Bascule Bridge Design and Construction

Bascule Bridge Design and Construction â€Å"DOUBLE LEAF BASCULE BRIDGE† 1. OBJECTIVES: Become familiar with the wood work. Become familiar with lathe machine and drilling machine. Build a simple pulley. 2. INTRODUCTION: A bascule bridge (commonly referred to as a drawbridge) is a moveable bridge with a counterweight that continuously balances a span, or leaf, throughout its upward swing to provide clearance for boat traffic. It may be single or double leafed. 3. METHOD: Cut out an arch with the scroll saw from the 5-by-7-by-2-inch block of pine wood. Make the arch about 3 inches wide and 4 inches high. Be sure to cut in the longest direction, so that the bottom of the arch becomes the bottom of the tower, and there is 3 inches left above the top of the arch. Measure and mark with the pencil every 1/2 inch across the top of the tower, above the arch. At every other mark, cut a notch 1/2 inch deep and 1/2 inch wide with the scroll saw. These are the tower battlements. Center the tower on the 5-by-10-by-1/2-inch block and nail the two pieces together through the bottom to form the tower base. Lay down the two 4-by-1/2-by-1/2-inch blocks parallel to each other 3 inches apart on your work surface. Lay the eight 4-by-1/2-by-1/8-inch strips across the two blocks. Attach the strips to the blocks with finishing nails. This is your drawbridge. Turn over the drawbridge and tap in two finishing nails, one into each block, as close to the ends as you can without splitting the wood. Leave the nails sticking out past the edges of the drawbridge, about 1/4 inch. This will be the pivot end of your gate. Tap in two more finishing nails, one into each block, about 1/2 inch from the end opposite the pivot end of the drawbridge. Leave the nails sticking past the edges about 1/4 inch. Lay the drawbridge, block side down, on the tower base in front of the tower. Place an upholstery staple over the protruding nails on the pivot end and gently tap the staples into the tower base. This should hold the drawbridge in place while allowing it to rotate freely into open and shut positions. Adjust the staples and nails if needed. Tap two finishing nails into the tower, one on either side at the top of the arch. Make sure they are spaced 4 inches apart, as wide as the drawbridge. Angle the nails at about 45 degrees, and leave half of each nail sticking up. Attach one end of each chain to the nails at the top of the arch. Attach the other ends to the drawbridge. Stain the wood with the paintbrush, then allow to dry. 4. DISCUSSION: SAMPLE DIAGRAM: TERMS AND EXPLANATION: PRACTICAL INFORMATION ABOUT BASCULE BRIDGES: Almost all double leaf bascule bridges consist of two cantilever spans projected toward each other, connected at their tips by a suitable shear lock. Other types of double leaf bascule are comparatively rare, such as those which form arch bridges in the closed position, and are not the topic of this discussion. Double leaf bascule bridges are possibly the least practical, from a maintenance and operation standpoint, of all commonly used types of modern era movable bridges. They use two separate moving leaves when one would do, with all the associated expense in construction, operation, and maintenance of two totally independent movable bridge leaves. They also join these two moving leaves together for the support of live load, compounding the difficulties. There are advantages to double leaf bascules: they can open and close somewhat more quickly than any other type of movable bridge; a double leaf bascule is less affected by wind loads than a single leaf bascule spanning the same channel width; they use slightly less structural steel than other types of movable bridges with the same load rating spanning the same width of navigation channel; double leaf bascules are less susceptible to collision with vessels navigating past them than other movable bridge types, and they are generally consid ered more aesthetically pleasing than other types of movable bridges. One might ask, however, whether these advantages are worth putting up with the additional complications, particularly in regard to stabilizing the structures under live load. Double leaf bascule bridges, more so than most other movable bridge types, frequently have problems with seating. These problems arise from several