National Academies Press: OpenBook

Post-Extreme Event Damage Assessment and Response for Highway Bridges (2016)

Chapter: Chapter Two - Survey of State Bridge Engineers

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Suggested Citation:"Chapter Two - Survey of State Bridge Engineers." National Academies of Sciences, Engineering, and Medicine. 2016. Post-Extreme Event Damage Assessment and Response for Highway Bridges. Washington, DC: The National Academies Press. doi: 10.17226/24647.
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Suggested Citation:"Chapter Two - Survey of State Bridge Engineers." National Academies of Sciences, Engineering, and Medicine. 2016. Post-Extreme Event Damage Assessment and Response for Highway Bridges. Washington, DC: The National Academies Press. doi: 10.17226/24647.
×
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Suggested Citation:"Chapter Two - Survey of State Bridge Engineers." National Academies of Sciences, Engineering, and Medicine. 2016. Post-Extreme Event Damage Assessment and Response for Highway Bridges. Washington, DC: The National Academies Press. doi: 10.17226/24647.
×
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Suggested Citation:"Chapter Two - Survey of State Bridge Engineers." National Academies of Sciences, Engineering, and Medicine. 2016. Post-Extreme Event Damage Assessment and Response for Highway Bridges. Washington, DC: The National Academies Press. doi: 10.17226/24647.
×
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Suggested Citation:"Chapter Two - Survey of State Bridge Engineers." National Academies of Sciences, Engineering, and Medicine. 2016. Post-Extreme Event Damage Assessment and Response for Highway Bridges. Washington, DC: The National Academies Press. doi: 10.17226/24647.
×
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Suggested Citation:"Chapter Two - Survey of State Bridge Engineers." National Academies of Sciences, Engineering, and Medicine. 2016. Post-Extreme Event Damage Assessment and Response for Highway Bridges. Washington, DC: The National Academies Press. doi: 10.17226/24647.
×
Page 12

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7 of different hazard events occurring in each state. The hazards that were listed in the bridge engineer’s survey included earth- quakes, scour, wind, storm surge and waves, landslides, flood and debris flow, liquefaction, blasts, fires, overloads, and col- lisions. The hydraulic engineers’ survey included questions about the likelihood of scour, storm surge and waves, and flood and debris flow. It should be noted that the results represent the likelihood of the events from the perspective of the responding parties—mostly affected by the historical events—rather than an in-depth risk analysis. Bridge Engineers Collision was ranked first as it was considered to be an event with a high likelihood of occurrence by 34% of the responding engineers. The follow-up interviews showed that a majority of the cases were over-height collisions with a few that involved collisions with the piers or other structural bridge components. The collisions were followed by scour-related failures (with 20% considering it a high likelihood), wind-related failures (18% high likelihood), and flood and debris flow (16% high likelihood). Table 1 shows likelihoods of different hazards as identified by bridge engineers. It should be noted that after the follow-up interviews with the engineers ranked the winds as high likelihood, it was determined that wind events did not nec- essarily result in the structural failure of a bridges. Wind was ranked as a high likelihood of causing failure because the sec- ondary effects of the high winds had hindered the serviceabil- ity and performance of their bridges. This included conditions where high winds resulted in high surge levels that resulted in partial or full closure of the bridge or instances where winds resulted in falling debris, power lines, signs, etc., on the bridges consequently hindering its service. In an effort to have a better understanding of the hazard rankings, the different likelihoods of occurrence have been weighted (high likely = 4, likely = 3, possible = 2, unlikely = 1), and the responses have been sorted and ranked. Based on the weighted approach, a new ranking emerges with colli- sions ranking first, followed by scour and flood and debris flow as second and third. Table 2 shows the breakdown of states that considered collision, scour, and flood and debris flow to have the highest likelihood of occurrence. A list of the states that are affected by likely hazards—between 10% and 95% probability in next year—is shown in Table 3. In this category, 54% of states Bridges are one of the critical components of the transportation network and could act as bottlenecks in the event of failure. As such, the focus of this report will be on identification of hazards that could threaten the structural integrity of bridges and result in degradation of performance measures and performance of the transportation network as a critical civil infrastructure cru- cial to the quality of life, every day activities, and the economy of the nation. For this purpose, two sets of surveys were sent to the state bridge engineers and state hydraulic engineers asking them to identify the hazards or threats that they consider most critical to the bridges in their jurisdiction. The survey was sent to the state engineers who represented their states in the AASHTO SCOBS and AASHTO Technical Committee on Hydrology and Hydraulics. Forty-three of 50 state bridge engineers responded to their survey (86%), and 42 of 50 state hydraulic engineers responded to their survey (84%) (Figure 2). It should be noted that in most cases the responses do not rep- resent any in-depth risk analysis of the state under question and simply reflect the opinions of the state bridge and hydraulic engineers. The survey continued by asking the engineers to identify the rapid assessment technologies that were primar- ily used to detect and locate damage in bridges after extreme events. Based on the responses, it was shown that despite the availability of many modern damage detection technologies, the state engineers still substantially rely on visual inspection as the primary means of assessing the structural integrity of the bridges and as the first means of detecting and locating the sources of damage. Furthermore, the engineers were asked to share any emergency response plans that specifically address the treatment of damage in bridges after extreme events. The state engineers were also given the option to share their experiences on a number of relevant recent extreme events. This resulted in the collection of a significant amount of data regarding actual events where emergency response plans were followed. This chapter will provide a brief overview of the state engi- neer responses to the survey questions, a list of which can be found in Appendices A1 and A2. MULTIPLE THREATS AFFECTING TRANSPORTATION INFRASTRUCTURE Different hazards of natural or man-made origins could affect the structural integrity of bridges and result in partial or full closures. The first set of questions in both the bridge and hydraulic engineers’ surveys addressed the likelihood chapter two SURVEY OF STATE BRIDGE ENGINEERS

