360R-06 Design of Slabs-on-Ground
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- 4.7—Construction loads
- 4.8—Environmental factors
| 4.6—Unusual loads
Loading conditions that do not conform to the previously discussed load types may also occur. They may differ in the following manner: 1. Configuration of loaded area; 2. Load distributed to more than one axle; and 3. More than two or four wheels per axle. The load variables, however, will be similar to those for the load types previously discussed in this chapter. 4.7—Construction loads During the construction of a building, various types of equipment may be located on the newly placed slab-on- ground. The most common construction loads are pickup trucks, scissor lift concrete trucks, dump trucks, hoisting equipment and cranes used for steel erection, tilt wall erection, and setting equipment. In addition, the slab may be subjected to other loads, such as scaffolding and material pallets. Some of these loads can exceed the design limits and, therefore, the construction load case should be anticipated, particularly relative to early-age concrete strength. Also, limiting of construction loads near the free edges or corners of slabs should be considered. The controlling load variables for construction loads are the same as for vehicle loads, concentrated loads, and uniform loads. For construction trucks, the maximum axle load and other variables can usually be determined by reference to local transportation laws or to the AASHTO standards. Off-road construction equipment may exceed these limits, but in most cases, depending on local custom, construction equipment will not exceed the legal limits of the Department of Trans- portation. Figure 4.2 gives values of contact area for wheel loads that can be used for design. 4.8—Environmental factors Flexural stresses produced by thermal changes, expansive soils, and moisture changes in the slab (affecting curling due to the different shrinkage rates between the top and bottom of the slab) should be considered in the overall design. These |