adsense analytic

Tuesday, July 16, 2019

Guidelines for making perfect structural design

This civil engineering article focuses on the least standards which should be maintained for the design of various RCC structural elements like the columns, beams, slab and foundation as well as the least safe standards for the reinforcing bars to be applied for making the design of the above mentioned structural elements.
Minimum cross-sectional dimension for a Column should be 9″x 12″ (225 MM x 300 MM). It is the minimum approved size.
It is always recommended to utilize M20 grade concrete for construction as per IS 456:2000. The least steel in a 9″ x 9″ column should be 4 bars of 12 MM with stirrups of 8 MM steel rings at a spacing of 150 MM centre to centre. In a 9″ x 12″ column, more bars (6 bars with 12 mm diameter) should be added to sustain the total efficiently.
Least RCC beam size should not be lower than 9″x 9″ (225MM X 225MM), with an supplementary slab thickness of 125 MM.
Normally, there should be minimum of 4 bars, with 2 bars having 12 MM thickness in the bottom of the beam, and 2 bars having 10 MM at the top of the beam.
A concrete cover of 40 MM should also be provided. It is suggested to utilize M20 grade of concrete (1 part cement : 1.5 parts sand : 3 parts aggregate : 0.5 parts water).
Minimum thickness of RCC slab should be 5″ (125MM) since a slab may comprise of electrical pipes which are implanted into them which could be 0.5″ or more for internal wiring and as a result the depth of slab is decreased at specific places that lead to cracking, weakening and water leakage throughout rains. Therefore, a least thickness of 5″ should be retained.
Minimum size of foundation for a single storey of G+1 building should be 1m x 1m, where safe bearing strength of soil is 30 tonnes per square meter, and the anticipated load on the column does not surpass 30 tonnes.
The depth of footing should be minimum 4′under ground level. It is suggested to get to depths up to had strata.
Minimum Reinforcing bar details:
1. Columns: 4 bars of 12mm steel rods FE 500.
2. Beams: 2 bars of 12 mm in the bottom and 2 bars of 10 mm on the top.
3. Slab
a) One Way Slab: Main Steel 8 MM bars @ 6″ C/C and Distribution Steel of 6 mm bars @ 6″ C/C
b) Two Way Slab: Main Steel 8 MM bars @ 5″ C/C and Distribution Steel of 8 mm bars @ 7″ C/C
4. Foundation: Initially, there should be 6″ of PCC layer. Over it, a tapered or rectangular footing with minimum 12″ thickness should be arranged. Steel mesh of 8 mm bars @ 6″ C/C should be placed. In a 1m X 1m footing, there should be 6 bars of 8 mm on both segments of the steel mesh.
Guidelines for making perfect structural design

~~~~~~~~~~~~~~~~~~~~~~~~
Published By
Rajib Dey
www.constructioncost.co
~~~~~~~~~~~~~~~~~~~~~~~~

Monday, July 15, 2019

Common thumb rules for civil engineering works

Thumb Rules is very important for any civil engineer, Site engineer or civil supervisor to obtain instant decisions on the construction site. By applying thumb, the engineers can get the solution with a simple mathematical formula and take proper decisions wherever required. Before applying these thumb rules, it should be kept in mind that the thumb rule can only provide fairly accurate results never the correct results.

The following types of thumb rules for civil engineers are commonly used in construction work :-

Thumb rule for measuring the Concrete Volume relating to the area:
The volume of concrete necessary = 0.038 m3/square feet area.


As for instance, if Plan Area = 40 x 20 = 800 Sq. m., total necessary volume of concrete will be as follow :-
= 800 x 0.038m3 = 30.4m3


Thumb rule for Steel quantity necessary for Slab, Beams, Footings & Columns:
Essential quantity of steel in residential buildings = 4.5 Kgs – 4.75 Kgs / Sq. Ft.
Essential quantity of steel in commercial buildings = 5.0 Kgs-5.50 Kgs/Sq. Ft.


Thumb Rules For Civil Engineers recommended by B N Datta for the Steel quantity that will be applied for several members of the building :-

Proportions of Steel in Structural Members:

1) Slab – 1% of the total volume of concrete
2) Beam – 2% of the total volume of concrete
3) Column – 2.5% of total volume of concrete
4) Footings – 0.8% of the total volume of concrete


As for instance, suppose the length, width and depth of the slab are 5m, 4m and 0.15m. Now, the quantity of steel for the slab will be computed as follow :-

Initially, it is required to work out the concrete volume.
The total volume of concrete for the slab = 5x4x0.15 = 3m3


Secondly, work out the quantity of steel with formula as follow :-
Based on the guidelines provided in B. N. Dutta reference book, the quantity of steel in slab is 1% of the total volume of concrete used.
Thumb rule to work out the quantity of steel in above slab = Volume of concrete x density of steel x % of steel member.


