Analysis of TRUSSES

Analysis of TRUSSES

What is a Truss?

In engineering, a truss is a structure that "consists of two-force members only, where the members are organized so that the assemblage as a whole behaves as a single object".

A "two-force member" is a structural component where force is applied to only two points. Although this rigorous definition allows the members to have any shape connected in any stable configuration, trusses typically comprise five or more triangular units constructed with straight members whose ends are connected at joints referred to as nodes.

planar truss is one where all members and nodes lie
within a two-dimensional plane, while a space truss has members and nodes that extend into three dimensions. The top beams in a truss are called top chords and are typically in compression, the bottom beams are called bottom chords, and are typically in tension. The interior beams are called webs, and the areas inside the webs are called panels.

Truss types

For more truss types, see truss types used in bridges. A large timber Howe truss in a commercial building

There are two basic types of truss:

(i) pitched truss, or common truss

(ii) The parallel chord truss

The pitched truss, or common truss, is characterized by its triangular shape. It is most often used for roof construction. Some common trusses are named according to their web configuration. The chord size and web configuration are determined by span, load and spacing.

The parallel chord truss, or flat truss, gets its name from its parallel top and bottom chords. It is often used for floor construction.

A combination of the two is a truncated truss, used in hip roof construction. A metal-plate-connected wood truss is a roof or floor truss whose wood members are connected with metal connector plates.

Warren Truss

Truss members form a series of equilateral triangles, alternating up and down.

Pratt Truss

The Pratt truss was patented in 1844 by two Boston railway engineers, Caleb Pratt and his son Thomas Willis Pratt. The design uses vertical members for compression and diagonal members to respond to tension. The Pratt truss design remained popular as bridge designers switched from wood to iron, and from iron to steel. This continued popularity of the Pratt truss is probably due to the fact that the configuration of the members means that longer diagonal members are only in tension for gravity load effects. This allows these members to be used more efficiently, as slenderness effects related to buckling under compression loads (which are compounded by the length of the member) will typically not control the design. Therefore, for given planar truss with a fixed depth, the Pratt configuration is usually the most efficient under static, vertical loading.

Bowstring truss

A bowstring truss is used on the oldest metal bridge in Virginia

Named for their shape, bowstring trusses were first used for arched truss bridges, often confused with tied-arch bridges.

Thousands of bowstring trusses were used during World War II for holding up the curved roofs of aircraft hangars and other military buildings. Many variations exist in the arrangements of the members connecting the nodes of the upper arc with those of the lower, straight sequence of members, from nearly isosceles triangles to a variant of the Pratt truss.

Kingpost Truss

One of the simplest truss styles to implement, the king post consists of two angled supports leaning into a common vertical support.

The queen post truss, sometimes queen-post or qqueens post is similar to a king post truss in that the outer supports are angled towards the centre of the structure. The primary difference is the horizontal extension at the centre which relies on beam action to provide mechanical stability. This truss style is only suitable for relatively short spans.

Lenticular truss

The Waterville Bridge in Swatara State Park in Pennsylvania is a lenticular truss. Lenticular trusses, patented in 1878 by William Douglas (although the Gaunless Bridge of 1823 was the first of the type), have the top and bottom chords of the truss arched, forming a lens shape. A lenticular pony truss bridge is a bridge design that involves a lenticular truss extending above and below the roadbed.

Town's lattice truss

American architect, Ithiel Town designed Town's Lattice Truss as an alternative to heavy-timber bridges. His design, patented in 1820 and 1835, uses easy-to-handle planks arranged diagonally with short spaces in between them.

Vierendeel truss

A Vierendeel bridge, which lacks diagonal elements in the primary structure. The Vierendeel truss is a structure where the members are not triangulated but form rectangular openings, and is a frame with fixed joints that are capable of transferring and resisting bending moments. As such, it does not fit the strict definition of a truss (since it contains non-two-force members); regular trusses comprise members that are commonly assumed to have pinned joints, with the implication that no moments exist at the jointed ends. This style of structure was named after the Belgian engineer Arthur Vierendeel, who developed the design in 1896. Its use for bridges is rare due to higher costs compared to a triangulated truss.

