Failure of Minnesotas I-35W Bridge and Assets Managements Systems - Case Study Example

Failure of Minnesota’s I-35W Bridge Student’s Name Institutional Affiliation Failure of Minnesota’s I-35W Bridge I-35W Bridge for Mississippi River offered direct access to Minneapolis downtown, area business, University of Minnesota and the suburban destinations in North for at least 140,000 vehicles every day. The collapse of Minnesota’s I-35W bridge is one of the tragic incidences witnessed in the history of United States. It led to huge loss in terms of human lives, financial and resources. The paper discusses the occurrence of the collapse, its effects as well as the environmental factors that might have led to the incident. It also examines the investigation carried out after the event and the finding. Finally, the report highlights some of the assets managements systems that could have mitigated the incidents and future occurrence of the same. Incident Occurrence The collapse occurred on a day when roadway work was in progress on I-35W Bridge, and a half of the bridge was closed to traffic covering four of the eight lanes (Levinson, 2006). Early in the afternoon, construction aggregates such as gravel and sand and construction equipment had been brought and placed in the two closed inner southbound lanes. Some of the construction materials which were to be used from around 7.00 p.m. had been positioned appropriately by 2:30 p.m. However, at an about 6:05 pm a collapse occurred as recorded by a motion-activated video camera. According to the video camera, the bridge center span separated and fell into the river from the rest of the bridge (Bureau of Public Roads, 1964). According to National Transportation Safety Board, the collapse was as a result of inadequate load capacity caused by design error by the contractor company Sverdu & Parcel. The collapse of the bridge caused significant losses concerning safety and financial. Moreover, it caused conveniences, especially the large population Minneapolis. According to Minnesota Department of Transportation, the cost incurred by road users caused by unavailability of the river crossing was approximate $400,000 every day (Levinson, 2006). Moreover, further study’s conducted by DEED and Mn/DOT provided an economic impact estimate at approximately $17 million and $43 million in 2007 and 2008 respectively. The analysis carried out by Mn/DOT focused on valuing how the road users were affected by the unavailability of the river crossing and assigned them corresponding monetary value to commercial truck travel time, auto travel time and variable operating cost. The economic approach used by Mn/DOT focused on economic factors affecting Minnesota directly. However, the study did not include auto travel time because non-business travel by personal vehicles does not contribute to the economy (Metropolitan Council, 2003). Additionally, there is some road-user cost that may not be considered as offsetting since they could have been spent in the state on other goods and services. Some of the impacts experienced by road users resulted from transportation detours they had to take due to unavailability of the road. The researchers collected data from numerous sources and analyzed using Policy Insight econometric model. The model helped analyze cost effect due to the detours as well as access to goods and services. Also considered in the model was how the cost of the economy could be prevented by commuters and business strategies. Transportation Cost Alternative routes had been identified to serve the 140,000 vehicles inconvenienced by the collapse including about 5,000 heavy truck that used the bridge each day. According to the transportation department, an approximate cost of road user as a result of the detours was estimated at $400,000 every day (Metropolitan Council, 2003). The research team assigned a monetary value to the detours provided to auto travel time and commercial truck travel time at $247,000 and $15,000 daily and the variable operating costs resulting from increased travel distance. The study team asserted that a loss of $247,000 of auto travel per day was huge for individuals but, it did not have a great impact on the general economy. However, another cost such as those resulting from longer road-time experienced by commercial truck impacted greatly on the economy. Moreover, higher operating cost among the affected populations using the roads resulting collapse had a significant effect on the economy. Nonetheless, part of this money would be spent in the state without traveling. Net Economic Impact The transportation department estimated the daily economic net impact at an average of $113,000 as a reduction in the economic output of the state or a total of $17 million and $43 million for 2007 and 2008 respectively. The study team also stated that the effects constituted about 0.01% of the overall state economy and were found to be concentrated mostly in the Twin cities from which a large population used the roads. Moreover, the department noted that the economic loss let to great unemployment across the economy (Minnesota Department of Transportation, 2007). Actual job losses were, however, based on how effectively the economic losses were prevented as well as the reaction of the employer to a temporary reduction of sales. For example, some of the people who lose their jobs included the drivers of the heavy commercial truck. Although detours were