SWitmer
Structural
- Mar 10, 2020
- 4
ACI 318-19 expanded table 19.2.1.1 (minimum f'c for various concrete applications) from the version of the table found in ACI 318-14 to include more applications. One new application addressed in this table is "precast-nonprestressed driven piles / drilled shafts", with a minimum value of 4,000 psi.
IBC 2021 table 1808.8.1 has a table with some over-lapping minimum concrete strengths and applications for foundations. Line 1 addresses "Foundations for structures assigned to SDC A, B or C" with a minimum value of 2,500 psi. Line 4 addresses "Socketed drilled shafts" with a minimum value of 4,000 psi. IBC 2021 section 18.3.9.6 specifically defines "socketed drilled shafts" as having "a permanent pipe or tube casing that extends down to bedrock and an uncased socket drilled into the bedrock, both filled with concrete." Other sections in chapter 18 address belled piers as well as other "deep foundations" which may or may not require temporary casing, as differentiated from "socketed drilled shafts."
In my experience with low-rise building design projects in Texas, it has been common to specify 3,000 psi for compressive strength for drilled piers, unless a higher strength was required for flexure or shear reasons. For many projects, the geotech report recommends straight shaft piers which may or may not extend into a bedrock strata, but never with permanent casing which is required to fall into the "socketed drilled shaft" category as defined in the IBC.
It seems like ACI 318-19 may have revised table 19.2.1.1 in an attempt to align with the IBC Chapter 18 table, but has included more foundation elements than the IBC table includes.
Are other engineers using 4,000 psi as a minimum f'c for typical drilled piers when under ACI 318-19 based on this table?
IBC 2021 table 1808.8.1 has a table with some over-lapping minimum concrete strengths and applications for foundations. Line 1 addresses "Foundations for structures assigned to SDC A, B or C" with a minimum value of 2,500 psi. Line 4 addresses "Socketed drilled shafts" with a minimum value of 4,000 psi. IBC 2021 section 18.3.9.6 specifically defines "socketed drilled shafts" as having "a permanent pipe or tube casing that extends down to bedrock and an uncased socket drilled into the bedrock, both filled with concrete." Other sections in chapter 18 address belled piers as well as other "deep foundations" which may or may not require temporary casing, as differentiated from "socketed drilled shafts."
In my experience with low-rise building design projects in Texas, it has been common to specify 3,000 psi for compressive strength for drilled piers, unless a higher strength was required for flexure or shear reasons. For many projects, the geotech report recommends straight shaft piers which may or may not extend into a bedrock strata, but never with permanent casing which is required to fall into the "socketed drilled shaft" category as defined in the IBC.
It seems like ACI 318-19 may have revised table 19.2.1.1 in an attempt to align with the IBC Chapter 18 table, but has included more foundation elements than the IBC table includes.
Are other engineers using 4,000 psi as a minimum f'c for typical drilled piers when under ACI 318-19 based on this table?
