D13.C.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 SNiP 2.01.07.- 85 Loads and Actions.

The coefficient of reliability for destination GAMA n according to SP 20.13330.2011 shall be taken in to account determining loads or their combinations.

According to the European standards, 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.

Note: If there are doubts about the conformance of the European steel type and the standard, it is necessary that the steel type designation used by the ENSGR parameter be set the same as the standard selected in the ENMAIN parameter. If the chosen steel type is not present in the chosen standard, then the program exits with the error code MEMBER NO.145 STEEL S275 IS NOT PRESENT IN EN 10025-6 * ERROR * The calculation will be terminated if the thickness of the designed member web or flange thickness is outside the limits of the steel standard. The error code will be issued: MEMBER NO. 1000 CURRENT THICKNESS IS OUT OF EN 100219-1 * ERROR *

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/R_yy_c presented in calculation results. A section is economical when said ratio equals to 0.9 – 0.95.