8 FIGURE 2 (Top) State bridge engineers; (bottom) state hydraulic engineers responding to the survey.

9 Hazard Type Highly Likely**** Likely*** Possible** Unlikely* Collision 34 39 24 3 Scour 20 54 26 0 Wind 18 27 31 24 Flood/debris flow 16 53 29 2 Landslide 14 16 34 36 Fire 5 11 46 38 Storm surge/waves 2 20 18 59 Earthquake 2 11 31 56 Blast 0 0 16 84 Liquefaction 0 5 30 65 *Unlikely: Less than 1% probability in the next year. **Possible: Between 1% and 10% probability in the next year. ***Likely: Between 10% and 95% probability in the next year. ****Highly Likely: Almost 100% probability in the next year. TABLE 1 EXPECTED LIKELIHOOD OF DIFFERENT HAZARDS ACROSS THE STATES IN THE U.S. IDENTIFIED BY STATE BRIDGE ENGINEERS (In percent) Hazard Type State Affected Collision CA, CO, DE, GA, IL, KY, LA, MN, MS, MO, NY, NC, OR Scour AL, IA, ME, MO, MT, OR, TX, UT, WY Wind AR, IN, MO, MT, NYC, OR, UT, WY TABLE 2 STATES AFFECTED BY COLLISION, SCOUR, AND WIND AS EVENTS WITH HIGH EXPECTED LIKELIHOOD Hazard Type State Affected Scour AK, AR, AZ, CA,CO, DE, FL, GA, HI, IN, KY, LA, MA, MD, MN, MS, NC, ND, OK, SD, VA, VT, WA, WI Flood/debris flow AK, AL, AR, AZ, CO, CT, DE, GA, HI, IA, KY, LA, MA, MD, MS, ND, OK, SD, TN, TX, VT, WA, WI, WY Collision AK, AL, AZ, CA*, IA, IN, ME, OK, PA, RI, SD, VT, WA, WI, WY *Pier collision in addition to over-height collision. TABLE 3 STATES AFFECTED BY SCOUR, FLOOD AND DEBRIS FLOW, AND COLLISION AS EXPECTED LIKELY EVENTS

