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Initially people lived in the open or under the canopies of trees or in caves or in any sheltering hole they could find comfort suiting to the prevailing weather conditions.

As the population multiplied they felt the need for creating shelters using broad leaves, tree branches, stones, soil, etc.

Gradually they developed building many varieties of structures as their needs increased.

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1 bar is 14.50377 PSI, so 2.8 bars is 40.610 PSI.

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It's an arch.

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I am using a product called Stop Salt. I have been using this product for the last six months, I am amazed! It produces outstanding mortar, the pointing up is brilliant and it cuts out the efflorescence that we all hate as Bricklayers. I hope this can be of some help to you, try it.

If the intent is to "Prevent" efflorescence a penetrating sealer that migrates into a concrete based material, either concrete or cement based mortars should be considered. You should use a sealer that enters the Gel-Pore or Capillary System where it reacts with the alkali to form a solid Inside the matrix. Once this solid is formed, internal chemistry does migrate out to a surface to react with an atmosphere. I use one that does not leave a membrane or film on the surface and has exceptional adhesion bonds with any coatings that may be applied later.

The one I use also has a 15 year waterproofing warranty which prevents contaminates from entering to bring chlorides and low pH conditions to an interior. This creates a No-Low moisture and high pH interior to prevent corrosion cell formation on embedded steel. Choose a sealer carefully and avoid any product that allows for a reapplication at a later date! [What happened to the First coat?] and one that has a 15 year warranty for Waterproofing. This will "Prevent" Efflorescence and a host of other problems you may encounter!

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most are prevailing wage jobs and greatly varies from state to state,im in the union so its a big difference . anywhere from 30 to 50 dollars an hour,again depending on what part of the country you are working

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Vibration is the harmonic reaction of a structure to a force load.

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They have different modulus of elasticity. This would cause ces in thermal expansion and therefore fracturing of both materials.

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Their both the same, really, just two different names for sand with clay in it, however one might have more clay in one (sandy clay) than the other (clayey sand), but only by miniscule amounts.

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Nothing! Sociologists forcefully enforces it on engineers

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Sieve analysis allows the determination of the distribution of particles sizes in granular materials. Since many separation processes and reactions depend on the amount of surface area relative to mass and that ratio increases as particle size decreases, knowing the distribution of sizes can be very important. Particle size distribution can also be important when using slurries to move particulates from one place to another.

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204.08

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Mass is the measurement of inertia, or resistance to change in motion. It is not to be confused with weight, a measurement of the force due to gravity exerted on an object.

For many practical purposes, mass and weight vary numerically by a constant, namely gravitational acceleration. Due to the common misconception of mass and weight being the same thing, units can often get confusing. For example, the English unit for mass is the slug, rather than the pound (a unit of weight). Some unit systems, such as the American Engineering System, take up the convention of making mass and weight numerically equal. In such a case, the units specify whether mass or weight is intended, so you would have pound mass (lbm) and pound weight (lbw). The SI unit for mass is the kilogram (kg), which, like the pound, is commonly and erroneously used as a unit of both mass and weight.

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You can add citric acid and sugar to stop hydration. But then the concrete is unusable and you need to throw it away.

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A looped domain is a series of chromatin fibres that are arranged into a loop. These are arranged into chromosomes. For more help view the related link.

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lap length in tension including anchorage value of hooks in flexural tension shall be greater of development length or 30 times dia of bar.

In compression, its equal to development length.

In general, 50 times dia is provided.

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• The Great Kersten Blunder. (Kersten was the programer that made the error). The Vigor space probe was sent towards Venus, but because of a computer programing error installed on it, a convertion from millimeters to inches was incorrect. It divided by 24.5 instead of 25.4. This error caused it to miss Venus completely and was sent hurling into space. Over 2 billion dollars of technology was lost because of one simple error.
• The Mars Climate Orbiter had a problem when trajectory programming teams from Europe and USA were working in two different measurement systems, imperial and metric. It missed the planet completely and was lost.
• Not exactly engineering but it was an aviation blunder. An Air Canada flight was fuelled in Toronto using pounds instead of liters of fuel. The pilot calculated how much he needed thinking he was getting his fuel in liters and eventually ran out of fuel near Winnipeg. He successfully landed the plane safely at a semi-abandoned WW2 airstrip at Gimli Manitoba.
• The Hubble Space Telescope or HST originally had an incorredtly ground mirror (Link below.)

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Live load

Both are the same

Live load is all the live loads which can be consider as variable load.

Roof live load

This is limited to few categories. man who climbed on to the roof can be consider as roof live load.

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Truss bridges are lighter than beam girder bridges. They take up more height but are strong and carry loadd in tension and compression rather than bending.

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The mixes of grades M5 M10, M15, M20 and M25 correspond approximately to the mix proportions (1:4:8), (1:3:6), (1:2:4), (1:1.5:3) and (1:1:2) respectively.

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the bridge having a deck from where truck n all vehicles pass by having a pratt which bridge is having...

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In this M refer to Maximum compressive strength and 20 refer that concrete that with stand upto 20KN compressive strength.