Structure is the backbone of any type of building , which bear the entire load of the building including the interior & external feature of the building.

The structural design of any building depend upon the basic three factor,

- Entire Load of the Building.
- Type of Soil (It’s load bearing capacity & Earthquake zone)
- The Water level of the plot which get constructed

The basic requirements for an efficient structural design is that the response of the structure should be acceptable as per various specifications, i.e., it should at least be a feasible design. There can be large number of feasible designs, but it is desirable to choose the best from these several designs. The best design could be in terms of minimum cost, minimum weight or maximum performance or a combination of these. Many of the methods give rise to local minimum/maximum. Most of the methods, in general give rise to local minimum.

This, however, depends on the mathematical nature of the objective function and the constraints.

**Optimization Problem**

The optimization problem is classified on the basis of nature of equations with respect to design variables. If the objective function and the constraints involving the design variable are linear then the optimization is termed as linear optimization problem. If even one of them is non-linear it is classified as the non-linear optimization problem. In general the design variables are real but some times they could be integers for example, number of layers, orientation angle, etc. The behavior constraints could be equality constraints or inequality constraints depending on the nature of the problem.

Minimum Weight Design of Structural Elements (Simultaneous failure mode theory) One of the earliest techniques employed for the optimization of structural elements is the Simultaneous Failure Mode Theory (SFMT). The approach has been employed to obtain Optimum Design (minimum strength to weight ratio) of elements like columns, plates, beams, cylinders,sheet-stiffener combination etc. The requirement for optimum design is that all the failure modes occur simultaneously for the possible design variables. As the number of design variables increase or the constraints on the behavior variables increase, this approach does not lead to global optimum solution. A structural design problem can be represented as a mathematical model whose constituent elements are parameters, constraints and objective or merit function. The design parameters specify the geometry and topology of the structure and physical properties of its members. Some of these can be independent design parameters and others could be dependent on the independent design variables. Some of the design parameters are chosen by judgment and experience of the designer so as to reduce the size of the problem. This results in large savings in computational time, which in-turn reduces the cost of the design. From the design parameters, a set of derived parameters are obtained which are defined as behavior constraints e.g., stresses, deflections, natural frequencies and buckling loads etc., These behavior parameters are functionally related through laws of structural mechanics to the design variables. The objective or the merit function is formed by the proper choice of the design parameters. This function is either maximized or minimized. For example, if this function is cost or weight, then the function is minimized. On the other hand if it is some other function, it is maximized.