What is Quartzite?

What is Quartzite?

ANSWER-Quartzite (from German Quarzit) is a hard, non-foliated metamorphic rock which was originally pure quartz sandstone Sandstone is converted into quartzite through heating and pressure usually related to tectonic  compression within orogenic belts. Pure quartzite is usually white to grey, though quartzites often occur in various shades of pink and red due to varying amounts of iron oxide (Fe₂O₃). Other colors, such as yellow, green, blue and orange, are due to other mineral impurities.

Orthoquartzite is a very pure quartz sandstone composed of usually well rounded quartz grains cemented by silica  Orthoquartzite is often 99% SiO₂ with only very minor amounts of iron oxide and trace resistant minerals such as zircon, rutile and magnetite. Although few fossils are normally present, the original texture and sedimentary structures are preserved.

In true metamorphic quartzite, also called meta-quartzite, the individual quartz grains have recrystalized along with the former cementing material to form an interlocking mosaic of quartz crystals. Minor amounts of former cementing materials, iron oxide, carbonate and clay, are often recrystalized and have migrated under the pressure to form streaks and lenses within the quartzite. Virtually all original textures and structure have usually been erased by the metamorphism.

                                                 This is a typical quartzite seen in lab:

 This is a green variety of quartzite. 

USES

Because of its hardness and angular shape, crushed quartzite is often used as railway ballast. Quartzite is a decorative stone and may be used to cover walls, as roofing tiles, as flooring, and stair steps. Its use for countertops in kitchens is expanding rapidly. It is harder and more resistant to stains than granite. Crushed quartzite is sometimes used in road construction. High purity quartzite is used to produce ferrosilicon, industrial silica sand, silicon and silicon carbide .During the Stone Age quartzite was used, in addition to flint, quartz and other lithic raw materials, for making stone tools.

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Types of bridges

BRIDGES

A bridge is a structure built to span physical obstacles such as a body of water, valley, or road, for the purpose of providing passage over the obstacle. There are many different designs that all serve unique purposes and apply to different situations. Designs of bridges vary depending on the function of the bridge, the nature of the terrain where the bridge is constructed and anchored, the material used to make it, and the funds available to build it

TYPES OF BRIDGES

Bridges can be categorized in several different ways. Common categories include the type of structural elements used, by what they carry, whether they are fixed or movable, and by the materials used

1. Arch Bridge

Ancient arches were made of stone. Arches work by putting the material into compression. Stone (as well as steel and concrete) work well in compression. A material is in compression when its particles are being pushed together. A column holding up a building is a long thin compression element.

PARTS OF ARCH BRIDGE

The compression forces in an arch have to press ultimately against the ground. To receive those large forces large abutments have to be created

The longest arch bridge in the world (until last year) was the New River Gorge Bridge in West Virginia, built in 1977. It has a central span of 1700 feet and a total length of 4224 feet. The Lupu Bridge in Shanghai now exceeds it by 105 feet. The New River Gorge Bridge is still the highest bridge; it rises 360 feet above the river and weighs 88,000,000 lbs

New River Gorge Bridge

Arches are often heavy. They can carry more load by getting deeper. With its full length in compression, the material can buckle. One way of overcoming buckling is to use more material, and make the arch heavier. At some point too much of its strength is used to support just its own

weight and too little strength is left to carry the superimposed loads of traffic.

2. Suspension Bridge

Ancient suspension bridges were made of rope, vines or chains. Newer suspension bridges use steel plates or super-strong steel cables. Cables work by putting the material into tension. Stone and concrete do not work well in tension; they are too brittle and usually too heavy. A material is in tension when its particles are being pulled apart. A rope holding a weight at its end is a long thin tension element.

Parts of a suspension bridge

A suspension bridge has a curved tension member. Look back at the diagram of “curved tension” back in the forces section. Examples of suspension bridges include rope bridges like those in ancient China, or the Roebling Bridge in Cincinnati Suspension bridges use a combination of tension and compression. The cables can only carry tension loads. By stretching across the towers, they pull down and create compression in the towers.

How a suspension bridge works

The cables that go from the top of the towers down to the ground are the backstays. The backstays are connected to huge rock or concrete piers buried in the ground. The backstays keep the towers from bending in. There are some experiments later in this tutorial that will let you see what happens if the bridge doesn’t have backstays. Look at the second black and white photo of the Roebling Bridge. Can you see that the cables in the center span curve upward to the towers, but the outer cables, called the backstays, are straight? Can you determine the direction of force on the backstays? It is always in the same direction because the force must run in the same direction of the cable. What is the direction of force on the main cables? What makes them curve?

