Tabbert, Hahn Earnest & Weddle retained CTLGroup to observe distressed and defective conditions of a subsurface parking structure during its construction. The parking structure was constructed of post-tensioned beams, conventionally reinforced columns, and a foundation system that combined both a reinforced structural mat and isolated footings.
CTLGroup engineers conducted a site visit/condition assessment that included a visual inspection, notes, and photo documentation, and limited nondestructive testing of the conditions. A questionable beam was found during this initial walk-through and was immediately shored to prevent a possible collapse. Findings and recommendations were presented to Tabbert, Hahn Earnest & Weddle and the Library Board. Based on the initial findings, CTLGroup was subsequently retained to conduct a complete field investigation and provide subsequent recommendations for repair.
CTLGroup worked closely with the design structural engineer of record. Closely spaced reinforcement, reinforcement congestion, visible voids in the soffits of the majority of beams, and missing or misplaced shear stirrups were observed. As part of the investigation, CTLGroup performed a review of the construction documents, including structural drawings, structural specifications, reinforcing shop drawings, and selected project documentation including RFIs and RFI responses. This field investigation team forwarded existing condition information onto the repair engineering team, documenting structural conditions before and after demolition as well as before and after repairs were completed.
Responsibilities of the structural analysis team included document review to determine the as-designed and/or as-detailed conditions, determine capacity of documented structural design, determine the design loads used by the structural engineer of record, model the structure, compare output demands with computed capacities, and to assist the concrete repair team by providing design requirements and capacities. Additional responsibilities included coordination with the structural engineer of record for concrete repair techniques, review of field documentation, review of structural requirements, determination of capacity of existing conditions, design of structural repairs, and issuing structural repair drawings and specifications.