Welding on In-Place Embed Plates
AISC’s Steel Solutions Center frequently receives questions related to welding in situations that are not ordinary or where special fixes are needed after something has gone wrong. To address these questions and other welding dilemmas, special care was taken in Design Guide 21: Welded Connections (Second Edition) to expand upon Special Welding Applications. Enhanced since the First Edition, the Design Guide now includes a chapter on Problems and Fixes which addresses commonly encountered problems with practical advice to solve the issues.
In the August 2019 SE University session, Duane Miller, PE, from The Lincoln Electric Company, presented Introducing Design Guide 21: Welded Connections (Second Edition). Duane covered some unique requirements for special welding applications, suggested potential solutions to frequently encountered problems associated with welded construction, and reviewed the approach used in AWS D1.1 to address unusual situations and the role of the EOR.
Duane began by offering 10 tips to avoid pitfalls with welding on in-place embed plates as covered in Chapter 14.14 of Design Guide 21. Welding to in-place plates can cause cracking of the surrounding concrete due to expansion or distortion of the heated steel.
The following tips can minimize the heat effects from welding:
1. Use embed plates that are ½” [13mm] thick.
2. Select steel grades and thicknesses for which preheat of the embeds will not be required.
3. Arrange anchorage elements away from the locations where field welds will be required.
4. Design embed plate assemblies to resist distortion.
5. Design the field welded connection to allow for the smallest weld size possible.
6. Provide a perimeter gap between the edge of the embed and the concrete.
7. Allow the concrete to dry and cure before field welding.
8. Avoid overwelding in the field.
9. Control interpass temperature.
10. Test critical assemblies with mock ups.
Additional consideration should be taken when welding to stainless steel embed plates, as stainless steel distorts significantly more than carbon steel, thus making these tips more critical to the success of welding to stainless steel embeds. Welding to galvanized steel is addressed in Chapter 14.2 and the concepts covered there would apply to galvanized embed plates as well. Using these tips will minimize many of the issues that can arise when welding to in-place embed plates.