sources. The bridge may be carrying live loads larger than those designed for, overstressing the support system. The bridge stabilizing devices may have suffered deterioration so that they cannot contain the forces imposed on them. The bridge stabilizing devices may be improperly adjusted so that they do not perform their intended function. The entities which contribute to stability of a double leaf bascule include: live load shoes which form stops for each moving leaf as it attains its seated position; center or shear locks forming a vertical tie between the two leaves of a double leaf bascule bridge when in the closed position; live load anchors which are capable of exerting a downward force at the rear of bridge counterweight; tail locks Which form a shear connection at or near the rear of the bridge counterweight, and adjustment of th e balance of the moving leaf about its axis of rotation. Bascule is French for see-saw. All modern bascule bridges consist of a large moving mass of superstructure, deck, and counterweight, which can be considered balanced for structural purposes. The span can be considered essentially rigid for balancing purposes, as it rotates between opened and closed positions. This applies whether it is a simple trunnion leaf, or a rolling lift of the Scherzer or Ball type. It also applies to the many variations on the articulated counterweight type, as developed by Strauss and others, with the counterweight pivoting about an axis or arc separate from the bridge leaf. An exception to this rule are bascules with operating struts or ropes such as many heel trunnions, some early Scherzer rolling lifts, and others, which do not add simply to the balancing calculations, as they move in a different path than the superstructure. The operating strut could be heavy enough to have a noticeable effect on the balance, but this usually only happens with single lea f railroad bridges. Heel trunnion and articulated counterweight bascule bridges have the counterweight rotating about an axis separate from the leaf itself. The counterweight is always in a fixed position with regard to gravitational moment relative to the bascule span on these bridges, due to the parallelogram arrangement of the pivot points. Double leaf bascule bridges become unstable because they are poorly designed, poorly constructed, or poorly maintained. They are more susceptible to deficiencies from these causes because they are more delicate than other common types of movable bridges. It is very difficult to correct the faults of a poorly designed bridge, but sometimes possible to correct construction defects. It is very difficult to correct the results of poor maintenance except by replacing the components affected. A properly designed double leaf bascule bridge should be very rigid, particularly in regard to primary live load deflections. The leaves of the double leaf bascule should be firmly supported on very solid live load shoes located adjacent to the pier sea wall, as far as possible from the center of rotation. The balance of the double leaf bascule should be such that a dead load reaction exists on the live load shoes, when the bridge is closed, that is substantially in excess of any possible negative reaction, from live load or other sources. The roadway surfaces of the double leaf bascule should be formed so that there is no misalignment at the joints, either at the heels of the leaves or at the toes. This applies to profile as well as elevation the vertical curve should be continuous from one leaf to the other and from each leaf to its approach. Tail locks should be provided as a backup to the stabilization achieved by balancing. The tail locks should firmly grasp the tail end of each leaf with minimum clearances and hold it in the closed position. This will eliminate the possibility of drive machinery being damaged due to live load deflection. CONCLUSION AND RECCOMENDATION: Double leaf bascule bridges become unstable because they are poorly designed, poorly constructed, or poorly maintained. They are more susceptible to deficiencies from these causes because they are more delicate than other common types of movable bridges. It is very difficult to correct the faults of a poorly designed bridge, but sometimes possible to correct construction defects. It is very difficult to correct the results of poor