Contractors install protective coating on a parking deck floor slab in accordance with ACI 562, which was developed specifically for concrete repair. A new guide to the code helps clarify designers’ and contractors’ requirements and responsibilities.
Credit: ACI Contractors install protective coating on a parking deck floor slab in accordance with ACI 562, which was developed specifically for concrete repair. A new guide to the code helps clarify designers’ and contractors’ requirements and responsibilities.

When a popular Southwestern resort agreed to host a large tradeshow, handling the crowd of attendees wasn’t an issue. But housing exhibitors’ 18-wheelers in the upper parking deck was another story.

Not designed for such heavy loads, the early-1980s, two-level structure literally cracked under the pressure. A support girder was heavily damaged, and rain leaked through reflective cracking on the top deck into a storage area and valet parking spaces below. Deterioration of the bearing pads under precast double-tee beams also caused extensive deck cracking.

Repair and rehabilitation specialist Brian D. Merrill, P.E., of engineering firm Wiss, Janney, Elstner Associates (WJE), Northbrook, Ill., was asked to devise a repair strategy. Merrill is part of WJE’s team in Austin, Texas, that focuses on structural, architectural, and materials solutions.

“With existing structure repair, you’re faced with whether to follow the original design intent or the current code for specifications,” Merrill says. He researched the building code that applied when the parking deck was built, but needed a current reference to determine the best code to use.

Merrill used the first code written specifically for concrete repair: the American Concrete Institute’s (ACI) Code Requirements for Evaluation, Repair, and Rehabilitation of Concrete Buildings (ACI 562-13). Developed in response to a need expressed in the Vision 2020 plan, which was established by the ACI Foundation’s Strategic Development Council and supported by the International Concrete Repair Institute (ICRI) and other industry leaders in 2006, ACI 562 addresses many considerations that are unique to concrete repair.

“In cases where the code has changed over the years, it provides a specific process for determining the most applicable code to follow in repairing a damaged structure,” he says.

Focusing on performance

Vision 2020 recognized the need for consistent practices to improve quality, safety, and efficiency. Without the benefit of a specific standard, repair practices were inconsistent. Building inspectors often referred to codes for new construction, resulting in unnecessarily costly repairs or even demolition in lieu of rehabilitation.

ACI Committee 562 on Evaluation, Repair, and Rehabilitation of Concrete Buildings spent seven years creating a common resource for designers, contractors, municipalities, and building inspectors that clearly establishes each party’s responsibilities. Because repair involves so many variables (materials used, strength needed, age of the structure), the code is ACI’s first to include both performance and prescriptive requirements.

The performance-based approach allows licensed design professionals to use their judgment in determining the best repair approach while still following minimum baseline requirements. For instance, repairing a parking structure involves different evaluations and strength requirements than converting a warehouse space into apartments. However, both must meet minimum code provisions.

“The performance criteria give direction for determining the level of repair needed, rather than making it conform to specific criteria,” says Merrill.

For the resort’s damaged parking deck, he evaluated how much strength was needed to restore the structure to current code specifications. The deck’s layout didn’t prevent oversized vehicles from returning to the top deck, so he opted to design it to the highest strength and safety levels. That turned out to be the original code.

To return the structure to full use, Merrill employed both structural and surface repairs.

Temporary shoring was installed under the damaged girder immediately after WJE’s field assessment, according to ACI 562. A supplemental support column will be installed to support the damaged girder and the double-tee beams will be lifted to facilitate bearing replacement. The top deck will also be resurfaced to repair the reflective cracking.