What ratio defines a one-way slab in contrast to two-way slabs?

• A. Long end to short end ratio less than 1
• B. Long end to short end ratio equal to 1
• C. Long end to short end ratio greater than or equal to 2
• D. Long end to short end ratio less than or equal to 2

Answer: (C)

A one-way slab is characterized by its geometry and loading conditions, specifically the ratio of its long span to its short span. To be classified as a one-way slab, the ratio of the long end to short end must be greater than or equal to 2. This means that the slab primarily supports loads in one direction, whereas the shorter direction has less influence on its structural behavior.

When the long-to-short span ratio reaches this threshold, the slab will distribute loads mainly along the longer span, allowing for bending to occur predominantly in that direction. This results in design considerations that focus on reinforcement primarily along the longer span. Such slabs are typically found in conditions where the length of the slab greatly exceeds its width, such as in corridors or pull-through parking areas.

By contrast, two-way slabs are used when the slab spans are more uniform in length, which allows for load distribution in both directions equally. This balance is evidenced by a long-to-short span ratio that does not meet the threshold established for one-way slabs. Understanding these distinctions is critical for structural design and ensuring that slabs are adequately reinforced and supported for their intended use.