existing Post Tensioned Concrete Slab without Original Construction Drawings

Structural assessment and evaluations were performed for the post tensioned (PT) concrete facility located in Williamsburg, Virginia. The facility is a six-level, concrete framed structure constructed in the 1970s and includes two levels of underground parking and four levels of occupied residential spaces. The project initiated from the exposed failed PT tendons observed at several locations in the garage level, and the scope expanded to other remaining floors concerning the failure of the PT tendons and structural stability of the structure. Furthermore, a condition assessment was performed to evaluate the damages of the PT tendons, to examine the as-built conditions of the structure, to find the cause of the damages, and to develop the repair design. The original construction drawings were not available, and the project required development of the base drawings including general concrete floor construction, locations of construction joints, and PT tendon layout in plan. Non-destructive testing was used to locate the PT tendons and their profile, exploratory openings were made to examine the conditions of the PT tendons, samples were taken to examine the material properties of the concrete and PT tendons, structural analyses were performed to evaluate the existing structure, and a repair design was developed to remediate the conditions. Various repair techniques were applied including concrete repair, PT tendon replacement, tendon splicing, and new anchorage placement.