In Part 1 of this series, typical precast concrete deficiencies were identified and discussed, in addition to periodic maintenance and inspection recommendations. In Part 2, we will highlight typical repair methodologies of the aforementioned deficiencies and provide examples of completed repair projects.
As discussed, corrosion of embedded steel components is typically the main cause of deterioration at precast garages, especially in the regions where deicing salt use is prevalent. Repair at deteriorated concrete areas due to corrosion induced spalling involves removal of concrete to sound concrete, cleaning of the reinforcing steel and embedded steel connectors, commonly by sand blasting, and forming and pouring of the concrete repair material. A concrete repair material with a corrosion inhibiting admixture is often used. The repair of precast concrete is quite similar to repair of conventional concrete. If the deteriorated area involves exposure of the prestressed steel reinforcing tendons, care must be taken to not disturb or damage the tendons. In a case where the repair exposes a larger section of the prestressed tendons, then the tendons will need to be restressed to their design capacity following the completion of the repair, allowing adequate time for the concrete to reach the design strength. Alternatively, additional reinforcing can be added or an external reinforcing, such as post tensioning, carbon-fiber or steel plate may be implemented based on the result of structural analysis.
Repairs at the flange-to-flange connections and beam end connections typically fall into four separate conditions. Once a connection is exposed and inspected by a qualified engineer, the repair may involve:
Each of these four repairs are followed by application of sealant and backer-rod at the joint between the precast members. Repair programs will generally involve the removal and replacement of all sealants with new backer-rod and sealant, as urethane sealants have a service life of 5 to 8 years at precast parking garages. Other miscellaneous repairs involve routing and sealing of cracks, installation or replacement of drains and drain-lines, replacement of expansion joint seals, wash-down and line-striping.
The concrete repairs often require shoring to be installed and may extend over several levels of a multi-level parking garage. A repair program will involve the closure of a portion or all of a parking garage, depending on the layout of the garage. Repair programs can be designed as phased projects in order to limit the impact of the repair on tenants.
As structural engineering consultants, TCE has assessed and designed repair programs for numerous precast parking structures. Our services ensure a proper, long-lasting repair in a cost effective manner. Some examples of completed projects by TCE are provided following the repair photos below.
