Engineering World

What is concrete vibrator and its types?

Engineering World 0 Building Guides September 27, 2018

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A concrete vibrator is a construction tool typically used on concrete pouring sites. These machines and an assortment of attachments are designed for multiple applications built by a variety of manufacturers. The vibrators are used to ensure that the pour is free of air bubbles and are even. This is so that the concrete remains strong and has a smooth finish even after removal of the form work. It is not exactly necessary for small jobs but it can be essential for large load bearing projects.</div>
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The machines range in sizes from small battery powered wands to larger plug in versions that are used on very deep pours. A concrete vibrator can reach to the bottom of the pouring forms should be used in all cases. This ensures even treatment during the entire concrete pour process. Attachments are selected on the basis of depth and type of concrete used during the concrete pour.</div>
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A typical concrete vibrator utilizes an off-center weight that spins at 10000 times a minute. This results in a large air pocket within the concrete to disperse as the concrete is being gradually shaken. Especially in the concrete pours of low slump concrete that uses minimal amount of water. The use of a vibrator is essential in order to ensure that the concrete does not form bubbles or holes. In cases where consumers look at the finished concrete, this tool will help to create an even and attractive surface instead of one that is ragged filled with bubbles on the surface. It is commonly seen in schools of design where they usually employ concrete counters and floorings to be done.</div>
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The proper use of a concrete vibrator would require some form of training. The head should be slowly lowered then pulled out gradually to avoid the formation of an air pocket in the pour. The tool should also never be dragged through a pour. This will leave a groove in the concrete behind it. The time required varies and is dependent on the mix. That being said, the mix should not take more than 30 seconds to settle the concrete sufficiently moving on to the next section of the concrete.</div>
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If the concrete vibrator is being used incorrectly on a concrete mix that has a wide range of material sizes, this can cause the larger rocks to settle at the bottom which then makes the concrete weaker. Additionally, the tool can push rock and gravel away from the area that is being shaken. This causes the weaker concrete paste to fill the area. This again may result in instability. The main goal is to build a strong matrix of material that could withstand the many years of usage. However, if it is being used correctly, the operator will be able to see large bubbles floating towards the surface of the concrete pour. A layer of mortar will also appear on the surface. This is to indicate that the concrete is mixed evenly and is unlikely to have honeycombing and air pockets.</div>
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<span style="font-weight: normal;">The first thing to take into consideration when choosing a concrete vibrator would be the size of it. The size depends on how much concrete you will need to vibrate. When considering this, it is crucial to think whether the concrete has to be vibrated quickly or some time allowance is provided. It is advised to spend a little extra on a vibrator that has a lot of horsepower if speed is a large considering factor. On top of that, there are also external and internal concrete vibrators to choose from. However, the latter is the more commonly used option for many projects these days.</span></div>
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<b>TYPES OF VIBRATORS USED FOR CONCRETE COMPACTION</b></div>
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<li style="text-align: justify;">Internal or Immersion or Poker or Needle Type Vibrator</li>
<li style="text-align: justify;">Shutter form or External Type Vibrator</li>
<li style="text-align: justify;">Surface or Screed or Pan Type Vibrators</li>
<li style="text-align: justify;">Vibrating Tables</li>
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<b>       1. Internal or Immersion or Poker or Needle Type Vibrator</b></h4>
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These concrete vibrators are also referred to as poker or immersion vibrator. These are extensively used in building industry. A needle vibrator consists of a cylindrical casing made of steel and is vibrated by means of a flexible drive with an outer tube run from an operating machine which can be run by electricity, petrol, diesel or compresses air. The frequency of vibrations of an immersion vibrator is very important as higher frequency gives better compaction. It varies from 3500 to 12000 cycles per minute. Frequencies below 3500 cycles per minute are inefficient for concrete compaction. The diameter of the vibrating part varies from 20 to 75 mm and its length varies from 25 to 90 cm.</div>
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<b>       2. Shutter form or External Type Vibrator</b><br />
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These vibrators are clamped to the formwork horizontally and vertically at suitable spacing not exceeding 90 cm in either direction. As the work progress they are shifted. They vibrate the concrete from the vibration of the forms and thus much energy is wasted.These vibrators can compact upto 450mm from the face but have to be moved from one place to another as concrete progresses. These vibrators operate at a frequency of 3000 to 9000 rpm at an acceleration of 4g.</div>
<span style="text-align: justify;">They are only used if the use of internal vibrators is not practicable as in the case of thin and congested sections, arches and tunnel lining, etc and these external vibrators are also used for pre-casting of thin in-situ sections of such shape and thickness as can not be compacted by internal vibrators.</span><br />
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       <b>3. Surface or Screed or Pan Type Vibrators</b></div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjMpPhvNcu2qdipXMHNmnJ0up3xRGXXYIl_bhTMEC_HRQFu3FzbTxk1rfivpVkQNG-s9elNuJ9O1VrlzWVz94FCd-bnfh65iLRDkj-aeb3PcoQ7pyEg4477pBl3thE3UzwnhwNbCnw-7Ekx/s1600/concrete-surface-vibrator-screed-gasoline-for-sales.jpg_350x350.jpg" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" data-original-height="350" data-original-width="350" height="200" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjMpPhvNcu2qdipXMHNmnJ0up3xRGXXYIl_bhTMEC_HRQFu3FzbTxk1rfivpVkQNG-s9elNuJ9O1VrlzWVz94FCd-bnfh65iLRDkj-aeb3PcoQ7pyEg4477pBl3thE3UzwnhwNbCnw-7Ekx/s200/concrete-surface-vibrator-screed-gasoline-for-sales.jpg_350x350.jpg" width="200" /></a>They are also called screed or pan vibrators.They are clamped to the screed.Very dry mixes can be most effectively compacted with surface vibrators. They vibrate the concrete from the surface at the time when screeding (striking off) of the concrete is carried out. They are effective only if depth of concrete is upto 20 cm. if the depth is more they can be used in combination with internal vibrators. They are used for long horizontal surfaces such as pavements and slabs.The operating frequency is about 4000 rpm at an acceleration of 4g to 9g.</div>
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<b>        4. Vibrating Tables</b></div>
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The vibrating table consists of a rigidly built steel platform mounted on flexible springs and is driven by an electric motor.The normal frequency of vibration is 4000 rpm at an acceleration of 4g to 7g. </div>
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The concrete is placed in moulds mounted on the platforms and securely clamped to the vibrating table, so that mould and concrete vibrate in union.</div>
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The vibrating tables are very efficient in compacting stiff and harsh concrete mixes required for manufacture of precast elements in the factories and test specimens in laboratories.</div>
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What is concrete vibrator and its types?

