CROSS Safety Report
Differing reinforcement couplers
This report is over 2 years old
On a recent project, because of supply problems, the contractor decided to change from the specified rebar couplers (type ‘A’) to those of another manufacturer (type ‘B’).
Key Learning Outcomes
For construction professionals:
Any proposed changes to the specified connection detail should be approved by the design engineer
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On a recent project, because of supply problems, the contractor decided to change from the specified rebar couplers (type ‘A’) to those of another manufacturer (type ‘B’). This was done without informing the consulting engineer. Although they look similar unless closely inspected, the two types have different tapered threads and thread pitches.
The threaded bars of type ‘B’ will not go into the couplers of type ‘A’ because they are slightly larger; however the threaded bars of type ‘A’ will go into the couplers of type ‘B’. The problem is that because the threads and taper are different the threaded bars of type ‘A’ do not engage properly with the type ‘B’ couplers and render the coupler joint ineffective.
The problem was discovered because the concrete cracked at the affected connection. The reporter concludes that it is important to ensure that couplers are not replaced with different makes on the same project.
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Another confirmation of the need for alert site engineers. Also, confirmation that any propriety product must be used exactly as given in the manufacturer’s instructions.