The design of steel sections subjected to axial compressive loads requires to an initial estimation of the stresses and the dimensions of the sections. Then, the design calculations are performed to check the safety of the estimated section against the applied compressive load, according to Clauses (3-6-4) and (3-7-4) in the Egyptian Steel Specifications, (E.S.S.). Operations of the estimation and check of the sections
may be repeated until the safe section is obtained. The amount of safety of the
selected section, (i.e., the percentage of value of the permissible compressive stress –
to- that of the actual stress of the section), depends on the accuracy of the designer.
Thus, an extensive time and more design calculations are carried out in order to obtain the minimum safe area of the section that is called the optimum section,
(T.O.S.).
The idea of the research is to convert the non-linearity in the design of compression members to a direct solution for the design of these members. A simple design equation, (D.E.) is formulated to provide, directly, T.O.S. with no need to more calculations. The D.E. depends, mainly, on shape of the section and includes the design criteria of compression members, in addition to the design data.
The D.E. is represented, graphically by charts to determine the best dimensions of common steel shapes of sections used for compression members, such as: single angle, double angles, circular tubes, and I- section.
Numerical examples on the design of compression members are solved using the design charts, then, the stresses of the selected sections are checked by the classic manner of the design. It is clearly found that the design of compression members by graphical charts is more easy to use, saves in the design calculations, as well as, it provides T.O.S. |
