The ACI 318 Building Code contains requirements limiting flexural reinforcement spacing to regulate crack widths when the yield strength Æ’y of the reinforcement exceeds 40,000 psi (Art. 9.50). Crack width is proportional to steel stress. The tensile area of concrete tributary to and concentric with each bar, and thickness of the concrete cover are important to crack control. The minimum concrete cover requirements of the ACI 318 Building Code for reinforcement in beams and girders are given in Table 9.22.
Generally, any vertical member whose length and height are both much larger than the thickness may be treated as a wall. Walls subjected to vertical loads are called bearing walls. Walls subjected to no loads other than their own weight, such as panel or enclosure walls, are called nonbearing walls. Walls with a primary function of resisting lateral loads are called shear walls. They also may serve as bearing walls. See Art. 9.89.