Design of Beam

1. Estimation of constants. -For the specified set of stresses, determine KC, JC and RC.

2. Kc= M~cbc/M~cbc+~st

3. Jc= 1-(Kc/3)

4. Rc= 0.5*L*Kc Jc

5. Estimation of bending moment. Suppose appropriate values of overall depth and breadth of beam, and find out the effective span. Work out the self-weight and total U.D.L. and maximum bending moment in the beam.

6. Design of the section. Workout the effective depth of the beam with the following expression:

7. d= [(M)/ (RC*b)] 0.5

8. Reinforcement. Workout the area with the formula.

9. Shear Reinforcement. Workout the maximum shear force in the beam.

10. Verify for Development length at the end.

11. Ld<= (M1/V) +L0.

Design of column:

1. Find out the allowable stresses in concrete, longitudinal bars and ties.
2. Determine the super impose load that should be borne by the column.
3. Find out the area from the following expression - P= ~cc *Ac+~sc*Asc.
4. After getting details about the area, find out the dimensions of column. If it is a square of side b, then b=Ag.
5. For the specified end conditions, find out the effective length of column. Measure lef/b ratio to determine whether the column is short or long.
6. If lef/b ratio<12 it will be designed as short column or else as long column; define the area of steel Asc.
7. Determine the diameters of bars utilized as ties and find out its pitch according to the rules.

DESIGN OF FOOTING: The width B of the footing will obviously be equivalent to [W+W‟]/qo. The thickness is measured based on the bending moment as well as punching shear.

1. Depth for bending moment.
d= [M/B*Rc] 0.5
2. Depth for shear.
3. tv=V/B*d
4. Steel Reinforcement. Ast=M/tjcd

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Published By
Rajib Dey
www.constructioncost.co
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Some useful tips on reinforced concrete design

While designing the reinforced concrete members, it is necessary to check the steel reinforcement in jobsite prior to arrange concrete. Besides, ensure the concrete foundations, beams, columns, etc. are constructed as per design norms. Often, it is observed that steel beam stirrups employed in reinforced concrete design, are not installed properly.

The beam stirrups are extensively utilized in residential construction. In order to produce perfect architectural design and satisfy building occupant requirements, the sizes of concrete beam are made thinner and their lengths are increased.

In our experience, this has been the result of architectural design and. The higher cost of foundation components like drilled piers is also a major concern. To lessen the requirement of extra piers, the lengths of concrete beam are raised and it leads to the application of steel stirrups.

Concrete beams differ in depth. The shear strength of the beam will be increased by making beam deeper. For insufficient depth, steel stirrups should be included to raise the shear strength of the beam. These stirrups generally belong to one piece of steel that is twisted into a rectangular shape. Often small diameter steel like #3 and #4 rebar is applied. The stirrup normally wraps around the bottom and top bars of the beams.

It is essential to indicate the size, distance and position along the length of the beam where the stirrups will be assigned. Besides, the dimensions of stirrup should also be indicated in the sections in order that the stirrup is manufactured before installation.

Stirrups are suitable for the areas of high shear, like bearing points and under large point loads.

The installer should take proper care for fabrication of the stirrup from one piece of steel and sufficiently overlap each end (speak to the Structural Engineer or refer to the ACI code for variations). Sometimes, the stirrup is not pre-fabricated and the installer attempts to produce the stirrup in the field, once the horizontal bars are already in position. It is normal since the stirrup is built up from two pieces with insufficient lap splice.

The method is simple to set up a stirrup simultaneously the horizontal reinforcement is being installed. To avoid last-minute modifications, it is recommended to consult with the Structural Engineer with any confusion regarding size, shape, spacing and installation of stirrups before inspection.



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Construction of post-tensioned slabs on grade is equivalent to applying reinforcing steel, with the exception of the tensioning step.

The placing of cables is done according to the suggestions provided by the engineer and managed to run through the center of the slab. For residential construction, tendons at 48 inches on center are mostly found.

There are huge amount of steel for commercial foundations. Tendons are routed around obstructions without difficulty.

A residential post-tensioned concrete slab will generally be available as 8 inches thick and made of 3000 psi concrete. Once the concrete has attained strength to 2000 psi, normally within the 3 to 10 days suggested by PTI, the tendons are stressed.

Tendons belong to seven high-strength steel wires which are cut jointly and arranged inside a plastic duct. At each end a PT anchor is situated and these are positioned in pockets which are implanted into the slab edge. If the strands are stressed, the wires will also stretch—about 4 inches for a 50 foot strand—to employ 33,000 pounds of load.

Stressing should only be performed with skilled workers. Once the stressing is completed, the tendon is cut off and the pocket in which the anchors are positioned is filled with grout to get rid of corrosion.

Larger structural concrete members are also post-tensioned, particularly in bridges and floors and beams in parking structures. The method is very user-friendly as compared to that utilized for slabs, apart from a bigger scale. The tendons will be "draped" frequently in order that they are low at the center of a beam and high at the supports—this settles the steel at the point of highest tension to retain the concrete kept together firmly.

By applying structural members the duct is frequently grouted entirely following stressing to tie the strand to the concrete along its complete length—these are known as bonded tendons. Unbonded tendons are mainly found in residential slabs and can freely move inside the duct and are safeguarded against corrosion with grease.

PT tendon placement and stressing is generally performed by companies with certified workers who have good skills in this work.

