The macro-models method is one of the main categories for modeling infills based on the equivalent
strut method. The basic parameter of these struts is their equivalent width, which affects the
stiffness and strength. This paper presents a general review of several expressions proposed by
researchers to calculate this equivalent width. The comparative study of different expressions shows
that the Paulay and Priestley equation is the most suitable choice for calculating the diagonal
equivalent strut width, due to its simplicity and because it gives an approximate average value
among those studied in this paper. Consequently, the model will be used in our further study for
analysis of RC infilled frames.