The weight of steel necessary for above slab = 3x7850x0.01 = 235 kgs

To make perfect calculation, use bar bending schedule.

To learn how thumb rules are applied to calculate the shuttering area and the quantity of cement, sand, course aggregate in several grades of concrete, click on the following link civiconcepts.com

Read more

Common thumb rules for civil engineering works

~~~~~~~~~~~~~~~~~~~~~~~~
Published By
Rajib Dey
www.constructioncost.co
~~~~~~~~~~~~~~~~~~~~~~~~

Saturday, July 13, 2019

Inspection & Testing Method of concrete

This civil engineering article focuses on the test method required for evaluating the concrete work.
Concrete construction activities should be done on the basis of the job site specifications, methods and drawings. Concrete inspection and testing should be executed by experienced personnel to ensure that requirements of the specifications, methods and drawings are satisfied.
Tests of concrete is conducted to make sure that the compliance to specifications should be performed by a certified Concrete Field Testing Technician.
If not mentioned anywhere else in the specifications and/or drawings, at least six concrete cubes should be developed and treated as a set. If not mentioned anywhere else, the cubes will be tested in the following ways :-
2 cubes at 7 days
2 at 28 days
2 held in reserve
The results obtained from the test, should be noted on a spreadsheet and in a way conformable to QC procedure: Statistical Techniques.
Unless stated otherwise in plan specifications or drawings, one set of cube should be created for each 150 cubic yards of concrete laid as defined in building codes. Minimum one set of cubes should be formed on each day concrete is laid irrespective of the quantity of concrete.
Application of QC procedures: Process Control as a guide, Contractor should fix a meeting with the subcontractor before pouring the first concrete. This meeting will be conducted so that the subcontractor can narrate his/her plans for the concrete pour along with all the areas scheduled in this section of the procedure.
Batch Plant Inspection: Contractor retains the power to examine any and all concrete batch plants which will deliver concrete to the construction site. A “walk through” inspection should be carried out before the production of concrete is started.
If it is required, examinations can be done throughout concrete production. Given below, the major inspection items for every type of batch plant inspection:
Preliminary Inspection
• Check that aggregates are loaded in exact bins
• Examine that aggregates are not polluted
• Examine that scales and measuring devices contain current calibration stickers and seem to function perfectly
• Examine that the plant contains a current local authority approval certification
• Examine that concrete trucks remain in proper working condition
• Examine that entire operation of the plant seems to be professional, systematic, relatively clean, well maintained, etc.
• Examine that batch plant operators should have adequate knowledge (verify their certificates or certifications)
• Examine that batch tickets provide crucial information (amount of hold back water, list of ingredients, batch times, size of load, indication of mix ordered, etc.)
• Examine that the plant and delivery equipment can form homogeneous concrete as per the requirements of ASTM C-94
• Make sure that the plant and delivery equipment satisfy the capacity requirements of the job
Throughout Concrete Production (if necessary):
• Examine that correct mix has been loaded into the batch plant computer
• Examine that equipment is working properly (admixture dispensers, scales, moisture indicators, etc.)
• Examine that truck counters have been reset to zero once the mixing water has been added to the mix
• Examine that water used to “wash down” the concrete truck prior to leaving the plant area does not enter the concrete mix
• Examine that the amount of hold back water is stated on the batch ticket
• Make sure that the concrete coming out from the plant will satisfy the specifications for temperature, air content and slump (testing at the plant should be conducted if required)
Concrete Mix Design: All proposed concrete mixes should be provided to Consultants via main contractor for verification and approval before application. The projected mixes delivered for use shall comprise of a concrete strength break history as stated in ASTM and shall include suitable test results and/or certificates of conformance on all constituents which will be applied in the certain concrete mixes.
Inspection & Testing Method of concrete

~~~~~~~~~~~~~~~~~~~~~~~~
Published By
Rajib Dey
www.constructioncost.co
~~~~~~~~~~~~~~~~~~~~~~~~

