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
