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Tuesday, August 14, 2018

How To Set Out Your Building Foundation – Profiles

The Design: In order to set out the foundation of any Pompeii over, the design should be arranged on paper. Then, it is required to make a proper plant and follow it. Small changes can occur in the plan in due course.

The Plans:

Excavating Your Foundations: After getting the plans organized and a position in the property for Pompeii oven, then dig out the base. The strength of the foundation is based on the following

Ground conditions:

Weight of your structure: This set of drawings illustrates a re-inforced concrete foundation that should persist for a long time devoid of any movement. It should be kept in mind that the foundation should be digged minium 150mm greater than your finished oven.

All the timber profiles should be cut with equivalent size and make them level to each other. The width of the profiles can be increased extensively. You can make the string lines for the profiles when the foundation is built up or you will keep snagging them. The profiles can be inserted as far away from the foundation to get rid of dislodging.

Concreting Your Foundation: The foundation base can be designed according to your preference. You can only utilize concrete and there should be no re-inforcement detail.

Some steel re-inforcement mesh can also be applied. It is available in several sizes. You can take help from your local builder merchant to select the proper sizes.

Setting Out the Brickwork: Now, it is possible to reset your profiles on a proper concrete slab. Put each of the nails consistently to place your oven centrally on your new slab. Apply your square to ensure that everything is perfect. Now, the first course of brickwork can be arranged.

Here, the concrete base is dimensioned to facilitate the design and the brickwork is perfectly co-ordinated in order that there are no cuts at this stage.

How To Set Out Your Building Foundation

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Published By
Rajib Dey
www.constructioncost.co
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Monday, August 13, 2018

How temperature plays an important role on concrete

The concrete is extended with the rise in temperature and contracted with reduction in temperature. The range in difference in temperature differs from areas to areas, seasons to seasons and day to day.

The crack may happen in concrete because of contraction integrated with the impact of shrinkage.


Sometimes, big and injurious stress may produce owing to deformation that takes place for temperature variation.


The coefficient of thermal expansion of contraction is dependent on the type and quantity of cement, aggregate, proportionate humidity and sizes of section.



In high temperature, the concrete is influenced by the following factors :-
1. The elimination of evaporable water
2. The elimination of combined water
3. Modification in cement paste
4. Disruption (of beam) from discrepancy of expansion and resultant thermal stresses
5. Modification of aggregate
6. Alteration of bond among aggregate and paste
Cycles of temperature can provide a gradual impact on the curtailment of strength and even long-lasting curing can’t improve the loss.
Tensile strength of concrete is mostly affected with temperature.
If the heating is adequately fast, high stresses can be added and therefore, failure and instability may occur.
How temperature plays an important role on concrete

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Published By
Rajib Dey
www.constructioncost.co
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Thursday, August 9, 2018

How the strength of concrete is influenced by the temperature

The concrete strength performance in initial phase is significantly affected by the temperature control. In cold weather, the temperatures of concrete should be managed with powerblanket™ concrete curing blankets so that proper compression strengths are attained as soon as possible. Once, the concrete attains the perfect strength, the construction process is started.

The following four phases of works are required for building up RCC column :-
Column layout work
Column reinforcement work
Column formwork
Concrete Pouring into column



Given below, the detail segregation of strength gains after three days at different temperatures:
Temperature – Compressive Strength (psi)
70°F – 2,700
60°F – 2,150
50°F – 1,600
40°F – 1,200
30°F – 850
20°F – 400
In order to keep most favorable concrete strength, the following activities should be undertaken while placing concrete in cold weather:
Utilize a heated or warm concrete mix.
Keep an eye so that the concrete can’t be freezed – Apply powerblanket™ concrete curing blankets to manage temperature.
Ensure that the concrete should be arranged on a frozen sub-grade – Apply powerblanket™ concrete curing blankets to manage temperature.
Safeguard concrete against extreme drying.
Include accelerators to retain strength and normal set time.
Stay away from quick changes in concrete temperature with powerblanket™ concrete curing blankets.
How the strength of concrete is influenced by the temperature


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Published By
Rajib Dey
www.constructioncost.co
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Wednesday, August 8, 2018

Details of screw thread and its various components

Screw thread stands for a incessant helical groove of specific cross-section that is created on the external or internal surface. If a screw thread is developed on a cylinder, it is called as straight or parallel screw thread, whereas screw thread developed on a cone or frustum is called as the tapered screw thread.

Application of screw threads :-

1. To retain parts jointly
2. To modify the parts with respect to each other.
3. To transfer power


Given below, some vital components of screw threads :-

Root
Bottom part of the thread where both sides intersect.


Crest
Top part of the thread where both sides intersect.


Flank
It refers to the straight sides which attach the crest with root.


