Biaxial Interaction Exponent for Concrete Columns

A general method of computing the biaxial interaction exponent directly, for rectangular reinforced concrete columns is presented. The method takes into account all variables involved and employs the actual stress strain curve instead of the rectangular stress block. This method, which leads to the evaluation of the exponent directly, is considered simpler and more practical compared to the tedious process of obtaining the biaxial bending design constant first. The method is illustrated by three examples, the results of which are compared with those obtained from the existing aids. It was also applied to four other cross sections of columns that were tested to failure and the results of which are reported in the literature. The calculated and the test results are compared.