What are ribs & lugs in reinforcement steel bars?-Functions of ribs & lugs.

 1. What are ribs & lugs in reinforcement bars?

The embossed pattern formed over the reinforcement bars is known as ribs or lugs in the construction field.

The ribs that are in the longitudinal direction are known as longitudinal ribs or simply ribs.

The embossed pattern in the transverse direction having an angular slope is known as transverse ribs or lugs.

The angularly spaced lugs provide a good interlocking bond with surrounding materials & enhance the anchorage between the steel & concrete.

2. Why are ribs & lugs present on steel bars?

In the earlier days, plain smooth bars were used as reinforcement steel in structural members. After several years, slight deflection & cracks were observed in such structures.

After doing research on this subject, bars are introduced having ribs & lugs over their surface to overcome such defects.

Ribs & lugs provide a good bond strength with concrete & prevent the slippage of the bar from concrete.

This enhanced anchorage in turn provides a longer lifespan for the structures. They prevent cracks formed due to structural deflection & help to construct stable structures.

3. How are ribs provided to TMT bars?

When the steel rods are red hot at around 550° celsius, they are passed through a series of rollers having slots or rib-shaped depressions machined over them. The steel rods get pressed through these slots creating embossed patterns known as ribs.

4. Why do steel bars have different types of ribs?

The geometry of the rib pattern governs the two main properties of steel bars. They are, bending capability & bond formation with concrete. 

Spiral ribs crossing over the lugs provide a good bond formation but reduce the bending capacity of the rebar.

Again, the increase in the depth of the ribs leads to a decrease in the bending ability of the bars.

So, the bars are manufactured having different rib patterns to achieve the required yield strength & design norms.

5. What is the significance of lugs & ribs on TMT bars?

◆. Anchorage:

Lugs & ribs provide a good anchorage with concrete that creates a strong bond within the structural elements.

◆. Deflection cracks:

The strong interlocking bond between the steel & concrete avoids slippage between these two materials at the time of structural deflection. This helps to reduce the deflection cracks in the structural members.

◆. Stability:

Higher bonding strength minimizes construction failures, thereby providing a stable & safe structure.

◆. Tensile strength:

Ribs & lugs enhance the load-carrying ability of the structural members. The superior bonding between the steel & concrete help to achieve good tensile strength within the structure.

◆. Life span:

 The buildings & other constructed structures will have a longer lifespan due to the enhanced reliability & stability in construction. 

 ◆. Resistance to calamity:

The danger to life & properties due to natural calamities like earthquakes, floods, earth settlements, hurricanes, etc. will be minimized. The higher withstanding ability of the structures provides good resistance to such natural disasters.

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How to measure the painting area of steel rolling shutters?

 Steel rolling shutters consume more paint due to their undulated surface areas. Now, let us calculate the total painting area of steel rolling shutters.

As per IS:1200 -1987, we can find the painting area of the rolling shutters by multiplying the total size of the opening with the coefficient factor of 1.10 (observe below).

Now, let us go through the area calculation procedure for the steel rolling shutter, as shown below.

Given data:

Height of the rolling shutter = 2.4m.

Width of the rolling shutter = 2.1m.

Multiplying factor = 1.10 ( as per IS:1200- 1987)

Calculation:

Area of the rolling shutter opening

= [height ✖  width]

= [2.4m. ✖ 2.1m]

= 5.04 m².

The total painting area for each side

= [area of the rolling shutter ✖  multiplying factor]

= [5.04 m² ✖ 1.1]

= 5.55 m².

Total painting area for both sides

 = [5.55 ✖ 2 sides]

 = 11.10m².

Note:

As per IS:1200-1987, the painting area of the top cover should be measured separately. We should calculate the surface area of the top cover directly as it has a plain surface as shown below.

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Safe railing height & its design as per building bye laws.

 1. Why we should provide a safe railing height for our balcony, parapet, & staircase?

I am showing you the clipping of images, which is enough to answer this question.

 You might have observed such incidents occur all over the world, which is due to faulty design & unsafe railing heights.

If a family contains toddlers, aged elder members, & pets, a safe railing design becomes a must for the safety of their life.

