The data and equations from the Building Code Requirements and Specifications for Masonry Structures (BCRSMS), 2008 edition, cover minimum requirements for the structural design and construction of masonry elements consisting of masonry units bedded in mortar. This case explores a scenario that is not covered in the code.
The strength of concrete in tension is negligible, requiring the use of steel reinforcement. This example corresponds to steel reinforcement that is placed centrally in a beam-column made from concrete. This article demonstrates that the contribution of steel reinforcement to the total moment of inertia can be neglected when the steel is placed at the center of the cross section of the concrete beam-column.
During the calculation of the structural capacity of a reinforced masonry wall (or beam-column), it is necessary to calculate the gross (net) moment of inertia with respect to the centerline of the cross section. In the case of a centrally located reinforcing bar (rebar), it is normally known that the moment of inertia about the centerline is normally negligible for small areas. However, the area of steel, though small (a No. 5 bar is 5/8 of an inch in diameter, for instance) compared to the gross cross-sectional area of the concrete cell being reinforced, when transformed from steel to concrete area, Ast, is the product of As times the moduli ratio n, where n is the dimensional parameter and normally exceeds 15 (i.e., n = Es/Ev = Ast/As > 10). This case demonstrates that the area of rebars transformed from steel to concrete may not be neglected when rebars are centrally located, and further investigation is warranted