10 consider damage from scour as likely, followed by flood and debris flow (53%), and collisions at 34%. Hydraulic Engineers Table 4 shows that flood and debris flow and scour were ranked as the events with the highest likelihood of occurrence (28% of respondents). One state also mentioned that the over- topping of bridges is an issue; however, the issue normally resolves itself after the water subsides and the failure is most of the time in service rather than the structural integrity of the bridge. A review of the surveys revealed that in contrast with current statistics that underline hydraulic reasons (such as flood, scour, and debris accumulation) as the major reason for bridge failures (e.g., Wardhana and Hadipriono 2003; Briaud et al. 2005), state bridge engineers have identified collision as the primary reason of failures or disruption in service for the bridges. This discrepancy can mainly be attributed to the concept that in most of the state departments of trans- portation (DOTs), the issues related to hydraulic events are first referred to hydraulic engineers and as such are not nec- essarily noted as a primary cause of concern for the bridge engineers. This hypothesis was confirmed by reviewing the responses from the states that had common personnel in struc- tures and hydraulics. DAMAGE DETECTION TECHNIQUES USED BY STATES As part of the survey, state bridge engineers were asked to list the type of damage detection techniques used after extreme events. The survey, combined with the follow-up inter- views, showed that 100% of the respondents count on visual inspection, either cursory or more detailed at an arm-reach inspection technique, as the first approach for examining the damage to bridges. In many cases, the final decisions would be made based on the results of visual inspection; however, in some other cases other methods were used for a more in-depth detection of damage. Figure 3 (top) shows the breakdown of the states that use different damage detection techniques and the percentage of popularity of the different techniques. The hand-held nondestructive testing techniques (NDT) is ranked second after visual inspection. A similar question was sent to hydraulic engineers. Simi- lar to state bridge engineers, visual inspection was consid- ered as the primary approach for damage detection, used by 100% of responding states, followed by portable sonar surveys (36.4%), and manned or unmanned sonar surveys (21.2%). Figure 3 (bottom) lists the different damage tech- niques used by the state hydraulic engineers with correspond- ing percentages. The state bridge and hydraulic engineers were also asked to comment on whether the damage detection techniques currently in use by their agency are capable of providing sufficient data for bridge damage assessment following exposure to natural hazards. Figure 4 shows the responses from the engineers. AVAILABILITY OF EMERGENCY RESPONSE PLANS One of the questions in the survey addressed the availability of pre-defined emergency response plans within each agency. Eighty-three percent of responding states mentioned that such plans are available, with 17% noting that their agency has not developed such plans. From those states that have existing emergency response plans, many do not share the plans for a variety of administrative, security, and operational reasons. In addition, considering that Japan has been one of the countries dealing with the consequences of different extreme events, the emergency response plan of the Public Work Institute of Japan was acquired and is shared in the e-appendix of this report. Hazard Type Highly Likely**** Likely*** Possible** Unlikely* Flood/debris flow 28 44 28 0 Scour 28 35 35 2 Storm surge/waves 2 23 26 49 *Unlikely: Less than 1% probability in the next year. **Possible: Between 1% and 10% probability in the next year. ***Likely: Between 10% and 95% probability in the next year. ****Highly Likely: Almost 100% probability in the next year. TABLE 4 EXPECTED LIKELIHOOD OF DIFFERENT HAZARDS ACROSS THE STATES IN THE U.S. IDENTIFIED BY STATE HYDRAULIC ENGINEERS (In percent)

FIGURE 3 Type of damage detection techniques in percentage used by (top) state bridge engineers; (bottom) state hydraulic engineers.

12 FIGURE 4 Perspective of (left) bridge; (right ) hydraulic engineers on the adequacy of existing technologies used by their agency.

Next: Chapter Three - Bridge Damage Detection Techniques: Current Practice and Future Directions »
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TRB's National Cooperative Highway Research Program (NCHRP) Synthesis 497: Post-Extreme Event Damage Assessment and Response for Highway Bridges reviews the procedures that state departments of transportation and two local authorities, New York City and Los Angeles County, use to assess the damage in bridges in response to extreme events and conduct emergency response activities. Extreme events include those with geological sources (such as earthquakes and landslides), from hydro-meteorological sources (such as hurricanes and floods), or those of man-made origin, either accidental (such as truck crashes) or malicious (such as terrorist attacks).

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