A concrete vibrator is a construction tool typically used on concrete pouring sites. These machines and an assortment of attachments ar...

What was the history of Civil Engineering?

Engineering World 0 History May 29, 2018

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It is hard to decide the historical backdrop of development and start of structural designing, be that as it may, that the historical backdrop of structural building is a reflection of the historical backdrop of people on this planet. Man utilized the old safe house caverns to secure themselves of climate and brutal condition, and utilized a tree trunk to cross the stream, which being the exhibit of antiquated age structural designing.  </div>
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Structural Engineering has been a part of life since the beginnings of human presence. The most punctual practices of Civil engg may have initiated in the vicinity of 4000 and 2000 BC in Ancient Egypt and Mesopotamia (Ancient Iraq) when people began to surrender an itinerant presence, in this manner causing a requirement for the development of safe house. Amid this time, transportation turned out to be progressively essential prompting the advancement of the haggle.  </div>
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Until current circumstances there was no unmistakable refinement between common engg and design, and the term engineer and architect were mostly land varieties reffering to a similar individual, regularly utilized conversely. The development of Pyramids in Egypt (around 2700-2500 BC) may be viewed as the main occurrences of vast structure developments.  </div>
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Around 2550 BC, Imhotep, the primary reported specialist, fabricated a popular ventured pyramid for King Djoser situated at Saqqara Necropolis. With basic apparatuses and arithmetic he made a landmark that stands right up 'til the present time. His most prominent commitment to designing was his disclosure of the specialty of working with molded stones. The individuals who tailed him conveyed designing to wonderful statures utilizing ability and creative energy.  </div>
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Old memorable structural building developments incorporate the Qanat water administration framework (the most established more established than 3000 years and longer than 71 km,) the Parthenon by Iktinos in Ancient Greece (447-438 BC), the Appian Way by Roman designers (c. 312 BC), the Great Wall of China by General Meng T'ien under requests from Ch'in Emperor Shih Huang Ti (c. 220 BC) and the stupas developed in old Sri Lanka like the Jetavanaramaya and the broad water system works in Anuradhapura. The Romans created common structures all through their realm, including particularly water passages, insulae, harbors, extensions, dams and streets.  </div>
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Other surprising recorded structures are Sennacherib's Aqueduct at Jerwan worked in 691 BC; Li Ping's water system extends in China (around 220 BC); Julius Caesar's Bridge over the Rhine River worked in 55 BC, various scaffolds worked by different Romans in and around Rome(e.g. the pons Fabricius); Pont du Gard (Roman Aqueduct, Nimes, France) worked in 19 BC; the broad arrangement of interstates the Romans worked to encourage exchanging and (all the more essentially) quick moving of armies; broad water system framework developed by the Hohokam Indians, Salt River, AZ around 600 AD; first dykes protecting against high water in Friesland, The Netherlands around 1000 AD; El Camino Real - The Royal Road, Eastern Branch, TX and Western Branch, NM (1500s AD).  </div>
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Machu Picchu, Peru, worked at around 1450, at the tallness of the Inca Empire is viewed as a designing wonder. It was worked in the Andes Mountains helped by a portion of history's most shrewd water asset engineers. The general population of Machu Picchu fabricated a peak city with running water, seepage frameworks, sustenance generation and stone structures so propelled that they persevered for more than 500years.  </div>
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A treatise on Architecture, Book called Vitruvius' De Archiectura, was distributed at 1AD in Rome and made due to give us a glance at designing training in old circumstances. It was most likely composed around 15 BC by the Roman designer Vitruvius and committed to his benefactor, the sovereign Caesar Augustus, as a guide for building ventures.  </div>
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All through antiquated and medieval history most compositional plan and development was done by craftsmans, for example, stonemasons and woodworkers, ascending to the part of ace manufacturer. Learning was held in societies and only from time to time supplanted by progresses. Structures, streets and framework that existed were monotonous, and increments in scale were incremental.  </div>
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One of the soonest cases of a logical way to deal with physical and numerical issues material to structural designing is crafted by Archimedes in the third century BC, including Archimedes Principle, which supports our comprehension of lightness, and useful arrangements, for example, Archimedes' screw. Brahmagupta, an Indian mathematician, utilized number-crunching in the seventh century AD, in view of Hindu-Arabic numerals, for uncovering (volume) calculations.  </div>
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<b>Educational and Institutional History of Civil Engineering </b></div>
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In the eighteenth century, the term structural building was instituted to fuse everything regular citizen rather than military designing. The primary designing school, The National School of Bridges and Highways, France, was opened in 1747. The main self-declared structural specialist was John Smeaton who built the Eddystone Lighthouse. In 1771, Smeaton and a portion of his associates shaped the Smeatonian Society of Civil Engineers, a gathering of pioneers of the calling who met casually finished supper. In spite of the fact that there was proof of some specialized gatherings, it was minimal in excess of a social society.  </div>