The benefits of PT that there is no cracking (or minimum very narrow cracks) and it has capacity to span additionally. PT slabs on ground can be arranged and stamped similar to any other concrete slab. Surfaces are stained or coated. It should be kept in mind that no cutting or drilling should be done to post-tensioned concrete slabs, because once a tendon is cut, it becomes complicated to repair. Many post-tensioned slabs are stamped to notify the owner and any renovation contractors to make sure that the slab is post tensioned.

Source: https://www.concretenetwork.com




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Published By
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www.constructioncost.co
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How to determine grades of concrete following IS 456:2000 standard

This construction video tutorial explains the grades of concrete with adherence to IS 456:2000 as well as process for detecting the characteristics strength of concrete.

IS 456-2000 refers to an Indian standard code of practice for general structural use of plain and reinforced concrete.

Grade of concrete determines the compressive strength of concrete. To calculate grade of concrete, standard compression test is carried out on concrete cube of 150 mm. Grade of concrete is demonstrated with M10, M20, M30 etc. where M stands for Mix i.e. mix of constituents used for concrete. Numeric figure in M stands for characteristics compressive strength (fck) that is stated MPa (N/mm2).

Characteristics compressive strength means the strength of material under which not over 5% result is presumed to fall.

As for example if 20 samples of concrete cubes are casted and carried out compression tests for them in the laboratory to determine their compressive strength. Results for test are 27.3, 25.4, 26.9, 25.1, 23.8, 27.6……20 results. If these are organized in increasing order, here 23.8 is less than 25 and remaining are greater than 25 in MPa. So, it signifies that one result falls under 25 MPa and it is detected that only 5% of results fall under 25. Therefore, grade of concrete remains M25.

As per IS code, there are three comprehensive categories for concrete as follow :-

Type of concrete	Grade
High Strength Concrete	Over M 60
Standard Strength Concrete	M25 to M55
Normal Strength Concrete	M10 to M20

For online demonstration, watch the following video.

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Different types of clear cover in reinforcement concrete

This construction video tutorial provides brief instructions on how to arrange clear cover in different areas in proper quantities in reinforcement concrete. It is dependent on the exposure condition and fire resistance.

Clear Cover stands for the minimum distance among the surface of embedded reinforcement and the exterior surface of the concrete (ACI 130). The depth of clear cover is calculated with a cover meter.

Given below the details of clear cover :-

For water retaining structures – The clear cover should vary from 20 mm to 30 mm
For flat slab – The clear cover should be 20 mm
For slab – The clear cover will be 15 mm
For column – The clear cover should have been 40 mm
For strap beam – The clear cover should be 50 mm

For raft foundation at bottom – The clear cover should be 75 mm
For shear wall – The clear cover should be 25 mm
For footing – The clear cover should be 50 mm
For staircase – The clear cover should be 15 mm

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Overview of Peikko DSA Punching Reinforcement System for Cast-in-Place Concrete

This construction video tutorial provides the demonstration Peikko DSA Punching Reinforcement. It belongs to a Transverse Reinforcement System for Cast-in-Place Concrete. It is specifically designed to improve the strength of punching shear concerning elevated concrete slabs and slabs on grade devoid of raising their thickness.

DSA rails consist of steel double-headed DSA Studs welded to a steel shape. The steel shape ensures the exact spacing and placing of the studs throughout their set up in concrete as per ASTM-A1044 standard. It should be used for both top and bottom installation.

Peikko DSA Punching Reinforcement offers an easy and consistent solution toward punching and shear failure which may happen in elevated concrete slabs, slabs on grade and footings.

If DSA Punching Reinforcement is applied in elevated slabs like reinforced concrete slabs or post-tensioned slabs, DSA Punching Reinforcement system disregards the requirement for column capitals. Therefore, forming and concrete costs are minimized significantly.

DSA reinforced cast-in-place elevated slabs are designed slimmer to minimize the entire construction height. It leads to huge savings in construction and running costs. The DSA system also provides a ceiling with uninterrupted clearance facilitating adaptability and simplicity of planning and installation of building services.

The fabrication process for DSA studs is done with low carbon steel grades C1010 through C1020. DSA Punching Reinforcement system adheres to the standard specification for steel stud assemblies for the shear reinforcement of concrete ASTM A-1044. It should be designed according to ACI 318-14 and CSA A23.3-14 which make it relevant in North America and Middle East.

Punching Reinforcement systems are also employed in foundations to curtail the thickness of footings, pile caps and slabs on grade. Other applications range from DSA rails are utilized as shear reinforcement in beams, walls and other concrete elements.

To get more information, click on the following link. www.peikkousa.com

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Published By

Rajib Dey

www.constructioncost.co

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Some useful construction tips to provide clear cover for reinforced concrete structure

This construction video tutorial will provide detailed guidelines on how to provide perfect clear cover in reinforcement concrete structure.

With the intension of safeguarding the reinforcement from corrosion as well as arranging fire resistance to bars implanted in concrete, clear cover is set for Reinforced Concrete Structures.

Clear cover stands for the distance among C.G of reinforcement bars and bottom most point of concrete.

The thickness of cover is dependent on ecological conditions and nature of structural member.

The depth of concrete cover is calculated by applying a cover meter.

The clear cover that should be provided is determined by Indian Standards. IS 456:2000.

Watch following youtube video to learn the complete process :-

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