maintenance except by replacing the components affected. A properly designed double leaf bascule bridge should be very rigid, particularly in regard to primary live load deflections. The leaves of the double leaf bascule should be firmly supported on very solid live load shoes located adjacent to the pier sea wall, as far as possible from the center of rotation. The balance of the double leaf bascule should be such that a dead load reaction exists on the live load shoes, when the bridge is closed, that is substantially in excess of any possible negative reaction, from live load or other sources. The roadway surfaces of the double leaf bascule should be formed so that there is no misalignment at the joints, either at the heels of the leaves or at the toes. This applies to profile as well as elevation the vertical curve should be continuous from one leaf to the other and from each leaf to its approach. rail locks should be provided as a backup to the stabilization achieved by balancing. The tail locks should firmly grasp the tail end of each leaf with minimum clearances and hold it in the closed position. This will eliminate the possibility of drive machinery being damaged lue to live load deflection. Movable bridges have been an important part of our nation’s infrastructure for centuries. They present unique challenges to the structural engineer and require extensive coordination of the  structural, mechanical, and electrical systems to achieve a durable and operationally reliable structure. FINAL PROJECT: REFERENCES: http://en.wikipedia.org/wiki/Bascule_bridge http://heavymovablestructures.org/assets/technical_papers/00525.pdf

Ophelia in William Shakespeares Hamlet Essay -- William shakespeare h

Ophelia in William Shakespeare's Hamlet â€Å"Follow her close, give her good watch, I pray you† (IV.5.73). Ostensibly, Shakespeare’s Hamlet is the riddling, enigmatic, inscrutable theatrical character par excellence. His motives, madness, conflicting morals and existential struggles are ambiguous to say the least. When analysing his character, Laertes and Fortinbras are often brought in as examples of less extreme characters dealing with similar but more tangible dilemmas. The idea that there may be someone who exceeds Hamlet in instability and incomprehensibility is unfathomable. But if one looks at the character of Ophelia, this notion not only becomes a viable possibility: it becomes unignorable. For while Hamlet is constantly struggling to define himself, leaving a trail of cast-off identities, disgustedly flinging one black outfit after another out of his wardrobe as he tries to remain true to himself, his father’s memory, and his stirring unconscious, we only see Ophelia in borrowed robes. She is dressed up like a dummy, paraded around, and dismissed. With her f inal exit, we are left with a handful of ill-fitting stage costumes, none of them designed by her. It is significant that in the whole play, she is referred to by name nineteen times in total-- the majority of the time, she is Polonius’ daughter, Laertes’ sister, or merely â€Å"she† or â€Å"her.† Ophelia’s first two lines are questions, but not of the â€Å"To be or not to be† variety. â€Å"Do you doubt that?† and â€Å"No more but so?† (I.3.4-9) imply a state confusion, insecurity, and disorientation-- of â€Å"blinkered† experience, of externally-imposed tunnel vision that leads to a staggering, stilted walk through life. From her first entrance, we are presented with ... ... ultimate act of self-assertion. For not only is she shaming the court and her family, talking in riddles to the brother who preached to her, and acting out to an extreme the lesson constantly reiterated by her father, the inability to live without his guidance. She is not merely distorting the pastoral â€Å"green girl† image, making a gruesome picture of the carefree, virginal â€Å"Rose of May.† She is spitting in the face of the God who placed her in such an impotent position in the first place. And this is the real tragedy of Ophelia’s life and death. Because while Hamlet dies with the knowledge that he has fulfilled his mission, Ophelia has no mission. Her first independent act, what ought to denote the beginning of a life composed of her own initiatives, is the truncating of that life. Her beginning is her end-- the house pet, released into the wild, withers and dies.