Friday, July 12, 2019

Sample quotation for constructing an indoor badminton court

In this civil engineering article, you will get a sample quotation with quantities of construction material to design and develop an indoor badminton court.
SPECIFICATIONS: MAIN FEATURES –
• The structure should contain a basement height of 1’0” from Natural ground level.
• Footing pit size 4’x4’x6’-10mm dia @8” c/c main, 8mm dia @8” c/c alternate.
• Column size – 9”x9” (6 nos 16mm dia and stirrups 8mm dia @8” c/c)
• Plinth size – 9”x9” (4nos 12mm dia main reinforcement and stirrups 8mm dia @ 8” c/c)
• Brickwork should be done with superior quality chamber bricks containing cement mortar in 1:6.
• Basement height 2’-0” Basement inside filling with soil. Over the soil PCC is laid with 1:4:8 with 40mm blue metal.
• Plastering with cement mortar 1:4 exterior wall.
• One coat of white cement and two coats of Asian exterior emulsion should be applied.
• Grano flooring with blue metal chips over PCC in the basement.
THE FOLLOWING MATERIALS ARE UTILIZED:–
• CEMENT: Dalmia/Ultratech/Ramco
• BRICKS: Chamber
• STEEL: ISI
• SHEET: JSW CCGL0.47
• PAINT: ASIAN Paint
Total Area of the Building is supposed to be 54’-0” x 54’-0” = 2916.sq.ft.
Subject: Metal Roofing Shed
‘A’ Truss Length x Width: 58’ Feet x 54’ Feet =3132.Sq. Ft
CLADDING WORK (27’x54’) + (27’x54’) + (30’x54’) + (30’x54’) =6156. Sq. ft
Sub: Fabrication and construction of traditional steel structure with Cooler coated Galvalume.
Columns: Delivery and installation of 12 Numers.150×100 Columns (MS I BEAM Height 32’ Feet) Columns Base Plates should have 20 mm thickness 300 mmX300mm & Columns top Plates should have 8 mm thickness.
Base foundation 25 mm 1’5’Feet 48 Numbers
Columns Bracing Support ( X 4 Numbers)
A Type Trusses: Delivery and installation of of 4 Numbers. Trusses 54.0” Feet span formed 50X50mm MS Square Pipe Bottom Rafter as 50X50mm MS pipe with inner cross 30X30 Straight as 30X30 mm pipes medium (ISI 2mm thickness) Lighting Support 1 No Inclusive.
Paint Works: One coat of premier & two coats of enamel paint.
Roof Sheet: Color coated Galvalume CCGL JSW sheet (0.47mm) and its accessories.
Purlin > 60×40 (ISI 2mm thickness) Square Tube purlin.(1000+1300=1Numbers)
To get more details, click on the following link www.onlinecivilforum.com
Sample quotation for constructing an indoor badminton court

~~~~~~~~~~~~~~~~~~~~~~~~
Published By
Rajib Dey
www.constructioncost.co
~~~~~~~~~~~~~~~~~~~~~~~~

Thursday, July 11, 2019

Corrective measure to check pile foundation failure

Pile foundation contains sound bearing strength, good durability and small differential settlement with regards to other foundation types.
Pile foundations are normally provided in the following conditions :-
1. Low bearing strength of soil.
2. Non-existence of perfect bearing stratum at shallow depths.
3. Greater loads from the super structure for which shallow foundation may not become inexpensive or feasible.
But pile foundations become damaged and collapse specifically throughout earthquakes because of the following purposes.
1. Inadequacy of sufficient boring
2. Improper soil grouping
3. Soft strata under tip of pile
4. Insufficient driving formula (wrong data)
5. Imperfect size of hammer leads to deficient penetration, too light or get damaged if too heavy
6. Misapprehension of load
7. Damaged of encased piles
8. Buckling of piles
9. Cracking of piles
10. Vibration that leads to lateral or vertical movement
11. Flowing strata resulting from adjoining excavation or bank sloughing
12. Tension failure of concrete pile for shortage of reinforcement
13. Eccentricity because of bowing or falling out of plumb
14. Deterioration caused by lower ground water level
15. Insect and marine borer attack and erosion
16. Detachment of concrete caused by poor quality of concrete or reactive aggregate
17. Failure of the thin shell of the piles
18. Overweight owning to earthfill.
Corrective measures to get rid of failure of pile foundation:
1. Preliminary repair like encasement or replacement
2. Extraction of partial load
3. Underpinning
Corrective measure to check pile foundation failure

~~~~~~~~~~~~~~~~~~~~~~~~
Published By
Rajib Dey
www.constructioncost.co
~~~~~~~~~~~~~~~~~~~~~~~~