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In 1818, world's first building society, the Institution of Civil Engineers was established in London, and in 1820 the prominent architect Thomas Telford turned into its first president. The foundation got a Royal Charter in 1828, formally perceiving structural designing as a calling. Its contract characterized structural designing as: "Structural building is the use of physical and logical standards, and its history is unpredictably connected to propels in comprehension of material science and arithmetic all through history. Since structural designing is a boundless calling, including a few separate particular sub-trains, its history is connected to learning of structures, material science, topography, geography, soil, hydrology, condition, mechanics and different fields." </div>
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The principal private school to educate Civil Engineering in the United States was Norwich University established in 1819 by Captain Alden Partridge. The principal degree in Civil Engineering in the United States was granted by Rensselaer Polytechnic Institute in 1835. The main such degree to be granted to a lady was conceded by Cornell University to Nora Stanton Blatch in 1905.</div>
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What was the history of Civil Engineering?

It is hard to decide the historical backdrop of development and start of structural designing, be that as it may, that the historical b...

Why should we use Fiber Glass Rebars in our Projects?

Engineering World 0 Building Guides May 29, 2018

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The popularity of Glass Fiber Reinforced Polymer (GFRP) is on the ascent especially in applications where erosion safe is a noteworthy concern. We realize that consumption is an exorbitant issue. Trillions of dollars are spent every year on settling issues identified with metallic erosion. So far as realities are concerned, the yearly direct cost of metallic consumption is more than 2.2 trillion US dollars. The United States alone burn through 423 billion dollars as a yearly cost of consumption.</div>
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Steel corrosion is a characteristic and worldwide marvel. You can see now how much cash we can spare in the event that we utilize corrosion assurance techniques appropriately. How about we discuss consumption in detail before we can proceed onward to how glass fiber fortified polymer can spare your undertakings from destructive specialists.</div>
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<b>Definition and impacts of consumption</b></div>
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Steel and iron have that regular propensity to stir up with concoction components so they could come back to their least vitality states, like the inclination of water that streams to the most reduced point. Whenever iron and steel join with water and oxygen, hydrated iron oxides, additionally called rust, is framed. Consumption can just be characterized as a substance response between a material and its condition. This compound or electrochemical response causes disintegration of materials. </div>
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We are very much aware of how consumption has been affecting administration lives of our belonging. Occurrences, for example, crumbled connects and harmed areas of roadways are a portion of the normal sights that straightforwardly connected to erosion. Following are the reasons why you should utilize fiberglass rebar with a specific end goal to significantly build the administration life of your undertaking. </div>
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<b>1. Fiberglass Rebar is corrosion resistant </b></div>
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As it is said in the begin that glass fiber fortified polymer has increased impressive space over steel in applications where corrosion is a major risk. Fiberglass rebar offers a complete consumption arrangement. A solid structure strengthened with fiberglass rebar does not respond to the chloride-rich condition. </div>
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<b>2. A perfect alternative to traditional concrete reinforcement</b></div>
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Glass fiber strengthened polymer (GFRP) rebar has ended up being an ideal other option to conventional support materials, for example, dark rebar and epoxy covered rebar. Customary fortification strategies have neglected to build up an erosion free component that can keep solid structures fit as a fiddle.</div>
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<b>3. Long administration life</b></div>
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Glass fiber strengthened polymer, artificially dormant fortification, is a sparing method for accomplishing a long administration life of your venture. Old fortification materials may appear to be cheap, be that as it may, they can cost you a great deal of cash in the long haul. By applying fiberglass rebar, you can spare cash in long haul as well as make your undertaking totally rust free. </div>
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<b>4. A extensive variety of uses </b></div>
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Fiberglass rebar can be utilized as a part of an extensive variety of utilizations including marine structures, IT, and restorative offices. It is non-conductive and non-attractive development material perfect for medicinal and logical offices. </div>
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<b>5. Save time and cash </b></div>
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Maintenance cost duplicates the sum spent on economical solid support bars. Supportability is one of the greatest worries for the ventures worked with steel rebar. Fiberglass rebar gives supportability by making solid structures safe to destructive operators. Ensure you are utilizing the correct material for your development extends that can spare you cash and time in the long haul.</div>

