General Steel Design Requirements: Basis For Design

The general design requirements are outlined in Section 3 of IS 800:2007.

 BASIS FOR DESIGN

The bases of the design are given in Section 3.1 of IS 800:2007. It is as follows.

1. Design Objective

The objective of design, as outlined in Cl.3.1.1 of IS 800:2007, is the achievement of an acceptable probability that structures will perform satisfactorily for the intended purpose during the design life. With an appropriate degree of safety, they should sustain all the loads and deformations, during construction and use and have adequate resistance to certain expected accidental loads and fire. Structure should be stable and have alternate load paths to prevent disproportionate overall collapse under accidental loading.

2. Methods of Design

Method of Design of steel structures is given in Cl. 3.1.2 of IS 800:2007. In the previous version of the code, the design of steel structures was essentially using Working Stress Method. But IS 800:2007 permits us to design the structure to satisfy the various Limit States. It also advocates the use of Working Stress Method only to the situations where Limit State cannot be conveniently employed. As per Cl. 3.1.2.1 of IS 800:2007, Structure and its elements shall normally, be designed by the limit state method. Account should be taken of accepted theories, experimental information and experience and the need to design for durability. This clause admits that calculations alone may not produce Safe, serviceable and durable structures. Suitable materials, quality control, adequate detailing and good supervision are equally important. As per Cl. 3.1.2.2 of IS 800:2007, where the limit states method cannot be conveniently adopted; the working stress design (Section 11 of IS 800:2007) may be used.

3. Design Process

Clause 3.1.3 of IS 800:2007 specifies structural design, including design for durability, onstruction and use should be considered as a whole. The realization of design objectives requires compliance with clearly defined standards for materials, fabrication, erection and in-service maintenance.