Distinctive Construction Joints Details and Spot for Beams and Columns

During the need of concreting termination for the day or more than 30 minutes or so; construction joints in RCC beams and columns are necessary. In such circumstances, regular construction joints shall be provided for the reason that bond is maintained between set concrete and fresh concrete properly.

The provided images below portray proper process of construction joints to be provided in columns, beams and beam-column junction.

1. Construction Joints in Column

The figure below highlights accurate procedure of supplying construction joint in column. One thing should be kept in mind that smooth or tilted surface is not appropriate for providing construction joint in column. With parts of visible coarse aggregates the column’s top surface should be rough.

2. Construction Joints in Beams and Beam-Column Joint

The figure as following give you an idea about the typical construction joint to be provided in beams and beam column joints.

~~~~~~~~~~~~~~~~~~~~~~~~

Published By

Rajib Dey

www.constructioncost.co

~~~~~~~~~~~~~~~~~~~~~~~~

DETAILS OF ONE WAY SLAB REINFORCEMENT

Reinforcement detailing of a slab is performed on the basis of its support conditions. Support to slab is generally provided through walls or beams or columns.

A slab is called one way if the supported is provided from two opposite edges. So, the prime load is transmitted onward the spanning direction. Here, the proportion of longer extent to shorter extent is over 2. In one way slab, one side is greater than the other one. In one way slab, the bending occurs mainly in one direction only (spanning direction).

Consequently, the main reinforcement is necessary to withstand the moments produced and designed for the same. The main reinforcement is arranged at the bottom of the slab that is usually described as the tension face.

In one way slab, as one side is larger as compared to the other one, the greatest load is carried by the larger side. To give more support on the larger side, main reinforcement is set perpendicular to that side or parallel to the shorter direction. Distribution steel is arranged in the extended direction that will not be very useful for carrying any load.

In one way slab, the main reinforcement is calculated with a formula (In limit state design) and to obtain the result the comparison is made between the comparing compressive force and tensile forces.

Ast = 0.5 Fck/Fu[1-√1-2.6Mu/Fck.b.d]b.d

and the distribution steel is calculated as

0.15% of Ag, for mild steel.

0.12% of Ag, for tor steel.

Where, Ast denotes Area of the steel in tension.

Fu denotes Ultimate strength of steel.

Mu denotes Ultimate moment of resistance.

b denotes Breadth of the slab section.

d denotes Depth of the slab section.

Ag denotes Gross area of the section.

Article Source : www.dailycivil.com

~~~~~~~~~~~~~~~~~~~~~~

Published By

Rajib Dey

www.constructioncost.co

~~~~~~~~~~~~~~~~~~~~~

How to measure Reinforcement with column & footing

This construction video provides step-by-step guidelines on estimation of Reinforcement with column and footing as per construction drawing. The video will be very useful for foundation design.

Reinforcement is essential for reinforced concrete members like footings, beams, columns, slabs, lintels etc. It is recommended to estimate reinforcement quantity before tendering phase for measuring cost of project or construction work roughly.

If working drawings and schedules for the reinforcement are unavailable, then it is required to create an estimate of the projected quantities. The quantities are usually defined according to the requirements of the Standard method of measurement of building works.

~~~~~~~~~~~~~~~~~~~~~

Published By

Rajib Dey

www.constructioncost.co

~~~~~~~~~~~~~~~~~~~~~

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

~~~~~~~~~~~~~~~~~~~~~

Published By

Rajib Dey

www.constructioncost.co

~~~~~~~~~~~~~~~~~~~~~