Viscosity With Exams Based MCQ IMP for GATE , SSC JE , PSU

Viscosity : It is the property of the fluid  which opposes the relative motion between the two surfaces of the fluid in a fluid that are moving a different velocity.

Viscosity can be two types:

1: Dynamic Viscosity Or Absolute Viscosity Or Coefficient of Viscosity or Viscosity

2: Kinematic Viscosity ( This is imaginary not really present in real life)

The main difference between Dynamic viscosity and Kinematic Viscosity is:

Dynamic Viscosity: One way is to measure a fluid's resistance to flow when an external force is applied , This is Dynamic viscosity , always it is used for practical purpose.


Units: SI : N.S/ m2

C.G.S Unit: Dyne-Sec/ Cm2 ( It is also called Poise)

M.K.S. Unit: Kgf-Sec/ m2


Kinematic Viscosity: The other way is to measure the resistive flow of a fluid under the weight of gravity , the result is kinematic vicosity . Do not use it by your own, until  there is no mention of particulate word (Kinematic Viscosity) in numerical .

Units:  SI : m2/s

CGS unit: cm2/sec ( It is called stoke )

M.K.S =m2/Sec

IMP Point:-

Two fluid that have the same Dynamic viscosity can have different kinematic viscosity  This is due to kinematic viscosity dependent on the density of the fluid , density is not a factor with Dynamic viscosity .

Some Other Key Points regarding Viscosity:


1: The dynamic viscosity of pure water at 20 degree Celsius is 0.01 poise or 1 centi poise

2: The viscosity of fluid decreases with increasing the temperature ( Because fluid has a tendency to flow in stream line in most of the cases , when velocity of flow is low)

3: The viscosity of gases increases with increasing the temperature ( REASON:  when we heat the gases then gas molecules travel in zig zag motion, so the momentum of gases particles increases and they generate high shear stress due to high momentum)

4: Water has higher viscosity than Mercury.

 Now test youself  : MCQ :  based on Viscosity:

Q1: Poise is the C.G.S unit of:
A: Viscosity
B: Kinematic Viscosity
C: Surface Tension
D: Capillary


 Q2: C.G.S unit of Kinematic Viscosity is:
A: Newton-Sec
B: Stoke 
C: Dyne
D: Poise

Q3: The increase of the temperature :
A: Increase the viscosity of liquid
B Increase the viscosity of gases 
C: Decrease the viscosity of gases
D: No effect


 Q4: Newton law of viscosity states that :

A: shear stress is directly proportional to the velocity
B: Shear stress is directly proportional to velocity
C: shear stress is directly proportional to rate of shear strain
D: Shear stress is directly proportional to the viscosity

Q5: Which has higher viscosity : A : Mercury, B: Water  

Q6:  What measures a material's resistance to flow?
  


A: Matter , B: Volume C: Viscosity, D: Surface Tension
Q7: When friction increases what else increases?                                                                                        A: Elasticity , B: Density , C: Viscosity, D: Matter


 







                                                                                

 BEST BOOK FOR FLUID MECHANICS BY R.K. Bansal : Basic and conceptual : https://amzn.to/2HXQj3O

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10 Tallest Bridges In The World== >

1. Millau Viaduct, France – 343 metres (1,125 ft) tall. Opened in 2004, this 4 lanesbridge is a cable-stayed bridge that spans the valley of the River Tarn near Millau in southern France. The bridge has 7 piers of different heights. The second one is the tallest with a height of 244.96 m (803 ft 8 in) – making it the tallest structure in France, taller than the Eiffel Tower!

