BCGBC4010A Apply structural principles to residential low-rise constructions

Structural principles - Structural members

Concrete slabs

Suspended slabs
One way slab 
One way slabs are usually rectangular where the length is two or more times the width. These slabs are considered to be supported along the two long sides only even if there is a small amount of support on the narrow ends.
A diagram of a concrete slab with two supporting sides is shown. The width of the slab is also the short span.
One bend slab
It is assumed that one way slabs bend only in the direction of the short span, so the main steel reinforcement runs in this direction across the slab.
A diagram of a concrete slab with two supporting sides is shown. Compression on the slab pushes towards the middle of the slab which causes the slab to bend inwards. Tension is distributed across the supporting sides.
One reo slab
Secondary steel reinforcement (which has a smaller bar diameter) is used in the direction of the long span. This reinforcement is placed in the bottom region of the suspended slab to reduce shrinkage cracks.
A diagram of a concrete slab with two supporting sides is shown. In the slab is steel reinforcement in the direction of the long span.
Two way slab
Two way slabs are approximately square where the length is less than double the width and the slab is supported equally on all four sides.
A diagram of a concrete slab with four supporting sides is shown. The pressure spans equally across the width and length of the concrete slab.

Two bend slab
These slabs are assumed to bend in both directions, so main steel reinforcement of equal size and spacing is run in both directions.
A diagram of the compression that occurs in a two bend slab is shown. The pressure runs to the middle of the slab which causes all four sides to bend equally.
Two reo slab
Steel reinforcing is usually placed in the slab at both top and bottom edges. However, it is the bottom reinforcement that is doing all the work as the top layer is primarily used to control concrete shrinkage cracks.
A diagram of steel reinforcing placed evenly down the width and across the length is shown.

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