D13.E.1 General

Design Code SP Steel Structures –as is the case in the majority of modern codes– is based on the method of limit states. The following groups of limit states are defined in the Code.
• The first group concerns losses of general shape and stability, failure, and qualitative changes in configuration of the structure (i.e., ultimate limit states). Appearance of non-allowable residual deformations, displacements, yielding of materials or opening of cracks.

Analysis of structures for the first limit state is performed using the maximum (design) loads and actions, which can cause failure of structures.

• The second group concerns states of the structure which worsen their service or reduce durability due to exceeding allowable deflections, deviations, settlements, vibrations, etc. (i.e., service conditions).

Analysis of structures for the second limit state is performed using service (normative) loads and actions. Relation between design and normative loads is referred to as coefficient of load reliability, which is defined in SP 16.13330.2017.

The coefficient of reliability for destination GAMA n according to SP 20.13330.2017 shall be taken into account determining loads or their combinations.

According to SP 16.13330.2017, the strength of steel is represented by the characteristic value. To obtain the design value, the steel reliability coefficient GAMM is used. The default value of GAMM is 1.0.

Only members from rolled, tube, and roll-formed assortment sections, and compound sections (such as double angles of T-type sections, double channels) are may be designed in STAAD.Pro.

Economy of selected section is indicated by ratio the ration (which can be set using the RATIO parameter) σ/Ryyc presented in calculation results. A section is economical when said ratio equals to 0.9 – 0.95.

Various checks are made according to SP 16.13330 Design Code, particularly implementing Clauses:
• 7.1. Calculation of elements in central tension and compression with solid sections
• Cl. 7.1.1 Eq. (5)
• Cl. 7.1.3 Eq. (7)
• 7.3. Stability check of walls and flanges of center-compressed elements with solid sections
• 8. Calculation of elements in bend
• Strength calculation of bending elements with solid sections
• Cl. 8.2.1 Eq. (41), (42), (43), (44) – for 1st Class Elements
• Cl. 8.2.3 Eq. (50), (51), (53), (54), (55) – for 2nd and 3rd Class Elements
• Calculation of general stability of bending elements with solid sections
• Cl. 8.4.1 Eq (69), (70)
• 9. Calculation of elements in sinuous central force
• Strength calculation of elements with solid sections
• Cl. 9.1.1 Eq. (105), (106)
• Cl. 9.1.2
• Calculation of stability of elements with solid sections
• Cl. 9.2.1
• Cl. 9.2.2 Eq. (109)
• Cl. 9.2.4 Eq. (111)
• Cl. 9.2.5 Eq. (112), (113), (114)
• Cl. 9.2.7
• Cl. 9.2.8
• Cl. 9.2.9 Eq. (116), (117)
• Cl. 9.2.10 Eq. (120), (121), (122)
• 10.4. Ultimate Slenderness of Elements
• Cl. 10.4.1
• Steel Grades are determined from Appendix C, Tables C.3, C.4, C5.
• Coefficients for the calculation of the stability of centrally- and eccentrically- compressed elements are determined from Appendix E (normative), Tables E.1, E.2, E.3, E.4, E.6.
• Coefficients for calculation of constructional elements with regard to the development of plastic deformations are determined from Appendix F (normative), Table F.1
• Stability coefficient ϕb at a bend is calculated according to Appendix G (obligatory).

Also, the Selection of steel of hot rolled sections, plates, tubes and pipes is implemented.