Table of Contents
Why do we reinforce slab?
Tensile Resistance Fails First in Slabs – The reason reinforced concrete slabs are necessary is because it is not the compressive integrity of a slab that fails first. It is the tensile resistance that gives way. The tensile strength of concrete is ten times less than the compressive strength.
What is the main reason for reinforcing slabs on grade?
Reinforcement will reduce the strains caused by the impact loading, thereby preventing premature cracking, and provide structural strength to the slab if the impact is so much that cracking does actually occur.
What is bottom reinforcement?
The bottom reinforcement is continuous through the slot and transmits beam moments to the column. The yielding of the bottom reinforcement governs the flexural strength of the beam in both positive and negative moment directions during an earthquake.
Does a slab need reinforcement?
Slabs that will support structures, heavy equipment, machinery, or supplies should also contain steel reinforcing to prevent cracks, breaks, or separation at expansion joints. Rebar isn’t necessary for concrete slabs but greatly improves its strength and lifespan.
Why is concrete reinforced?
Reinforcement for concrete is provided by embedding deformed steel bars or welded wire fabric within freshly made concrete at the time of casting. The purpose of reinforcement is to provide additional strength for concrete where it is needed.
Where should reinforcement be placed in the slab?
Steel reinforcing bars and welded wire reinforcement should be positioned in the upper third of the slab thickness because shrinkage and temperature cracks originate at the surface of the slab. Cracks are wider at the surface and narrow with depth.
How do you reinforce a concrete slab?
Steel reinforcing and welded wire reinforcement should be supported and sufficiently tied together to minimize movements during concrete placing and finishing operations. Otherwise, reinforcement may not be properly located in the slab. Support reinforcement with chairs or precast-concrete bar supports.
How do you strengthen a concrete slab?
There are also some other techniques used for strengthening a reinforced concrete slab such as:
- Increasing the shear bearing capacity of the slab by adding steel plates strengthened by vertical screw bolts.
- Strengthening of the slab by post stressed reinforcement.
- Adding steel beams.
Why is Reinforcement placed at the bottom of a concrete slab?
Structural reinforcement is typically placed in the bottom portion of the slab thickness for the purpose of increasing the slab’s load capacity. Most structural slabs-on-ground have both top and bottom layers of reinforcement for controlling crack-widths and increasing load capacities.
Where should rereinforcement be placed on a slab?
Reinforcement should also be placed low enough so saw cutting does not cut the reinforcement. For welded wire reinforcement, the Wire Reinforcement Institute recommends steel placement 2 inches below the surface or within the upper third of the slab thickness, whichever is closer to the surface.
What is the minimum reinforcement in steel slabs?
Minimum reinforcement is 0.12\% for HYSD bars and 0.15\% for mild steel bars. The diameter of bar generally used in slabs are: 6 mm, 8 mm, 10 mm, 12mm and 16mm.
How is the thickness of the slab decided?
Thickness of the slab is decided based on span to depth ratio specified in IS456-2000. Minimum reinforcement is 0.12\% for HYSD bars and 0.15\% for mild steel bars.