Wednesday, July 10, 2019

How to determine the cutting length of chair bar in slab & footings

The chairs in reinforcement are provided for the following reasons.
1. It retains the gap among the two bars as well as upper and lower cage reinforcement.
2. It provides strong supports to the bars.
3. It improves the strength of the structure and retains the tension in RCC.
4. It raises the tension property of concrete.
5. It reduces the scope for collapsing of the building because of the failure of compression and tension zone.
6. While vibrating, it holds the upper cage bar from collapsing.
7. The diameter of the bar should not be lower than 12 mm.
The chair bars should be made of the scraps in the jobsite.
In this civil engineering article, detail information is given for finding out the cutting length of chair bar in slab and footings.
The height is treated as the most crucial part of any chair as when the height is known, it becomes easier to determine the leg and the length of head.
The height of the chair bar will be determined with the following formula :-
Height = Height of footing – (2 x clear cover) – (dia of bottom main bar) – (dia of top main bar + dia of top distribution bar)
The head of the chair bar will be determined with the following formula :-
Head = (2 x spacing of top distribution bar) + 100
The leg of the chair bar will be determined with the following formula :-
Leg = (2 x spacing of bottom main bar) + 50
To learn the detail calculation process, go through the following video tutorial.
How to determine the cutting length of chair bar in slab & footings

~~~~~~~~~~~~~~~~~~~~~~~~
Published By
Rajib Dey
www.constructioncost.co
~~~~~~~~~~~~~~~~~~~~~~~~

Tuesday, July 9, 2019

How to get rid of common errors in concrete floor slab construction

To get rid of common errors in concrete floor slab construction, various steps like perfect base preparation, mix design, placement, finishing, and curing should be taken.

Typical concrete floor slab thickness in residential construction should be 4 inches. In case the concrete has to sustain extreme loads irregularly, the thickness should be five to six inches; as for instance, motor homes or garbage trucks.

To arrange the base, the ground level should be dug according to the perfect depth to provide for the slab thickness. Take out all organic material and large hard objects like stones and tree roots to a depth of minimum 4 inches. If it is required to develop the grade, apply gravel or sandy soil, and compress the final base with a vibratory plate or equivalent device.

The edge is built up with any straight material that can be fixed into position. If case of constant non-availability of straight lumber, plastic or metal forms should be used. Fix a string line with grade stakes or batter boards to provide a square, level reference prior to place the formwork.

For the concrete mix, it should satisfy the compressive strength requirements (normally 3000 pounds per square inch) devoid of measures that lead to extreme shrinkage. The shrinkage and cracking are increased because of the existence of water, a plasticizer should be used to attain required slump.

Also provide fibers to check plastic shrinkage cracking. Greater strength and entrained air are necessary for exterior slabs susceptible to freezing weather or deicing chemicals.

It is suggested not to add water at the jobsite more than 1 to 2 gallons per cubic yard. In case, extra slump is essential, take advice from the mixer truck driver concerning the quantity of water to be included devoid of taking the concrete out of specification.

Spread the concrete accross the slab area as close to its final position as possible, and then rake it into exact location. Hardens low-slump mixes manually with a vibrator or apply a vibratory screed. Complete with the least force and strokes of the float required to attain a smooth surface.

Develop control joints no farther apart than 24 to 30 times the slab thickness and at no time exceeding 15 feet along both the width and length of the slab by pushing a 1-inch deep grooving tool into the surface.

To keep Joint spacing more than 15 feet, different types of load transfer devices should be used which range from dowels or dowel plates. For slabs with long joint spacing or no joints, steel reinforcement will be suitable.

It will raise the chances for random cracking, but will maintain cracks firmly to keep up superior structural performance.

The curing process should be initiated when the finished surface can counter damage. The concrete should not be enabled to freeze or dry out. Arrange a curing compound over the surface, or apply proper moist curing.

In case of freezing, the slab should be wrapped with an insulator, like insulating blankets or a 4-inch-thick layer of straw that is weighted down so that it can’t blow away. Unless the concrete attains a strength of minimum 500 psi, put the insulator in place. It normally happens within a few days.

Read more

How to get rid of common errors in concrete floor slab construction

~~~~~~~~~~~~~~~~~~~~~~~~
Published By
Rajib Dey
www.constructioncost.co
~~~~~~~~~~~~~~~~~~~~~~~~