Your Inner Fish

Your Inner Fish: A Review of Chapter 4 In Your Inner Fish, a book about the study of evolution in mammals, chapter four is dedicated to the study of teeth. Neil Shubin is explicit in his insistence that teeth are extremely important when studying evolution of the human body. He uses three main points to explain this to the reader. First, through the function of teeth. Then by revealing the anatomy of teeth. And finally by discussing tooth-to-tooth occlusion. Teeth are used to manipulate larger objects so that they may fit into a smaller mouth.Shubin writes †Mouths are only so big, and teeth enable creatures to eat things that are bigger than their mouths† (Shubin 60). Without teeth creatures would have a smaller variety of options when it came to food choices. Bigger fish could only eat smaller fish and so on. As explained by Shubin â€Å"†¦ teeth can be the great equalizer: smaller fish can munch on bigger fish if they have good teeth† (Shubin 60). So we deri ve from this that teeth can play an important role in the food chain and thus in evolution. However, teeth play a more important part than this.By studying the anatomy of teeth many secrets can be revealed about ancient reptiles and mammals. For instance, Shubin relates that â€Å"The bumps, pits and ridges on teeth often reflect the diet† (Shubin 60). By knowing the diet of an ancient creature, it is reasonable to see how a paleontologist and evolutionist can follow the emergence of the omnivore over the carnivore and herbivore. And the hardness of teeth make it the â€Å"best-preserved animal we find in the fossil record for many time periods† (Shubin 61).This clue to these ancient animal’s diets can â€Å"give us a good window on how different ways of feeding came about† (Shubin 61). So, the shape of the teeth and the general mineral make-up both contribute to the usefulness of teeth to the scientist. Still it remains that the tooth-to tooth occlusion is an imperative discovery when shaping the history of the human body. Reptiles do not have an upper and lower jaw that meet precisely. They rip and tear their food. On the other hand, mammals have an upper and lower jaw that meet in a precise position (Shubin 60-61).Shubin discusses that in lower rock forms, thus earlier years, fossil records show only reptilian-like mouths that do not have occlusion. As the paleontologist moves up into higher rock formations, he finds more mammalian like tooth formations and smaller jaws. â€Å"Go higher in the rocks and we see something utterly different: the appearance of mammalness. The bones of the jaw get smaller and move to the ear. We can see the first evidence of upper and lower teeth coming together in precise ways† (Shubin 62).From Shubin’s portrayal of the evolution of the mouth and teeth and teeth’s usefulness, it stands to reason that teeth are an important part of the study of ancient mammals and the evolution of the human body. Your Inner Fish:Chapter 4 A Review In his book, Your Inner Fish, Neil Shubin mentions the fact that although the study of teeth are highly important to the study of ancient mammalian history, it is often overlooked or only briefly discussed in anatomy. However, Shubin successfully shows how extremely serious evolutionists and paleontologists take the study of tooth fossils.In the beginning of chapter 4: Teeth Everywhere, he states that â€Å"the tooth gets short shrift in anatomy class: we spend all of five minutes on it† (Shubin 60). But because he fills the chapter with relative stories of paleontologists and himself searching solely for tooth fossils, he reveals that teeth are vital in the study of ancient mammals. Entire expeditions for tooth hunting are explored. Shubin even states that â€Å"teeth have a special significance for me, because it is in searching for them that I first learned how to find fossils and how to run a fossil expedition† (S hubin 60).Thus, implying he had gone on an expedition with the sole purpose of hunting for ancient teeth.. From his references to paleontologists’ search for teeth it seems that teeth are a prominent study in evolution, even if touched on only briefly in anatomy classes. Shubin narrates a story of his first leading expedition where a tiny ancient mammal was discovered in rock and the most significant finding was the revelation of tooth occlusion. He even reports that he was â€Å"†¦being treated like a conquering hero†¦Ã¢â‚¬  (Shubin 70) back on campus following the return from the expedition.This is a definite sign that the importance of tooth and tooth occlusion are extremely recognized in the world of evolutionary studies. Time, money, and energy are offered to tooth expeditions, and findings are celebrated amongst paleontologists and evolutionists alike. Therefore, it can be concluded from Shubin’s examples that teeth are an important study among scient ists who study the history of the human body. Your Inner Fish: A study of Chapter 4 In his book Your Inner Fish, Shubin dedicates an entire chapter to the importance of studying the evolution of teeth when figuring the evolution of the human body.In order to study ancient teeth and jaws, however, fossil hunting for tooth fossils is imperative. In chapter 4, Shubin reveals just how difficult this