Code Basics
It has come to the attention of this author that pour strips/leave outs have been replaced by gapless leaves out using a dowel device has been used to connect cast-in-place-slabs. The traditional pour strips/leave outs have always included a code permitted lap splices. The location is often near a point of inflection (i.e., 1/5 span).
The dowel device:
- not ICC-ES code certified.
- Product shear tables do not follow code (ACI) by ACI values are much lower.
- Not made in USA.
- Uses epoxy which is combustible
With the purpose of creating gapless pour strips, and not expansion joints, dowel devices have been used to “connect” (i.e., make continuous) slabs and diaphragm chord steel rebar. Dowels are not one of the three code permitted methods to connect rebar. A dowel of any kind, even headed dowels, are not permitted to connect rebar. The concrete code, American Concrete Institute (ACI) permits 3 types of splices for connecting rebar. 1) lap splices, typically used in pour strips/leave outs, 2) welded splices, and 3) mechanical splices. The key to all ACI 318 designs involving rebar is ductility (i.e., provides warning before collapse). Concrete pull-out anchoring is not a permitted method of connecting any rebar. Further, dowels are not permitted to be part of the diaphragm chord rebar.
Code Basics
Though out all the additions to our structural code books, American Institute of Steel Construction (AISC) or ACI, ductility is paramount to structural safety. Some professionals may have forgotten the basic fundamentals of structural design. These fundamentals are the reason steel structures and concrete structures have continued in use for well over 100 years. Through their ductile behavior these structures give us safety warnings both audio and visual when these structures are near failure. Further, all registration canons start with our obligation to public safety.
The main reason that these two types of structural systems can give us warnings is there ductility. This is the ability of steel to stretch (i.e., yield) considerably prior to total failure or collapse.
One of the problems mostly having to do with reinforced concrete is the inclusion of some critical components that are not ductile. (i.e., dowel action to connect rebar). In 2002 ACI 318 -2002 initially introduced appendix D Anchoring to Concrete, since ACI 318 – 2014 this information is in chapter 17 and continues there in the current ACI 318 – 2019. This severely limited tension values in concrete anchorages. But dowel anchoring devices have never been permitted as a method of connecting rebar through a method that is non-ductile (i.e., pull-out of anchor devices).
Conclusion
Dowels can be used to create an expansion joint between two elevated slabs. Dowels are not a code permitted method to connect rebar. Dowels are not permitted to connect slabs or to connect diaphragm chord rebar. Any use of dowels to structurally connect rebar is not code permitted and is outside of the standard of care for the structural engineer.