Analysis of frames:

A frame is a structure made of several bars/ rods welded / riveted together. The bars are angle irons/ channels of “i” or “t” sections. These are called members on application of load on to the structure, the members remain loaded with tensile/compressive load.

Members under tension are called “tie”, Members under compression are called “strut”. The structure formed by the members (tie/ strut) is called “truss”.Extensively used in roof, bridge, sheds etc.

Perfect Truss:

Structure is made of members just sufficient to keep it in equilibrium, when loaded without any change of shape

N = 2j – 3 

                               where,        ‘n’ is the number of members, and
                                                   ‘j’ no of joints

It is efficient and optimized structure.

Imperfect Truss:
Structure is made of members more or lesser than the minimum numbers necessary to keep it in equilibrium, when loaded

N ≠ 2j – 3

if                                               N > 2j – 3 ----------------------- it is redundant Imperfect Truss

          if                                         N < 2j – 3  ---------------------it is Deficient imperfect Truss      

                 

Nobel Prize winners....2017

Nobel Prize winners....2017

Physics 

Kip Stephen Thorne (born June 1, 1940) is an American theoretical physicist and Nobel laureate, known for his contributions in gravitational physics and astrophysics. A longtime friend and colleague of Stephen Hawking and Carl Sagan, he was the FeynmanProfessor of Theoretical Physics at the California Institute of Technology (Caltech) until 2009 and is one of the world's leading experts on the astrophysical implications of Einstein's general theory of relativity. He continues to do scientific research and scientific consulting, most notably for the Christopher Nolan film Interstellar.

In 2017, Thorne was awarded the Nobel Prize in Physics along with Rainer Weiss and Barry C. Barish "for decisive contributions to the LIGO detector and the observation of gravitational waves".

Rainer "Rai" Weiss (born September 29, 1932) is a German-born American physicist, known for his contributions in gravitational physics and astrophysics. He is a professor of physics emeritus at MIT and an adjunct professor at LSU. He is best known for inventing the laser interferometric technique which is the basic operation of LIGO. Rainer Weiss was Chair of the COBE Science Working Group.

In 2017, Weiss was awarded the Nobel Prize in Physics, along with Kip Thorne and Barry Barish, "for decisive contributions to the LIGO detector and the observation of gravitational waves".

Barry Clark Barish (born January 27, 1936) is an American experimental physicist and Nobel Laureate. He is a Linde Professor of Physics, emeritus at California Institute of Technology. He is a leading expert on gravitational waves.

In 2017, Barish was awarded the Nobel Prize in Physics along with Rainer Weiss and Kip Thorne "for decisive contributions to the LIGO detector and the observation of gravitational waves".

Chemistry

Richard Henderson FRS FMedSci (born 19 July 1945) is a Scottish molecular biologist and biophysicist and pioneer in the field of electron microscopy of biological molecules. He shared the Nobel Prize in Chemistry in 2017 with Jacques Dubochet and Joachim Frank.

Joachim Frank (born 12 September 1940) is a German-born American biophysicist at Columbia University, New York City and a Nobel laureate. He is regarded as the founder of single-particle cryo-electron microscopy (cryo-EM), for which he shared the Nobel Prize in Chemistry in 2017 with Jacques Dubochet and Richard Henderson. He also made significant contributions to structure and function of the ribosome from bacteria and eukaryotes.

Jacques Dubochet (8 June 1942 (age 75), Aigle, Switzerland) is a retired Swiss biophysicist. He is a former researcher at the European Molecular Biology Laboratory in Heidelberg, Germany, and an honorary professor of biophysics at the University of Lausanne in Switzerland.

Prize amount: 9 million Swedish krona, to be shared equally between the Laureates.

Physiology or Medicine

Jeffrey Connor Hall (born 3 May 1945) is an American geneticist and chronobiologist. Hall is Professor Emeritus of Biology at Brandeis University and currently resides in Cambridge, Maine. Hall spent his career examining the neurological component of fly courtship and behavioural rhythms. Through his research on the neurology and behaviour of Drosophila melanogaster, Hall uncovered essential mechanisms of biological clocks and shed light on the foundations for sexual differentiation in the nervous system. He was elected to the National Academy of Sciences for his revolutionary work in the field of chronobiology. 