Monday, July 8, 2019

Benefits of rock reinforcement

Rock reinforcements provide extra supports to the rock structures so that the stability and load bearing strength of the rock is enhanced. Rock reinforcements are arranged in the type of rock bolts, rock anchors or rock dowels.
Types of Rock Reinforcement: The support given with rock reinforcements ranges from active type or passive type.
For active support, a predefined load is enforced on the rock surface while being set up. Under passive type, a load is formed when the rock mass deforms or dislocates.
The following types of rock reinforcements are commonly found :
1. Rock Bolts: This type of rock reinforcement is frequently used at the end of the borehole. These belong to steel rods which are grouted into the rock. These comprise of a grout anchor or friction on the rock. As soon as the anchorage is obtained, it is tensioned and a compressive force is produced into the adjacent ground.
The axial force produced operates on the rock-mass discontinuities which enhance the shear strength of the mass. This shear strength is produced through the pre-tensioning of the bolt.
2. Rock Dowels: This is a passive type of rock reinforcement for which a ground displacement is required for its activation. When the discontinuities in the rock mass are susceptible to displacement, the dowel undergoes both shear and tensile stresses.
3. Rock Anchors: This method of rock reinforcement employs compressive or uplift force to make any structure or rock mass stable which exist in the ground or underground. These belong to high tensile strength bars. These are pre-tensioned by fixing at the end of the borehole.
Rock anchors belong to either un-tensioned anchors or tensioned anchors. To combat failure of the rock mass caused by shear, rock anchors are used.
Usages of Rock Reinforcement:
The purpose of rock reinforcement is to give safety and temporary supports for several underground construction works. Given below, the different uses of rock reinforcement :-
1. Rock reinforcement is mainly applied to pre-load the foundation.
2. It is applied for the purpose of producing a reaction throughout the pile load test.
3. Rock reinforcements (Rock Anchors) can fasten the suspension cables and guy wires for the bridges.
4. It facilitates to bind the wire cables with the foundation under the sea.
5. Rock reinforcement combat uplift occurred in transmission towers, foundation and hydraulic structures caused by lateral forces.
6. Rock anchors are provided to support sheet piles.
Benefits of rock reinforcement

~~~~~~~~~~~~~~~~~~~~~~~~
Published By
Rajib Dey
www.constructioncost.co
~~~~~~~~~~~~~~~~~~~~~~~~

Friday, July 5, 2019

Some vital tests to check the quality of concrete

Concrete is mainly a composite material that comprises of fine & coarse aggregate, water, cement, and admixtures.

To obtain high-quality concrete, the sample should be examined thoroughly to ensure whether it is formed according to requirement or not. If the test for concrete is not conducted, the following problems will occur :-

• Cracks and voids in the finished concrete.
• The concrete of Low compressive strength.
• Bleeding


Given below, the details on some vital tests of concrete:

1. Workability test
2. compressive strength test
3. Non-destructive test
4. Destructive test
5. Durability test


WORKABILITY TEST: Workability test plays a crucial role since it is associated with the strength of concrete. Workability means the capacity to fill the mould perfectly with the vibrator but the quality of concrete is not affected. The Workability of concrete is calculated with the following test:

• SLUMP TEST
• VEE-BEE TEST
• COMPACTING FACTOR TEST


Compressive strength of concrete: The concrete can’t sustain the compressive load. So, it becomes essential that any concrete member could withstand a good amount of compressive load.

Under this test, the maximum compressive strength of the concrete sample is ascertained after 28 days of curing. Based on the standard code of India, 150 mm concrete cubes are utilized in this test. Under this test, the concrete sample should be immersed for 28 days and after each 7 days water should be changed. After 28 days of curing, the concrete specimen is arranged on the machine plate.

Now load is provided slowly to the specimen unless the collapsing of the concrete cube occurs. Destructive and Non-destructive Test of Concrete These tests are carried out to find out the compressive strength of the existing concrete structure where the required concrete sample is not available.

This types of tests are conducted with the destructive or Non-destructive way.

If Non- destructive way is followed, compressive strength should be established devoid of affecting the structure or any concrete member. The Non-destructive test is conducted on the following ways :

• Rebound hammer test
• Penetration and pullout techniques
• Surface hardness test
• Radio-active method


Most common Destructive tests are as follows:

• Concrete core test
• Cube test
• Tensile strength test


Durability Test: With the purpose of maintaining the sustainability of concrete, the stability of concrete is required. To enhance the stability of concrete, it's vital that concrete should contain the following qualities :

• Water resistance
• Chloride attack resistance
• Resistance to infiltration of water.


Read more

Some vital tests to check the quality of concrete

~~~~~~~~~~~~~~~~~~~~~~~~
Published By
Rajib Dey
www.constructioncost.co
~~~~~~~~~~~~~~~~~~~~~~~~