2. Russky Bridge, Russia – 320.9 metres (1,053 ft) tall. Located in Vladivostok, the bridge was completed in 2012. It connects the mainland part of the city with Russky Island

3. Sutong Bridge, China – 306 metres (1,004 ft) tall. Opened in 2008, this bridge spans the Yangtze River between Nantong and Changshu

4. Akashi-Kaikyo Bridge, Japan – 298.3 metres (979 ft) tall. This beautiful suspension bridge was opened in 1998. It links the city of Kobe on the mainland of Honshu to Iwaya on Awaji Island. It is the tallest suspension bridge in the world

5. Stonecutters Bridge, Hong Kong – 298 metres (978 ft) tall. A high level cable-stayed bridge which spans the Rambler Channel in Hong Kong, connecting Nam Wan Kok, Tsing Yi island and Stonecutters Island. The bridge deck was completed and opened to the public in 2009

6. Yi Sun-sin Bridge, South Korea – 270 metres (890 ft) tall. Except of being the 6th tallest bridge in the world, it’s also the second tallest suspension bridge in the world and the fourth longest suspension bridge in the world

7. Jingyue Bridge, China – 265 metres (869 ft) tall. This cable-stayed bridge in Jianli County was opened in 2010 and crosses the Yangtze River

8. Great Belt East Bridge, Denmark – 254 metres (833 ft) tall. Opened in 1998, this bridgeruns between the Danish islands of Zealand and Funen. It is the third tallest bridge in Europe

9. Zhongxian Huyu Expressway Bridge, China – 247.5 metres (812 ft) tall. Completed in 2010, this bridge crosses the Yangtze River in Zhong County

10. Jiujiang Fuyin Expressway Bridge, China – 244.3 metres (802 ft) tall. A Cable-stayed bridge under construction and should be completed by the end of 2013. With a main span of 818 m (2,684 ft) it will become one of the longest cable-stayed bridges in the world upon its completion

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10 Highest Bridges In The World = =>>

1. Sidu River Bridge, China – Height of 496 m (1,627 ft). This 1,222 m (4,009 ft) long suspension bridge is the world’s highest bridge since 2009. Located in the Hubei Province, it  crosses the valley of the Sidu River

2. Baluarte Bridge, Mexico – Height of 403 m (1,322 ft). A cable-stayed bridge, located along the Durango–Mazatlán highway. The bridge has a total length of 1,124 m (3,688 ft), the second-highest bridge overall

3. Baling River Bridge, China – Height of 370 m (1,210 ft). A suspension bridge in Guizhou Province. The bridge spans over the Baling River Valley. The bridge has a total length of 2,237 m (7,339 ft)

4. Beipanjiang River 2003 Bridge, China – Height of 366 m (1,201 ft). A suspension bridge in Guizhou Province. The bridge has a span width of 388 metres. Between 2003 and 2005, it was the world’s highest bridge

5. Aizhai Bridge, China – Height of 350 m (1,150 ft). A suspension bridge in Hunan, China. It is the world’s highest and longest tunnel-to-tunnel bridge

6. Beipanjiang River 2009 Bridge, China – Height of 318 m (1,043 ft). A suspension bridge in Guizhou Province. It crosses the Beipan River. It was opened to the public in 2009, just 6 years after another (and higher) bridge crossing the same river was opened (see number 4 in this list)

7. Liuguanghe Bridge, China – Height of 297 m (974 ft). A beam bridge in Guizhou, China. It held the record for world’s highest bridge between 2001 and 2003. It is still the highest beam bridge in the world

8. Zhijinghe River Bridge, China – Height of 294 m (965 ft). The highest arch bridge in the world. The bridge crosses the valley of the Zhijinghe River and is opened to the public since 2009

9. Royal Gorge Bridge, Colorado, United States – Height of 291 m (955 ft). The Royal Gorge Bridge is a tourist attraction within a theme park. The bridge deck crosses the Royal Gorge 955 feet (291 m) above the Arkansas River, and held the record of highest bridge in the world from 1929 until 2001. The bridge is 1,260 feet (384 m) long It is the highest in the United States

10. Beipanjiang River Railway Bridge, China – Height of 275 m (902 ft). The world’s highest railway bridge. The bridge spans a deep canyon on the Beipan River in Guizhou province. This is the third bridge within this list spanning over the Beipan river

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FACTS ABOUT DAM

• A dam is a barrier designed and constructed to contain the flow of water. It is often built in conjunction with a hydroelectric power station to provide electricity.
  