Suspension bridges are very light. This allows them to span very long distances. The longest suspension bridge in the world is the Askashi Kaikyo Bridge in Japan. In addition to the long span, this bridge was designed to resist huge earthquakes (8.5) and hurricane force winds (220 MPH).

3. Beam Bridge

Ancient beam bridges were made primarily of wood. Modern beam-type bridges are made wood, iron, steel or concrete. How a beam operates is more complex than a cable or an arch. In the cable all of the material is in tension, but in a beam part of the material is in tension and part of the material is in compression. Look at the example of the Royal Albert Bridge design by I. K. Brunel in England.

A beam needs to be made of material that can work well under both compression and tension forces. Wood is a good material for this. Stone is not a good material for a beam - it is strong in compression, but weak in tension. That’s why it is good for arches but bad for beams. The same is true of concrete. To make a concrete beam, we need to add steel rods or cables at the bottom (in the tension area.) Long-span beams came into great use after 1850 when the production of large batches of steel became possible. None of the big bridges crossing the Ohio River are beam-types because the span is too long and their weight would be too great. Beams are more often found in shorter spans such as those at many overpasses. Next time you are driving with your parents on the highway, look at the structure beneath the overpasses as you travel beneath them, and you will more often than not see steel wide-flange beams supported by concrete columns.

4. Truss Bridge

Trusses work much like beams: they carry a combination of compression and tension forces. The main difference is that trusses are less bulky (heavy) than beams. Beams use extra material in some areas; these areas don’t use the full strength available to them. Engineers and builders can determine which portions of beams can be removed. The resulting truss concentrates the forces into many smaller members and eliminates the under-stressed areas of beams.

The Taylor-Southgate is a modern example (1995) of a truss bridge over the Ohio River in Cincinnati. It replaced the Central Bridge built in 1890.Compare the differences. The Taylor-Southgate uses fewer, longer spans than the Central Bridge. These longer spans produce much larger forces in the Taylor-Southgate, yet this bridge is not as deep as the Central Bridge. The tubes in the Taylor-Southgate Bridge must carry much higher stress, but they can do so, primarily, because they use a stronger type of steel than the types available in 1890.

Taylor-Southgate Bridge

5. cable-stayed

The newest type of bridge to be developed is the cable-stayed bridge. They have gained great popularity in recent years because of their great beauty and economy. They cannot be used for truly large spans like a suspension bridge, but they are very good for the more moderate spans that trusses have been used for.

The closest cable-stayed bridge near Cincinnati is the William H. Harsha Bridge near Maysville, KY. It has a main span of 320 meters, or about 1,050 feet. It was completed in October 2000.

                                                 William H. Harsha Bridge

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CIVIL ENGINEERING-FRESHER: List of Longest Bridges In The World

CIVIL ENGINEERING-FRESHER: List of Longest Bridges In The World: List of Longest Bridges In The World Danyang–Kunshan Grand Bridge  is a longest bridge on planet Earth with a length of 164.8 kilome...

List of Longest Bridges In The World

List of Longest Bridges In The World

Danyang–Kunshan Grand Bridge is a longest bridge on planet Earth with a length of 164.8 kilometers (102.4 mi)! It is a long viaduct and a network of bridges of many types, made to be a part of 1302 km long Beijing–Shanghai High-Speed Railway. This massive bridge runs through five cities – Danyang, Chanzhou, Wixo, Shunzou and Kunshan.

Second largest bridge on earth is Tianjin Grand Bridge, also part of Beijing–Shanghai High-Speed Railway. This viaduct bridge spans the distance of 113.7 km.

Jiaozhou Bay Bridge is one of the largest bridges in the world. It crosses Jiazhoy Bay with the lengthy of 26.7 kilometers (16.59 mi) and holds the record as the “longest bridge over water”.

Lake Pontchartrain Causeway is the largest over water bridge in the world outside of China. It runs over Lake Pontchartrain in southern Louisiana, United States, and has total length of 38.442 km (23.87 mi). It’s held over water with 9500 concrete pilings and its build in a formation of two parallel bridges with total of 4 lanes.