Thread Angle
Angle at which both sides of the thread intersect.


Axis of a screw
Longitudinal centerline via a screw


Base of the thread, Bottom section of the thread., Highest section among the two adjoining roots.

Depth of thread
Space from crest to root computed vertically.


Lead
Distance covered by a nut in one complete revolution.
Single start threads – Lead = Pitch
Multi start threads – Lead = Pitch x number of starts.


Threads per inch
Number of threads in one inch.
Length of screw. It is called TPI in short form.


Thickness of threads
Space among the adjoining sides of the threads computed along the pitch line.


Depth of engagement
Depth of the thread in contact of two mating parts calculated radically.


Length of engagement
Length of contact among two mating parts calculated axially.


Details of screw thread and its various components

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Published By
Rajib Dey
www.constructioncost.co
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Tuesday, August 7, 2018

Details of Cast in Situ Concrete Piles and their advantages

Cast In Situ belongs to a construction item or structural member similar to a beam or in this case a Pile that should be built up, assembled or poured at site instead of prefabrication in a factory. Normally, in cast in place or cast in situ construction, concrete is delivered from a batch plant to site where it is poured and compressed into the formwork that is fixed in required shape and dimensions at site.

Cast in situ or cast-in-place piles are cast in position inside the ground; generally in such type of piles, drilling of necessary diameter and depth into the ground is done with an auger drilling device or a drill bit.

There is a helical screw blade generally known as a “fighting blade” inside the device that functions as a screw conveyor to eliminate the drilled out material. Besides, auger drilling an old method known as percussion drilling is also applied for excavating the hole. Under this method, a heavy cutting or hammering bit affixed to a roper or cable is lowered in the open hole or inside a temporary casing.

After entering deep into the ground, a temporary steel casing is lowered in the borehole to safeguard loose soil from dropping in the borehole.

The verticality of the casing should be examined precisely prior to start. Once the optimal depth is attained, the reinforcement cage with vertical rebars and stiffeners is lowered within the borehole, and the upper part is hanged at the top. The concreting is generally performed with Tremie method of concrete piling.

There are normally 6 types of cast in situ piles as below:-

1. Simplex Pile, 2. Franki Pile, 3. Vibro Pile, 4. Vibro Expanded Pile, 5. Raymond Pile, 6. Mac Arthur Pedestal Pipe

Benefits of Cast In Situ Concrete Piles: The cast in situ piles are set up with pre-excavation and reduce the vibration because of driving as in case of driven piles.

In housing area, sound pollution may occur if the piles are entered by hammering. To get rid of this issue, situ piling is suitable in such areas.

For water logged area, cast in situ piling with permanent casing is very effective.

The skin friction resistance with the ground is fully used in cast in situ piles throughout the design phases that is not recommended in case of driven piles where only the end bearing is applied.

Normally, there is no need of any foreign materials and tools and the original equipments and materials will meet the requirements of a project, as a result the cast-in-situ piles become as a cost-effective and adjustable type of pile foundation.

Precast piles should be designed to satisfy the handling and driving stresses thus enhancing the essential reinforcement that does not happen in the case of cast in situ piles and therefore, the amount of necessary reinforcement is minimized.

Cast in situ piles are attached over the ground with a pile cap that applies a monolithic approach. The top ground is excavated up to pile cut off level from where the slushy low quality concrete is eliminated with hand hilty to retain developed rebars into the pile cap.

Because of this monolithic connection, cast in situ pile provides good resistance against the earthquake and wind forces.

As soon as the piles are casted, no maintenance is required.

Since the materials and machinery applied are obtained from the local community, local contractors can perform the job and not any skilled labor is required for cast in situ piles.

No serious consideration should be provided for joints in cast in situ piles with regards to precast driven piles.

Details of Cast in Situ Concrete Piles and their advantages

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Published By
Rajib Dey
www.constructioncost.co
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Monday, August 6, 2018

Mechanical properties of building materials

All the building structures are developed with various types of materials. These materials are either known as building materials or materials of construction. The cost of material in a building varies from 30 to 50 percent of entire building cost.

Given below, the detail mechanical properties of materials :-

Strength:

a. Strength is defined as the strength of material to resist the load.
b. Strength of materials – Capacity to resist an applied stress devoid of failure.
c. Compressive strength – Capacity to resist axially directed pushing forces.
d. Tensile strength – Highest stress at the time of being expanded or dragged prior to necking.
e. Shear strength – The capacity to resist shearing.
f. Elasticity – In a material if exterior load is employed it experiences deformation and on elimination of the load, it gets back to it’s actual shape.


Plasticity: If a material fails to retrieve it’s actual shape while eliminating the exterior load, it is defined as plastic materials.