  
• Dams are built for purposes such as generating hydroelectricity, creating recreational areas, minimizing flood risks, diverting water for irrigation, and providing water for towns and cities.
  
  
• The type of dam built in any given situation depends on factors such as the intended purpose, environmental considerations, available finances and the location.
  
  
• Different types of dams include masonry dams, embankment dams and arch-gravity dams.
  
• Beavers create their own dams from sticks and mud as protection from predators and also to help provide easy access to food.
  
  
• Dams are huge engineering projects that require vast financial resources. For example, the construction of the Itaipu Dam on the border of Brazil and Paraguay (completed in 1984) cost around US$20 billion.
  
  
• Built along the Colorado River between 1931 and 1936, The Hoover Dam reaches 726 feet in height (221 metres).
  
  
• When the Hoover Dam was completed it was both the world’s largest concrete structure and largest hydroelectric power station.
  
  
• The Hoover Dam is made of enough concrete to make a two lane highway from New York to San Francisco, that’s around 4000 miles (2500 kilometres).
  
  
• As of 2010, the tallest dam in the world is Nurek Dam in Tajikistan. Completed in 1980, it reaches 300 metres (984 feet) in height.
  
  
• Many dam failures have occurred in the past, these disasters can cause significant damage and threaten lives.
  
  
• In 1889 a failure of the South Fork Dam near Johnstown, Pennsylvania, USA, killed over 2200 people.
  
  
• In 1975, the Banqiao Dam in China was among many dams that were destroyed after the extreme rains of Typhoon Nina. It is estimated that between 90000 and 230000 lives were lost as a result of the Banqiao Dam breaking.
  

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Building Facts

• The word skyscraper originally referred to a type of sail on a sailing ship.
  
  
• A skyscraper is held together by a steel skeleton of vertical columns, horizontal girder beams and often diagonal beams for extra support. This structure distributes the immense weight in a way that ensures the integrity and safety of the building.
  
  
• Restoration work in 1990 and 2001 shifted the Leaning Tower of Pisa back to an angle of 4 degrees after it was previously leaning at an angle of 5.5 degrees.
  
  
• The roofs of the Sydney Opera House are covered in a total of 1056006 tiles.
  
  
• The Colosseum in Rome, Italy, is an elliptical amphitheatre that was completed in 80 AD. It held around 50000 spectators and was used for a variety of events including gladiator contests, animal hunts and mythology based dramas.
  
  
• Around 20000 workers helped build the Taj Mahal, a famous mausoleum and landmark in Agra, India, that attracts millions of visitors every year.
  
  
• The world’s largest office building by floor size is the Pentagon in Virginia, USA, with over half of its 6500000 square foot (604000 square metre) floor area used as offices.
  
  
• The Empire State Building in New York was the first building to have over 100 floors and was the tallest building in the world from 1931 until 1972.
  
  
• The Chrysler Building in New York was built at a time when there was a strong desire to build the world’s tallest skyscraper, before being overtaken by the Empire State Building, the Chrysler Building was the world’s tallest for around 11 months. During the construction, floors were being completed at a staggering four per week. Despite the rush, no workers died during its construction.
  
  
• The Petronas Towers in Kuala Lumpur, Malaysia, are the world’s tallest twin buildings, standing at a height of 452 metres (1483 feet).
  
  
• The Burj Khalifa in Dubai, UAE, is the tallest building in the world. It reaches an amazing 828 metres (2717 feet) in height. Check out our top ten list of the tallest buildings in the world.
  
  
• Tall buildings need fast elevators, recent developments have led to elevators that can travel up to, and sometimes over, 1000 metres a minute (3280 feet a minute).