2. What is safe railing height as per building bye-laws in India?

Below given are the safe railing height for the staircase, balcony, & parapet, as per building bye-laws.

3. What are the points to be considered while designing safe railings for a building?

Some points which should be known before installing the railings are,

◆. Railing height:

 

The safe height of the staircase railing is measured from the top level of the tread to the top surface of the railing pipe.

In balcony railings, the safe height is measured from the floor surface to the top railing patti.

◆. Gaps or openings within the railing:

The gaps between the partition grills should not be more than 125mm. (5"), either vertically or horizontally.

 The openings of more than 5" provide a way for toddlers or pets to pass through them.

◆. Railing design:

Horizontal grill design provides climbing access to toddlers, whereas vertical grills hold them back from doing such expeditions.

◆. Fasteners for installation:

Proper-sized fastener bolts & holdfast should be used while installing the railings. The thickness of the railing support brackets should be as per the specifications.

The railing should be firmly anchored in such a way that when you lean over them by putting your body's weight, it should not shake or wobble.

4. What if you already have an unsafe railing installed for your balcony?

There is nothing to worry about, regarding the existing unsafe railings in your house. You can use safety nets to cover the balcony area as per your requirements.

Different types of safety nets are available in the markets, made of various materials and patterns.

Some of them which you can utilize to cover the balcony openings are, 

◆. Bird nets:

These nets not only assure child safety but also ban the entry of birds into your balcony.

To know more about bird nets,

Go through the article 👇

👀. What is an anti-bird net? / What is a balcony safety net?

◆. Invisible balcony safety net: 

These nets are made of stainless steel material having a wire diameter of 2mm. to 3mm. They provide an aesthetic appearance to the balcony & they do not block the scenic view.

◆. Fabric net:

Fabric nets are available in a wide range of colors to match well with your balcony interiors. According to the mesh weaving pattern, they come in opaque to semi-transparent designs.

◆. PVC nylon fencing net:

They are UV-stabilized nets having hexagonal openings. They are multipurpose materials that can be used for fencing, balcony, staircase, gardening, etc.

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What is sq. mm. in copper wire cable & how they are calculated?

 1. What is meant by sq mm. in a copper wiring system?

 The size & current carrying capacity of the copper, aluminum, or any cables are referred to or recognized in sq. mm. 

But, what does that mean?

sq. mm. refers to the sectional area of an individual strand, multiplied by the no. of strands present in a single wire.

In the case of solid wires, the sectional area of a single wire present in the cable is denoted in sq. mm.

We will understand it clearly when we go through the calculation procedure as given below.

2. How to calculate the copper wire size?

As you can observe in the above drawing, a copper wire is cut by section -AA  & the sectional diameter of the wire (strand) is d.

The sectional area of the wire is calculated by the formula = [πd² ➗ 4]

In solid cables, the sq. mm. of the cable is calculated by the formula

= Sectional area of the wire

= [πd² ➗ 4]

In the case of stranded wires, the sq. mm. of the cable is calculated by the formula

= [ no. of strands 🇽 sectional area of the individual strand.]

= [ n  🇽 (πd² ➗ 4)]

Example:

Let us consider the diameter of a single strand of the above cable as 0.674mm. The no. of strands present in the cable is 7. 

Now, 

The size of the cable

 =  [n 🇽 (πd² ➗ 4)]

=  [7 🇽 (π 🇽 0.674² ➗ 4)]

= [ 7🇽 (1.427  ➗ 4)]

= [ 7 🇽 0.357]

= 2.499 sq. mm. 

By rounding off, the size of the cable = 2.50 sq. mm. 

Note:

If you want to calculate the sq mm. of a particular cable by yourself, you have to use a vernier caliper to find the diameter (d) of a strand.

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How to calculate the surface area & volume of stone pitching quadrant?

Let us calculate the surface area of the stone pitching quadrant as shown below.

As you can observe in the above diagram, the stone pitching covers the quadrantal surface area of a cone.

 i.e. 1/4th the lateral surface area of a cone. 

 Now, the lateral surface area of the cone is calculated by the formula  = πrl

Where,

 l = taper length.

r = radius of the cone.

h = height of the cone.

Let us observe the detailed drawing of the stone pitching as shown below.