Why should we use Fiber Glass Rebars in our Projects?

The popularity of Glass Fiber Reinforced Polymer (GFRP) is on the ascent especially in applications where erosion safe is a noteworthy ...

Why Has The Leaning Tower Of Pisa Survived Strong Earthquakes Since The Middle Ages?

Engineering World 0 History May 28, 2018

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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjY8qcjd72MSr6q9mdnR_0AI7K2dbbWsCQNb52Jj30ADn-mPXOpVBSsSd3IsoXGjdZcz0ZBvXqesL0lO168gIFVoplfJteJn-av0xe5fmk2vBwHq1K3ILXnF9awGTK4LubnjNvDhqKpNJg4/s1600/towerofpisa.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="450" data-original-width="800" height="360" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjY8qcjd72MSr6q9mdnR_0AI7K2dbbWsCQNb52Jj30ADn-mPXOpVBSsSd3IsoXGjdZcz0ZBvXqesL0lO168gIFVoplfJteJn-av0xe5fmk2vBwHq1K3ILXnF9awGTK4LubnjNvDhqKpNJg4/s640/towerofpisa.jpg" width="640" /></a></div>
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This is a long-standing inquiry an exploration gathering of 16 engineers has researched, incorporating a main master in quake designing and soil-structure communication from the University of Bristol.  Educator George Mylonakis, from Bristol's Department of Civil Engineering, was welcome to join a 16-part inquire about group, drove by Professor Camillo Nuti at Roma Tre University, to investigate this Leaning Tower of Pisa secret that has perplexed specialists for a long time. </div>
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In spite of inclining dubiously at a five-degree edge, prompting a counterbalance at the highest point of more than five meters, the 58-meter tall Tower has figured out how to survive, undamaged, no less than four in number seismic tremors that have hit the area since 1280. </div>
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Given the weakness of the structure, which scarcely figures out how to stand vertically, it was relied upon to maintain genuine harm or even fall on account of the direct seismic movement. Shockingly this hasn't happened and as of recently, this has perplexed specialists for quite a while. </div>
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In the wake of concentrate accessible seismological, geotechnical and auxiliary data, the examination group inferred that the survival of the Tower can be credited to a wonder known as Dynamic Soil Structure Interaction (DSSI).  </div>
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The impressive stature and solidness of the Tower joined with the delicateness of the establishment soil, makes the vibrational attributes of the structure be altered significantly, such that the Tower does not reverberate with seismic tremor ground movement. This has been the way to its survival. </div>
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The remarkable blend of these qualities gives the Tower of Pisa the world record in DSSI impacts.  </div>
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Educator Mylonakis, Chair in Geotechnics and Soil-Structure Interaction, and Head of Earthquake and Geotechnical Engineering Research Group in the Department of Civil Engineering at the University of Bristol, stated: "Amusingly, the extremely same soil that caused the inclining flimsiness and conveyed the Tower to the skirt of fall, can be credited for helping it survive these seismic occasions."</div>
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Why Has The Leaning Tower Of Pisa Survived Strong Earthquakes Since The Middle Ages?

This is a long-standing inquiry an exploration gathering of 16 engineers has researched, incorporating a main master in quake designing...

How to test the quality of cement ?

