I-35W Bridge Research Articles

Route Choice Set Generation on High-Resolution Networks

This study seeks to find a strategy to capture the most observed trajectories with a minimum number of algorithms. GPS information on 4,538 real trips from 131 travelers in 2008 was collected and analyzed in Minneapolis-St. Paul (the Twin Cities) as part of the I-35W Bridge Collapse study. The high-resolution road network of the Twin Cities includes 108,561 nodes and 277,747 links. Labeling and link penalty approaches are combined to generate alternatives based on either observed or free-flow speed. Overall, with the best 10 labels, on average, 40 unique routes are generated for each origin-destination pair, and around 80% of all observed trips could be captured with an 80% overlap threshold. About 88% of all observed trips have an average deviation within 50 m compared with the best matching result when combining all labels introduced in this study. Freeway-preferred routes cover more observed trips than freeway-avoided routes, and the peak coverage occurs when freeway travel is weighted between 0.8 to 1 of travel on non-freeway links. A random effects panel model is used for predicting the overlap between alternative route and observed trajectory. Multinomial and mixed logit models with a path-size term are applied to model the route selection. These models indicate that alternative routes which are shorter in distance, have faster average free-flow speed, contain a higher freeway percentage, and incur fewer traffic lights, are more likely to have higher overlap with observed trajectories and are more likely to be selected.

Assessment of Provisions for Load Rating Gusset Plates in Steel Truss Bridges

Many states have load rated their truss bridge gusset plates following the guidelines published in 2009 by the Federal Highway Administration in response to the catastrophic failure of the I-35W Bridge. As the Manual of Bridge Evaluation released new load rating provisions after 2014, the urgency in adopting and applying these mandated provisions became a pending burden for state agencies requiring extensive work to update the ratings of gusset plates. Moreover, this paper argues that the current states’ load rating practices do not involve the rating for the welded gusset plate owing to the lack of established provisions. In addition, the gusset plate with no plans also poses particular challenges for the state agencies. To provide state agencies with better insights on the load rating approach of gusset plates, this paper presents a study that carefully reviewed the states’ current practices and load rating provisions. The results of the study indicate the necessity of adopting the new provisions, as the former load rating methodology exhibited inaccurate results in some cases. Additionally, this paper reviews extensive work done for welded connections and proposes a load rating guidance for welded gusset plates. To deliver better interpretations, a case study is provided for the welded gusset plates. This paper also reviews the evaluation method for deteriorations and staggered bolt patterns with relevant case studies. Lastly, the paper provides guidance on estimating the unknown bolt strength as well as weld metal strength for the gusset plate.

Route choice dynamics after a link restoration

ABSTRACTThe original I-35W bridge collapsed on 1st August 2007, and the replacement bridge opened to the public on 18 September 2008. This study explicitly considers the day-to-day behavior of travelers after that bridge reopening. Subjects react to day-to-day travel times on a specific route according to thresholds. These thresholds help discriminate whether a travel time is within an acceptable margin or not, and travelers may decide to abandon the chosen route depending on the frequency of travel times within acceptable margins. Subjects' previous experience, and perception of the alternatives, also influence their decision to abandon the chosen route.

Learning to Build Resilience into Transportation Systems

There is increased recognition of the value of resilience thinking yet few studies have examined key experiences and lessons for the transportation industry. This paper presents eight case studies on natural and man-made disasters focusing on transportation impacts, lessons learned, and efforts to increase resilience. The cases are the Atlanta snowstorm, I-35W bridge collapse, Boston Marathon bombing, Puna lava highway closing, superstorm Sandy, Hampton Roads sea level rise study, Fukushima disaster, and the Oregon Resilience Plan. The cases are used to inform transportation agencies to better respond to and recover from disasters, as well as improve the resilience of transportation systems. In addition to integrating resilience into the management of transportation assets, new technologies and tools relevant to transportation resilience are described.

