Mississippi River Bridge: Engineering Accident - Case Study Example

Mississippi River Bridge Engineering Accident 1. Introduction The Interstate 35W Mississippi River Bridge in Minneapolis was opened to traffic in 1967. It has 14 spans, 1,907 feet long, and carry a daily average of 140,000 vehicles north and south over four lanes between University Avenue and Washington Avenue. It is believed to be the busiest bridge in the US over the Mississippi River. On August 1, 2007, at around 6 in the evening, the 40-year old bridge collapse into the river and its banks without warning, killing 13 and injuring 121 more. At the time of accident, there were about 120 vehicles on the bridge. The impact of the fall broke the span into multiple planes of broken steel and crushed concrete. Cars, buses, and trucks all resting dangerously along guardrails or abruptly unprotected edges, crashed into other vehicles, in part entrenched in the muddy rive bank, or dropped abruptly into the river. Disasters such as this can cause tremendous damage and loss of life. It is therefore necessary to be familiar with the origin and consequences of such disaster so that improvement can be made in the earliest possible time. More importantly, lessons learned can be use to educate other communities of the significant measures that should be taken to avoid such distressing accident. The objective of this report is to analyse what, how, and why such accident happened to the I-35W Mississippi river bridge. The report would also present the consequences or after effects and the lessons learned from such accidents. Finally, it would assess the implications of such accident when it occurs elsewhere. 2. Analysis of the Accident In August 1, 2007, the Interstate Highway 35W Bridge in Minneapolis collapsed into the Mississippi River. The collapse was the worst bridge disaster since the 1967 failure of the Silver Bridge spanning the Ohio River (Gardner and Delony 2008, Afterword). The tragedy highlighted the aging state of such infrastructure. A large portion of the bridge broke apart and plunged 20 meters into the Mississippi River. The strong river current made it difficult for rescue crews searching for victims believed to be trapped in the wreckage. Five people have been confirmed dead and various reports say between eight and thirty people are missing. Hospitals confirmed at least seventy-nine people were injured in the bridge collapse. In addition, the catastrophic collapse of the I-35W bridge across the Mississippi River created a colossal congestion that clearly showed the importance of the Interstate highway system. The presence of hazardous materials at the scene was another concern that had to be deal with. There were several threats, cars and trucks containing fuel were in the river and there was the risk of disease from decaying human remains. Most of the bridge surface and structure, with related contaminants, were submerged (FEMA 2007, p.53). The eight-lane bridge, which passes near the University of Minnesota, near downtown Minneapolis, was the scene of some repair or road maintenance work at the time of the collapse, but there is no indication as to whether that played a role in the disaster. The University of Minnesota School of Engineering inspectors had examine the bridge in 2001 and found no serious problems, although their report does mention signs of fatigue on a steel truss under the roadway (Icon Group International 2008, p.9). In the wake of the sudden collapse of the I-35W bridge in Minneapolis, the US Congressional Research Service reported that of the 600,000 public road bridges listed in the National Bridge Inventory, roughly 12% or 74,000 are classified as structurally deficient (Konigsberg 2008, p.274). Moreover, the bridge was designed without a backup system, so if one member or connection failed, the whole bridge would collapse. According to Astaneh-Asl (2008, p.1), steel deck truss bridges are determinate system and do not have redundancy thus its entire span could collapse if a single primary member or gusset plate connection of the main trusses fails. Edge buckling is one of the major failure modes of gusset plate connections in braced frames as well as in trusses. This failure mode were know from the early days of bridge building using steel riveted trusses, and edge stiffeners often are found in old bridges that are added to edge of gusset plates to prevent the edge buckling. Prior to the collapse, there were construction activities and loads on the I-35W which according to Astaneh-Asl (2008, p.6) consisted of removing the top 5 cm wearing surface concrete as well as cutting about 100cm of the entire deck slab at location of the expansion joints and replacing the expansion joints as well as the removed part of the deck. The construction load on the bridge was ‘extra-ordinarily heavy’ and according