Abstract
The Schoharie Creek Bridge was built in 1955 to serve the motorist across the Creek river. Since 1955, there was a designing error on Schoharie Creek Bridge because of cracks in the pier shortly after finishing the construction of the bridge in 1955. The collapse of Schoharie Creek Bridge in 1987 was as a result of error in the engineering design, and one of the major causes of the collapse of the Schoharie Creek Bridge was the excessive impact of the scour on the plinths of the bridge that led to the vertical crack.
The findings of the research reveal the errors in design led to the shallow footing of the bridge, and the dept of the footing was not enough to resist the scour. The paper provides recommendation that there is need for further research on how the bridge could resist the scours for a very long time to prevent engineering disaster. There should be changes in engineering practice in order to enhance the credibility of engineering profession.
Introduction
The major engineering disasters, which range from collapse of building to plane crash have been argued to manifest from error in engineering design. The designed process has caused the classical cases of engineering failures, the engineering designing error can be manifested from any stage, and such error can lead to engineering disaster when the prototype is tested. (Petroski, 1991). Typically, studying of engineering disasters plays huge role in engineering profession. The layman in engineering, who is not aware of the important role the disaster plays in engineering practice may not understand the significant aspect of engineering disaster. (Research paper). Many engineering disasters are caused by error in fundamental design principle that lead technical fault, which inevitably lead to disaster. (Hales, Gooch, 2004).
The purpose of this paper is to provide an informative research on the collapse of the Schoharie Creek Bridge.
The next section gains insight into the general background of the collapse of the Schoharie Creek Bridge, how the incidents is related to engineering disaster.
Background
The Schoharie Creek Bridge is located in Amsterdam serving motorist for more than three decades when the catastrophe occurred in April 5, 1987. The catastrophe was the collapse of the Schoharie Creek Bridge, which led the accident of five vehicles and death of ten people occupying the vehicles. The bridge was structurally designed to resist hydraulic forces, as well as carrying traffic loads and weight. However, with the method the Schoharie Creek Bridge was designed, its construction altered the flow of the river that lead to deposition and erosion on the bridge. (Storey, Delatte, 2003).
The conclusion of National Transportation Safety Board was that the bridge footing relatively had shallow foundation because the footing was vulnerable to sour. The collapse of Schoharie Creek Bridge was the typical example of engineering disaster. (Mueser Rutledge Consulting Engineers).
The Schoharie Creek Bridge was among the several bridges constructed by the New York State Thruway Authority (NYSTA) to serve superhighway across the State of New York in 1950. The Schoharie Creek Bridge was 165 meter (540-foot) in length purposely designed for motorists to cross Schoharie Creek. The nominal length of the Schoharie Creek Bridge was 30.5, 33.5, 36.6, 33.5, and 30.5 meters (100, 110, 120, 110 and 100 feet). Each ends; the concrete pier frames supported the spans of the bridge spans along its abutments. Storey, Delatte, 2003). (See fig 1 for the detail illustration of the Schoharie Creek Bridge)
The skeleton of the bridge was steel stringers with 200 mm (eight-inch), however the super structure consists of longitudinal main girders, which contains transverse floor beams. (Storey, Delatte, 2003).
Thus, reason for the breakdown of the Schoharie Creek Bridge in April 5, 1987 is discussed in the next section.
Investigation
The history of the collapse of Schoharie Creek Bridge started from 1955, shortly after the construction of the bridge, when the bridge was opened to be used by the motorists. However, it was not long after the Schoharie Creek Bridge was opened to be used by the motorists, the pier plinths of the bridge started to show some vertical cracks. The width of the crack ranged from 3 to 5 mm (1/8 to 3/16 inches).
Typically, the reason for the crack was as a result of high tensile stresses that occurred at the concrete plinth. It was also found out that it is difficult for the plinth to resist the bending stresses between the two columns in the concrete plinth, and the problem had contributed to brittle of the plinth. Typically, other technical problems occurred after the completion of the bridge. For example, it occurred the road drainage of the bridge was poor. Moreover, the expansion bearing of the bridge was noticed to be out-of-plumb. In addition, in the west embankment, there were sufficient supporting materials of the dry stone pavement. All these overall problems since 1955 contributed to the collapse of the Schoharie Creek Bridge in 1987. (Storey, Delatte, 2003).