Luisiana is also home to the second longest bridge of the United States – Manchac Swamp Bridge. Created as twin concrete trestle bridge, it has total length of 36.7 kilometers and represents one third of the total highway length of Louisiana.

Hangzhou Bay Bridge connects Chinese municipalities of Jiaxing and Ningbo in Zhejiang province and features six lanes, longest span between ground supports of 448 meters (cable stayed) and total length of 35.6 kilometers (22 miles).

Runyang Bridge is one of the longest suspension bridges in the world. Its main span has a length of incredible 1,490 meters (4,890 ft, almost 700 feet more than Golden Gate Bridge). Entire viaduct bridge complex of Runyang Bridge is 22.1 miles long.

Donghai Bridge is one of the largest cross-sea bridges in the world. With a a total length of 32.5 kilometers (20.2 mi) it connects mainland china with a offshore island Yangshan which hosts large deep-water port. Majority of the bridge structure is low-level viaducts, with several high cable-stayed sections that allow passage of ships underneath it (largest span is 420m).

Atchafalaya Swamp Expressway is one of the most ambitious bridge complexes in the United States. It features 19 kilometers (12 miles) of trestle bridge, 1.6 kilometers of tunnels, two high clearance bridges, four artificial islands, 3.5 km of causeway, and 8.9 km of access roads (everything with 4 driving lanes) . Its total length is 28.3 km (17.6 miles).

Vasco de Gama Bridge is made from combination of viaducts, rangeviews and cable stayed bridge that run over the Tagus River near Lisbon, capital of Portugal. Total length of the bridge is 17.2 km (10.7 mi) and larges span is 420m (1,378 ft.).

Rio–Niterói Bridge is a box girder bridge located at Guanabara Bay, state of State of Rio de Janeiro, Brazil. It has total length of 13.2 kilometers (8.25 miles), 8 traffic lines, and it still holds the record of longest prestressed concrete bridge in the southern hemisphere.

types of Joint in concrete construction

Types of Joint in concrete construction:

Joints in concrete building construction are construction joints, expansion joints, contraction joints and isolation joints. They prevent cracking of concrete. Types of joints in concrete are described below:

Construction Joints:

Construction joints are placed in a concrete slab to define the extent of the individual placements, generally in conformity with a predetermined joint layout. They must be designed in order to allow displacements between both sides of the slab but, at the same time, they have to transfer flexural stresses produced in the slab by external loads. Construction joints must allow horizontal displacement right-angled to the joint surface that is normally caused by thermal and shrinkage movement. At the same time they must not allow vertical or rotational displacements. Figure 1 summarizes which displacement must be allowed or not allowed by a construction joint.

Expansion joint:

The concrete is subjected to volume change due to many reasons. So we have to cater for this by way of joint to relieve the stress. Expansion is a function of length. The building longer than 45m are generally provided with one or more expansion joint. In india recommended c/c spacing is 30m. The joints are formed by providing a gap between the building parts.

Contraction Joints:

A contraction joint is a sawed, formed, or tooled groove in a concrete slab that creates a weakened vertical plane. It regulates the location of the cracking caused by dimensional changes in the slab. Unregulated cracks can grow and result in an unacceptably rough surface as well as water infiltration into the base, subbase and subgrade, which can enable other types of pavement distress. Contraction joints are the most common type of joint in concrete pavements, thus the generic term “joint” generally refers to a contraction joint. Contraction joints are chiefly defined by their spacing and their method of load transfer. They are generally between 1/4 – 1/3 the depth of the slab and typically spaced every 3.1 – 15 m

Isolation Joints

Joints that isolate the slab from a wall, column or drainpipe

Isolation joints have one very simple purpose—they completely isolate the slab from something else. That something else can be a wall or a column or a drain pipe. Here are a few things to consider with isolation joints:

• Walls and columns, which are on their own footings that are deeper than the slab subgrade, are not going to move the same way a slab does as it shrinks or expands from drying or temperature changes or as the subgrade compresses a little.
  

                                         Even wooden columns should be isolated from the slab.

•  If slabs are connected to walls or columns or pipes, as they contract or settle there will be restraint, which usually cracks the slab—although it could also damage pipes (standpipes or floor drains).
• Expansion joints are virtually never needed with interior slabs, because the concrete doesn’t expand that much—it never gets that hot.
• Expansion joints in concrete pavement are also seldom needed, since the contraction joints open enough (from drying shrinkage) to account for temperature expansion. The exception might be where a pavement or parking lot are next to a bridge or building—then we simply use a slightly wider isolation joint (maybe ¾ inch instead of ½ inch).
• Blowups, from expansion of concrete due to hot weather and sun, are more commonly caused by contraction joints that are not sealed and that then fill up with non-compressible materials (rocks, dirt). They can also be due to very long unjointed sections.
  

