Dear all, I would like to know the any graph or relation ship between form work stripping time vs compressive strength of concrete. As per IS 456: 2000 Amendment 5 mentioned the form work stripping duration for different type of structures. But I ...
What does FLOOR AREA RATIO mean: FAR is a technical term used in Urban Planning that determines the total built-up space of the building on a plot of land. Generally, the FAR of the City or the Area is fixed by the government, based on various parameters like infrastructure, population or populationRead more
What does FLOOR AREA RATIO mean:
FAR is a technical term used in Urban Planning that determines the total built-up space of the building on a plot of land. Generally, the FAR of the City or the Area is fixed by the government, based on various parameters like infrastructure, population or population growth. These you will understand once you are going through this issue.
So by Definition FLOOR AREA RATIO (FAR) is the ratio of BUILDING’S TOTAL COVERED AREA to THE SIZE OF THE PLOT on which it is built.
BUILDING’S TOTAL COVERED AREA is the Gross Floor Area.
Formula for FAR
FAR = TOTAL COVERED AREA (ALL FLOORS)/ AREA OF PLOT.
For e.f. If there are 4 Floors and each Floor is of 5000 Sq feet, then the Total Covered Area of all the Floors is 20000 Sq Feet and the size of the plot is 10000 Sq Feet, then FAR = 20000/10000 = 2. In some areas it is mentioned as % i,e, 200% or somewhere it is mentioned simply 200. So if it is 200 then it means the FAR of the City or Area is 2, meaning one is authorized to build up the covered area 2 times to that of the plot area.
But Generally FAR is fixed by the government, for particular City or Area and the FAR can be used to calculate the Total Covered Area that is built on a plot of land.
NOTE: There is one more term FLOOR SPACE INDEX i.e. FSI. The meaning of FAR and FSI is the same. There is a difference of only denoting these two. FAR is always mentioned in percentage. For e.g. the FAR of any City / Area is 200% then the FSI of the same City / Area will be denoted as 2.0.
Let us understand with the help of an illustration as in the image below:
For e.g. the total Plot Area is 10000 Sq feet
CASE 1: If FAR of a place is 0.5, then the total area to be built up is allowed only 5000 sq feet.
OPTION A: One can construct in 50% of the plot area, only one floor of 5000 sq feet. So FAR = 5000/10000=0.5
OPTION B : One can construct in 25% 2 Stories of 2500 sq feet of each. So FAR = (2X2500)/10000=5000/10000 = 0.5
CASE 2: If FAR of a place is 1.0, then the total area to be built up is allowed only 10000 sq feet.
OPTION A: One can construct in 100% of the plot area, only one floor of 10000 sq feet. So FAR = 10000/10000=1.0
OPTION B : One can construct in 50% of the plot area ,2 Stories floor of 5000 sq feet. So FAR = (5000 X 2) /10000 = 10000/10000=1.0
OPTION C : One can construct in 25% 4 stories of 2500 sq feet of each. So FAR = (2500 X 4) /10000=10000/10000 = 1.0
CASE 3: If FAR of a place is 2.0, then the total area to be built up is allowed only 20000 sq feet.
OPTION A : One can construct in 100% of the plot area ,2 Stories of 10000 sq feet each. So FAR = (10000 X 2 )/10000 = 20000/10000=2.0
OPTION B : One can construct in 50% of the plot area ,4 Stories floor of 5000 sq feet. So FAR = (5000 X 4) /10000 = 20000/10000=2.0
OPTION C : One can construct in 25% 8 stories of 2500 sq feet of each. So FAR = (2500 X 8) /10000=20000/10000 = 1.0
So if you know the FAR, you can calculate the total covered area that can be built on the plot.
How much open area you have to leave or how much area can be built up depends on the zoning and planning regulations also. For e.g. how much area to be left for:
- Setback.
- Parking
- Ground Coverage or Maximum Ground Coverage.
- Height Restrictions
FACTORS URBAN DEVELOPMENT AUTHORITY CONSIDER WHILE DECIDING FAR:
- The current population of the City / Area: When the population of the City / Area is high, the FAR is also high, it means the government is intending for Vertical Development as compared to the spread-out development,
- Population Growth: If the population growth rate is high, then also the FAR of the City / Area is high
- Infrastructure: Infrastructure also plays a key role while deciding the FAR of the City / Area. If Infrastructure is low then FAR will be kept low otherwise there will be pressure on infrastructural facilities viz, water, power supply, transport etc. If Infrastructure of the City / Area is already high and developed by the government relative to population density, then FAR can be kept at a higher level by the Authorities.
Note: If in the City / Area, the infrastructure is low but the population is growing at a faster rate, then the government has to increase the infrastructure and FAR has to be kept higher to accommodate the high growing population.
So when FAR increases the Population Density of the City / Area increases.
IMPACT OF HIGH FAR:
- Higher Population Density
- Stress on Infrastructure
- Better Profitability for Developers
- High Land Value
- Better Walkability
IMPACT OF LOW FAR:
- Lower Population Density.
- Better Per Capita Infrastructure
- Reduced Profitability for the Developers.
- Low Land Prices.
- Long Travel Distances
Kuldeep Singh
Hello there Me. Chamarhy! I read the complete thread and I understand that you haven't exactly got the answer you are looking for. Well, that's partly because you are slightly misinterpreting cl. 11.3 of IS 456 (2000). It says that formwork must not be removed until concrete gains at least twice theRead more
Hello there Me. Chamarhy! I read the complete thread and I understand that you haven’t exactly got the answer you are looking for. Well, that’s partly because you are slightly misinterpreting cl. 11.3 of IS 456 (2000). It says that formwork must not be removed until concrete gains at least twice the strength it needs to stand the stresses it will experience during formwork removal. Now, if you look carefully, this doesn’t mean that the code has given this advice with concrete’s final compressive strength in view. It is solely there for the safety of the structural member during formwork removal.
The table within that clause, says that for ordinary conditions (OPC is used, ambient temperatures >= 15°C, adequate curing is done), these stripping times for the concrete to reach that above mentioned strength will be so and so for so and so types of formwork. It is not talking about the compressive strength of concrete.
Apparently there is indeed no specific mathematical relationship between the formwork stripping time and the final (28 days) compressive strength. This guideline is solely for the protection of concrete during formwork removal. Obviously concrete gains strength the better the better it’s cured. So, if someone wishes to strip early and begin curing early, the code is trying to advice against it. Furthermore, concrete indeed attains strength in direct proportionality with the quality control in production, the quality of the materials and the adequacy of curing. As far as I think, there could be only a little implication that concrete gains strength well if it retains heat in very early age and formwork does insulate the concrete. But that’s not much important because you can’t wail too long to strip formwork so that you can start curing when it’s the right time.
Now, the next point is the theoretical or experimental evidence that you are seeking. I’d like to humbly tell you that the table in 11.3 which claims that these are the times for achieving double the strength requirement for formwork stripping must indeed be based on experimental data. It is easy to model the stresses induced at the time of stripping. Now, the strength of concrete within formwork can also be estimated via pull out test and a few non destructive tests. You can Google ‘concrete strength tests during maturity period’ and it’ll pop up with a number of papers and articles. The pull out test for instance, corellates the compressive strength to the force required to pull out a core of specific shape and size, in a specific way from the maturing concrete.
To conclude, the code is not talking about a relationship between removal time and the compressive strength. It’s only talking about the corelation between removal time and the strength at that very time of formwork removal, for which, experimental evidence has long been found.
Sorry for a long explanation. But, I’ll be more than pleased if it clears your doubt. Thank you!
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