Thursday, July 4, 2019

Shallow Foundation and its types

The shallow foundation is categorized as follow :-
1. Spread Footing
2. Combined Footing
3. Raft Foundation
4. Annular Slab or Ring Foundation.
Type 1. Spread Footing: Foundation that transmits the load from a wall or column to a deeper width is called spread foundation or footing. The spread footing intended to the walls of a load bearing structure is called wall footing, continuous footing, or strip footing.
i. Strip Footings: Strip footing is made of stone masonry or concrete and it contains a stepped cross section. Now-a-days, the concrete is gaining popularity in construction industries and the load bearing structures & strip footings become outdated to some extent exclusive of small lightly loaded residential buildings. It is also called continuous footing or wall footing.
ii. Isolated Footing: Spread footing arranged to the columns of a framed structure is known as isolated footing, column footing, or pad foundation.
It is arranged underneath the column to disperse the loads securely to the bed soil. This type of footing is provided to support single-columns and when the columns are placed comparably at long span. It is very cost-effective.
Type 2. Combined Footing: Combined footing is effective when footings of two adjoining columns are provided too narrowly or overlap. It is categorized as follow :-
i. Rectangular Footing: Combined footing is usually rectangular in shape to resist equivalent column loads.
ii. Trapezoidal Footing: For irregular column loads, trapezoidal footing should be utilized to make sure that the centre of gravity (CG) of the column loads overlaps with the CG of the foundation in plan.
iii. Strap Footing: For footings located adjacent to the property lines, a strap footing should be applied to make sure that the edge of the footing adjacent to property line is not expanded into the nearby site. Under the situation, the footing adjacent to the property line (exterior footing) is attached with the footing inside the site (interior footing) via a strap beam.
The strap beam transmits the load of the exterior column footing merely to the interior footing during structural action.
Type 3. Raft Foundation: Raft foundations also known as raft footings or mat foundations, are provided with reinforced concrete slabs having consistent thickness (normally 150 mm to 300 mm) which are extended for a wide area, often the entire footprint of a building. They disperse the load enforced through a number of columns or walls over the area of foundation.
Raft foundation is mainly arranged when the entire area of all footings surpasses 50% of the loaded area. It is also suitable for heavy structures situated over highly compressible and weak soils expanding to large depth.
Type 4. Annular Slab or Ring Foundation: A ring foundation is sometimes arranged for a bigger water tank with its columns attached through a ring beam and supported across an annular slab.
Shallow Foundation and its types

~~~~~~~~~~~~~~~~~~~~~~~~
Published By
Rajib Dey
www.constructioncost.co
~~~~~~~~~~~~~~~~~~~~~~~~

Wednesday, July 3, 2019

Different types of vibrators generally found for concrete compaction

The objective of a vibrator is to compact concrete on the construction site easily and efficiently. At the time of vibration, compacting is influenced by cutback in internal friction among different particles of concrete because of oscillation of particles which lead to a solid and compact mass of concrete.
Vibrations can be accomplished in the following ways :-
a. Provided in the interior of the concrete with Internal vibrator, or
b. Provided in concrete by vibrating formwork with Shutter form vibrators, or
c. Provided on the surface of concrete with Surface vibrators, or
d. Provided in the total concrete mass with Vibrating table.
The following types of vibrators are generally found for compaction :-
1. Internal or Immersion or Poker or Needle Type Vibrator
2. Shutter form or External Type Vibrator
3. Surface or Screed or Pan Type Vibrators
4. Vibrating Tables
1. Internal Vibrators: These are also known as immersion, poker or needle vibrators. They basically comprise of a power unit and a long adjustable tube, at the end of which a vibrating head is connected. Power is supplied through electric motor, compressed air or petrol engine. The long tube comprises of a flexible shaft that revolves an eccentric weight inside the vibrating head. The frequency of the vibrator remains approximately 700 cycles per minute.
The vibrating head is included in the concrete. They are very useful since the vibrating head gets in touch with concrete closely.
2. Form Vibrators: They are also known as external vibrators. They are secured with the formwork horizontally and vertically at exact distance not surpassing 90 cm in either direction.
With the advancement of the work progress they are transferred. They vibrate the concrete from the vibration of the forms and consequently lots of energy is exhausted.
Form vibrators will be applicable when the internal vibrators can’t be used in the case of thin and congested sections, arches and tunnel lining, etc.
3. Surface Vibrators: They are also known as screed or pan vibrators. They are secured to the screed. They vibrate the concrete from the surface while screeding (striking off) of the concrete is performed. They are useful when the depth of concrete remains up to 20 cm.
In case the depth is higher they should be utilized along with internal vibrators. They are suitable for long horizontal surfaces like pavements and slabs.
4. Vibrating Tables: These are inflexible and constructed with steel platforms secured on steel springs and operated by electric motors. The concrete is provided in moulds mounted on the platforms and firmly secured to the vibrating table, to facilitate mould and concrete vibration conjointly.
Vibrating tables are utilized for compacting hard and rough mixes utilized in precast structural members in factories and laboratory samples.
Different types of vibrators generally found for concrete compaction

~~~~~~~~~~~~~~~~~~~~~~~~
Published By
Rajib Dey
www.constructioncost.co
~~~~~~~~~~~~~~~~~~~~~~~~

