Month: July 2019
Following are the recommended value of safe stopping sight distance for different speeds of the vehicle as per I.R.C.
| Design Speed (Km/h) | Safe Stopping Sight Distance (m) |
| 20 | 20 m |
| 25 | 25 m |
| 30 | 30 m |
| 40 | 45 m |
| 50 | 60 m |
| 60 | 80 m |
| 65 | 90 m |
| 80 | 120 m |
| 100 | 180 m |
Read More:
Stopping Sight Distance Formula
How to Calculate Stopping Sight Distance – Mathematical Example
| Acoustics | Reverberation Time in Seconds |
| Very very bad | Above 5 seconds |
| Very bad | 3 – 5 Seconds |
| Fairly good | 2 – 3 seconds |
| Good | 0.5 – 2 seconds |
| Very good | 0.5 – 1.5 seconds |
There are two reasons to use dummy activity one is grammatical purpose another one is logical purpose.
We will try to understand it by seeing the picture. The activity ‘A’ starts from node 1, and B also starts from node 1, and both activities end at node 2.
We can represent it as follows:
Now you can see that both identities are the same, so they lose their identity. Here, the main logic is that they both start at the same time and also finish at the same time. To find out their identity with logic, we used a dummy activity as fig.2
Now we can represent like as
A ⇒(1, 3)
B ⇒(1, 2)
You can not provide the same activity twice in your network diagram.
In the above picture, it shows that the P activity is two times in a single network diagram. So to avoid these types of errors in the network diagram, we provide a dummy activity.
You can use as many dummy as you wish, but sometimes it asks to remove dummy which is not required. Five golden rules are used for removing redundant dummy.
If the dummy originated from one node.
Here, the P1 dummy is not required
If a dummy is the only arrow going into a node.
Here, A3 dummy is not required
If two activities have set of a predecessor.
If two activities have the same set of a successor.
Here, A2 and B2 dummy activities are not required
Do not repeat already implied logic.
We can determine the bearing capacity of the soil by using the following two methods.
In this article, we are discussing the dropping weight method.
The dropping weight method is used to determine the approximate value of the soil-bearing capacity.
⇨At first, assume a weight W that is dropped from a certain height on the bottom surface of the foundation trench.
⇨Due to falling a weight, an impression made on the soil of the bottom surface of the foundation trench, which is noted.
Now, the bearing capacity of the soil can be calculated by establishing the following equation: Let,
We know that the potential energy of the falling weight is equal to the energy lost in penetration.
So we can write, Wh = Rd Or, R =Wh/d
Now, safe bearing capacity of the soil per unit area equal to = R/Af = Wh/dAf
Where f is the factor of safety.
As it is an approximate method, it is used only for the construction of the minor structure.
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Advantages of precast concrete piles are as follows:
1. During concreting, the reinforcement which is used in the piles is not disturbed from its actual position.
2. Proper control in casting and curing can be exercised and if any defect after casting is noticed, it can be corrected before piles are used.
3. They can also be driven underwater.
4. Precast concrete piles are not affected by the chemical action of the subsoil.
5. They can be taking load immediately after their placing to their required place and no time is wasted.
6. Several piles can be manufactured side by side at a time, so its manufacturing cost is less than other types of piles.
Following are the disadvantages of precast piles
1. Being very heavy, transporting, handling and driving theme is very hard.
2. extra steel must be provided near the top and bottom of the piles, in order to avoid the stresses developed during handling and driving.
3. The precast concrete piles can not be cast in a correct length unless trial bores are made. Therefore, it becomes very difficult to cut extra length, if the pile is casted longer than the required length.
4. It may break without proper handling and driving.
5. The pile length is also restricted depending on the mode of transportation available.
Read Also:
Difference Between Prestressed and Reinforced Cement Concrete
20 Advantages And Disadvantages of Concrete – As a Construction Material
Flat roofs can be made waterproof by utilising the following methods:
In the case of ordinary and cheap construction, the surface of the roof should be finished with cement mortar preferably in the ratio of 1:4.
