360R-06 Design of Slabs-on-Ground
tải về 2.35 Mb. Chế độ xem pdf
|
- Điều hướng trang này:
- 4.5—Line and strip loads
| 4.4—Distributed loads
In many warehouse and industrial buildings, materials are stored directly on the slab-on-ground. The flexural stresses in the slab are usually less than those produced by concentrated loads. The design should prevent negative moment cracks in the aisles and prevent excessive settlement. For the higher load intensities, distributed loads that cover a large plan area (which will affect the deeper soil layers), and long-term uniform loads, the effect of the differential soil settlement should also be considered in the design of the slab. The effect of a lift truck operating in the aisles between uniformly loaded areas is not normally combined with the uniform load into one loading case, as the moments produced generally offset one another. The individual cases are always considered in the design. For distributed loads, the variables affecting the design of slabs-on-ground are: • Maximum load intensity; • Duration of load; • Width and length of loaded area; • Aisle width; and • Presence of a joint located in and parallel to an aisle. Load intensity and layout may not be constant during the service life of a slab. Therefore, the slab should be designed for the most critical case. For a given modulus of subgrade reaction and slab thickness, there is a critical aisle width that maximizes the center aisle moment (Packard 1976). 4.5—Line and strip loads A line or strip load is a uniform load distributed over a relatively narrow area. A load may be considered to be a line or strip load if its width is less than 1/3 of the radius of relative stiffness of the slab. When the width approximates this limit, the slab should be reviewed for stresses produced by line loading and uniform load. If the results are within 15% of one another, the load should be taken as uniform. Partition loads, bearing walls, and roll storage are examples of this load type. For higher load intensities and long-term loading, the effect of differential soil settlement should also be considered in the design of the slab. The variables for line and strip loads are similar to those for distributed loadings and include: • Maximum load intensity and duration of load; • Width, length of loaded area, and if the line or strip loads intersect; • Aisle width; • Presence of a joint in and parallel to an aisle; • Presence of parallel joints on each side of an aisle; and • The amount of shear transfer across the slab joint (this is especially important when the line load crosses perpendic- ular to a joint or is directly adjacent and parallel to a joint). tải về 2.35 Mb. Chia sẻ với bạn bè của bạn:
|