Along with Michael W. Young and Michael Rosbash, he was awarded the 2017 Nobel Prize in Physiology or Medicine "for their discoveries of molecular mechanisms controlling the circadian rhythm"


Michael Warren Young (born March 28, 1949) is an American biologist. He has dedicated over three decades to research studying genetically controlled patterns of sleep and wakefulness within Drosophila melanogaster. During his time at Rockefeller University, his lab has made significant contributions in the field of chronobiology by identifying key genes associated with regulation of the internal clock responsible for circadian rhythms. He was able to elucidate the function of the period gene, which is necessary for the fly to exhibit normal sleep cycles. Young's lab is also attributed with the discovery of the timeless and double-time genes, which makes proteins that are also necessary for circadian rhythm. 

He was awarded the 2017 Nobel Prize in Physiology or Medicine along with Jeffrey C. Hall and Michael Rosbash "for their discoveries of molecular mechanisms controlling the circadian rhythm"

Michael Morris Rosbash (born March 7, 1944) is an American geneticist and chronobiologist. Rosbash is a professor at Brandeis University and investigator at the Howard Hughes Medical Institute. Rosbash's research group cloned the Drosophila period gene in 1984 and proposed the Transcription Translation Negative Feedback Loop for circadian clocks in 1990. In 1998, they discovered the cycling gene, clock gene, and cryptochrome photoreceptor in Drosophila through the use of forwarding genetics, by first identifying the phenotype of a mutant and then determining the genetics behind the mutation. Rosbash was elected to the National Academy of Sciences in 2003. 

Along with Michael W. Young and Jeffrey C. Hall, he was awarded the 2017 Nobel Prize in Physiology or Medicine" for their discoveries of molecular mechanisms controlling the circadian rhythm".

Literature

Kazuo Ishiguro (Japanese: born 8 November 1954) is a British novelist, screenwriter and short story writer. He was born in Nagasaki, Japan; his family moved to England in 1960 when he was five. Ishiguro graduated from the University of Kent with a bachelor's degree in English and Philosophy in 1978 and gained his Master's from the University of East Anglia's creative writing course in 1980.

Ishiguro is one of the most celebrated contemporary fiction authors in the English-speaking world, having received four Man Booker Prize nominations and winning the 1989 award for his novel The Remains of the Day. 

His 2005 novel, Never Let Me Go, was named by Time as the best novel of 2005 and included in its list of the 100 best English-language novels from 1923 to 2005. His seventh novel, The Buried Giant, was published in 2015.

In 2008, The Times ranked Ishiguro 32nd on their list of "The 50 Greatest British Writers Since 1945". In 2017, the Nobel Prize in Literature was awarded to Ishiguro "who, in novels of great emotional force, has uncovered the abyss beneath our illusory sense of connection with the world.

Why the F/A-18 Is Such a Badass Plane?????

Why the F/A-18 Is Such a Badass Plane?????

The 35-year odyssey of the mighty Hornet.

On the first day of the Persian Gulf War, four F/A-18Cs took off from the USS Saratoga to bomb an airfield in southwestern Iraq. These F/A-18s were heavy. Each carried four MK 84 2000-lb. bombs, two AIM-7 Sparrows, two AIM-9L Sidewinders, and a centerline drop tank. As the Hornets from VFA-81 (the "Sunliners") made their approach, an E-2 Hawkeye airborne control aircraft passed the word to the pilots: Two Iraqi MiG-21s were on the hunt.

The MiGs turned to intercept the Hornets, closing at 1.2 Mach. While two of the Hornets stood off, Navy Lieutenant Commander Mark I. Fox and his wingman, Lieutenant Nick Mongilio, turned into the enemy. Fox locked onto one plane, firing both a Sparrow and a Sidewinder, while Mongilio launched a single Sidewinder at the other. In a heartbeat, both Iraqi planes were destroyed. A mere 40 seconds passed from the initial E-2 warning to downing the Iraqi jets.

