Extensive research has been carried out on the behavior and shear strength of reinforced concrete beams. The available literature is voluminous and the state of the art review is given elsewhere. Numerous tests on beams have been conducted and reported in the literature. Many theories for predicting the shear strength have been advanced. The shear strength is based on an average shear stress on full effective cross section       (b*d), where b = section width and d = section depth. For calculating shear resistance for Trapezoidal beams with variable width there is many methods and provisions in different codes to calculate the effective width of the section as shown below: -E C:  minimum Web width. -ACI 318: average web width. -AASHTO: the minimum of average width and 1.2 min width. -LRFD: Minimum web width. -BS 8110: average web width. Results obtained by experimental work indicated that the shear behavior of the trapezoidal beams depend on the average width of the section.