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The above CEB expression was intended to calculate crack spacings on the surface of the member. Crack spacings become larger as the distance from the reinforcement increases. For this case, it is suggested to use the maximum distance from the reinforcement, instead of cover distance c (Collins & Mitchell).
Providing not less than the minimum permitted percentage of reinforcement. Limiting the spacing of tension reinforcement. Using “deemed to satisfy” empirical methods. If actual deflections are required, then the structure must be analysed for the serviceability limit state, using design service loads.
Concrete and steel reinforcement bars combine to create strong, resilient structures in the following ways: Upon contact with each other, the cement paste and steel rebar form a non-reactive surface film preventing corrosion. Reinforcement bars or beams can be strategically set throughout the concrete to achieve the required support system.
A corrugated slab is designed when the concrete is poured into a corrugated steel tray, more commonly called decking. This steel tray improves strength of the slab, and prevents the slab from bending under its own weight. The corrugations run in one direction only. A ribbed slab gives considerably more strength in one direction. This is ...
When a concrete structure is designed, it is usual to specify the concrete cover for the rebar (the depth of the rebar within the object). The minimum concrete cover is normally regulated by design or building codes. If the reinforcement is too close to the surface, early failure due to corrosion may occur.
The ACI Building Code Requirements put the following restrictions on amount of spiral reinforcement. ACI Code 7.10.4.2: For cast-in-place construction, size of spirals shall not be less than 3/8 in. diameter. ACI Code 7.10.4.3: Clear spacing between spirals shall not exceed 3 in., nor be less than 1in.
In US use, the grade designation is equal to the minimum yield strength of the bar in ksi (1000 psi); for example, grade 60 rebar has a minimum yield strength of 60 ksi. Rebar is most commonly manufactured in grades 40, 60, and 75 with higher strength readily available in grades 80, 100, 120 and 150.
The name waffle comes from the grid pattern created by the reinforcing ribs. Waffle slabs are preferred for spans greater than 40 feet (12 m), because, for a given mass of concrete, they are much stronger than flat slabs, flat slabs with drop panels, two-way slabs, one-way slabs, and one-way joist slabs. [2]