Unexpected versus expected network disruption: Effects on travel behavior

This paper discusses the observed evolution of traffic in the Minneapolis-St Paul (Twin Cities) region road network following the unexpected collapse of the I-35W Bridge over the Mississippi River. The observations presented within this paper reveal that traffic dynamics are potentially different when a prolonged and unexpected network disruption occurs rather than a preplanned closure. Following the disruption from the I-35W Bridge's unexpected collapse, we witnessed a unique trend: an avoidance phenomenon after the disruption. More specifically, drivers are observed to drastically avoid areas near the disruption site, but gradually return after a period of time following the collapse. This trend is not observed in preplanned closures studied to date. To model avoidance, it is proposed that the tragedy generated a perceived travel cost that discouraged commuters from using these sections. These perceived costs are estimated for the Twin Cities network and found to be best described as an exponential decay cost curve with respect to time. After reinstituting this calibrated cost curve into a mesoscopic simulator, the simulated traffic into the discouraged areas are found to be within acceptable limits of the observed traffic on a week-by-week basis. The proposed model is applicable to both practitioners and researchers in many traffic-related fields by providing an understanding of how traffic dynamics will evolve after a long-term, unexpected network disruption.

Indifference bands for boundedly rational route switching

The replacement I-35W bridge in Minneapolis saw less traffic than the original bridge though it provided substantial travel time saving for many travelers. This observation cannot be explained by the classical route choice assumption that travelers always take the shortest path. Accordingly, a boundedly rational route switching model is proposed assuming that travelers will not switch to the new bridge unless travel time saving goes beyond a threshold or “indifference band”. Indifference bands are assumed to follow lognormal distribution and are estimated in two specifications: the first one assumes every driver’s indifference band is drawn from a population indifference band and the second one assumes that the mean of drivers’ indifference bands is a function of their own characteristics. Route choices of 78 subjects from a GPS travel behavior study were analyzed before and after the addition of the new I-35W bridge to estimate parameters. This study provides insights into empirical analysis of bounded rationality and sheds light on indifference band estimation using empirical data.

Failure of Chauras bridge

Sudden collapse of 190m long Chauras bridge in Uttarakhand, India, which was a three span (40m+110m+40m) continuous deck type truss bridge, took place during casting of the deck slab after successful launching of the truss. The incidence occurred when 52.5m length of the deck slab was cast starting from middle of the 110m span towards the right pier. Whereas, collapse of I-35W bridge took place due to failure of one of its gusset plates, analysis results show that Chauras bridge collapsed due to buckling of its U13U14 top chord compression members when 173.8N/mm2 stress in the member occurred against calculated permissible compressive stress of 149.8N/mm2. Sudden collapse of the bridge claiming six lives with it, due to slight increase in stress beyond the permissible compressive stress indicates that steel girder bridges must also be checked for reserve strength at the limit state of strength. As per Indian and European Standards, in addition to 1.1 material safety factor and 1.5 load factor used for compression and tension members in limit state of serviceability for fatigue design, additional load factor of 1.5, both for dead and live loads, for laterally unsupported compression members should be used for checking the design at the limit state of strength. No such additional load factor for tension members and joints is required.

Minnesota I35W steel bridge collapse: lessons learned and challenges revealed

This article discusses an independent investigation and associated forensic analysis of the old Minneapolis highway I35W Bridge that collapsed on 1 August 2007, which is based on a thorough examination of the original design drawings, a series of detailed 2D/3D finite elements computations of the bridge and the material evidences disclosed by National Safety Transportation Safety Board (NTSB) official investigation. The results have been organised into four reports submitted to the related government agencies during the first three years after the incident. Particularly, material evidences of fatigue damages in the bridge are examined in this article.

Numerical investigation of collapse of the Minnesota I-35W bridge

The I-35 Bridge over the Mississippi River in Minneapolis, Minnesota catastrophically failed during the evening rush hour on August 1, 2007, collapsing to the river and riverbanks beneath. In the years prior to the collapse, several reports cited problems with the bridge structure. This research analytically investigated the cause of the collapse using the Applied Element Method, which recently presented its capability to study the behavior of collapsing structures. The bridge was modeled using the original construction drawings, where all the structural details were taken into consideration (steel truss, gusset plates, concrete slabs, concrete piers, etc.). All the loads at the time of collapse were taken into consideration including traffic and construction loads. It was proven that AEM was capable of analyzing and investigating the cause of collapse of the I35-W bridge. The cause of collapse was found to be the failure of the gusset plates at connections L11 and U10, which well agreed with the field investigations of the collapsed bridge. The under-designed thickness of the plates, their corrosion, and the over loading due to traffic and construction loads at time of collapse were the reasons for the bridge collapse.

