Hi, everyone. I am trying to put together a Strength Reduction Factors table, per ACI 318-05, similar to the one from Notes on ACI 318-95. I hope all of you will join me in this "project" and help make it a success.
As you all know, the strength reduction factors have recently undergone some changes, as ACI tightens up the factors based on new research and findings. From responses to this forums, not all of us are still aware of this changes.
Please check the table for accuracy for accuracy, and completeness, and add on other factors that may have been left out. Place a Section reference beside the phi factpr (where there is none now) for ease of verification. If possible, please add specific situations or locations where the factors may be used for those who are still not very familiar with their usage. Look for typos and general inaccuracies, too.
The aim is to produce as comprehensive as possible a one-stop Strength Reduction Factors Table that each one can print out, tabulate, and place it somewhere for easy and convenient reference. Remember, many hands make light work. Let's make it a good one.
[red]ACI 318-05
STRENGTH REDUCTION FACTORS*[/red]
FLEXURE, WITHOUT AXIAL LOAD = 0.90
AXIAL TENSION, OR AXIAL TENSION WITH FLEXURE = 0.90 (Section 9.3.2.1)
AXIAL COMPRESSION, OR AXIAL COMPRESSION WITH FLEXURE (Members with spiral reinforcement conforming to Section 10.9.3) = 0.70** (Section 9.3.2.2 (a))
AXIAL COMPRESSION, OR AXIAL COMPRESSION WITH FLEXURE (Other reinforced members) = 0.65** (Section 9.3.2.2. (b))
AXIAL COMPRESSION, OR AXIAL COMPRESSION WITH FLEXURE (Members in high seismic zones with factored axial compressive forces exceeding (Agf'c/10) if transverse reinforcement does not conform to Section 21.4.4) = 0.5
SHEAR AND TORSION = 0.75 (Section 9.3.2.3)
SHEAR AND TORSION (in regions of high seismic risk)(Nominal shear strength of the member is less than the nominal shear corresponding to the development of the nominal flexural strength of the member) = 0.6
SHEAR AND TORSION (in regions of high seismic risk)(Shear in joints of buildings) = 0.85
BEARING ON CONCRETE (except fo post-tensioned anchorage zones and strut-and-tie models)*** = 0.65 (Section 9.3.2.4)
FLEXURE IN PLAIN CONCRETE = 0.65
POST-TENSIONED ANCHORAGE ZONES = 0.85 (Section 9.3.2.5)
STRUT-AND-TIE MODELS****, and struts, ties, nodal zones, and bearing areas in such models = 0.75 (Section 9.3.2.6)
FLEXURAL SECTIONS IN PRE-TENSIONED MEMBERS WHERE STRAND EMBEDMENT IS LESS THAN THE DEVELOPMENT LENGTH AS PROVIDED IN SECTION 12.9.1.1 (from the end of the member to the end of the transfer length) = 0.75 (Section 9.3.2.7 (a))
FLEXURAL SECTIONS IN PRE-TENSIONED MEMBERS WHERE STRAND EMBEDMENT IS LESS THAN THE DEVELOPMENT LENGTH AS PROVIDED IN SECTION 12.9.1.1 (from the end of the member to the end of the development length, phi shall be permitted to be linearly increased from 0.75 to 0.9 (Section 9.3.2.7 (b))
*Design strength provided by a member shall be taken as the nominal strength, calculated from the design aids given in this handbook, multiplied by the appropriate strength reduction factor, phi. Alternate strength reduction phi factors for use with ASCE 7 load factors are included in ACI 318-05, Appendix C.
**See ACI 318-05 Section 9.3.2.2, or Appendix B, for adjustment to these phi values for low levesl of axial compression.
***See also ACI 318-05, Section 18.13.
****See also ACI 318-05, Appendix A
Thanks, y'all and have a great weekend.
As you all know, the strength reduction factors have recently undergone some changes, as ACI tightens up the factors based on new research and findings. From responses to this forums, not all of us are still aware of this changes.
Please check the table for accuracy for accuracy, and completeness, and add on other factors that may have been left out. Place a Section reference beside the phi factpr (where there is none now) for ease of verification. If possible, please add specific situations or locations where the factors may be used for those who are still not very familiar with their usage. Look for typos and general inaccuracies, too.
The aim is to produce as comprehensive as possible a one-stop Strength Reduction Factors Table that each one can print out, tabulate, and place it somewhere for easy and convenient reference. Remember, many hands make light work. Let's make it a good one.
[red]ACI 318-05
STRENGTH REDUCTION FACTORS*[/red]
FLEXURE, WITHOUT AXIAL LOAD = 0.90
AXIAL TENSION, OR AXIAL TENSION WITH FLEXURE = 0.90 (Section 9.3.2.1)
AXIAL COMPRESSION, OR AXIAL COMPRESSION WITH FLEXURE (Members with spiral reinforcement conforming to Section 10.9.3) = 0.70** (Section 9.3.2.2 (a))
AXIAL COMPRESSION, OR AXIAL COMPRESSION WITH FLEXURE (Other reinforced members) = 0.65** (Section 9.3.2.2. (b))
AXIAL COMPRESSION, OR AXIAL COMPRESSION WITH FLEXURE (Members in high seismic zones with factored axial compressive forces exceeding (Agf'c/10) if transverse reinforcement does not conform to Section 21.4.4) = 0.5
SHEAR AND TORSION = 0.75 (Section 9.3.2.3)
SHEAR AND TORSION (in regions of high seismic risk)(Nominal shear strength of the member is less than the nominal shear corresponding to the development of the nominal flexural strength of the member) = 0.6
SHEAR AND TORSION (in regions of high seismic risk)(Shear in joints of buildings) = 0.85
BEARING ON CONCRETE (except fo post-tensioned anchorage zones and strut-and-tie models)*** = 0.65 (Section 9.3.2.4)
FLEXURE IN PLAIN CONCRETE = 0.65
POST-TENSIONED ANCHORAGE ZONES = 0.85 (Section 9.3.2.5)
STRUT-AND-TIE MODELS****, and struts, ties, nodal zones, and bearing areas in such models = 0.75 (Section 9.3.2.6)
FLEXURAL SECTIONS IN PRE-TENSIONED MEMBERS WHERE STRAND EMBEDMENT IS LESS THAN THE DEVELOPMENT LENGTH AS PROVIDED IN SECTION 12.9.1.1 (from the end of the member to the end of the transfer length) = 0.75 (Section 9.3.2.7 (a))
FLEXURAL SECTIONS IN PRE-TENSIONED MEMBERS WHERE STRAND EMBEDMENT IS LESS THAN THE DEVELOPMENT LENGTH AS PROVIDED IN SECTION 12.9.1.1 (from the end of the member to the end of the development length, phi shall be permitted to be linearly increased from 0.75 to 0.9 (Section 9.3.2.7 (b))
*Design strength provided by a member shall be taken as the nominal strength, calculated from the design aids given in this handbook, multiplied by the appropriate strength reduction factor, phi. Alternate strength reduction phi factors for use with ASCE 7 load factors are included in ACI 318-05, Appendix C.
**See ACI 318-05 Section 9.3.2.2, or Appendix B, for adjustment to these phi values for low levesl of axial compression.
***See also ACI 318-05, Section 18.13.
****See also ACI 318-05, Appendix A
Thanks, y'all and have a great weekend.
