When carrying out code checks, Steel Designer uses the following clauses of the applicable codes to check your structure. No other checks are performed unless they are specifically listed below.
Checks are not carried out on composite members or tapered members. Checks on mono-symmetric I sections are not considered as are checks using actions computed using plastic analysis.
§ LRFD
§ LRFD SAM
"Load and Resistance Factor Design Specification for Structural Steel Buildings”, American Institute of Steel Construction, December 27, 1999.
The design checking procedure is as follows:
The net area of the section is computed by subtracting the area of holes in the section. The effective area is then calculated as the net area (An) times the area reduction coefficient (U).
If the member is been checked for tension of compression, the slenderness of the section is checked to ensure that it meets the limits set out in Section B7. For angle members, the slenderness about either of the geometric axes is determined using the minimum radius of gyration of the section.
If the member is a plate web girder, the section is checked to determine is if meets the web slenderness limits specified in Appendix G1.
For each serviceability load case:
The maximum local displacement of the member is compared to the deflection limits specified deflection limits.
For each load case representing a strength limit state,
The design actions, or required strengths, of the member are determined as the maximum moment, shears and axial forces within the member.
For first order analyses, the design bending moments are amplified using the factors determined using clause C2. Only moment amplification of braced frames is considered which corresponds to the situation in which no moments result from the lateral translation of the frame. As such, moment amplification is computed using only the first term of the right hand side of equation C1-1. Amplification factors for sway frames are not considered and a second order analysis should be used for sway frames requiring moment amplification.
The plate elements of the section will be classified as Compact/Non-Compact/Slender as per the requirements of clause B5.1 and Table B5-1. These elements may also be classified as Very Slender if they exceed the limitations set out in Table A-F1.1. If the moments in the member are less than one ten thousandth of the yield moments the section is considered to be in pure compression and will be classified accordingly. If an element of the section is found to be slender, the stiffness reduction factors Q, Qa and Qs will be determined as set out in Appendix B.
For tension checks, the capacity of the member is determined in accordance with section D1.
For compression checks, the capacity of the member is firstly computed for the limit states of flexural buckling about the major and minor axis is accordance with clause E2. The capacity of the member for the limit state of flexural torsional-buckling is then computed using clauses E3 and Appendix E. The compressive capacity of the member is regarded as being the minimum capacity determined for these three limit states.
For bending checks the provisions of Appendix F1 are used. For each of the failure modes, yielding, flange local buckling, web local buckling and lateral torsional buckling, l, lp and lr values are calculated. The values are based upon the section shape and the axis of bending and are derived from Table A-F1.1. After the various l values have been calculated they are then compared to find the appropriate equation to calculate Mn, Equ. A-F1-1 to 4. Each Mn value for the failure modes are then compared with the lowest value governing.
Flange local bucking will only be considered for sections with non-compact flanges. Similarly, web local buckling will only be considered for sections with non-compact webs.
The design for shear is carried out in accordance with clause F2 using the provisions of Appendix F2.2 when a stiffener spacing is specified. For plate girders with slender web elements, the provisions of Appendix G3 will be utilised instead. No calculations are conducted using Chapters K or J.
For the biaxial bending check, interaction equations of Appendix H1 are evaluated ignoring the axial force term. The expressions are computed using the maximum actions in the members. If this check fails, the user
For the combined action check for flexure and compression, the member is checked in accordance with clause H1.1 using the design moments about the major and minor axes. A more refined
"Load and Resistance Factor Design Specification for Single Angle Members”, American Institute of Steel Construction, November 10, 2000.
The design checking procedure is the same as described above for LRFD except that:
The section is classified using the limits set out in clause 4 of LRFD SAM. The same clause is used to compute the slenderness reduction factors and effective area of the section.
Clause 2 of LRFD SAM is used to determine the tensile capacity of the member.
For the bending checks, the shear is determined using clause 3 of LRFD SAM while the flexural capacity is determined using clause 5 of LRFD SAM.
The lateral-torsional buckling capacity of the member for the limit state of lateral-torsion buckling of unequal angle sections without lateral torsion restraint or sections modelled about their principle is not yet supported. When such a section is encountered, the member will have determined to have no flexural capacity.
The capacity of a member under combined forces is computed using clause 6 of LRFD SAM in place of the provisions in clause H or LRFD.