Very long unjointed sections can expand enough from the hot sun to cause blowups, but this is rare.

• Isolation joints are formed by placing preformed joint material next to the column or wall or standpipe prior to pouring the slab. Isolation joint material is typically asphalt-impregnated fiberboard, although plastic, cork, rubber, and neoprene are also available.
• Isolation joint material should go all the way through the slab, starting at the subbase, but should not extend above the top.
• For a cleaner looking isolation joint, the top part of the preformed filler can be cut off and the space filled with elastomeric sealant. Some proprietary joints come with removable caps to form this sealant reservoir.
•  Joint materials range from inexpensive asphalt-impregnated fiberboard to cork to closed cell neoprene. Cork can expand and contract with the joint, does not extrude, and seals out water. Scott Whitelam with APS Cork says that the required performance is what determines the choice of joint materials. How much motion is expect, exposure to salts or chemicals, and the value of the structure would all come into play—and of course the cost.

Polyethylene foam isolation joint material comes in various colors. C2 Products

• At columns, contraction joints should approach from all four directions ending at the isolation joint, which should have a circular or a diamond shaped configuration around the column. For an I-beam type steel column, a pinwheel configuration can work. Always place the slab concrete first and do not install the isolation joint material and fill around the column until the column is carrying its full dead

Diamond Crossing at Nagpur

Diamond Crossing at Nagpur:

Railway Crossing at Nagpur called Diamond Crossing. It is the point where India cross from North to South & east to west..

Situation-1: Trains from West Terminating at Nagpur: (Sewagram, Nandigram, Pune-Nagpur GR, Prerana) - No Diamond Crossing

Situation-2: Trains from Itarsi side terminating at Nagpur (BSL-NGP, INDB-NGP, etc.) – No Diamond Crossing

Situation 3: Trains from Bilaspur side terminating at Nagpur: Pass through Diamond Crossing to enter NGP station

Situation 4: Trains from West going to East (Azad Hind, Jnaneshwari, PUNE/CSTM-HWH Duronto, etc.) – Cross the Diamond crossing to continue their journey towards Gondia / Bilaspur

                                        A schematic diagram of a dual gauge diamond crossing

Situation 5: Trains from South going to North (Rajdhanis/TN/GT/Kerala/AP/Dakshin/APSK/TNSK/KSK, etc.)  

– These trains enter Nagpur from Balharshah – Sewagram side. As Sewagram is on the CSTM-NGP-HWH Mainline, these trains enter NGP from mainline itself just like the trains from West-East do. As a result, you can see the above trains on any of PFs at NGP. 

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When they depart NGP, they take a left turn towards Amla / Itarsi side. The passengers in these trains are able to see the diamond crossing on the right side, but they do not cross it as the train is entirely on a different track. 

Situation 6: Narrow Gauge trains of NGP (SECR) Cross the Diamond Crossing (NGP-CWA Passenger)

Watch this video...

   

Dubai Rotating Skyscraper: World first building in Motion

Dubai Rotating Skyscraper: World first building in Motion

The world’s first moving building, an 80-storey tower with revolving floors giving a shifting shape, will be built in Dubai, its architect says. The Dynamic Tower design is made up of 80 pre-fabricated apartments which will spin independently of one another.

“It’s the first building that rotates, moves, and changes shape,” said architect David Fisher, who is Italian, at a news conference in New York. “This building never looks the same, not once in a lifetime,” he added. The 420-metre (1,378-foot) building’s apartments would spin a full 360 degrees, at voice command, around a central column by means of 79 giant power-generating wind turbines located between each floor.

