I'm not a bridge guy, but it may be that the language in the IBC regarding drilled shafts was borrowed from the LRFD Bridge Design Manual and not meshed well with the other sections of the IBC. I don't have the Bridge Manual in front of me, but I found Missouri's online version and it sounds...
Ok, so it is plausible that the code's intent could be to ensure adequate load transfer to the rock in skin friction by requiring concrete with similar stiffness & strength properties as the surrounding rock. Makes sense. But, @dauwerda, you also bring up a good point: IBC very specifically...
I agree with Aesur, I see it all the time. I just don't know how it's justified given Table 1808.8.1. (Aesur, What does SSI stand for?) Dauwerda, fair point. The tensile strength difference between 3 & 4 ksi is negligible (maybe 100 psi at best) so probably not what the code is after. But...
Ron, expansive soils swell laterally and upwards simultaneously essentially grabbing onto the perimeter of the pier and heaving it upwards. If properly socketed, the pier will remain in place but will develop a tensile force in the pier. Most geotechnical reports that I've seen address this...
IBC Table 1808.8.1 specifies that the minimum compressive strength for socketed drilled piers is 4,000 psi. I've routinely seen drilled piers specified as 3,000 psi when longitudinally reinforced with a minimum 0.5% steel cage. This section of IBC does not specify if it is in reference to all...
In the Structural Engineering Reference Manual they give a direct solution for solving for rho for beams with tension reinforcing but they do not derive the formula. This seems like a pretty basic step that I should know but I'm having trouble with the math. I think they're using the quadratic...