According to Swenson, Ingraffea (1990), “The primary cause of failure was scour beneath a plain concrete pier footing. However, a necessary secondary cause was unstable propagation of a single crack in the pier. Conditions for initiation of the curvilinear crack are first evaluated. It is concluded that about 28 feet of scour had to occur to initiate stable process zone formation at the point of initiation, but that at least 44 feet was required to cause unstable cracking.” (p. 1)
It should be noted that the cracks occurred because of the tensile stresses and the result led the plinth not to be able to resist bending stresses between the two columns of the bridge.
The spring flood also contributed to the collapse of the bridge because the pier of the bridge had become weak. The rainfall that led to the collapse was around 150 mm (6 inches). Typically, the collapse occurred when there was toppling of pier in the bridge, which resulted in the collapse of span 3 and span 4. (Storey, Delatte, 2003).
It should be noted the excessive scour of the pier 3 was the major contribution to the collapse. Scour is an excessive removal of sediment, which was because of excessive action of erosion. (Storey, Delatte, 2003).
The overall findings of the collapse of the Schoharie Creek Bridge are discussed in the next section.
Findings and Recommendations
The outcome of the investigation of the collapse of the Schoharie Creek Bridge reveals that it was typical example of engineering disaster. The paper reveals that the collapse of the bridge was as result of the lapses in the engineering design of the bridge. For example, shortly after the bridge was ready for use by the motorists, it was revealed that there was an engineering design error in the bridge. Part of design error was the shallow footing of the bridge, and the dept of the footing was not enough make the wall of the bridge to resist the scour. Typically, the important factor for the collapse of the bridge was the vulnerability of the scour… (Storey, Delatte, 2003).
It should be noted that the pier 3 of the bridge was not strong enough; it was also installed at the bearing of the soil prone to erosion. Typically, since 1955, the velocity of the flood was calculated and an estimated at velocity of 4.6 meters per second (15 fps) while the estimated flow was calculated at 2.17 million liters per second (76,500 cfs). Thus, the Schoharie Creek Bridge was designed top resist the velocity and flow of the flood at that time.
However, after the construction of the bridge in 1955, it is revealed that “the flood was greater than that anticipated by the designers, and followed the 1955 flood and others that had disturbed the riprap. A curve in the river upstream of the bridge directed a higher-velocity flow toward pier 3. Drift material caught against the piers directed water downward at the base of pier 3. Berms built in 1963 directed floodwaters under the bridge. An embankment west of the creek channel increased flood velocities.” (ASCE Forensics Congress, 2003).
Thus, the scours removed the materials from the bridge through three mechanisms.
First, there had been long-term degradation of the channel bottom of the bridge, and the resulted to the gradual elevation of soil cavity that occurred through the deposition and erosion of riverbed, and the consequence was the shallow of the riverbed. The result of this led to the degradation of the bridge. For example, the process of erosion through natural process has narrowed the pier construction and this resulted to the low resistant of the bridge. For instance, this equation illustrates that Q= Av (the v = velocity, A = cross-sectional area, Q= flow rate). (ASCE Forensics Congress, 2003).
According to National Transportation Safety Board, the magnitude of water velocity was very high that it could move a given rock. Thus, the turbulence of the velocity moving around pile 2 and 3 was very high to the extent that it could remove 300-pound riprap. In addition, the turbulence and velocity of the water were larger than what pier 3 and pier 2 could resist. (National Transportation Safety Board, 1988).
Thus, from the result of the findings, the paper provides the following recommendations.
Recommendations
The evidence has revealed that scours were the major caused of the collapse of the Schoharie Creek Bridge. Typically, there were several methods that the collapse could have been prevented. The insurgence of scour could have been prevented by pier. In addition, the scour could also be prevented by riprap, which could be done by supporting piers with piles. It should be noted that hydraulic force occurs during power flood, and the velocity of the powerful flood can lead to the increase in the damage done by the scour.