Engineering World 0 Building Guides May 28, 2018

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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiXNSJfX_OLrFFGEIiykZiB4QA5PRIhLZXQpH2LegRFPrgW7voHi8sgzdePXzOwqFwAJeaRx5i2WZo_J88KUpspmMa8dXEkEl0hRUD7-F7mlTscNM4m21fEyKz3yOqXYOp8C8zqzFVSv1yj/s1600/cement-quality-test.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="365" data-original-width="680" height="342" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiXNSJfX_OLrFFGEIiykZiB4QA5PRIhLZXQpH2LegRFPrgW7voHi8sgzdePXzOwqFwAJeaRx5i2WZo_J88KUpspmMa8dXEkEl0hRUD7-F7mlTscNM4m21fEyKz3yOqXYOp8C8zqzFVSv1yj/s640/cement-quality-test.jpg" width="640" /></a></div>
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Quality tests on concretes at development site (likewise called field tests on bond) are conveyed to know the nature of concrete provided at site. It gives some thought regarding concrete quality in view of shading, touch and believe and different tests.<br />
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<b>Tests on Cement at Construction site  </b><br />
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The accompanying are the quality tests on concrete at development site:  </div>
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1.Color test  </div>
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2.Presence of Lumps</div>
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3.Concrete Adulteration Test </div>
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4.Temperature test  </div>
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5.Float tests  </div>
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6.Strength test  </div>
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7.Setting test  </div>
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8.Date of packing</div>
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<b>1.Color Test of Cement </b> </div>
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The shade of the bond ought to be uniform. It ought to be dark shading with a light greenish shade.</div>
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<b>2.Presence of Lumps  </b></div>
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The bond ought to be free from any hard bumps. Such irregularities are framed by the assimilation of dampness from the environment. Any pack of concrete containing such bumps ought to be rejected. </div>
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<b>3.Concrete Adulteration Test </b> </div>
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The concrete should feel smooth when touched or rubbed in the middle of fingers. On the off chance that it is felt unpleasant, it shows defilement with sand.  </div>
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<b>4.Temperature Test of Cement </b> </div>
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In the event that hand is embedded in a pack of concrete or stack of bond, it should feel cool and not warm. </div>
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<b>5.Float Test</b></div>
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On the off chance that a little amount of bond is tossed in a pail of water, the particles should glide for quite a while before it sinks.<br />
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<b>6.Setting Test</b><br />
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A thick glue of concrete with water is made on a bit of glass plate and it is kept submerged for 24 hours. It should set and not break.  </div>
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<b>7.Quality of Cement Test  </b></div>
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A piece of concrete 25 mm ×25 mm and 200 mm long is readied and it is drenched for 7 days in water. It is then set on underpins 15cm separated and it is stacked with a weight of around 34 kg. The piece ought not hint at disappointment.  The briquettes of a lean mortar (1:6) are made. The span of briquette might be around 75 mm ×25 mm ×12 mm. They are drenched in water for a time of 3 days subsequent to drying. In the event that bond is of sound quality such briquettes won't be broken effectively.  </div>
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<b>8.Date of Packing</b>  </div>
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Quality of bond diminishes with time, so it is essential to check the assembling date of the concrete. For the most part, the concrete ought to be utilized before 90 days from the date of assembling.</div>
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How to test the quality of cement ?

Quality tests on concretes at development site (likewise called field tests on bond) are conveyed to know the nature of concrete provid...

How to Check the Quality of Sand at Site?

Engineering World 0 Building Guides May 28, 2018

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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi9dcFOtW8u5sUUr2JDCPW8KojHKzfcLFJhe0p8USh-BzRb4NrsjwZD0z1KW0CHpHOOv9AsgEir6FFqJwrxVcyTee67HKPOn0M9z8MgQyk0ZAjWMzP0agAkVYIZYVlT1xgyfolXGatTUO3v/s1600/21.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="362" data-original-width="923" height="250" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi9dcFOtW8u5sUUr2JDCPW8KojHKzfcLFJhe0p8USh-BzRb4NrsjwZD0z1KW0CHpHOOv9AsgEir6FFqJwrxVcyTee67HKPOn0M9z8MgQyk0ZAjWMzP0agAkVYIZYVlT1xgyfolXGatTUO3v/s640/21.jpg" width="640" /></a></div>
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Sand is a critical development material. It is a fine total which is either normal or as pulverized stones and smashed rock sand. It is better than rock and coarser than residue.  </div>
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Sand is an essential crude material utilized as a part of the development enterprises. It is fine total having the molecule estimate between 150 microns and 4.75 mm.  </div>
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It ought to be perfect and very much reviewed (all particles that have the relatively same size). Fine totals ought to be strong and free from abrasive particles and harmful particles like clean, kankar, delicate and flaky particles of shale. Fine totals ought to likewise be free from soluble bases and salts.  </div>
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The sand ought not contain over 8% of sediment (molecule estimate under 150 microns), and it ought to be dictated by "residue content field test".  </div>
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There are some field test which are encourages the property holder to check the nature of sand (Fine Aggregate) utilized on the site. Here are the best approach to check the nature of sand (fine totals) at the site.  </div>
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1. Rub the example of the sand with wet palms. Great clean sand won't adhere to the hand, while sand with dirt will stick and change the shade of the palm. Such sand contains dirt and sediment molecule. You have to test it for "residue content" nearby.  </div>
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2. Take a glass of water and include some amount of sand and blend the blend. Presently enable the blend to settle and watch it following 60 minutes. Clean sand will settle quickly yet in the event that it shapes the unmistakable best layer of sediment than sand contains residue or earth particles. The thickness of the residue layer ought not surpass the thickness of the sand layer by 8%. On the off chance that it contains over 8%, the sand ought to be washed with clear water. The width of glass ought to be uniform all through tallness.</div>
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3. To discover natural polluting influences in the sand, you should rehash the above technique and include harsh pop (salt) in the glass of water. On the off chance that the water changes the shading to dark colored, at that point there must be some natural pollutions. Such sand ought not be utilized.  </div>
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4. You should taste a squeeze of sand and in the event that it tastes salty, the salt must be available in sand and henceforth it ought not be utilized at all in any development. Such sand is normally from the stream however it is possible that it is ocean sand or from a zone of waterway oftentimes influenced by tidal water close to the ocean.</div>
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5. The measure of particles and sharpness of sand (fine totals) is checked by perception. Sand ought to be free from natural debasements (like shell, shingle, and different pollutions) or they ought to be in limits which are effectively distinguished by perception. </div>
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6. The above are essentially field tests. To at last support it there are sure lab tests like Fineness Modulus and Silt Content by Weight which additionally should be finished. Such research facility tests are suggested for huge ventures.</div>