provided, the cost of detour roads was much higher for some truck businesses and had to take a break to re-strategize. A break in business means no operations, and hence, jobs are at a standstill. For workers who were compensated on an hourly basis, this meant mean lack of income. Moreover, there were businesses located along the roads offering goods and services to road-users. Thus, the collapse affected them as well resulting in reduced sales and some even closed down since there were no customers. Safety Impacts Despite the fact that a few vehicles were submerged, some people were stuck on a section of the bridge that collapsed. Many vehicles that were involved in the rubble caught fire such as the semi-trailer truck whose driver got burnt and was pulled out later. A school bus which was returning children from a field trip was also trapped and rested against a guardrail of the structure next to the burning truck. Most children occupying the bus were assisted by a staff member who kicked out the emergency door and escorted them to safety. It is, however, noted that a youth worker was injured during the collapse (Minnesota Department of Transportation, 2007). About thirteen people lost their lives from the ordeal, as 50 victims were routed to the area hospitals by triage centers while some were transported in trucks due to short supply of ambulances. Some injured individuals had blunt trauma injuries. The injured who were close to the south end were rushed to Hennepin County Medical Center (HCMC) while those close to north end were taken to Fairview University Medical Center. About 22 children were injured from which 13 were treated at Minnesota’s Children’s Hospitals and Clinics, five at HCMC and four at North Memorial Medical Center. Besides the injured, many victims were missing as on August 5, 2007, when some individuals held an interfaith service which included Islamic, Christians, Jewish, Hindu, police, musicians, Hispanic communities, the governor and mayor to show solidarity. There were several hundred people consisting of the deceased families, survivors, as well as the first responders who were directly affected by the collapse but, did not have disaster insurance of United States. As noted by the president of Minneapolis Foundation, Sandy Vargas, the disaster fund which had been produced was not enough to cover all the uninsured medical cost, He added that the fund was only able to make a mild gesture of acknowledgment (Minnesota Department of Transportation, 2005). Although a 1 million plan for the victims was announced, it was limited by the state laws of an amount below that. The administrator thus required an approval on claims from Joint House-Senate Subcommittee as bipartisan support, which on receipt, a $38 million agreement was made to compensate the victims especially those without the disaster insurance cover. Post-Failure Investigation After the failure of the general public was perplexed by the instantaneous collapse and hence arose a lot of questions which required immediate answers. Most people including the media demanded answers at to what might have been the cause of the failure. Some of the answers to such questions were proposed by structural engineering experts who attributed the failure to the growth microscopic length which grew undetected to catastrophic stages (Minnesota Department of Transportation, 2005). They suggested that the reduction in the strength of the steel components produced environmentally-caused corrosion, and settlement of piers which transferred bridge weight to the ground were major causes. The first people to be blamed for the tragedy were the engineers that conducted a repair construction up to the time of failure. The argument is understandable since there were hundreds of tons of water trucks and gravel used for repair were positioned in the main span. However, the event was catastrophic that could not be solved by mere speculation but needed an in-depth investigation to understand the cause and mitigate future occurrence. The four lanes of Traffic Bridge were 1,907 feet long supported with thirteen piers with fourteen spans. The central portion of the bridge which was 1,064 foot long crossed Mississippi River and composed of trusses of parallel Warren type. Every major truss was made of 56 connection points where the riveted gusset plates were joined (Minnesota Department of Transportation, 2005). The post-failure investigation was conducted by NTSB to find out the causes of failure. As part of the investigation, NTSB analyzed the photos taken in 1999 and 2003 during the working life of the bridge. From the photographs the investigation team observed that there was an out-of-plane displacement. Moreover, the displacement occurred on the line of the gusset plate thickness. The FHWA then performed an assessment of the adequacy of the gusset plate failure by applying the same methodologies used during the design of the bridge. They observed that U10 and L11 nodes’ gusset plates did not meet the required thickness. The NTSB thus concluded that inadequacy of gusset plate was a design error caused by the original design company. They asserted that the company failed to perform necessary calculations for the proper design of the gusset plate. The investigation team collected post-collapse forensic evidence from the final deformed shape of the failed truss which showed that U10 node could have been the beginning of the collapse. However, the