The slender building would be energy self-sufficient as the turbines would produce enough electricity to power the entire building and even feed extra power back into the grid, said the Italian architect at the unveiling of the project in New York. The apartments, which will take between one and three hours to make a complete rotation, will cost from $3.7m to $36m. There are also plans to build a similar, 70-storey skyscraper in Moscow. “I call these buildings designed by time, shaped by life,” said the Florence-based architect, who has never built a sky-scraper before. “These buildings will open our vision all around, to a new life.” The skyscraper will cost an estimated $700m to build and should be up and running in Dubai in 2010.

earthquakes

Ground-improvement methods might protect against earthquakes

Source: Purdue University

Summary:

Researchers are developing ground-improvement methods to help increase the resilience of homes and low-rise structures built on top of soils prone to liquefaction during strong earthquakes. Findings will help improve the safety of structures in Christchurch and the Canterbury region in New Zealand, which were devastated in 2010 and 2011 by a series of powerful earthquakes. Parts of Christchurch were severely affected by liquefaction, in which water-saturated soil temporarily becomes liquid-like and often flows to the surface creating sand boils.

     Researchers are using T-Rex, a 64,000-pound shaker truck, in research to increase the resilience of homes andlow-rise structures built on top of soils prone to liquefaction during strong earthquakes. T-Rex is based at a University of Texas at Austin facility that is part of the George E. Brown Jr. Network for Earthquake Engineering Simulation (NEES), a distributed laboratory with 14 sites around the United States

Researchers from the University of Texas at Austin's Cockrell School of Engineering are developing ground-improvement methods to help increase the resilience of homes and low-rise structures built on top of soils prone to liquefaction during strong earthquakes.

      Findings will help improve the safety of structures in Christchurch and the Canterbury region in New Zealand, which were devastated in 2010 and 2011 by a series of powerful earthquakes. Parts of Christchurch were severely affected by liquefaction, in which water-saturated soil temporarily becomes liquid-like and often flows to the surface creating sand boils.

     "The 2010-2011 Canterbury earthquakes in New Zealand have caused significant damage to many residential houses due to varying degrees of soil liquefaction over a wide extent of urban areas unseen in past destructive earthquakes," said Kenneth Stokoe, a professor in the Department of Civil, Architectural and Environmental Engineering. "One critical problem facing the rebuilding effort is that the land remains at risk of liquefaction in future earthquakes. Therefore, effective engineering solutions must be developed to increase the resilience of homes and low-rise structures."

Researchers have conducted a series of field trials to test shallow-ground-improvement methods.

     "The purpose of the field trials was to determine if and which improvement methods achieve the objectives of inhibiting liquefaction triggering in the improved ground and are cost-effective measures," said Stokoe, working with Brady Cox, an assistant professor of civil engineering. "This knowledge is needed to develop foundation design solutions."

      Findings were detailed in a research paper presented in December at the New Zealand -- Japan Workshop on Soil Liquefaction during Recent large-Scale Earthquakes. The paper was authored by Stokoe, graduate students Julia Roberts and Sungmoon Hwang; Cox and operations manager Farn-Yuh Menq from the University of Texas at Austin; and Sjoerd Van Ballegooy from Tonkin & Taylor Ltd, an international environmental and engineering consulting firm in Auckland, New Zealand.

    The researchers collected data from test sections of improved and unimproved soils that were subjected to earthquake stresses using a large mobile shaker, called T-Rex, and with explosive charges planted underground. The test sections were equipped with sensors to monitor key factors including ground motion and water pressure generated in soil pores during the induced shaking, providing preliminary data to determine the most effective ground-improvement method.

    Four ground-improvement methods were initially selected for the testing: rapid impact compaction (RIC); rammed aggregate piers (RAP), which consist of gravel columns; low-mobility grouting (LMG); and construction of a single row of horizontal beams (SRB) or a double row of horizontal beams (DRB) beneath existing residential structures via soil-cement mixing.

   "The results are being analyzed, but good and poor performance can already be differentiated," Stokoe said. "The ground-improvement methods that inhibited liquefaction triggering the most were RIC, RAP, and DRB. However, additional analyses are still underway."

The test site is located along the Avon River in the Christchurch suburb of Bexley. The work is part of a larger testing program that began in early 2013 with a preliminary evaluation by Brady Cox of seven potential test sites along the Avon River in the Christchurch area.

     Funding for the research has been provided, in part, by the National Science Foundation and is affiliated with the NSF's George E. Brown Jr. Network for Earthquake Engineering Simulation (NEES). The remainder of the funding has been provided by the Earthquake Commission of the New Zealand Government.

     The 64,000-pound T-Rex, operated by NEES@UTexas at UT Austin, is used to simulate a wide range of earthquake shaking levels.

NEES is a shared network of 14 experimental facilities, collaborative tools, centralized data repository and earthquake simulation software, all linked by high-speed Internet connections.