Design Yield Strength
Methods used to determine the design yield strength using various standards.
AISC (All Codes)
The design yield strength, Fy, is the value specified by the user. No reduction is made for thick sections.
CAN/CSA S16
The design yield strength is associated with the members material grade as defined in Table 6-3 of the CISC handbook of Steel Construction, Seventh Edition, Tenth Edition, and Eleventh Edition in the S16-01, S16-09, and S16-14 respectively. To assign the grade for a member the engineer selects the appropriate material type using the command in the RAM Managerr. In the RAM Modeler the engineer assigns a nominal yield strength, Fy, to the beam section. Based on the combination of the nominal yield strength and the material type a grade is selected. For example a nominal Fy of 350N/mm2 and a material type W results in a section of grade 350W. Note that a nominal yield strength slightly less than 350N/mm2 will result in a section of grade 300W. If no appropriate grade is available (based on the user-entered values) then the design yield strength will effectively be set to 0.0 and "NoGrade" will be assigned as the grade for the section.
BS 5950
The design yield strength is the yield strength according to the material grade as defined in Table 6 of BS5950:Part1:1990 and in Table 9 of BS5950:Part1:2000. To assign a grade to a section the engineer assigns a nominal yield strength (py) to the beam section. Based on the magnitude of the nominal yield strength the section is assigned a grade from the table. If the nominal yield strength is within a range of yield strengths indicated in the table then the associated grade is assigned to the section and the rules relating material thickness to design yield strength are followed. If the nominal yield strength is not within a range of yield strengths indicated in the table then the design yield strength is assigned the nominal yield strength value, and no reduction is made for material thickness. The design yield strength will never be larger than the engineer provided nominal yield strength. For composite construction, py is limited to 355 N/mm2 as required by Clause 3.1.
Eurocode
For steel with nominal fy between 275 N/mm2 and 460 N/mm2 the design yield strength is adjusted to account for material thickness. In , the Eurocode Factors tab has an option to specify that the Design fy rules be used based on either EN 1993-1-1 or EN 1993-1-1 UK NA.
EN 1993-1-1: For hot-rolled shapes, Table 3.1 of BS EN 1993-1-1:2005 rules per EN 10025-2 are used except for S420 and S460, for which the rules of EN 10025-3 are used. For structural steel hollow sections the rules of Table 3.1 of BS EN 1993-1-1:2005 rules per EN 10210-1 are used.
EN 1993-1-1 UK NA: For hot-rolled shapes, rules from Table 1.5 of BS EN 10025-2 are used. For structural steel hollow sections the rules of Table A.3 of EN 10210-1 are used, except for S420 and S460 which use the rules for Table B.3.
For steel with a nominal Fy not recognized by those tables, the section will be assigned a small yield strength and fail in design. A large interaction value on a design is indicative of assigned yield strength outside the ranges indicated above.
Both nominal and design Fy appear on all design output.
AS 4100
The design yield strength is a function of both the material and the element thickness properties of the section. The user-provided Nominal Yield Strength (Fy) is first mapped to an appropriate material according to Table 2.1 of the AS 4100-98 code. The material that is used is based on the material that most closely matches the yield strength specified and the section shape.
The following materials are used based on the yield strength assigned to the member.
| Specified Fy (MPa) | Shape | Material Used |
|---|---|---|
| 250-280 | I, Channel | AS/NZS 3679.1 250 |
| 280-330 | I, Channel | AS/NZS 3679.1 300 |
| 330-380 | I, Channel | AS/NZS 3679.1 350 |
| 380-400 | I, Channel | AS/NZS 3679.1 400 |
| 200-350 | Tube | AS/NZS 1163 450 |
| 350-450 | Tube | AS/NZS 1163 350 |
| 450-500 | Tube | AS/NZS 1163 250 |
For steel with a nominal Fy outside of the ranges specified no steel material will be found and the section will be assigned a small yield strength and fail in design. A large interaction value on a design is indicative of assigned yield strength outside the ranges indicated above.
Each of these materials provides different yield strength depending on the thickness of the elements (flange, web etc) of the cross section being designed. Refer to Table 2.1 of AS 4100-98 for details on the material and yield strengths for different thickness elements.