team considered the node L11 as an alternative cause of the collapse that needed to be investigated. A finite element analysis method was used to investigate the strain and stress in the gusset plate at the joints of L11W and U10W to determine the potential instability in the structure. The investigation was performed by embedding three-dimensional models of U10W and L11W joints to the bridge model. The models provided by FHWA were made according to the original design of the bridge plans. To improve its accuracy, the model was also created to reflect the several modification the bridge had undergone. The team measured properties of the materials of undamaged portions recovered from the wreckage. A loading history was used in numerous steps to simulate the actual bridge design weight, traffic loads, additional concrete weight, and construction loads. Concentrated loads were used to simulate wet concrete to represent weight before failure. Moreover, shell elements were used to represent hardness and stiffness of concrete. They then joined local global models using tie kinematic and constraints (Davis, 2002). The unstable bending movement of gusset plate was examined using risk analysis approach. Through the use displacement methods, loads were solved concurrently using arc length formulation. This helped offer insight into the behavior of gusset plate near collapse. The findings of the investigation revealed that the highest value failure happened in the gusset plate. Moreover, the risk method predicted that the load had to decrease to maintain equilibrium, the analysis could not exceed this point since the structure was softening. In conclusion, the team applied Abaqus/Standard to examine the unstable behavior of the bridge. Through the use of numerous nonlinear modeling capabilities, the evaluation predicted that the failure resulted from a bending instability in gusset plates at U10W node. Suggestions for Asset Management Asset management is important as it helps ensure the long-term sustainability of structures or assets. It helps utility manager in proper decision making on various activities such as rehabilitation, repair, and replacement of particular assets. Additionally, by creating a long-term funding strategy, stability of the asset can be ensured to deliver the expected level of service (Davis, 2002). The most crucial questions an asset manager should address for proper management of asset are: what do I own? Where is the asset? What condition is it? What are the assets remaining useful life, and what is the assets value? The asset manager needs to understand the assets regarding its capability and size. There is a need for state government to understand the complete asset inventory. However, there are some difficulties especially in accessing full asset inventory such as inaccurate or missing information (Tribune, 2016). Therefore, it may not be possible to develop a complete asset inventory. Numerous methods can be used to determine asset inventory. First, it is important to identify the firm responsible for operation and management of the structure during its original design, interviewing the population served by the assets, and examining other engineering and design factors. Another way of ensuring appropriate maintenance of the asset is to continuously assess the condition of the assets for repair. The management team can use a condition ranking approach to rate performance of the asset. The information can then be used for planning and decision making to make appropriate adjustments as a way of mitigating future failures. References Bureau of Public Roads, (1964). Traffic assignment manual. Washington, DC: US Department of Commerce, Urban Planning Division. Davis, G. and Sanderson, K., (2002). Building our way out of congestion? Highway capacity for the twin cities. Minneapolis, MN: Minnesota Department of Transportation, TechnicalReport, Mn/DOT 2002-01. Kaszuba, M. and Foti, J., (2007). Wednesday: Colorado firm wins I-35W bridge contract. Star Tribune, 20 September. Available from: http://www.startribune.com/local/11594166.html Accessed 30 April 2016. Laurent, F.M., (1995). Contributions to logit assignment model. Transportation Research Record. Levinson, D., de Oca, N.M., and Xie, F., (2006). Beyond business as usual: ensuring the network we want is the network we get. Minneapolis, MN: Minnesota Department of Transportation,Technical Report, Mn/DOT 2006-36 [online]. Available from: http://nexus.umn.edu/Projects/BBAU/BBAU-Final.pdf Accessed 30 April 2016. Levinson, D., Xie, F., and de Oca, N.M.,( 2009). Forecasting and evaluating network growth. Networks and Spatial Economics [online]. Available from: http://nexus.umn.edu/Papers/FENG.pdf Accessed 30 April 2016.. Metropolitan Council, (2003). 2000 travel behavior inventory: home interview survey data and methodology, Technical Report. Minneapolis, MN: Metropolitan Council. Available from: http://www.metrocouncil.org/planning/transportation/TBI_2000.htm Accessed 30 April 2016. Minnesota Department of Transportation, 2005. Benefit-cost analysis for transportation projects. Technical report. Minneapolis, MN: Office of Investment Management. Available from: http://www.dot.state.mn.us/planning/program/benefitcost.html Accessed: 30 April 2016. Minnesota Department of Transportation, (2007). Road-user cost due to unavailability of Interstate 35 W Mississippi river crossing at Minneapolis, Minnesota, Technical report. Read More