I-35W Bridge Collapse and Response

I-35W Bridge Collapse and Response

Closure to “I-35W Bridge Collapse” by S. Hao

Closure to “I-35W Bridge Collapse” by S. Hao

The I-35W Bridge Collapse: Crimes of Commission and Omission Resulting from the Confluence of State Processes and Political-Economic Conditions

The Interstate-35 West Bridge collapse offers a unique case of state crime. First, it illuminates a new topical area in the state crime literature, public infrastructure. Second, it illustrates how the bridge collapse was not a discrete act (Tombs in State Crime 1(2):170–195, 2012), but rather the outcome of relationships between different social institutions. Specifically, it demonstrates how processes within a state, in confluence with the broader political economy, produced decisions (omissions) not to invest in infrastructure repair, take expert advice, and improve coordination between agencies. Simultaneously, these same processes resulted in deliberate actions (commissions) to invest in new infrastructure rather than in maintenance and repair of existing infrastructure, and to reduce both regulatory oversight and safety procedures. We provide a detailed overview of the bridge collapse, then utilizing Kauzlarich and Kramer’s (Crimes of the American nuclear state, Northeastern University Press, Boston, 1998) integrated theoretical framework, contextualize the causes of the collapse and highlight how state processes and political-economic conditions resulted in the simultaneous occurrence of crimes of omission and commission on the part of the state.

Instability of steel gusset plates in compression

As a result of the structural failure of the I-35W Bridge in Minneapolis in 2007, the Federal Highway Administration (FHWA) issued guidelines for the load rating of gusset plates and recommended that the capacity of these plates on non-redundant steel truss bridges be verified. The purpose of this study is to examine the buckling behaviour of steel gusset plates in greater detail, accounting for parameters that were not explicitly included in the guidelines, such as initial deformations of the gusset plate, stiffness of the framing members, load distribution from the framing members to the plate and load eccentricity. For this purpose, a finite-element model of a gusset plate was developed and verified against experimental measurements. Results show that, for in-plane compressive loads with no moment and no eccentricity, the FHWA guidelines for load rating are conservative and safe for initial out-of-plane deformations up to one plate thickness.

Early Contractor Design Involvement to Expedite Delivery of Emergency Highway Projects

Events such as Hurricanes Katrina and Irene and the sudden collapse of the I-35W bridge in Minnesota forced state departments of transportation (DOTs) to step into the public spotlight and implement expedited procurement procedures to restore vital links in the transportation network as the media scrutinized their work every night on the evening news. This paper presents the results of case studies from Florida, Maine, Minnesota, Missouri, New York, and Utah where the DOT brought the construction contractor into the design process as the primary means to expedite the delivery of emergency projects. The case studies include the use of design–bid–build, indefinite delivery and indefinite quantity (IDIQ), construction manager–general contractor (CMGC), and design–build (DB) contracts as mechanisms to gain substantive contractor input on materials, means, and methods during design. The paper concludes that completing the design is the first obstacle to surmount in emergency procurements and that the surest tool to expedite emergency project delivery is to design around immediately available materials, equipment, and proven accelerated construction methods—information that is best developed by the contractor that will eventually complete the construction. The paper recommends that agencies develop expedited procurement procedures for IDIQ, CMGC, and DB contracts before emergencies occur and furnishes case study information for specific methods used to streamline routine procurement procedures.

Forensic Information Modeling: A New Forensic Tool

The investigation into the causes of the collapse in Minneapolis in August 2007 of the I-35W bridge required sifting through a vast amount of design, retrofit, and maintenance data prior to initiating the complicated work of analyzing the condition and loading of the bridge at the time of collapse. A new forensic tool—forensic information modeling—was created to store all of these data, as well as the geometry, as a three-dimensional visual database, enabling the engineers to pinpoint possible trouble areas in need of further inquiry.

Capacity analysis of gusset plate connections using the Whitmore, block shear, global section shear, and finite element methods

The 2007 collapse of the I-35W Bridge in Minneapolis, Minnesota led to additional load rating requirements for gusset plates. The Federal Highway Administration provided the direct tension and block shear methods to assess tensile capacity for use in load rating, as well as a mechanics based method to assess shear capacity on critical planes. However, the three methods provide limited information about ultimate behavior for complex connections. Using finite elements, the authors modeled the connection from Whitmore’s 1952 study to evaluate the plate capacity and failure mechanism. The analysis showed that the direct tension method was conservative, but predicted neither capacity nor behavior. Model performance corresponded well with the critical block shear capacity load in the left diagonal, and shear capacity on the gross horizontal plane. Yielding on this plane began around critical bolt holes and spread to either side of the plate, forming the critical failure mechanism.