Tuesday, July 2, 2019

Benefits of I-beams in construction

Hot-rolled steel beam having I-shaped cross section, and tapered flanges closer than wide flanged beam is known as I-beam.
I Beam contains one vertical plane and two horizontal planes or flanges which develop 'I' or 'H' structure. The vertical plane withstands the shear stress , whereas horizontal planes withstand the bending movement. I Beam is majorly utilized in construction industry like construction of manufacturing plants, multi-story buildings etc.
I-beam is frequently applied as important support trusses, or the primary framework, in buildings. Steel I beams retain structure’s integrity with persistent strength and support. The extreme power of I beams minimizes the requirement for several support structures and as a result huge time and money is saved. The stability of the structure is improved considerably.
Some vital jargons of I-Beam:
1. Flange thickness: Top and bottom horizontal plate-like segments of an I-beam are known as flange. The density of the flanges is defined as the flange thickness.
2. Flange width: The width of the flanges is known as flange width.
3. Beam depth: The height among the top and bottom surface of the steel I beam is termed as beam depth.
4. Web thickness: The vertical segment of steel I beam is known as web, and the thickness of the web is termed as web thickness.
5. Fillet radius: The curved section, where the changeover among the web and flange occurs is known as a fillet. The radius of the fillet is defined as the fillet radius.
A properly sized I Beam can be chosen on the basis of the following criterion :-
The entire method of choosing the proper size of the I beam is dependent on the basic mechanical design calculations as given below:
1. The first input necessary belongs to the steel I beam load specifications or loading details on the steel I beam.
2. Draw bending moment diagram for the specified loads and get the value of maximum bending moments (suppose M) that the steel I beam is likely to experience.
3. Select an exact size of steel I beam from a standard I beam table.
4. Determine the area moment of inertia (suppose I) of the selected steel I beam.
5. Obtain the beam depth (suppose d) of the selected steel I beam.
6. The stress developed (f) in the beam can be measured with the formula given below :
f/(d/2)=M/ I
f denotes the bending stress.
M denotes the moment at the neutral axis.
y denotes the perpendicular distance to the neutral axis.
I denotes the area moment of inertia about the neutral axis x.
7. Compare the calculated value of the bending stress with the yield stress of the steel with the purpose of verifying the safety factor of your design.
The structural design will be perfect when the size of the I-beam is accurate. The method described above is dependent on static I beam load specifications. In case where dynamic loads are concerned, it is necessary to apply FEA tools like ANSYS, Pro Mechanica, etc.
Benefits of I-beams in construction

~~~~~~~~~~~~~~~~~~~~~~~~
Published By
Rajib Dey
www.constructioncost.co
~~~~~~~~~~~~~~~~~~~~~~~~

Monday, July 1, 2019

Details about Rebar Support and Chair Spacing

So you are involved in a construction project comprising of heavy steel rebar and you are wondering what different types of rebar support are available in the market and what could the best choice be for rebar chair for seamless spacing.
Reinforcement is placed in concrete at specific distance and orientation to provide sufficient area of steel at each section of the structural component. Therefore, the rebar will not be suitable, when the order of distance and orientation is not retained at site according to the design intent.
In large construction projects, 12 meter long dowels are provided in inclined positions and in multiple layers keeping distance of around 150 mm. Under such situations, Contractor should incur huge amount for the purpose of getting rebar supports and rebar chairs.
Collapsing of any of these supports may lead to destruction at the site. So, there should be proper rebar support in a construction project.
A rebar chair also known as rebar spacer stands for a rebar support device that tie the rebar in exact location and in required spacing before the concrete is poured. These supporting devices are treated as essential part of the permanent structure and implanted in the concrete.
Types of Rebar Support - The following types of rebar supports are commonly used:
1. Rebar Chair Support or Stools
2. Rebar Spacer Support
The word Rebar Chair is generally applied for support system towards reinforced concrete slabs, floors, sidewalks or driveways; they uplift the rebar off the ground by securing its position and arranging the necessary cover from the ground. If the slab contains multi-layers of rebar, these chairs should comprise of slots for two or three layers as per the structural design.
Rebar spacers stand for those types of rebar supports which are found in reinforced concrete walls, columns, piers or piles etc. They fix the vertical and horizontal rebar in exact location with the center to center clearance among various layers of rebar as well as arrange the necessary cover from the edge of the formwork.
Rebar Support Variations: The flat bottom chairs are also available to avoid the chair tips from suspending the vapor barrier and retaining a more secure surface.
Steel chairs with plastic tips cab also be used. They are cost-effective and can be utilized when small spots of erosions are found on the surface. Stainless steel chairs also exist, but they are little expensive as compared to traditional chairs, and when plastic can’t be provided into the concrete or when the weight is heavy for the plastic chairs.
Rebar Support Problems: Often, chairs will be overturned, when necessary cover is in excess of 2.5 inches, since the height to width ratio is insufficient, to facilitate the workers from walking over.
Besides, when they are too far away, the rebar will bend in the middle because of its weight, and extra chairs will be needed for some areas or the chairs can actually rupture owning to extreme weight. Some steel chairs having a plastic tip might untie the plastic protection all through the installation process, providing a feasible area on which corrosion can occur and the concrete surface will be damaged.
Details about Rebar Support and Chair Spacing

~~~~~~~~~~~~~~~~~~~~~~~~
Published By
Rajib Dey
www.constructioncost.co
~~~~~~~~~~~~~~~~~~~~~~~~