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Effective/total stress in soil

Vertical normal stress σ_z is defined as:

where:	σz	-	vertical normal total stress
	γef	-	submerged unit weight of soil
	z	-	depth bellow the ground surface
	γw	-	unit weight of water

This expression in its generalized form describes so called concept of effective stress:

where:	σ	-	total stress (overall)
	σef	-	effective stress (active)
	u	-	neutral stress (pore water pressure)

Total, effective and neutral stress in the soil

Effective stress concept is valid only for the normal stress  σ, since the shear stress τ is not transferred by the water so that it is effective. The total stress is determined using the basic tools of theoretical mechanics, the effective stress is then determined as a difference between the total stress and neutral (pore) pressure (i.e. always by calculation, it can never be measured). Pore pressures are determined using laboratory or in-situ testing or by calculation. To decide whether to use the total or effective stresses is no simple. The following table may provide some general recommendations valid for majority of cases. We should realize that the total stress depends on the way the soil is loaded by its self weight and external effects. As for the pore pressure we assume that for flowing pore water the pore equals to hydrodynamic pressure and to hydrostatic pressure otherwise. For partial saturated soils with higher degree of it is necessary to account for the fact that the pore pressure evolves both in water and air bubbles.

Assume conditions	Drained layer	Undrained layer
short – term	effective stress	total stress
long – term	effective stress	effective stress

In layered subsoil with different unit weight of soils in individual horizontal layers the vertical total stress is determined as a sum of weight of all layers above the investigated point and the pore pressure:

where:	σz	-	vertical normal total stress
	γ	-	unit weight of soil
			- unit weight of soil in natural state for soils above the GWT and dry layers
			- unit weight of soil below water in other cases
	d	-	depth of the ground water table below the ground surface
	z	-	depth bellow the ground surface
	γw	-	unit weight of water

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Reinforced Concrete Beam Design : Failure Mode

In reinforced concrete beam design, failure is designed for safety. If the structure fails by sudden crushing, huge damage and loss of life may take place. So, it is designed so that structure would give a warning before collapse. Reinforced concrete beam failure may take place in 3 ways.

1. Concrete failure: Crushing of concrete
2. Steel failure: Yielding by steel
3. Concrete & steel combined failure

Concrete Failure

In concrete failure, concrete reaches to its ultimate strength before steel reaching to its yield point. As a result concrete crushes down before steel yields. This type of beam failure is unwanted as the concrete crushes without giving any warning. Concrete failure occurs due to the following reasons.
1.       If large amount of reinforcement is used.
2.       Compressive strength of concrete is less than tensile strength of steel.
3.       Sudden destruction occurs without giving any warning.

Steel Failure

In steel failure, steel reaches to its yield point before concrete reaches to its ultimate strength. So, steel yields before crushing of concrete which gives ample warning to the inhabitants. So, steel failure is preferable during structure design. Some common notes on steel failure of rcc beams are given below.
1.       Relatively moderate amount of reinforcement are employed.
2.       Tensile strength of steel is less than compressive strength of steel.
3.       Steel yields and stretches and tension crack propagates concrete cracks.
4.       Secondary compression failure.
5.       Steel failure of rcc beams gives ample warning to the inhabitants. So, damage can be avoided.
6.       For engineering, steel failure is preferable.

Combined Concrete Beam Failure

In this type of failure, concrete and steel fails at the same time. That means concrete should reach to its ultimate strength just at the same time when steel fails so that both fails together. Combined failure is practically almost impossible because it is not possible to tell the exact behavior of concrete & steel so that they fail at the same time.

Basic Reinforced Concrete Beam Design Question

Question: Which type of failure is preferable in design of reinforced concrete beam?

Answer:  Steel failure. It gives ample warning to the inhabitants reducing the damage.

