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re: threaded rebars

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Szuchuan,
 
You could weld the bars to the bottom of a base plate and cast that into the footing. We use all-thread rods with a small steel square plate (PL1/4x2x2) on the end of each rod and use bar development values, though I don't know if this is in ACI or not, always assumed an all thread rod with threads through the length would have as much surface bond strength as a deformed bar. The oversized washers are there for insurance.
 
Or with really big uplifts we have used an embed plate the same size as the base plate, then can design the plate for upward punching shear rather than pull-out of each rod. For additional cheap safety detail a couple of bars laying on top of the plate for additional shear resistance. Like a big upside down truncated pyramid, basically similar to the failure mode of a group of 4 bolts that are not spaced very far apart.
 
Finally, you can often get higher values from various epoxy and expansion bolt mfr tables then you would from ACI App D, as they base their values on repetitive testing rather than formulas that cannot account for everything.
 
Also, I have found Simpson's ACI APP D program pretty useful for (4) bolt connections, which covers most base plates...
 
HTH,
Andrew
 
Andrew Kester, P.E.
Principal/Project Manager
ADK Structural Engineering, PLLC
1510 E. Colonial Drive, Suite 301
Orlando, FL 32803