Reinforcement Detail for Isolated Footing

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There’re various categories of footings such as combined footing, isolated footing, raft footing, strip footing, pile foundations that could be utilized based on constructional requirement and conditions of the ground.

Reinforcement footing detailing is of great importance for the category of footing and footing constructional blueprint. A fine particularization tells the blueprint condition about the footing considering constructional stability. A fine reinforcement particularization comprises matters such as covering toward reinforcement based on conservation subjects for durability, minimum reinforcement as well as bar diameters, suitable footing measuring, etc.

Isolated Footing Analysis:

Reinforcement covering: The minimum width to main reinforcement in footing must not be less than 50 mm in case footing is alongside surface level straightforwardly, also 40 mm for external open face such as surface leveling PCC. In case surface leveling stays vacant, in that case it is required to lay down a covering of 75 mm to safeguard uneven excavation plane. Considering raft foundation, the minimum covering to reinforcement must be 75 mm in case kept on PCC or right on surface level.

Minimum reinforcement and bar diameter: The minimum diameter for primary reinforcement must not be below 10 mm.

Isolated footing particularization technique: It is recommended that base should be specified in equally blueprint and rise in illustrations.

The isolated footing relates to rectangular or square in outline to abide by constructional requirement and powers functioning on the post. Moreover, spherical or additional forms are utilized for isolated footings as well.

The design of isolated footing is made on the basis of the guidelines set by ACI 318-14.

1. The compressive strength of concrete should satisfy the needs for both strength and stability. As per ACI 318-14, least concrete compressive strength should be 17MPa for normal applications.

2. With adherence to ACI 314-14 section 20.2.1.1, the deformed type steel bars should be used.

3. Factored forces and moments provided at the base of columns are transmitted to the foundation with reinforcement, dowels, anchor bolts, or mechanical connectors.

4. There should be least reinforcement even if the concrete bearing strength is not crossed.

5. Adequate anchorage should be arranged for tension reinforcement if reinforcement stress is not directly relative to the moment like in sloped, stepped or tapered foundation.

6. There should be sufficient anchorage length of both flexural and dowel reinforcement to get rid of bond failure of the dowels in the footing and to resist failure of the lap splices among the dowels and the column bars.

7. As per ACI 318-14 section 13.3, depth of footing over reinforcement should not remain under 150 mm.

8. The depth of the footing should be in such a manner that the shear strength of the concrete remains equivalent or surpasses the critical shear forces (one-way shear and punching shear) developed with factored loads.

9. In sloped, stepped, or tapered foundation, location and depth steps and angle of slope should satisfy design requirements at each section.

10. Concrete cover of 75 mm is necessary when the concrete is cast against soil.

11. With adherence to ACI Code specifications, base area of footing is set from un-factored forces and moments transferred by footing to soil and the permissible soil pressure evaluated through principles of soil mechanics. To get the necessary base area of the footing, the column service loads are divided with permissible net soil pressure of the soil. The net factored soil pressure is equivalent to factored load column loads by the selected footing area.