Ductility: When a material experiences a significant deformation devoid of rupture, it is known as ductile materials.

It experiences a large deformation throughout tensile test. It is considered as the most perfect material for tension member. Steel, copper, wrought iron, aluminum alloys belong to ductile materials.

Elongation is in excess of 15%

Brittleness:

a. If a material can’t experience any deformation if some external force functions on it and it collapses with rupture.
b. Brittleness means powerful in compression and poorer in tension.
c. Brittleness is found in C.I, glass, concrete, bricks etc.
d. Elongation remains under 5%


Malleability: Malleability is the capability of a material to distort under pressure (compressive stress). After being malleable, a material is flattened into thin sheets through hammering or rolling. Several metals with high malleability also contain high ductility.

Malleable materials are gold, silver, copper, aluminum, tin, lead steel etc.
Toughness: Toughness means the capability of a material to consume energy prior to rupture is known as toughness.
Toughness is found in mild steel, wrought iron etc.
Hardness: Hardness means the resistance of materials against abrasion, indentation, wear and scratches.
C.I is stronger material.
Stiffness: Stiffness refers to force that is necessary to create unit deformation in a material.
Creep: Creep means inelastic deformation because of sustained load.
Physical properties of materials
Bulk density = ρ = M/V
Water absorption
Permeability
Stability
Specific gravity (G): Mass of solids of specified volume / Mass of equal volume distilled water
Mechanical properties of building materials

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Published By
Rajib Dey
www.constructioncost.co
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Saturday, August 4, 2018

How to check the workability of concrete with flow table test

Workability belongs to a vital factor of concrete that directly affects the strength, quality and look of concrete as well as finds out how easily freshly produced concrete is blended, set, compacted and finished by retaining its consistency as it is.

To examine the functionality of the freshly mixed concrete, the following tests are generally conducted on field and lab.

Slump test, Kelly ball test, K slump test, Vee bee consistometer test, Flow table test

In this article, detail information is given on flow table test of concrete.

Flow table test of concrete: Under this test method, the functionality of concrete is established by checking the flowing property of concrete.

With Flow table test of concrete, the quality of concrete is found based on the uniformity, cohesiveness and the susceptibility to segregation.

This flow table test is adhered to BS 1881 part 105 of 1984 and DIN 1048 part I.

The following equipments are required for Flow Table Test:

Flow table is built up with metal with thickness 1.5mm and dimensions 750mmx 750mm, tamping rod constructed with hardwood, Scoop, Centimeter Scale, Metal Cone or mould (Lower Dia = 20cm, upper Dia = 13 cm, Height of Cone = 20cm). The central part of flow table is pointed with a concentric circle of dia 200mm to arrange a metal cone on it.

Flow table test is conducted with the following methods :-

Get concrete ready according to mix design and set the flow table on a horizontal surface.

Cleanse the dust or other gritty material on flow table and spray a hand of water on it.

Now, set the metal cone at the central part of the flow table and rest on it.

Pour the freshly mixed concrete in the mould containing two layers; each layer is tamped with tamping rod for 25times. Once the last layer is tamped, the overflowed concrete on the cone is jammed with a trowel.

Gradually, raise the mould upright & allow concrete to rest on its own devoid of any support.

The flow table is elevated at the height of 12.5mm and dropped. The same procedure is reiterated for 15times in 15secs.

Calculate the spread of concrete in diameter with centimetre scale horizontally and vertically. The arithmetic mean of the two diameters should be the calculation of flow in millimetres.

How to check the workability of concrete with flow table test

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Published By
Rajib Dey
www.constructioncost.co
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Friday, August 3, 2018

Some useful information on detailing of beam

Detailing is one of the most crucial basic features of any construction. The architect should evaluate and place different elements of RCC members with proper care.

Proper detailing of reinforcements with accurate drawings is necessary at the construction site to maintain perfect construction process. Normally, these drawings comprises of a bar bending schedule. The bar bending schedule defines the length and number, location as well as the shape of the bar.

The detailing of beams is normally related to the followings :-

a. Size and number (or spacing) of bars
b. Lap and curtailment (or bending) of bars
c. Development length of bars
d. Clear cover to the reinforcement
e. Spacer and chair bars


The steel that is applied in beams pertains to various categories on the basis of the following objectives :-

i) Longitudinal reinforcement at tension and compression face (at least two 12 mm diameter bar should be arranged in tension) in single or multiple rows should be supplied.

ii) Shear reinforcements in the type of vertical stirrups and or bent up longitudinal bars should be arranged. (The bar bent round the tensile reinforcement and delivered to the compression zone of an RCC beams is known as stirrups).

iii) Side face reinforcement in the web of the beam is placed when the depth of the web in a beam remains in excess of 750 mm. (0.1% of the web area and allocated consistently on two faces at a distance not surpassing 300 mm or web thickness whichever is lower).