It should be noted that at the time of construction of the bridge, the quantity piles estimated by the design engineer for the pile protection was not enough. (ASCE Forensics Congress, 2003).
Essentially, the bridge should be designed for geotechnical, and structural effects hydraulic, which should be able to support strength. There should be change in the engineering practice. It should be noted “that 494 bridges failed during the years 1951 and 1988 as a result of hydraulic conditions, primarily due to scouring” (ASCE Forensics Congress, 2003).
Typically, the current engineering practice revealed the tools used in building the bridge, there is not adequate prediction of scour. (ASCE Forensics Congress, 2003).
There is need for further research on the failure of the entire bridge system. The research should be made at microscopic level to examine the failure of the materials being used for the construction of the bridge. (Lee, Sternberg, 2008).
Although, with the collapse of the Schoharie Creek Bridge, several advances have been made to improve the engineering practice.
Impact on Engineering Practices
The collapse of Schoharie Creek Bridge has revealed that engineering practice has not fully developed. Essentially, the competent professional engineer should be able to provide the expiring date after a certain bridge should not be able to serve the purpose that has been designed for. The collapse of the Schoharie Creek Bridge revealed that there is need for further engineering research on many aspect of construction engineering.
The research aspect should be able to enhance greater understanding of some many aspects of designing of bridge. Further research is needed on the on the hydraulic aspect of the bridge construction, corrosion, impact of scours on the bridge construction. Thus, designing engineer needs to learn, from the past mistakes. The expertise in designing of bridge is highly needed. The design engineers ought to ensure that mistakes that lead to collapse of the bridge. (Lee, 2008).
Evidence has revealed the causes of most of the bridges’ catastrophic can be traced to the factors outside the structure of the bridge. For example, the surging of river current, earthquake acceleration, trucks carrying more weight than what the bridge could resist for a long time. The effects of this in engineering practice are that the whole system of engineering practice should be changed or amended. For example, the design engineers should aware that designing the bridge is for a long time and not for few years. Thus, the system of issuing licence to the engineers should be amended. There should be strict regulation to follow before licence is being issued to an individual to practice engineering. (Lee, 2008).
Conclusion
The paper investigates the collapse of the Schoharie Creek Bridge, which occurred in 1987. The paper finds out that the causes of collapse of the bridge have been articulated with the designing error of the bridge. It should be noted shortly after the finishing the construction of the bridge in 1955, there had been noticeable error in the engineering design of the bridge. Typically, the pier 2 and 3 of the bridge was not strong enough to resist the erosion which contributed to the weaken of the bridge. The paper also reveals that the major factor that contributed to the collapse of the Schoharie Creek Bridge was the scours that occurred due to the constant erosion from the flow and velocity of the water.
Thus, the paper recommends that there is need for further research on the improvement on the engineering practice in order to avert the future collapse of the bridge.
This paper enhances greater understanding of the civil engineers, construction engineers, government, private organization, and academic communities.
Reference list
ASCE Forensics Congress, (2003). The Collapse of the Schoharie Creek Bridge, Summarized from Storey and Delatte, Lessons from the Collapse of the Schoharie Creek Bridge. Web.
Hales, C. Gooch, S. (2004). Managing engineering design, London, Springer: London.
Lee, G.C. Sternberg, E. (2008). A New System for Preventing Bridge Collapses, Issues Online in Science and Technology. Web.
Mueser RutledgeConsulting Engineers.(n.d.). Schoharie Creek Bridge Collapse. Web.
National Transportation Safety Board, (1988). In reply refer t o : H-88-16 through -20, National Transportation Safety Board Recommendation, Washington DC.
Petroski, H. (1991). Paconius and the pedestal for Apollo: A case study of error in conceptual design, Research in Engineering Design, 3(2), 123-128.
Research paper. (n.d.). Content andFormat, Retrieved October 21, 2009, from Engineering_disasters_research_papers_lecture.pdf 151.
Storey, C. Delatte, N.(2003). Lessons from the Collapse of the Schoharie Creek Bridge. Web.
Swenson, D.V. Ingraffea, A. R. (1990). The collapse of the Schoharie Creek Bridge: a case study in concrete fracture mechanics, International Journal of Fracture, 15(1): 73-92.