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Errors in the Construction of Bridges
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Errors in the Construction of Bridges
Introduction
The relationship between failure and success makes up one of the most fascinating engineering paradox. Once engineers accumulate a number of successful experiences, they are emboldened to attempt even more ambitious and intrepid projects, which usually seem to end up in colossal failures that take up everyone by surprise. However, there seems to be a general renewed spirit that is now leading to robust and untested design notions. This has ironically proved to be extremely successful because the design mechanism takes little for granted. However, this cautiousness is at times forgotten following a period of self-confidence and optimism. A number of these errors in designing bridges occurred as a result of decreasing safety factors, increasing length span, increasing analysis confidence and increasing slenderness (Petrosky 166).
The Tacoma, the Dee, Quebec, and Tay narrow bridges errors occurred about three decades apart. In spite of whether this was by coincidence or not, the inherent pattern indicates that there is likely to be a fundamental bridge error in the future. Trusted girders were the error that caused the Dee bridge failure, but later, iron trusses replaced them. However, after they failed in the Tay accident, the cantilever design was employed in rail road bridges until it failed in the Quebec Bridge.
Discussion of How These Errors Can Be Avoided In Future Work
By comprehending how omissions and errors led to past failures while building bridges, engineers are likely to come up with a model for the vital evaluation of the current practice. Such an evaluation by itself could offer self-correction to the designing procedure in order to avert any more failures or at least reduce them. Engineers attempting new designs will therefore have to reason using the first principles and ensure that they take care of all possible errors. Only after a bridge has been standardized can engineers stop anticipating any errors (Petrosky 168).
An illustration of how this engineering case directly affected society
Owing to these errors, engineers began developing longer bridges and the reason behind it was that this defined the eminence by which an engineer was measured. The history of long bridges was inherent in the type of materials used and these new materials took about three to four decades to be accepted by engineers (Petrosky 170).
As new types of structures and materials became embedded into practice, a desire for more economical and ambitious designs seemed invariable. Economic objectives were achieved by decreasing safety factors. However, people in the society felt that in the face of these errors, engineers should not contemplate on how they can reduce safe margins for the bridges strengths and loads, but they should contemplate on how they could increase safe margins for corrosion and wear. This was particularly so for structures whose designers intended that they should last for more than a century (Petrosky 171).
Cable stayed bridges are the most recent types of bridges being developed by engineers and are becoming strong competitors for the long span designs. Even though they have been labeled as being exotic, cable stayed designs have the unique advantage of permitting construction without a lot of false work while sustaining a small roadway profile. Few cable-stayed bridges were still being used in the USA in the 1990s while contractors and engineers maintained their unwillingness to build more of such bridges. Engineers were scared because they could not build them from a set of their plans (Petrosky 171).
Despite this argument on structural types, it was perceived that while engineers demanded to have a proof of more than 10 decades of strong cable stayed bridges in service, the competing goals of longer life and fewer highly stressed cables were out rightly at odds. This is because an increase in a cable’s diameter results into a proportional increase in its fatigue strength. However, engineers perceived that the engineering design employed in designing cable stayed bridges exceeded the one required for more standard bridges. Amongst the analysis, complications is the structural combination that should be put into consideration to allow for missing cables brought about by fatigue failures or replacement. According to O’Neil, one bridge designer has defined the prospect of evaluating all feasible structural combinations as frightening (Petrosky 172).
As long as the cable bridges maintained their exotic forms, it was expected that its designers and engineers would treat it and its feasible modes of failure cautiously while employing large safety factors. The Firth of Forth Bridge demonstrated that an increase in maximum span length is not an effective way to curtail disaster. Its spans, which were completed in 1890, represent a full doubling of the optimum span known by then. The Quebec Bridge that collapsed in 1907 while still under construction represented a lighter span of almost the same magnitude that represented a 50% leap above modern practicing limits. The immensely successful Han River Bridge in Korea collapsed while still under construction. Nonetheless, this accident occurred before the stressing of any cables and was therefore ascribed to the poor quality of the concrete that was used in the construction.
Another case in point is the Australia’s West Gate bridge, which collapsed two years into construction in 1970 killing 35 constructors on site. The bridge collapsed as a result of structural failure. This occurred when the engineers discovered a difference of 14 cm in two of its girders that required joining. Ten concrete blocks each with a weight of eight tonnes were to weigh down the first girder. The span buckled due to overweight and the engineer was found to have erred in structuring the Bridge (Lay 23).