expedition for teeth can be. Discovering bones in rock took experience. The work demanded the naked eye notice the signs of bone in rock. This is a difficult feat. According to Shubin, â€Å"I’d set off looking for fossils, systematically inspecting every rock I saw for a scrap of bone at the surface. At the end of the day†¦. I had nothing, my empty bag a sign of how much I had to learn. (Shubin 63) But even after days walking and looking with an expert fossil finder who gave advice, it took time for Shubin to â€Å"see† the bones in rock. For days he asked questions and looked at the same rocks as the expert who found many and still came back emptyhanded each evening. Then finally, one day he discovered his first piece of bone, and it was only this discovery that made him actually understand what he was looking for. â€Å"The difference was this time I finally saw it, saw the distinction between rock and bone† (Shubin 64-65).After this, it was much easier for Shubin to discover fossilized bones, but still the search is tedious and difficult. Even after a haul of some promising rock during his first self-led expedition, Shubin was not hopeful. To his great surprise, he was hailed as a hero once the fossils were delicately revealed in the rock formation, and it was discovered that he had found a skeleton of a tiny ancient reptile, tritheledont. From the teeth and jaws on this fossil it could be derived that this was a breakthrough for the reptile as there was tooth-on-tooth occlusion.But once again, Shubin learned a greater lesson from this di scovery that happened not in the field but in the lab where the rock had been carefully manipulated to reveal the fossil within. â€Å"†¦I learned that some of the biggest discoveries happen in the hands of fossil preparators, not in the field† (Shubin 70). Fossil preparators are important and perform a very tedious job. In fact, this is one of the reasons fossil hunting is so difficult. Difficult to find, and difficult to prepare for study and viewing. The key point is that the early mammals were small. Very small†¦. If the tooth was covered by a crumb of rock or even by a few grains of sand, you might never see it† (Shubin 66). Thus, it is easy to see how fossil, especially tooth fossil, hunting is extremely difficult. It takes patience and experience and an eye for tiny details. As Shubin reveals, it takes a team of hunters and preparators to discover the most important findings. Without both, evolution would be missing an imperative study, the study of tee th and jaws.

Essay on Canadian National Identity Native Canadians

Native Canadians play an important role in our national identity, unfortunately, the culture has been slowly dying out for the past century as advancing generations lose the spoken language. Less identify themselves as a true Native for the little knowledge they have of their culture, especially those who live in an urbanized city. One of the greatest contributing factors to this outcome were residential schools, a tragic and critical part of Canadian history. The first government operated residential school opened in the late 1870s with the main objective to assimilate all Aboriginal culture. It was thought that by discarding their heritage, it would civilize them to the modern society. By 1920, there were more than fifty residential†¦show more content†¦The environment the kids spent their childhoods in was poor. Diseases spread from the unsanitary conditions and were given improper care. There was a reported case that some school nurses had even gave children different me dication for experimentation. The improper care of these schools dented a high death rate to those attending, all deaths including suicide. In 1960, the minister of Edmonton Residential Schools, James C. Ludford was convicted on charges of sexual abuse raised. He was given suspended from the school for one year to be given psychiatric treatment. Shortly after the year, he returned back to his normal position. Ludford was one of the few caught for unacceptable actions, but the consequences he was given from the Canadian government was not equal the deed that was done. It showed the unfairness hatred and lack of sympathy the government had to offer to the Native peoples at the time. Those who were able to make it out after graduation found a hard sense of belonging in the community. The ones who decided returned home found shame to and from their families because they were taught to be ashamed of their own heritage. Those who eagerly ventured to start their life in the city came to d iscover that they had little knowledge about the civilized world and had no idea how to survive on their own. They were stuck in a category in between both of the societies. This interview with survivor Chief Robert Joseph reveals the damageShow MoreRelatedThe Relationship Between Native Canadians And White Middle Class Population945 Words   |  4 Pagesrole in the growth and development of the given species. More so, it played an even bigger role when talking about the relation between the two ‘Canadian groups,’ natives and white men. Their cultural interaction shifts across the spatial context where people lived, worked and played. 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