to some report the weight of construction materials and equipment on the deck near the gusset plates was approximately 2600Kn. A study of the collapsed bridge further reveal that the I-35W had previous corrosion problems in the main river crossing particularly on some gusset plates and nearby areas resulting to thinning of some gussets and some members over the years. In 1998, an inspection report also revealed numerous fatigue cracks in the approach spans. The cracks were found located in negative moment regions where the diaphragm web stiffener was not welded to the flop flange. Understandably, the bridge was constructed at time when fatigue behaviour of welded members were not fully understands. Consequently, the fatigue-prone developed fatigue cracks that results in fracture of primary member causing the progressive collapse of the entire bridge span due to as mentioned earlier, lack of redundancy and a secondary load path (Astaneh-Asl (2008, p.8). In the official report by the National Transportation Safety Board, the probable cause of the collapse was the inadequate load capacity at the U10 nodes, which failed under a combination of considerably increased in the weight of the bridge due to recent modifications and the traffic and concentrated construction loads on the bridge on the day of the collapse. The design error was reported as the failure of Sverdrup & Parcel quality control procedures since the main truss gusset plate calculation were not properly performed. In addition, the Federal and State transportation officials inadequately reviewed the design and did not give much attention to gusset plates during inspections (National Transportation Safety Board 2007, p.15). 3. Consequences and Lessons Learned for the Accident The Mississippi river bridge carried 140,000 vehicles each day, providing direct access to businesses and north suburban destinations to down Minneapolis. The unexpected collapse of the bridge result to considerable loss of life and injury and considerably affected road-users and the local economy. The Minnesota government paid the victims and everyone on the bridge when the accident happen approximately $38million. Moreover, those who are severely affected would get more compensation such as medical costs and wage losses (Subramanian 2008, p.35). The I-35W Mississippi River bridge accident considerably affected road-users and the local economy. In a study conducted by local authorities in Minnesota, reported that road-user costs due to the absence of the river crossing would total $400,000 daily. Further study reveals that the economic impact or loss in 2007 is approximately $17 million and $43 million in 2008. The economic loss would cost the local community jobs and actual job losses depends greatly on how effectively road-users would mitigate the economic losses and employer reaction to a possible temporary decline in sales (Department of Employment and Economic Development 2008, p.1). Consequently, the Minnesota government had planned to build a 579m, multi-span, replacement bridge that would cost them approximately $300-350 million including financial incentives for accelerating the schedule. The replacement bridge was expected to be built in 437 days and was scheduled to open on December 24, 2008 (Subramanian 2008, p.36). The tragic collapse of the Mississippi river bridge demonstrates the need to make a commitment to invest in maintenance and reconstruction of old infrastructure. This is because as evidence of the collapse emerged, many facilities such as the 40-year old I-35W were stretched to its design limits. One of the lessons learned from the I-35W collapse and the subsequent loss of life is that it is more beneficial to invest on maintenance and replacement of functionally deficient and obsolete bridges. Another is the fact that the existing bridge inspection requirements and standards are weak and should be strengthen to ensure the overall safety of the highway bridges. Approximately 50 percent of bridges in America build before 1964 thus is significant to have reliable information on the safety of these structures. The existing standards for bridges inspection is a routine, visual inspection being done once every two years. They are subjective and varies depending on the professional judgment of individual inspectors thus uniform and consistent processes and standards for inspection is necessary (Oberstar 2008, p.3). Technological disaster can serve as a powerful stimulus for the development and creation of new engineering knowledge. The examination of a failed technology frequently brings to the fore previously unknown, underestimated, or neglected variables concerning the materials and components. While technological failures and disasters have a variety of negative consequences, in some instances the lesson they generate, if heeded, may improve the standards and safety of technological systems. The Mississippi river bridge disaster for instance, generate an understanding that the safety of an old infrastructure should not be taken for granted. It also teaches many of us that investment in maintenance and replacement is much better than spending needlessly on disasters. More importantly, it showed us how an incompetent and inadequate safety inspections or practices could lead to a large-scale disaster. 