1901.2 Plain and reinforced concrete. Structural concrete shall be designed and constructed in accordance with the requirements of this chapter and ACI 318 as amended in Section 1905 of this code. Except for the provisions of Sections 1904 and 1907, the design and construction of slabs on grade shall not be governed by this chapter unless they transmit vertical loads or lateral forces from other parts of the structure to the soil.
Commentary:The structural concrete provisions of the code comply strictly with the provisions of ACI 318/318R, except for the modifications contained in Section 1905. Slabs on grade are another important exception. Slabs on grade typically only convey the gravity dead load of the slab and the gravity live load superimposed on the slab directly to the soil; thus, slabs are not considered to be the “structural concrete” that must comply with the design provisions of ACI 318. Slabs on grade, however, must comply with the durability provisions of Section 1904 and the minimum thickness and vapor retarder provisions of Section 1907.
The last sentence of Section 1901.2 clarifies that slabs on grade used to transmit “vertical loads,” “lateral forces” or both from other parts of the structure to the soil must comply with all the applicable portions of this chapter and ACI 318. In many cases, slabs on grade are used to transmit lateral forces due to wind or earthquakes into the ground. A common example is a typical pre-engineered metal building in which the shear at the bottom of the columns is resisted by placing “hairpins” around the column anchor bolts in the footing and extending the hairpins into the slab on grade.
It is specifically stated in ACI 318 Section 1.4.7 that it does not govern the design and construction of soil-supported slabs, unless the slab transmits vertical loads or lateral forces from other portions of the structure to the soil
concrete repairs Brisbane. This does not preclude the application of any ACI 318 provision that would ensure the proper strength, durability, and abrasion resistance of concrete slabs on ground. Slabs on ground may be plain concrete without any reinforcement or may contain shrinkage and temperature reinforcement in the form of reinforcing bars or wire mesh.