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Reinforced Cement Concrete : Advantages of RCC

RCC (Reinforced Cement Concrete)

RCC (Reinforced Cement Concrete) is the combination of using steel and concrete instead of using only concrete to offset some limitations. Concrete is weak in tensile stress with compared to its compressive stress. To offset this limitation, steel reinforcement is used in the concrete at the place where the section is subjected to tensile stress. Steel is very strong in tensile stress. The reinforcement is usually round in shape with approximate surface deformation is placed in the form in advance of the concrete. When the reinforcement is surrounded by the hardened concrete mass, it form an integral part of the member. The resultant combination of two materials are known as reinforced concrete. In this case the cross-sectional area of the beam or other flexural member is greatly reduced.

Advantages of RCC

Nowadays, RCC is used in most of the structures. The advantages of RCC (Reinforced Cement Concrete) are as following.

1. Reinforced Cement Concrete has good compressive stress (because of concrete).
2. RCC also has high tensile stress (because of steel).
3. It has good resistance to damage by fire and weathering (because of concrete).
4. RCC protects steel bars from buckling and twisting at the high temperature.
5. RCC prevents steel from rusting.
6. Reinforced Concrete is durable.
7. The monolithic character of reinforced concrete gives it more rigidity.
8. Maintenance cost of RCC is practically nil.

It is possible to produce steel whose yield strength is 3 to 4 time more that of ordinary reinforced steel and to produce concrete 4 to 5 time more stronger in compression than the ordinary concrete. This may high strength material offer many advantages including smaller member cross-sections, reduce dead load and longer spans. But the high stress result in high strain and consequently large deflection of such member will occur under ordinary loading conditions. Also high strength reinforcing steel would include large crack in the concrete which reduce the durability of the structure. The commonly used yield strength of high strength reinforcing steel is 60 ksi.

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==>>Miracle in civil engineering

If you're among those eagerly awaiting a working invisibility cloak, get ready to be jealous. A South Korean skyscraper may get one before we humble (and highly visible) humans do.

International architectural firm GDS Architectsreports that it's received a construction permit to begin building "the world's first invisible tower." The Tower Infinity will stand 450 meters (1,476 feet) and be situated in Cheongna, near the Incheon Airport just outside of Seoul.

Like other concepts for invisibility cloaks that have tantalized the geeky imagination, this one relies on optical illusion.

The glass-encased Tower Infinity, also called City Tower, will be fitted with a high-tech LED facade that integrates projectors and 18 strategically placed weatherproof optical cameras.

The cams will snap real-time pictures of the area directly behind the building, digitally stitch the images into a panorama, and project them back onto the building's reflective surface. That will create the illusion that viewers are looking straight through the structure to the other side, making it appear to blend into the skyline at certain times of day.

"The tower subtly demonstrates Korea's rising position in the world by establishing its powerful presence through diminishing its presence," reads a description on the GDS site. "Korea will have the unique position of having the 'best' tower by having an 'anti-tower."

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Do note, though, that the concept's not just about symbolism.

"This same technology also allows the tower to become a 450-meter-tall billboard screen and urban focal point for all arriving at Incheon," GDS says in a statement. No word year on the relationship between the structure's invisibility and planes from the nearby airport.

In addition to possessing superhero capabilities, the tower will house a 4D theater, a water park, landscaped gardens, and the third-highest observation deck in the world. GDS has not revealed a target completion date.

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==>South Korea To Build World's First 'Invisible' Skyscraper

Though not actually transparent or otherwise mystically obscured, the building is designed to reflect its surrounding area with a complex system of glass, LED lights and cameras.

CNN reports that 'Tower Infinity' will project real-time images on its surface. Three sections each with 500 rows of LED screens will - at full power - appear to merge the skyscraper into the horizon.

The idea is to blend the skyscraper into the locale as closely and unobtrusively as possible.

"Instead of symbolizing prominence as another of the world's tallest and best towers, our solution aims to provide the world's first invisible tower, showcasing innovative Korean technology while encouraging a more global narrative in the process," said Charles Wee, GDS design principal, in a statement to CNN.

The 1,476-foot tower will be built by the Korean Land and Housing Corporation and GSD Architects close to Seoul's Icheon airport.

Once complete in 2014 the tower will have the third highest observation deck in the world.

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