Taking a new approach to concrete

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ACI 562 sets standards for routine repair methods not covered by previous building codes, such as considerations related to installing carbon-fibre-reinforced polymer (CFRP). The code’s companion guide gives a project example in which cracks were discovered in double-tee stems, supporting the roof at a water treatment plant (shown at left). ACI 562 provisions guide included installing CFRP sheets, finished with acrylic coating.

2. A repair-specific code saves money.
As ACI 562 does not require the repair and rehabilitation design to meet building codes for new construction, the designer can devise applicable, and often more economical, repair solutions. Techniques and materials can be tailored to the structure’s unique and specific needs, considering factors such as age, original materials used, and environmental conditions.

ACI 562 has also been referenced in expert reports for litigation cases, resulting in significantly reduced financial settlements. Denver-based J.R. Harris & Company (JRH) recently used it in several litigation reports assessing damages in existing concrete structures.

As an approved consensus standard (i.e. according to American National Standards Institute [ANSI] procedures), ACI 562-13 has been accepted as the source standard to use for damage assessment and repair design on individual projects by Greenwood Village and Pikes Peak Regional Building Departments in Colorado. In these instances, JRH was able to cite ACI 562 in its recommendation for structural remediation and determination of damages.

Chapter 4 of ACI 562 describes the compliance method to use in a repair project. In general,
the ‘original’ building code is used for minor alterations—the ‘current’ building code (e.g. 2012 IEBC or IBC) serves as the design basis for major alterations or significant load changes, while the ‘existing’ building code (e.g. 2012 IBC) applies to evaluation and design of rehabilitation of seismic damage. Unless structurally unsafe, deterioration or faulty construction in an existing building will not require modifications to satisfy the current building code.

By applying the lesser of the demand-to-capacity ratio required by the original building code or the current building code (if upgrades to the current building code are not required by the jurisdiction), the costs to correct faulty construction can be lower than if they are set strictly by current building code requirements. In one case involving rehabilitation work on four buildings with faulty construction, JRH was able to reduce the repair costs from $12 million to $3 million, with a repair plan based on the lesser of the demand-capacity ratio based on either the original or current building code per ACI 562.

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Faulty construction in four condominium buildings resulted in insufficient reinforcing being provided in some of the podium-level support beams. As shown above, the consulting engineer used provisions in ACI 562 in order to design an external post-tensioning system to strengthen the beams, in lieu of completely reconstructing the structural elements. Photos courtesy Gene R. Stevens

3. Stakeholder responsibilities are clarified.
For the first time, ACI 562 clearly establishes the responsibilities of owners, designers, and contractors involved in concrete repair. For example, Chapter 9 summarizes specific roles and responsibilities for three considerations often encountered in repair projects:

  • stability and temporary shoring;
  • temporary conditions; and
  • environmental issues.

According to ACI 562, a licensed design professional must include requirements for stability and temporary shoring in a repair project. The shoring engineer (typically a third party hired by the contractor) follows ACI 562 provisions to design shoring and bracing. The contractor is responsible for determining the means and methods of executing the repair process.

Once repairs are underway, the contractor should notify the licensed design professional to observe the deterioration, faulty construction, or damage during construction to determine whether it is more severe or different than anticipated. The designer can then determine what measures are necessary to maintain structural integrity while repairs are implemented.

When designers, contractors, owners, and building officials are working from the same code, the entire project team has the same expectations regarding the design and execution of concrete repairs.

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