Abstract
Usually, main parts of computer programs of structural calculation consist of complicated mathematical expressions, and generally speaking, these expressions are classified into two categories. One category represents relational expressions which are derived directly from physical laws, mathematical formulas and geometrical constraints, and the other category represents calculative expressions which are derived from numerical methods applied in the structural computation. The aim of this paper is to introduce a new tool in the object oriented programming for the purpose of making computer programs in structural calculation simple and easy to write. We introduce a new object class which represents an relational mathematical expression, and a new computational mechanism relating to the object class. One can assume that the relational expression holds throughout the program if one declares and makes the instances at the beginning of the program. By the use of the new tool of OOP in the structural calculation, one can separate relational expressions, which should be declared at the beginning of the program, and the other calculative expressions. As a result, one can make computer programs, whose main part consists of calculative expressions only, by assuming that the declared relational expressions hold throughout the program.