Designers have not been paying attention to the causes of these failures yet they have occurred over time in history. At the present rate of their development, the niche of cable bridges could result into an ultimate failure. The long span cable bridges are expected to be common. Pioneers of these bridges are no longer influential in designing its forms and with gains in successful bridges lasting for decades and supporting their technology, new cable span designers are expected to move towards more daring, lighter, more economical, and slenderer spans. Despite this, failure is not inevitable (Petrosky 176).
The cable designed form is therefore likely to continue with its three decades pattern but there are several factors that do not support a total failure of these designs. Paradoxically, if engineers follow the strong patterns pointed out by critics of this design, the pattern of failure witnessed in the last century is likely to be broken. As engineers learn from the past and through their cycle of successes and failures, they are likely to get rid of the complacency and overconfidence pitfalls in order to carry out their work with renewed attention to detail (Petrosky 176).
Works Cited
Lay .M.G. and Daley K.F. The Melbourne City Link Project: Transport Policy (2012): 23-24. Print.
Petrosky, Henry. Design in a human context: Research in engineering design (1992): 166-176
Erikssons Stages of Development
Human Development is a complex and gradual process. It is a process that takes into consideration the external world as well as the physical and mental aspects of the human person. In essence as humans develop from childhood to adulthood, these ‘worlds’ come into play and contribute greatly in determining their tapping into full potentials (Tudge 63). Eriksson’s and Piaget’s works on the stages of development have acted as eye openers in different fields that focus on human development, education being one of them. Brief discussions of these developmental stages, narrowing down to a specific stage and relating it with education applicability are the main focal points of this document.
Eriksson’s Stages of Development
To start with, Erik Eriksson was greatly influenced by Sigmund Freud who explores human development using the id, the ego and superego concepts in his work. Eriksson however differs with Freud and expresses that the ego exists from childbirth and that human behavior is not totally defensive. According to him, development incorporates body interactions that is, genetic biological functioning; the mind which is majorly psychological and; cultural influences (Bliss 25).
Eriksson organized the stages of development into eight extending from birth to death which is a unique classification as other theorists mostly focus only on childhood. His main premises are that the world enlarges both in size and complexity as one goes along and that failure accumulates over time. These stages are divided into infancy, early childhood, play age, school age, adolescence, young adulthood, middle adulthood and late adulthood (Bliss 75).
At infancy, also known as the Oral Sensory Stage, emphasis is on visual contact and touch as well as the mother’s positive and loving care. Trust is built at this stage where one develops confidence in the future or mistrust in cases where frustration is eminent which further culminates into suicidal incidences. Drive and hope are the basic strengths in this stage (Tudge 48). The significant relationship is with the maternal parent or constant care giver. Early childhood then follows, a period ranging from 18 months to 3 years where one masters skills such as walking, talking and feeding. Self esteem and self autonomy which determine self control, courage and will, are developed to a large extent at this stage. Doubt and shame as well as low self esteem are also evident and parents form the main significant relationships in this stage (Tudge 92).
The play age, 3 to 5 years takes over from early childhood and initiative or guilt as ego outcomes are a common scenario at this stage. One takes initiative of creating playing environments through copying adult activities such as driving or playing out roles. Guilt develops in the case where oedipal struggle fails to be resolved through social role identification. The basic family is the main significant relationship. The school age of 6 to 12 years incorporates industry and inferiority through the discovery of new skills that further influence method and competency. The significant relationship enlarges to the school and neighborhood (Bliss 58).
At the adolescent stage of 12 to 18 years, devotion and fidelity become the main strengths. This is driven by ego identity to fit in as well as attempting to discover one’s appearance to others. Role confusion steps in where this is not achieved positively. Intimacy and solidarity are the positive outcomes of young adulthood, a stage ranging from 18 to 35 years with love and affiliation being the basic strengths as individuals seek mutual relationships and start families. Isolation occurs as a defense mechanism where intimacy is at a distant. Furthermore, friends and partners are the significant relations.
