How to design and detail the RCC Beams

RCC beams structural elements are formed to bear transverse external loads that produce bending moment, shear forces and in some cases torsion over their length. Concrete performs well in compression but feeble in tension. The role of Steel reinforcement is to combat tensile stresses in reinforced concrete beams.

Now-a-days deformed and twisted bars are extensively used in RCC work. Deformed or High yield strength deformed bars (HYSD) contains ribs on the surface. It improves the stability of bond by minimum 40% with regards to that of mild steel bar.

Fine detailing of reinforcements with exact drawings is necessary at the job site to optimize the construction procedure. Usually, there is a bar bending schedule contained with these drawing. The bar bending schedule defines the length and number, position and the shape of the bar.

The detailing of beams generally involves the followings :

i) Size and number (or spacing) of bars,

ii) Lap and curtailment (or bending) of bars,

iii) Development length of bars,

iv) Clear cover to the reinforcement and

v) Spacer and chair bars

Anchorage in steel bars is demonstrated with bends and hooks. Hooks do not include Twisted steel bars or deformed steel bars. The anchorage value of bend of bar is captured as 4 times the diameter of bar for each 450 bend that depends on maximum of 16 times the diameter of bar. To expand the length of bars, bars are lapped over one another. Lowest lap length is identical to development length. Development length for bars in various concrete mix is provided in tables 4.2 to 4.4 of SP34.

The value of K given above is subjected to type of steel applied that is provided below :-

The beams are categorized as:

• Based on shape: Rectangular, T, L, Circular etc.
• Based on supporting conditions: Simply supported, fixed, continuous and cantilever beams
• Based on reinforcement: Singly reinforced and doubly reinforced

Depth of the beam is obtained on the basis of flexural strength and satisfying the deflection criteria. Usually the ratio of span to depth ratio is retained as 10 to 15 and the depth to width ratio of rectangular is maintained in the range of 1.5 to 2.

Lowest cover in beams should be 25 mm or not below the larger diameter of bar for all steel reinforcement together with links. Minimal cover provided in Table 16 and 16A of IS456-2000 should be applied to meet the stability criteria.

To read the complete article, go through the following link theconstructor.org

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Published By

Rajib Dey

www.constructioncost.co

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An Exclusive Construction Tutorial On Bending Moment And Shear Force Diagram

Get brief ideas on bending moment and shear force induced in beam section through this construction video tutorial. Also learn the detailed process to draw SFD and BMD on the basis of this type of foundation.

A bending moment refers to the reaction induced in a structural element while using an external force or moment to the element for bending it. Beam is generally considered as the elemental structural element that is dependent on bending moments. Shear Force alias shearing force can be described as a force that functions on a substance in a perpendicular direction to the extension of the substance. Shear forces frequently leads to shear strain. Defiance to such forces in a fluid is connected with its viscosity.

If the beam is loaded at random, the internal forces and moments are formed and the shear force and bending moments occurs to examine the beams further.

Sheer force diagram (SFD) and bending moment diagram (BMD) are the most vital process for making initial design calculations of structural or machine elements.

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Published By

Rajib Dey

www.constructioncost.co

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Build a concrete slab footing of modern buildings

A concrete slab is a common structural element of modern buildings. Horizontal slabs of steel reinforced concrete, typically between 100 and 500 millimeters thick, are most often used to construct floors and ceilings, while thinner slabs are also used for exterior paving.

In many domestic and industrial buildings a thick concrete slab, supported on foundations or directly on the subsoil, is used to construct the ground floor of a building. In high rise buildings and skyscrapers, thinner, pre-cast concrete slabs are slung between the steel frames to form the floors and ceilings on each level.

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Published By

Rajib Dey

www.constructioncost.co

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