Closure to “Nonlinear Finite-Element Analysis of Critical Gusset Plates in the I-35W Bridge in Minnesota” by Minmao Liao, Taichiro Okazaki, Roberto Ballarini, Arturo E. Schultz, and Theodore V. Galambos

Closure to “Nonlinear Finite-Element Analysis of Critical Gusset Plates in the I-35W Bridge in Minnesota” by Minmao Liao, Taichiro Okazaki, Roberto Ballarini, Arturo E. Schultz, and Theodore V. Galambos

Modeling the day-to-day traffic evolution process after an unexpected network disruption

Although various approaches have been proposed for modeling day-to-day traffic flow evolution, none of them, to the best of our knowledge, have been validated for disrupted networks due to the lack of empirical observations. By carefully studying the driving behavioral changes after the collapse of I-35W Mississippi River Bridge in Minneapolis, Minnesota, we found that most of the existing day-to-day traffic assignment models would not be suitable for modeling the traffic evolution under network disruption, because they assume that drivers’ travel cost perception depends solely on their experiences from previous days. When a significant network change occurs unexpectedly, travelers’ past experience on a traffic network may not be entirely useful because the unexpected network change could disturb the traffic greatly. To remedy this, in this paper, we propose a prediction–correction model to describe the traffic equilibration process. A “predicted” flow pattern is constructed inside the model to accommodate the imperfect perception of congestion that is gradually corrected by actual travel experiences. We also prove rigorously that, under mild assumptions, the proposed prediction–correction process has the user equilibrium flow as a globally attractive point. The proposed model is calibrated and validated with the field data collected after the collapse of I-35W Bridge. This study bridges the gap between theoretical modeling and practical applications of day-to-day traffic equilibration approaches and furthers the understanding of traffic equilibration process after network disruption.

Evaluating the effects of the I-35W bridge collapse on road-users in the twin cities metropolitan region

This study evaluates the effects of the I-35W bridge collapse on road-users in the Minneapolis-St Paul, Minnesota Twin Cities metropolitan area. We adopted the Twin Cities Seven-County travel demand model developed in previous research, re-calibrated it against July 2007 loop detector traffic data, and used this model to carry out an evaluation of economic loss incurred by increased travel delay in alternative scenarios before and after the bridge collapse. We conclude that the failure of the I-35W bridge resulted in an economic loss of US$71,000 to US$220,000 a day, depending on how flexible road-users in the system adjusted their trip destinations in response to the bridge closing. We also estimate that the major traffic restoration projects Minnesota Department of Transportation has implemented in quick response to the bridge collapse can save road-users US$9500–17,500 a day. This translates into a benefit–cost ratio of 2.0–9.0, suggesting these projects are highly beneficial in an economic sense. In this analysis, the use of a simplified, scaled-down travel demand model enabled us to carry out the analysis quickly and accurately, which could see its contributions in transportation planning under situations such as emergency relief and comprehensive design.

Dynamic Monitoring Systems for Structures under Extreme Loads

The dynamic monitoring of civil structures such as buildings and bridges is traditionally approached using acceleration and velocity sensors. When a monitoring program is designed to address concerns related to the level of strain in certain members, fatigue or displacements due to extreme loads, it is sometimes advantageous to measure those parameters directly, instead of deriving them from acceleration or velocity data. Inhomogeneous construction materials such as concrete, stone or masonry require the use of long-gauge sensors to measure strain, since local sensors can provide erroneous data due to local material changes. On the other hand, acceleration and tilt sensors are very useful to capture the global deformations and displacements. The development of long-gauge-length fiber optic sensors can be considered as a useful addition to the toolkit of those interested in the structural dynamics. The system can monitor structures over long periods of time at acquisition frequencies up to 10 kHz and with sub-microstrain resolution. The possibility of obtaining static and dynamic measurements from the same sensor is another advantage of this technology. For acceleration and tilt monitoring, MEMS sensors are now recognized as a powerful and low-cost alternative to more traditional sensor types. Fully-integrated sensors with 3-axis accelerometers and two-axis tiltmeters are now available in a compact packaging that also contain all data acquisition electronics and can be easily deployed in new or existing structures, connecting them directly to an Ethernet network. This contribution briefly introduces fiber optic and MEMS sensing technologies and will than illustrate their application to structural health monitoring through several examples, including the new I35W bridge in Minneapolis USA, the Ile d’Orléans suspension Bridge in Québec Canada and the shaking-table test of a full-scale masonry building reinforced with composite materials.