The objectives of structural design is to design the structure for stability, strength and serviceability. It must also be economical and aesthetic.
The design of a structure must satisfy three basic requirements:
1) Stability to prevent overturning, sliding or buckling of the structure, or parts of it, under the action of loads,
2) Strength to resist safely the stresses induced by the loads in the various structural members; and
3) Serviceability to ensure satisfactory performance under service load conditions – which implies providing adequate stiffness and reinforcements to contain deflections, crack widths and vibrations within acceptable limits, and also providing impermeability and durability (including corrosion resistance), etc.
There are two other considerations that a sensible designer ought to bear in mind, viz.,economy and aesthetics. One can always design a massive structure, which has more than adequate stability, strength and serviceability, but the ensuing cost of the structure may be exorbitant, and the end product, far from aesthetic.
In the words of Felix Candela, the designer of a remarkably wide range of reinforced concrete shell structures, It is indeed a challenge, and a responsibility, for the structural designer to design a structure that is not only appropriate for the architecture, but also strikes the right balance between safety and economy.