Saturday, June 29, 2019

Brick Bonds Types And Patterns

A brick bond belongs to a pattern where the bricks are placed. The applications of brick bonds are found on the walls as well as for brick paving for paths & patios, concrete blocks and different types of masonry construction.
Brick Bonds can improve the strength & stability of the structure, retain consistency to the structure and composition, and increase the visual appeal. Given below, the details of commonly used wall brick bonds :-
1. Stretcher Bond / Running Bond: It is also known as running bonds. The process is very simple to place this type of bond. Stretcher bond is useful when the walls of half brick thickness are required to be constructed. This bond is applied to build up several types of wall construction as follows :
• Sleeper walls
• Partition walls
• Division walls (internal dividers)
• Chimney stacks
Stretcher bonds should not be used for self-sustaining structural walls, but it is effective for building up the walls of less thickness. Remember, this bond can collapse when the thickness of the walls remains greater than half of the total length of the brick applied.
2. Header Bond: A header stands for the shorter face of the brick. In header bond brick masonry, all the bricks are built up in the header course. Under this type of bond, the overlap is done according to a half width of the bricks. The three-quarter brickbats are used as quoins in alternative courses. This bond is primarily applied for the erection of one brick thick walls.
3. English Bond: This bond contains alternating courses of headers and stretchers. Headers are placed in center position on the stretchers in the course underneath and each alternate row is arranged vertically. To rupture the continuity of vertical joints, a quoin closer is utilized at the start and end of a wall once the first header is provided.
A quoin close belongs to a brick that is cut into 2 halves according to length and applied to the corners in brick walls. This type of bond is useful for building up strong one brick thickness walls.
4. Flemish Bond: Under this type of bond, alternate headers and stretchers are contained in each course. Each header remains on the center of a stretcher over and below and each alternate course is started with a header in the corner. To rupture the vertical joints in the sequential courses, quoin closers are provided with alternate courses alongside the header.
5. Stack Bond: In a stack bond, all the bricks are simply loaded on top of each other and retained with mortar where all bonds are arranged properly. Due to its poor masonry structure and less strength, stack bonds are effective for decorative purposes.
As this bond is a non-structural bond, therefore it should not be used for the walls which need to transmit loads.
6. Dutch Bond: It is a customized form of the English cross bond that includes alternate courses of headers and stretchers. In this arrangement of the brick bond, each single stretching course is started at a quoin containing a 3-quarter bat. Each alternate stretching course contains a header set alongside the 3-quarter bat brick placed at the quoin. This bond is suitable for developing strong corners of the wall that is susceptible to extra loads.
7. Common Bond / American Bond: This bond contains courses of headers provided with each five or six courses. Header courses are placed in center position of the previous header course. This header bond usually functions as a tie brick among the fronting and the backing. To attain the plenty offset in a standard common bond, queen closers are provided at both ends of the header courses. The common bond is generally applied in outside load-bearing walls.
8. Facing Bond: This bond is effective for thick walls, where the facing and backing are selected for construction with bricks having different thickness. Normally, this bond comprises of heading and stretching courses which are provided in such way that one heading course comes after quite a lot of stretching courses. The load distribution of walls of this bond is irregular due to the variation among the facing and the total number of joints in the backing. It can also result in unequal settlement of the 2 thickness of the wall.
9. Diagonal Bond: It is perfect for walls with two to four brick thickness. This bond is generally provided at each 5th or 7th course along the height of the wall. Bricks in this bond are arranged end to end in such a way that extreme corners of the sequence gets in touch with the stretchers.
10. Rat Trap Bond: Under this bond, bricks are placed on edge or in a vertical location rather than the conventional horizontal position. It produces a cavity (hollow space) inside the wall as a result superior thermal comfort is maintained and the inside becomes cool as compared to the outside and vice versa. Because of the internal cavity, a little amount of materials is required for this type of walls.
Brick Bonds Types And Patterns

~~~~~~~~~~~~~~~~~~~~~~~~
Published By
Rajib Dey
www.constructioncost.co
~~~~~~~~~~~~~~~~~~~~~~~~