As Barnett 128 explains, middle and late adulthood are concerned with generativity and integrity respectively as positive ego outcomes, which culminate further into production care and wisdom as significant relationship broaden into the larger world of workplace, community and mankind.
Piaget’s Stages of Development
The classification stages of development by Piaget are categorized into four that is, Sensorimotor, Preoperational, Concrete operations and Formal operations. First of all, the sensorimotor stage covers the period from birth to 2 years where the infant interacts with the environment to build a basic understanding of him or herself and reality. This understanding takes the form of assimilation, where information is organized and absorbed into existing representation, and accommodation, whereby if an object cannot be assimilated, the scheme is modified to include the object. The sensory and motor systems are the main drivers in this developmental stage for purposes of discovery and coordination (Tudge 46).
The preoperational stage captures the ages from 2 to 4 years where the child is unable to conceptualize abstractly and therefore physical situations are included in the conceptualization process. Important features are then used to classify objects. The child at this stage is unable to differentiate similar objects and sees them as identical. In addition, egocentrism and self centeredness are a common occurrence at this stage. From 7 to 11 years which is the Concrete operations stage, accommodation increases with the accumulation of physical experiences. Here, physical experiences are explained through the creation of logical structures that are easily conceptualized (Tudge 52).
At the last stage of Formal operations, one is able to make rational judgments without the use of concrete objects as their thinking is similar to adults hence capable of hypothetical and deductive reasoning. This age stems from 11 to 15 years (Gannon 13).
The Formal Operational Stage and its relationship to education
From Piaget’s Cognitive Development, the formal operational stage develops from around 11years old where one is able to consider a variety of combinations in relation to the whole problem and reason out from a hypothetical perspective (Barnett 34). The main characteristics at this stage involve abstract thinking; idealistic thinking where one is able to think of practical mechanisms to come up with solutions and; logical thinking where they can deduce plans to solve problems and systematically test the availed solutions, also known as hypothetical- deductive reasoning. This stage is fundamental in education in various ways.
As students are able to think from diverse perspective, Barnett 38 discloses that, the function of the teacher would be to facilitate each student’s way of perceiving, understanding and constructing new knowledge through scaffolding to help them transform. At this stage also it is important to note that, qualitative approach in education is promoted whereby, students are able to utilize both extensively and intensively their intellectual and mental capacities to actively develop and construct meaning and their own personal understanding of what is being learnt.
Practical approaches are embedded in educational curricula to capture the hypothesis- deductive reasoning of students at this age range. Such include the use of science laboratories where students are able to deduce conclusive visible facts from practical applications. Their problem solving skills are also evident in the complex mathematical questions tackled at their level of education (Gannon 74).
In addition, the education system provides a wide array of choices for students. Several subjects are taught to students and they are then allowed to make choices of subjects they deem fit to undertake. At this level, students are able to make choices based on personal research and their confidence and attitudes towards the available options.
Furthermore, students originate from different backgrounds with different perceptions towards life’s opportunities and misgivings as well as to others. At this stage, individuals are caught with the need to find a sense of identity and belonging which would adequately be covered by the neutrality of the education systems as well promote personality development through leadership which is essentially covered in education (Gannon 128).
As a teacher therefore, I would promote group work activities where students get an opportunity to interact with one another and therefore obtain a sense of belonging and identity with the rest of the group hence a student is able to find their niche.
Secondly, with emphasis from Barnett’s perspective I would encourage an interactive process with the students whereby I would ask questions, let them brainstorm and work out solutions then evaluate these solutions and correct where they have gone wrong (40).
Thirdly, I would take into account the quiet students and give them an opportunity to express themselves either through answering questions, acting as leaders of their groups or asking questions.
Fourthly, in order to ensure full participation and collective responsibility, I would ensure the thumb rule of not leaving the classroom unless students ask questions.
Lastly, I would promote the use of practical application based on different topics to ensure that students utilize their deductive thinking for example through laboratory experiences (Gannon 130).
Works Cited
Barnett, Kevin. Supercomplexity Teaching. Oxford: Oxford UP, 2002.
Bliss, John and Grace,Osborn. Stages of Human Development: theorists’ views. London: Routledge, 2005.
Gannon, Lewis. Effective Training for Teachers. New York: Sage, 1996.
Tudge, David. A Child’s Moral Reasoning. New York: Plume, 1999.