Given data:

Height of the stone pitching = h = 1.7m.

The radius of the pitching quadrant = r = 2.2m.

The thickness of stone pitching = 300mm. = 0.3m.

Calculation:

The surface area of stone pitching 

= [1/4th the lateral surface of a cone]

 = [1/4 х πrl]

Here,

l² = [r² + h²]

(By Pythagoras' theorem.)

l = [√ (r² + h²)]

  =  [√ (2.2² + 1.7²)]

  = [√ (4.84+ 2.89)]

 l  = [ √ 7.73]

  l = 2.78m.

The surface area of stone pitching 

 = [1/4 х πrl]

 = [1/4 х 3.142 х 2.2 х 2.78]

= 4.804 m²

The volume of stone pitching

= [ surface area  х thickness of pitching]

= [ 4.804m²  х 0.3m.]

= 1.441 m³

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What is polymer modified mortar? - Their types & applications.

 1. What is polymer-modified mortar?

As the name suggests, polymeric admixtures are added with portland cement, sand, & water to enhance certain qualities of the mortar. 

The addition of polymer improves toughness, adhesion, bonding, tensile strength,  flexural strength, chemical resistance, etc. within the mortar.

2. What are the different types of polymers that are used in making polymer-modified mortars?

The different types of polymers are as follows.

▪  Latex polymers

▪ Emulsified polymers.

▪ Water-soluble polymers  👉  polyvinyl alcohol.

▪ Re-dispersible polymers 👉  ethylene vinyl acetate.

3. Where do we use polymer-modified mortar?

They are used in

▪ Waterproofing:

Polymer-modified mortars are good in providing resistance against chemicals & penetration of water. Therefore, they are used in structural works such as water tanks, septic tanks, basements, etc. 

▪ Grouting:

Polymer-modified mortars are the best suitable materials for grouting works in joints, tiles, structural members, walls, etc. 

▪ Repair works:

They have good adhesion & bonding properties. They are less susceptible to shrinkage & thermal variations.

Hence, they are good at patching, resurfacing, or overlaying works of damaged areas. It is also used in repairing cracks in concrete structures. 

▪ Flooring: 

Used in commercial & public buildings as a base layer of floorings. Mostly, they are utilized in the flooring work of warehouses, hospitals, factories, garages, etc.

4. What is the composition (ratio) of polymer-modified mortar?

Fine aggregate to cement ratio 👉 1:2 to 1:3 ( ratio by wt.)

 Water cement ratio 👉  0.3 to 0.5

The percentage of polymer added will be 5 to 20% of cement depending upon the type of polymer & specification.

5. Is polymer-modified mortar waterproof?

The addition of polymer improves the impermeability, viscosity, & durability of mortar. polymer modified mortar has higher crack resistance properties when compared to regular mortars. They also reduce the capillary water absorption & penetration depth of water to a certain extent.

However, they are not replacements for waterproofing compounds.  

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How to use tube level for transferring level?/How to transfer level using water level pipe?/Points to be known before using water level pipe.

Now, let us go through some of the basic queries regarding tube levels as given below.

 1. What is a tube level?

Tube level is a transparent plastic tube filled up with clean or colored water. Usually, the diameter of the water level pipe is 6mm. to 7mm. (1/4th inch).

 The length of the tube can be chosen according to our needs. Mostly, the ideal length will be in the range of 5m. to 15m.

They are used to transfer the vertical level from one point to another. 

2. What is the basic principle behind tube level or water level pipe?

The water has a tendency to stay at the same level in a horizontal plane. So, when we fill a tube with water, the surface of the water will rest at the same level. 

When we carry the two ends of the pipe at a larger distance, the level of water won't change regardless of changes in the ground level. We can transfer a particular level from one point to all over the construction site by taking advantage of this principle.

3. What are the points to be checked or followed before using the water level pipe?

1. The plastic tube should be transparent in its appearance. This provides us a clear view of the top surface level of the water without any difficulty.

2. If the water level pipe is dusty, or if the water visibility is low, we should add a tinted color to the water, to form a colored solution. The colored water provides good visibility to mark the required levels. 

