Some vital points to be considered for RCC false slab prior to casting

RCC false slab stands for a slab that is located under or over the main floor slab.

The false slabs are formed for different purposes. Some false slabs are created for the interior purpose and some other for concealing air conditioning ducts as well as any unnecessary things.

In this article, detail information is given for the false slab that is used in bathrooms for concealing the sanitary pipes, traps, fittings, etc.

The false slabs are formed with several types of materials. But, RCC (reinforced cement concrete) false slab is mostly recognized in bathrooms.

Benefits of RCC false slab:

The sanitary pipes laid on the false slab can be repaired easily.

Due to leakage in the joint of sanitary fittings, the water may fall directly in the bathroom, but false slab can be used to get rid of this issue.

The inhabitants can utilize this for retaining different household things.

Prior to casting the slab, consideration should be given on the following points :-

1. Verify The Clear Distance Among The Floor and The Ceiling of False Slab

Usually, seven feet of distance should be maintained among the bathroom floor and the false ceiling. It is treated as the clear height of the bathroom.

If the clear height is under 7′, lots of issue will be raised. Therefore, it is necessary to retain the false at 7′-2″ over the floor. When the tiles will be set up on the bathroom floor, it’ll be elevated 2″.

Hence, the clear height of bathrooms should be verified properly prior to cast RCC false slab in it.

2. Verify All The False Slab And Lintel Level are Equivalent On a Floor

The level of all lintel and false slab on a floor should remain identical.

For this reason, a level on the floor is settled. Generally, the level is chosen from the front of the lift lobby or stair lobby. Mark the level on a column in the lobby area. Get that level to all flats in that floor.

Prior to cast any false slab, verify the level of the slab relating to the level settled in the column of the lobby area. It should be done prior to cast false slabs to ensure all the lintels and false slabs remain at the similar level on the floor.

3. Verify If The False Slab Is Perfectly Horizontal

The false slab of a bathroom should be perfectly horizontal. Because, if one side of the false slab is raised and another side is down, the problem will arise at the time of wall tiling work of the bathroom.

To make the false slab perfectly horizontal, mark the level in the all four walls of the bathroom by applying a water level pipe. Now verify the spacing among the level mark and the bottom of the false slab in all four sides. If the distances are identical in all sides, then the false slab is perfectly horizontal.

To get further details, go through the following link acivilengineer.com



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Published By
Rajib Dey
www.constructioncost.co
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Detail construction method of RCC column

RCC (Reinforced Cement Concrete) column belongs to an inherent structural element of RCC frame structured building. It refers to vertical member that disperse loads from slab and beam directly to the soil underneath.

The entire building rests on columns. Most of the building failure happens because of the column failure. Both design error and the substandard construction practice are liable for column failure. So, there should be clear conception on the construction process of the RCC column.

The construction of the RCC (Reinforced Cement Concrete) Column is based on the following four phases of works –

1. Column layout work
2. Column reinforcement work
3. Column formwork, and
4. Pouring concrete into column.

Construction Process of RCC Column:

1. Column layout work: Under this stage, the location of columns is practically arranged in the jobsite. It is done by placing rope compliant with the grids presented in the drawing and then mark the position of the columns related to the rope.

In drawing, column locations are demonstrated according to grid-line with dimension. In construction field, the ropes are taken as grid-line. So, the columns should be placed to rope-line by calculating the dimension given in the drawing.

2. Column Reinforcement work: Once the positions of the column are marked, the reinforcement is placed with reference to the structural drawing.

It is usually stated in the drawing as following way :-

C1-12#16 mm⌀ and stirrup-10 mm⌀ @ 4″ c/c.

It indicates that column C1 will contain 12 numbers of 16 mm diameter bar as vertical bar and 10 mm diameter steel should be placed 4 inch center to center as stirrup.

or
C2-8#20 mm⌀ + 10#16 mm⌀ and stirrup-10 mm⌀ @ (4″+6“) c/c.

This C2 column’s reinforcement specification signifies that it’ll include 8 numbers of 20 mm diameter bar together with 10 numbers of 16 mm diameter bar as vertical reinforcement and (4″+6″) center to center of stirrups placement signifies that the middle-half portion of clear height of column will contain 6″ center to center spacing of stirrups and upper one-fourth and bottom one-fourth height of column’s clear height will retain stirrups at 4″ center to center spacing.

A sheet exists in structural drawing that comprises of structural notes from structural designer. In that drawing sheet, you’ll get suggested lap length for column’s steel of various diameter bar and other vital notes. One should understand those prior to column reinforcement work.

3. Column formwork: In building, floor height generally remains 10 feet. If there is beam in slab then we have to pour concrete up to beam bottom level. Assume that the height of beam in drawing is given as 1′-6″. Therefore, the casting height of the column should be 8′-6″. And the height of formwork will be 8′-6″. It should be remembered here that dropping concrete from over 5′ height isn’t recommended throughout pouring. Since it leads to concrete segregation, it is required to create one-side of column formwork within 5 feet height range. Once, 5 feet of column is cast, the short side should be lifted up to full-casting height of column next day.

Another way to cast column devoid of segregation is to maintain a small window at 5 feet level of full-height formwork. Once casting is completed up to that level, close the window and cast the remaining portion of the column.

4. Pouring concrete into column: The process is simple for casting column. For small quantity of concrete volume, machine-mix concrete is suitable and for large concrete quantity, ready-mix concrete will be preferred. If moving pump is used with ready-mix concrete and if it is required not to exceed 5 feet height range for dropping concrete that will be complicated.