How to Check the Quality of Sand at Site?

Sand is a critical development material. It is a fine total which is either normal or as pulverized stones and smashed rock sand. It is...

What is riveted and bolted joints?

Engineering World 0 Steel Structures April 14, 2018

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<b>2.1 RIVETING</b></div>
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Rivets of various shapes are made from mild steel bars as shown in fig.2.1.The rivet head is generally round and called a button head.The size of the rivets is the diameter of the shank.</div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgbVmqYM0dC5X1CYJ2-4GW8G_xkO1VNmjS66sLgUBwRL-GzAXOJavSlFLgVWuOUSqGz55c8jjvq9cRjzGAkU_BuPBl2fNlUmgmtW4D4_uYq1_qolANTBgrK4WxoucQ86KtdwzTysUHSSLdM/s1600/r3.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="441" data-original-width="614" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgbVmqYM0dC5X1CYJ2-4GW8G_xkO1VNmjS66sLgUBwRL-GzAXOJavSlFLgVWuOUSqGz55c8jjvq9cRjzGAkU_BuPBl2fNlUmgmtW4D4_uYq1_qolANTBgrK4WxoucQ86KtdwzTysUHSSLdM/s1600/r3.jpg" /></a></div>
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fig:2.1 </div>
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A flat head rivet may be used if the space is limited.Countersunk rivets are used to get a flatter surface.</div>
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Holes are drilled or punched in the plates to be riveted.The size of holes are 1.5mm larger than the size of rivets upto 25mm.For rivets of diameter more than 25mm,the diameter of the holes should be 2mm larger than the diameter of the rivets.For riveting,a rivet is heated uniformly to light red colour and then placed in the hole.The head is kept pressed on the plate,while the projected shank is hammered to form another head.On cooling the rivets contracts and grips the plate tightly. </div>
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Rivets may be driven by hydraulic or by pneumatic power,The rivets may br classified according to the method of driving them as follows:</div>
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(i)Power-driven shop rivets are power-driven in the fabrication shop.</div>
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(ii)Power-driven field rivets are power driven at site.Their strenght is less than the strength of the              power driven shop rivets.</div>
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(iii)Hand-driven rivets have less strength than the power-driven rivets.</div>
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(iv)Cold-driven rivets of diameter more than 10mm are not permitted by specifications.</div>
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<b>2.2 BOLTED JOINTS</b></div>
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Bolts may be used in place of rivets for structures not subjected to vibrations.the cost of bolts is more but it takes less time to fabricate structure with bolted connections.The fabrication work with bolts is noiseless and less skilled labours can also handle it.The stress concentration at the bolts can also be reduced by using high strength friction bolts.</div>
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The following types of bolts are used in the structures:</div>
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<b>(i)Black Bolts </b></div>
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   Hexagonal black bolts are commomly used in steel works.They are made from low or mediu         </div>
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carbon steels and should conform to IS:1363-1984.In metric sizes,black bolts are produced in sizes of 5mm to 36mm diameter and of lengths 3 to 10 times the diameter.They are designated as black bolts Md*L-IS:1363,where d=diameter and L=length of the bolts.</div>
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<b>(ii)Precision and Semi Precision Bolts</b></div>
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     They are also known as Close tolerance bolts conforming to IS:1364-1967.Sometimes to prevent excessive slip,close tolereance bolts are provided in holes of 0.15 to 0.12mm oversize,Thios may cause difficulty in alignment and delay in the progess of work.</div>
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<b>(iii)High-strenth friction grip bolts</b></div>
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HSFG bolts have a high yield strength.They should conform to IS:3757-1985.They are tightened by</div>
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torque wrenches and require hardened washers to induce initial tension,which causes friction between the plate surfaces.Due to friction,there is no slip in the joint and therefore the joints with HSFG Bolts are called friction type or non-slip joints.</div>
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<b>2.3 TYPES OF RIVETED AND BOLTED JOINTS </b></div>
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There are two types of riveted or bolted joints:</div>
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<b>(i)Lap joint </b></div>
