JohnnyB_
Structural
- Feb 1, 2022
- 82
Hello -
I am working on designing a grade beam foundation supported by micropiles. The foundation will be supporting light residential loads and the loads have been calculated using LRFD load combinations. The contractor is choosing to use micropiles as opposed to overexcavation. These two methods of design have been proposed due to the expansive shale at the build site.
I am using Publication No. FHWA NHI-05-039 to design the micropiles. In the publication there are a few design equations and examples but it does not look like they are incorporating any factors for ASD/LRFD design. As an example the equation for the allowable compression (Pc) load is attached. I have highlighted the grout portion of the equation in yellow and the steel portion of the equation in green. In order to get the design strength (ΦcPc) should I be multiplying the different portions of the equation by the appropriate Φ factors, (Φ concrete compression = 0.85 and Φ steel compression = 0.9)?
I am working on designing a grade beam foundation supported by micropiles. The foundation will be supporting light residential loads and the loads have been calculated using LRFD load combinations. The contractor is choosing to use micropiles as opposed to overexcavation. These two methods of design have been proposed due to the expansive shale at the build site.
I am using Publication No. FHWA NHI-05-039 to design the micropiles. In the publication there are a few design equations and examples but it does not look like they are incorporating any factors for ASD/LRFD design. As an example the equation for the allowable compression (Pc) load is attached. I have highlighted the grout portion of the equation in yellow and the steel portion of the equation in green. In order to get the design strength (ΦcPc) should I be multiplying the different portions of the equation by the appropriate Φ factors, (Φ concrete compression = 0.85 and Φ steel compression = 0.9)?