If moving pump is not used, there will be some issues. Assume, it is necessary to utilize ready-mix concrete excluding pump. Under this situation, the concrete should be unloaded by hand on job site from ready-mix concrete truck and poured into column manually. It will consume long time and initial setting time of concrete will be exceeded. Because of this, concrete will lose its quality. Therefore, it is suggested to cast column with machine-mix concrete.​



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Published By
Rajib Dey
www.constructioncost.co
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How to design R.C.C lintels

Now-a-days, the R.C.C lintels are mostly recognized to extent the openings for doors, windows, etc. in a structure owing to their firmness, inflexibility, fire resistance power, cost-effectiveness and simplicity in construction. R.C.C lintels are recommended for all the loads and for any span. The width of lintel is similar to width of wall. Depth of lintel is based on the length of span and magnitude of loading.

Lintel can be made from various materials. Such as steel, wood, stone, RCC, etc.

Generally, the most effective material for lintel is RCC (Reinforced Cement Concrete). Generally, applied concrete ratio for RCC lintel is 1:2:4.

On the basis of the casting methods, RCC lintel is classified as Pre-cast RCC lintel and Cast-in-place RCC lintel.

DESIGN METHOD OF R.C.C LINTEL

There are similarities between the design methods of a lintel (single span or continuous having a few openings) and the design methods of a simple beam.

1. The lintel width is same as the wall thickness.

2. Provide an appropriate depth of the lintel.

3. Select the operational span of the lintel (maintain rational end bearings and real depth).

4. Assume W as the aggregate weight of the masonry work wrapped in the triangle, supposing that conditions authorize triangular load of the workmanship on the lintel.

5. Estimate the extreme bending moment (M1) at the centre of the lintel ( because of the triangular load).

M1 = Wl/6

Now estimate the maximum bending moment (M2) because of the self-weight (w) of the lintel per metre length.

M2 = wl^2/8

To read the complete article, go through the following link www.dailycivil.com

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Published By

Rajib Dey

www.constructioncost.co

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Some useful construction tips for becoming a successful rebar checker

While developing a big project, there should be a perfect technical engineering perception and cautious observation. Besides, other crucial examinations, Reinforced Cement Concrete should be verified for rebar toward the supplied construction drawings / shop drawings or technical specifications.

It should be remembered that the obstacle and cost associated with this activity may cause imperfection from the contractors end and it should be resolved / settled by a well-known consulting firm assigning on the inspection of execution.

One should have sound knowledge and well versed with the binding method of the steel rebar. Given below, some useful construction tips suggested by the top peers:-

a. Initially, one should have good knowledge on how to study a rebar drawing as well as communicate with it in the jobsite. In order to become a proficient rebar checker, you should have the capability to read drawing.

b. Carry a measuring tape with yourself so that you can verify the spacing and the splice length or development length.

c. Use a plastic glove, when checking the rebars as holding steel with bare hands may cause harm to the skin of of your body.

d. Should be familiar with the physical features of the construction component i.e. installing the drainage pipe or electrical conduit or replacing water stopper and any other pipes / embedded item.

e. Use vernier caliper to verify rebar diameter, rebar spacing, rebar development length, lap / splice length, alignment. Other important things range from no sag or buckling in the bars, perfectly fixed & tightened couplers, rust free bars, verifying clear cover, counting no of bars as per drawing specifications and must not be below or over 2 bars.

f. As a newbie in this field, try to keep in touch with contractor’s foreman or site engineer as they know well how to arrange these bars.

g. You should have good knowledge concerning the steel quality tests like tensile strength check or torsion failure strength or coupler tension strength check etc. Make sure that the steel are used after proper verification and poor quality steels are used.

h. Because of rough field conditions and difficultly in setting up / fixing of rebars, the proper design can’t be created. But you must be very careful about it as improper design may lead to collapse of a building.

i. One of the very crucial factors is to retain the exact orientation of bars like main rebars should be always arranged under the distribution or temperature rebars. It can be verified from the drawings submitted to you.

Ref.: www.iamcivilengineer.com

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Published By

Rajib Dey

www.constructioncost.co

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Categories And Design Of RCC Slabs And RCC Structures

Reinforced Cement Concrete Slab

• A Reinforced Concrete Slab Component plays a vital role in a building. It is considered as a useful structural element of the current buildings. There are various columns and beams which provide support to Columns and Beams.

• The density of RCC Slabs varies from 10 to 50 centimetres which are generally found in developing floors and ceilings.

• Thin concrete slabs are also utilized for the objective of exterior paving.

• In several domestic and industrial buildings, a solid concrete slab, sustained on foundations or directly on the sub soil, is utilized to develop the ground floor of a building.

• Thinner, pre-cast concrete slabs are pushed among the steel frames of tall buildings and skyscrapers to construct the floors and ceilings on each level.

• At the time of creating structural drawings of the reinforced concrete slab, the slabs are shortened to “r.c.slab” or simply “r.c.”.

Design of various types of slabs and their reinforcement

There are lot of designs available for a suspended slab to develop the strength-to-weight ratio. In most cases the top surface stands flat, and the bottom is modulated:

• If the concrete is poured into a corrugated steel tray, generally it is called corrugated. It enhances the strength and avoids the bending of slab under its own weight. The corrugations happen on the short dimension, from side to side.

• A ribbed slab provides significant additional strength on one direction.

• A waffle slab provides extra strength in both directions. Reinforcement design

• A one way slab contains structural strength in shortest direction whereas a two way slab contains structural strength in two directions.

These slabs belong to cantilevered or Simply Supported Slabs.

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Published By

Rajib Dey

www.constructioncost.co

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