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  The first is the lap joint in which the plates to be connected over lap each other.The lap joint may have single-row,staggered or overlap each other. The lap joint may have single-row, staggered or chain riveting.</div>
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<b>(ii)Butt joint</b></div>
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   The second is the butt joint in which the plates to be connected butt against each other and the connection is made by providing a cover plate on one or both sides of joint.The butt joint may have a single row or staggered or chain riveting.</div>
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<b>2.4 Some Important Definition used for Riveted and Bolted joints </b></div>
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<b>(i)Nominal diameter</b></div>
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    The diameter of the shank of rivet before riveting,is called the nominal diameter.For a bolt,the diameter of the unthreaded portion os the shank is calles its nominal diameter.</div>
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<b>(ii)Effective diameter or gross diameter</b></div>
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    The effective or gross diameter of rivet is equal to the diameter of the hole it fills after riveting.For a bolt,the nominal diameter is same as the gross diameter.</div>
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<b>(iii)Gross area </b></div>
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    The gross area of a rivet or bolt is given by its gross diameter.</div>
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<b>(iv)Net area </b></div>
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    The net area of a bolt is the area at the root of the thread.</div>
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<b>(v)Pitch</b></div>
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   The distance between centres of any two adjacent rivets is called pitch.</div>
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   Diagonal pitch : The distance between two centres of any two adjacent rivets in the diagonal direction is called diagonal pitch.</div>
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   Staggered pitch : The distance between any two consecutive rivets in a zig-zag riveting,measured parallel to the direction of stressnin the member is called staggered pitch.</div>
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<b>(vi)Gauge</b></div>
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    A row of rivets parallel to the direction of force is called a gauge line.The normal distance between two adjacent gauge lines is called the gauge distance.</div>
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<b>(vii)Edge distance </b></div>
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    It is the distance between the edge of a member or cover plate of the centre of the earest rivet hole.</div>
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<b>(viii)Proof load</b></div>
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    Initial tension in HSFG bolts is known as proof load of the bolt.</div>
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<b>(ix)Slip factor</b></div>
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    Coefficient of friction in friction type joint is known as slip factor.</div>
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<b>(x)Property class</b></div>
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   Bolts are grouped under different grades or property classes depending upon their strength.For example,property class 4.6 indicates that the nominal ultimate tensile strength is 400 Mpa and the nominal yield stress is 0.6*400 = 240Mpa </div>
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<table border="0" cellpadding="0" cellspacing="0" style="border-collapse: collapse; width: 552px;"><colgroup><col span="3" style="width: 48pt;" width="64"></col><col span="9" style="mso-width-alt: 1462; mso-width-source: userset; width: 30pt;" width="40"></col></colgroup><tbody>
<tr height="20" style="height: 15.0pt;"><td class="xl72" colspan="12" height="20" style="height: 15.0pt;">        <b> TABLE:2.1 Rivet diameter,Pitch and Edge Distance</b><br />
<table border="0" cellpadding="0" cellspacing="0" style="border-collapse: collapse; width: 552px;"><colgroup><col span="3" style="width: 48pt;" width="64"></col><col span="9" style="mso-width-alt: 1462; mso-width-source: userset; width: 30pt;" width="40"></col></colgroup><tbody>
<tr height="20" style="height: 15.0pt;"><td class="xl65" colspan="3" height="20" style="height: 15.0pt; width: 144pt;" width="192">Nominal
  dia of rivets(mm)</td><td class="xl66" style="border-left: none; width: 30pt;" width="40">12</td><td class="xl66" style="border-left: none; width: 30pt;" width="40">14</td><td class="xl66" style="border-left: none; width: 30pt;" width="40">16</td><td class="xl66" style="border-left: none; width: 30pt;" width="40">18</td><td class="xl66" style="border-left: none; width: 30pt;" width="40">20</td><td class="xl66" style="border-left: none; width: 30pt;" width="40">22</td><td class="xl66" style="border-left: none; width: 30pt;" width="40">24</td><td class="xl66" style="border-left: none; width: 30pt;" width="40">27</td><td class="xl66" style="border-left: none; width: 30pt;" width="40">30</td></tr>