Those two Iraqi MiGs are the only aerial victories for the F/A-18 Hornet/Super Hornet during its decades of service—no surprise, since the opponents in America's recent conflicts lacked the air power to challenge the U.S. Even so, the swift manner of success showed what the F/A-18 could do and why it was built.

Hornets weren't always the Navy's first choice. But they became the go-to choice for decades.

Strike Fighter

The first thing to notice about the Hornet is the "F/A" in the F/A-18 designation, meaning the jet was designed to be both a fighter and an attack aircraft. This plane was a way for the Navy to replace multiple single-mission aircraft with a jet that could do it all, but it was a long time coming.

The aircraft carrier-based fighter planes of World War II, such as the Grumman F6F Hellcat and Vought F4U Corsair, could carry bomb loads as heavy as the dive bombers of the day, successfully combining fighter and attack capabilities into a single aircraft. But the low power-to-weight ratio of these early jets forced the U.S. military to go in a different direction. The carrier aircraft of the 1950s and '60s tended to be the specialized fighter or attack aeroplanes.

The legendary F-4 Phantom of the Vietnam War era demonstrated the potential of a fighter/attack aeroplane. Even so, the Navy's concern for air superiority and defending its carriers from enemy aircraft led it to order the Grumman F-14 Tomcat in 1969. The Tomcat was a good plane, but an expensive one. As a result, the Navy was directed to seek a cheaper alternative by adopting one of the competitors from the Air Force's Lightweight Fighter Program.

What Google's New Camera Doesn't Do...... ??

What Google's New Camera Doesn't Do...... ??

Amid new phones and a suite of smart speakers, Google announced a clever little camera at its hardware event today. The Google Clips is designed to sit on your counter, or your end table, or your desk, and point in a general direction where something interesting might happen. When its AI senses a picture, it takes the shot. But it's the best feature is what it doesn't do—it doesn't run your data over the internet automatically.

The advent of advanced machine learning opens up all kinds of technological superpowers. Google Photos can recognize faces. Smart speakers everywhere can recognize voices. Typically, these tricks require the internet. Because machine learning takes a lot of computing horsepower, the heavy lifting is done by a powerful server off in a data centre located who knows where. This is supercharged hardware that is too big and power-hungry and expensive to put in every phone.

This necessarily creates some security risks. Everyone who handles your data in transit (like your ISP) will have a chance to look at it. Even if the data is encrypted and unintelligible—as the recordings from all major smart speakers are—it can be tracked or saved for later. Perhaps worst of all, the servers where this work is done make a juicy target for hackers. They are accordingly well-protected, but their security is out of your hands. That's to say nothing of government pressure on tech companies to hand over information, often without a warrant. These are risks you run when you upload a picture to Google Photos for automatic optimization, for example.

Google's Clip camera does its AI work within the camera itself. It's an impressive technical feat made possible by new AI-processing chips, and which offers a few handy bonuses. First, it can work even if you don't have an internet connection. Second, anything you do not actively choose to expose to the internet will never leave the camera. It's a distinct and personal sort of security. You don't have to take Google's word that its infrastructure is secure, or your ISP's word that it is not snooping on your data, or the state's word that it is not slurping up all the data it can find—you know, just in case it needs that information later. Instead, you can know that the data never left your house. It's security that doesn't rely on trust.

This refreshingly analogue sort of security is more vital than ever in an increasingly online world. No doubt it is showing up in large part because small, cheap, powerful AI-processing chips enable it. But it's hard to deny that the always-listening, always-watching vision of the future has been appearing more dystopian by the day, especially in the face of government surveillance and seemingly constant data breaches. It's getting harder to sell a gadget that ignores these real security concerns.

features like this—as well as things like physical camera shutters and mute buttons that electronically disconnect the microphones they control—will become more prevalent as time goes on. Sure, companies like Google will always thrive on your data in a way that can still be uncomfortable, using your photos to fine-tune its own technology or your searches as a means of targeting advertising. But security that acknowledges the fact that you might not trust everyone out there in cyberspace and accommodates that very fair suspicion is a welcome bit of good news.