4. Assessment of the implications if accident happen in Preston The after effects of the disaster are worse than the disaster itself (Qing et. al. 1998, p.34). The complete disruption of all transportation passing through the bridge affects businesses and the economy in various ways. Once an event occurs and society has been disrupted, the impact phase of a disaster has been reached. Disaster impact and intensity may be moving targets, both spatially and temporally variable for individual societies. Normally, the aftermath phase is one of cleanup, relief management, and rehabilitation. The disaster and aftermath stages vary considerably between places and depend on both physical and human factors (Tobin and Montz 1997, p.30). Disasters are related more to socioeconomic components than to magnitude or duration of an event and it not only disrupts society but also may cause a total breakdown in day-to-day functioning. If such disaster happens in Preston, the impact would be quite similar since as explained above, disasters considerably affect the functioning of a community. However, similar to the people of Minnesota and affected area, solidarity will remain strong even in the most trying of circumstances. According to Mileti (1999, p.222), rather than being dazed and in shock, residents of disaster-stricken areas are active and willing to assist one another. Important community residents typically perform response work themselves and volunteer activity increases at the time of disaster impact and remains widespread during the emergency period. The US National Transportation Safety Board report on I-35W reveals that the some of the first to become involved in the rescue effort were citizens who were in or near the area when the collapsed occurred. These people included construction worker, passersby, a group of medical personnel training nearby, students and staff from the University of Minnesota. A bridge collapse in Mississippi or in Preston would have the same after effects as such disaster particularly on rush hours undoubtedly could result to loss of lives, injuries, economic difficulties. Disasters are crises characterized by the breakdown of social and economic order, civil administration, and general security (Clark 2006, p.91). The economic cost of disasters is encouraging more attention to the effective management of natural and technological hazards. In many cases, inhabitants, including investors and businesses of the area, are aware of the potential risk and may have some combination of structural and non-structural mitigation programs in place. Because of previous disasters, the Preston community may be now aware of the impact of such disaster and would adopt safety measures to ensure their well-being. 5. Bibliography Astaneh-Asl. 2008. Progressive Collapse of Steel Truss Bridges, the Case of I-35W Collapse. University of California, Berkeley, US Clark David.2006. The Elgar Companion to Development Studies. Edward Elgar Publishing. UK FEMA. 2007. I-35W Bridge Collapse and Response: Minneapolis, Minnesota. US Fire Administration/Technical Report Series. FEMA. US Gardner Denis P. and DeLony Eric Wood. 2008. Concrete, Stone, and Steel: Minnesota's Historic Bridges. University of Minnesota Press, US Icon Group International. 2008. Minneapolis: Webster’s Quotations, Facts and Phrases. Published by ICON Group International, Inc., US Konigsberg Charles. 2008. America's Priorities: How the U. S. Government Raises and Spends $3000000000000 (Trillion) Per Year. AuthorHouse, US Mileti Dennis S. 1999. Disasters by Design: A Reassessment of Natural Hazards in the United States. National Academies Press, US National Transportation Safety Board. 2007. Collapse of I-35W Highway Bridge, Minneapolis, Minnesota, August 1, 2007- Accident Report. NTSB, US Oberstar James. 2008. H.R.3999, The National Highway Bridge Reconstruction and Inspection Act of 2008. T&I, US Qing Dai, Thibodeau John, and Williams Philip B. 1998. The River Dragon Has Come!: The Three Gorges Dam and the Fate of China's Yangtze River. M.E. Sharpe, US Subramanian N. 2008. Bridge Collapse Averted. The Indian Concrete Journal. ICJ. India The Department of Employment and Economic Development. 2007. Economic Impacts of the I-35W Bridge Collapse. DEED. US Tobin Graham A. and Montz Burrell Elizabeth. 1997. Natural Hazards: Explanation and Integration. Guilford Press. US Read More