<tr height="20" style="height: 15.0pt;"><td class="xl65" colspan="3" height="20" style="height: 15.0pt;">Gross dia of
  rivets(mm)</td><td class="xl66" style="border-left: none; border-top: none;">13.5</td><td class="xl66" style="border-left: none; border-top: none;">15.5</td><td class="xl66" style="border-left: none; border-top: none;">17.5</td><td class="xl66" style="border-left: none; border-top: none;">19.5</td><td class="xl66" style="border-left: none; border-top: none;">21.5</td><td class="xl66" style="border-left: none; border-top: none;">23.5</td><td class="xl66" style="border-left: none; border-top: none;">25.5</td><td class="xl66" style="border-left: none; border-top: none;">29</td><td class="xl66" style="border-left: none; border-top: none;">32</td></tr>
<tr height="20" style="height: 15.0pt;"><td class="xl69" colspan="12" height="20" style="border-right: .5pt solid black; height: 15.0pt;">Minimum edge distance (mm)</td></tr>
<tr height="20" style="height: 15.0pt;"><td class="xl65" colspan="3" height="20" style="height: 15.0pt;">   (i)For sheared or rough edge</td><td class="xl66" style="border-left: none; border-top: none;">19</td><td class="xl66" style="border-left: none; border-top: none;">25</td><td class="xl66" style="border-left: none; border-top: none;">29</td><td class="xl66" style="border-left: none; border-top: none;">32</td><td class="xl66" style="border-left: none; border-top: none;">32</td><td class="xl66" style="border-left: none; border-top: none;">38</td><td class="xl66" style="border-left: none; border-top: none;">44</td><td class="xl66" style="border-left: none; border-top: none;">51</td><td class="xl66" style="border-left: none; border-top: none;">57</td></tr>
<tr height="20" style="height: 15.0pt;"><td class="xl65" colspan="3" height="20" style="height: 15.0pt;">   (ii)For rolled or plane edge</td><td class="xl66" style="border-left: none; border-top: none;">17</td><td class="xl66" style="border-left: none; border-top: none;">22</td><td class="xl66" style="border-left: none; border-top: none;">25</td><td class="xl66" style="border-left: none; border-top: none;">29</td><td class="xl66" style="border-left: none; border-top: none;">29</td><td class="xl66" style="border-left: none; border-top: none;">32</td><td class="xl66" style="border-left: none; border-top: none;">38</td><td class="xl66" style="border-left: none; border-top: none;">44</td><td class="xl66" style="border-left: none; border-top: none;">51</td></tr>
<tr height="20" style="height: 15.0pt;"><td class="xl65" colspan="3" height="20" style="height: 15.0pt;">Pitch, Minimum</td><td class="xl65" colspan="9" style="border-left: none;">2.5 times the diameter of
  the rivet hole</td></tr>
<tr height="20" style="height: 15.0pt;"><td class="xl65" colspan="3" height="20" style="height: 15.0pt;">Pitch,Maximum
  for </td><td class="xl65" colspan="9" style="border-left: none;"></td></tr>
<tr height="39" style="height: 29.25pt; mso-height-source: userset;"><td class="xl67" colspan="3" height="39" style="height: 29.25pt; width: 144pt;" width="192">  (i)any two adjacent
  rivets  (including tacking rivets) </td><td class="xl68" colspan="9" style="border-left: none;">32 t or 300mm whichever is
  less</td></tr>
<tr height="20" style="height: 15.0pt;"><td class="xl65" colspan="12" height="20" style="height: 15.0pt;">  (ii)rivets lying in a line parallel to the
  force in the member:</td></tr>
<tr height="20" style="height: 15.0pt;"><td class="xl65" colspan="4" height="20" style="height: 15.0pt;">                       (a) in tension</td><td class="xl65" colspan="8" style="border-left: none;">16 t or 200 mm,whichever is
  less</td></tr>
<tr height="20" style="height: 15.0pt;"><td class="xl65" colspan="4" height="20" style="height: 15.0pt;">                       (b) in compression</td><td class="xl65" colspan="8" style="border-left: none;">12 t or 200 mm,whichever is
  less</td></tr>
<tr height="20" style="height: 15.0pt;"><td class="xl65" colspan="12" height="20" style="height: 15.0pt;">                        where t= thickness of
  the thinner outside plate</td></tr>
</tbody></table>
<b>Note:when the edge of a rivet or bolt in the direction of the force it bears is less than 2 x effective diameter of rivet or bolt,the permissible bearing stress of that rivet or bolt on the connected part shall be reduced by the following ratio.<br />                                =   </b><u>actual edge distance</u><br />
                                    2 x effective dia of rivet or bolt<br />
<br />
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  <td class="xl65" colspan="3" height="41" style="height: 30.75pt; width: 108pt;" width="144">  </td></tr>
</tbody></table>
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</tbody></table>
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What is riveted and bolted joints?

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