3. When we fill the tube with water, we should take care that the filled water should not contain any air bubbles. If it contains any bubbles, they should be removed by gently tapping the tube with the fingers.

This is necessary as air bubbles do not allow the top level of water to be settled in the same horizontal plane.

4. The tube should not contain any twist or fold in its total length. Before filling the tube with water, stretch the tube by pulling its two ends to make them uniform & straight. 

5. The tube should not be completely filled with water. One to two feet of the tube should be left empty on both ends. This avoids overflow of water while we move by holding the tube in our hand.

 This procedure also provides a free space for water for its vertical movement, before settling at the same level.

 

4. What is the procedure to transfer the level by using a tube level?

Procedure:

1. Before starting the level transfer work, the two ends of the tube level should be held together to check the accuracy of the level of water. There should not be any mismatch in its top surface level.

2. This job needs two no. of persons for the transfer of the level. One end of the level tube is kept over the surface that already contains established level markings. The other end should be aligned with the surface where the level needs to be transferred.

3. The 1st person shall move the tube up or down so that the water level within the tube will fall in line with the established marking.

4. Once the water level settles in line with the given level marking, the second person at the other end will transfer the water level over the surface. The marking should be done only when the water stands still without any movements.

5. Now again, the 1st person comes at the 2nd person's position to align the water level with the transferred level. The 2nd person moves forward to that position where a further transferring of level is needed.

6. This process will be repeated until all the required level markings are established over the surface of the object. 

Note:

 The tube openings at both ends should be closed with the fingers (by both persons) while moving from one position to another. This prevents overflow of water as we cannot maintain the same level while we are walking.

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What are automatic water level controllers?/Significance of water level controller.

Let us go through, some of the FAQs related to automatic water level controllers as follows.

1. What are automatic water level controllers?

They are electronic devices having various sensors to monitor & control the water level in the tank. They automate the entire process of refilling water when the level drops below a certain level.

 It regulates the working of water pumps by switching them on & off to maintain the required water level.

2. What is the working principle of a water level controller?

The controller contains various sensors or probes fitted at pre-selected water levels. When the water goes below the pre-decided level, the probe triggers the led light on the control board. They send a signal to turn on the pump to refill the water to the pre-programmed level. Once the water reaches the required level, the probe fitted at that level transmits a signal to switch off the pump.

In this way, the multiple sensors or probes installed at the overhead as well as the sump tank monitor the water level & refilling is done automatically. 

3. Why we should use a water level controller?

Let us go through some of the points to understand the significance of water level controllers.

1. Completely automatic:

Pumping & filling the water tank is a daily routine of work that needs human supervision. Automatic water level controllers do this job without any human intervention.

2. Saves time:

They save our supervision time & we can utilize those hours for some other work.

3. Reduces wastage:

 When we manually fill the water tank, we keep the overflow pipe as an indicator to switch off the pump. By using water level controllers, the pump is switched off before the overflow & hence reduces the wastage of water.

 4. Motor life:

Water level controllers are enabled with dry run protection features. They sense the level of water in the sump tank, & switch off the pump when the level drops below 10%. This protects the pump from dry runs & enhances the life of the motor.

5. Shows present water level:

 The indicators provided over the controlling panels show us the present level of water. So, there is no necessity to open the tank lid to check the level. 

4. What are the points to be known before buying water level controllers?

⬥. Type of sensor:

 Two types of sensors are used to fit into the devices. They are,

Non-contact type sensors &

Contact type sensors.

The device having a universal sensor supporter is the right choice to be compatible with all types of sensors.

⬥.  Water quality:

The presence of salts & organic matter affects the efficiency of sensors. Beforehand, we have to check the quality of water to select the right type of controlling system.

⬥.  Device features:

The water level controllers come with different features such as dry run protection, glow light indicator, manual to auto changeable switch, etc. Study your requirements & install the proper device.

 ⬥.  Power consumption:

The power consumption of the motor should be compatible with the prescribed load of the water level controllers. Otherwise, it may disrupt the functioning of the device.

  ⬥.  Switches & connectors:

Check the certification & quality of the switches & connectors. If any one of them fails, it takes down the working ability of the entire system. The ampere ratings of all items should be checked, as they play a vital role in the efficiency & smooth running of the controller.

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