Building Design and Construction

Retaining Walls Supported on Four Sides

For walls more than 10 in thick, the ACI 318 Building Code requires two-way layers of bars in each face. Two-way slab design of this reinforcement is required for economy in basement walls or subsurface tank walls supported as vertical spans by the floor above and the footing below, and as horizontal spans by stiff pilasters, interior cross walls, or end walls.
This type of two-way slab is outside the scope of the specific provisions in the Code. Without an ‘‘exact’’ analysis, which is seldom justified because of the uncertainties involved in the assumptions for stiffnesses and loads, a realistic design can be based on the simple two-way slab design method of Appendix A, Method 2, of the 1963 ACI 318 Building Code.
Building foundations should distribute wall and column loads to the underlying soil and rock within acceptable limits on resulting soil pressure and total and differential settlement. Wall and column loads consist of live load, reduced in accordance with the applicable general building code, and dead load, combined, when required, with lateral loads of wind, earthquake, earth pressure, or liquid pressure. These loads can be distributed to the soil near grade by concrete spread footings, or to the soil at lower levels by concrete piles or drilled piers.

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