Some useful information on detailing of beam


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Published By
Rajib Dey
www.constructioncost.co
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Thursday, August 2, 2018

How to develop strong brick veneer cavity walls

Brick veneer cavity walls are mostly recognized product which can be used at the exterior of different types of buildings. With its conventional, rugged aesthetic and tested performance, bricks become a perfect choice for commercial, institution, and multifamily residential structures.

While designing, detailing, and constructing a brick wall assembly, considerations should be given on various factors. Given below, some useful tips to maintain moisture control, thermal performance, integrity, and durability of brick walls.

Never skimp on flashing materials within the cavity. Conventional materials like copper, lead-coated copper, stainless steel are very expensive but they are considered as the most long-lasting and trustworthy options.

Plan for thermal expansion/contraction of brick and concrete. Brick assembles frequently integrate brick and concrete components, both of which are extended and compacted at various rates and in diverse conditions. Due to this detailing becomes complicated for horizontal and vertical expansion joints, shelf angles, and modifiable veneer anchors.

Choose the feeble mortar for the job. If the mortar is extremely rigid, adjoining bricks can’t be moved and result in producing cracks and spalls.

Arrange minimum one inch of air space behind brick veneer. This void space operates as the drainage cavity where water is headed downward to the flashing and weeps and out of the brick veneer. If open weeps are utilized, this air space also allows to discharge the cavity, facilitating the interior components to get dried instantly.

Get clear ideas on vapor flow direction, and detail accordingly. For normal buildings, the direction of water vapor flow will differ by season and often on every day, based on the climate.

To get more details, go through the following link www.bdcuniversity.com

How to develop strong brick veneer cavity walls


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Published By
Rajib Dey
www.constructioncost.co
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Wednesday, August 1, 2018

Stress Control by Deflecting & Debonding Tendons in PSC Design

If precast beams contain straight, fully bonded tendons, they can be easily detailed and manufactured. The main benefit of pre-stressing is that it can apply the dead toad of the unit to minimize the transmission of the tensile stresses in the concrete.

But dead load is lost in such members since this tension remains most critical at the ends of the beams, where the alleviating effect owing to dead load is zero. The methods of deflecting and debonding tendons are frequently applied in pre-tensioned beams to obtain a pre-stress distribution much like that is obtained by the draped profiles of post-tensioned systems. It maintains some of the dead-load benefits, which lead to fewer tendons in the beams or a slightly smaller depth of beam than would be feasible with straight, fully bonded tendons.

Stress Control by Deflecting Tendons: The method of deflecting some of the tendons upwards towards the ends of a beam at a proper position along the span transfers the important section at transfer to this position, where vital relieving stresses as beam dead-load bending moment is accessible. Based on the stress computations for the end regions of the beam, the design engineer set the number of tendons to be deflected and the position of the deflection point.

The deflection point normally remains in the neighborhood of the quarter-span position, where three-quarters of the mid-span value of dead-load moment is accessible to neutralize the tensile stress (top fibre) because of pre-stress at transfer.

The angle of deflection of these tendons are placed in such a manner that the effective eccentricity and the pre-stressing force of the tendons do not generate a tensile stress of more than N/mm2 at transfer at the important sections, a limit set in the Code.

This method of deflecting tendons is specifically effective where continuity for live loads should be set in the finished structure since by deflecting some of the tendons upwards towards the ends of a beam, some compressive stresses are produced in the top fibre at the ends. This is useful for withstanding tensile stresses occurred because of the hogging moments caused by the passage of live loads on the superstructure. It also minimizes the formation of compressive stress in the bottom fibre because of prestress and live loads or any other loads at the ends of the beam.

Another benefit of deflected tendons is that the Code allows the vertical component of the tendon force to be applied in withstanding the imposed shear force on the beams in areas which stay flexurally uncracked at the ultimate limit state. This component is also suitable for the flexurally cracked regions and for examining the maximum shear stress condition in the member. Due to some limited test evidence, however, the Code does not allow relief against shear in these later conditions. Actually, the shear resistance of any section is decided in both flexurally cracked and uncracked modes and the lower value is selected. The shear links are then designed to bear the rest of the enforced shear force. Because only the tendons which are situated within the web width are deflected, the strand pattern for the whole unit should be cautiously chosen so that sufficient strands are available for deflecting upwards towards the ends to meet the stress conditions during the length of the beam.

To get more details, go through the following link engineeringcivil.org

Stress Control by Deflecting & Debonding Tendons in PSC Design

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Published By
Rajib Dey
www.constructioncost.co
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