Lime cream can be added to the finishing layer of mortar to resist the shrinkage and expansive impacts of cement concrete or mortar.
In his method, Before laying a layer of mud or limo concrete, a layer of mastic asphalt is placed on the roof surface.
The asphalt layer is also sometimes placed on the top finished surface of the roof which is later sanded and finished.
The top surface of the R.C.C. slab is kept rough while casting. A layer of brick-bat lime concrete 1:2:4 about 100 mm thick or brick-bat cement concrete preferably in the ratio of 1:6:12 laid over the R.C.C slab.
This concrete layer is known as bedding concrete. The bedding concrete surface is then finished with tiles or other finishing materials.
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We can use the “slowly applying load” method to verify the given bearing capacity of the soil.
⇒ Let’s assume the given safe bearing capacity of the soil is 16 t/m².
⇒ To verify the bearing capacity of this soil, add an initial test load on the platform. The initial test load should be twice the safe bearing capacity, i.e. 32 t/m², and write down the settlement.
⇒ When settlement stops, the load on the platform is increased by 50 per cent of the initial load, i.e. 16 t/m² and settlement is again noted.
⇒ Now, for both cases of loading, if the settlement does not exceed 17 mm and 25 mm respectively, So, we can say that the given safe bearing capacity of the soil is correct.
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Following are the 10 purposes of ventilation in buildings:
1. To create air circulation.
2. To prevent the inappropriate accumulation of carbon dioxide and moisture.
3. Ventilation is provided to prevent oxygen depletion in the air.
4. To avoid flammable gas vapour or dust concentration.
5. Ventilation is provided to prevent an excessive concentration of particles which carrying bacteria.
6. To stop undue body odours, fumes, dust, and other industrial products from being concentrated.
7. To avoid room condensation.
8. To remove heat which releases from the body and from the other equipment.
9. Ventilation is provided to receiving fresh air and pushing out contaminated air.
10. To avoid suffocating situations in board halls, cinema halls and other such buildings where the periodic characteristic is mass assembly.
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Air conditioning is known as the process of creating, controlling and maintaining indoor atmospheric conditions best suited to human or industrial needs. Following are the 8 objectives of air-conditioning.
1. One of the main objectives of providing air conditioning is to control indoor temperature. Air conditioning systems help regulate and maintain a comfortable level of temperature for the occupants., especially during hot weather.
2. Air conditioning not only helps control temperature but also reduces excessive humidity levels and creates a more pleasant and healthy indoor environment.
3. To give pleasant conditions in restaurants, cinema halls, auditoriums, etc.
4. Keeping a comfortable environment through air conditioning can improve productivity, particularly in workplaces. It helps to enhance the efficiency of commercial establishments like offices, shops, stores and banks.
5. To provide comfortable conditions while travelling by car, aeroplane, train, etc.
6. To enhance product quality in manufacturing processes such as cotton cloth, artificial silk, etc.
7. Air conditioning can also enhance the ventilation process by ensuring proper air circulation. It also helps to remove dust, allergens, pollutants, and odours and improves the overall indoor air quality.
8. The air conditioning system helps in improving the comfort level of the residents. And this is the ultimate purpose of providing air conditioning.
Soil exploration is a very important phase in the development of any structure. Although it costs a little more. But it’s favourable because it clears all doubts about the behaviour of the foundation.
Following are the 6 purposes of soil exploration or site investigation:
1. To determine the proper safe bearing capacity of the underlying soil.
2. To determine how deep the foundation should be taken.
3. To find out the depth of the underground water table and determine the ways to solve the problem due to groundwater if needed.
4. To select the safe and most profitable type of foundation.
5. Sit investigation or say soil exploration helps to overcome further any difficulties arise during construction work.
6. Make allowance for a possible settlement of the foundation.
Read Also:
Types of Foundation Settlement