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White Paper #3
Diagnosis Depends on Definitive Data
A White Paper by LifeSpan Technologies
Medical doctors cannot diagnose serious illnesses with a reflex hammer and a tongue depressor. Medicine in the 21st century has advanced well beyond reliance on simple diagnostic tools; replaced with highly accurate imaging, blood analysis and angiograms. Doctors use these sophisticated tools and the definitive data they generate to support more accurate diagnoses, especially before ordering expensive treatments.
Interestingly, highway bridges face the same diagnostic challenges as they age and become less capable of performing their intended function. However, many bridge doctors are reluctant to use the most advanced diagnostic tools to maximize a bridge’s healthy life span, enhance safety, and minimize cost to the taxpayers. Some object to cost; others to non-familiarity with the technologies, yet which one of us would refuse an expensive diagnostic procedure if our health was at risk?
Our acceptance of advanced medical diagnostic tools far exceeds our acceptance of advanced diagnostic tools to analyze bridge deficiencies. Given that visual inspection is useful as an initial screening tool, like the reflex hammer; why aren’t bridge doctors more willing to use the sophisticated, accurate and timely condition assessment technologies necessary to diagnose the health of our bridges and develop optimal treatment plans?
State Departments of Transportation (DOTs) across the United States have been using visual inspection as the primary means to diagnose bridge condition for nearly 40 years. Known as the National Bridge Inspection Standards (NBIS), inspectors receive several weeks of training and are then tasked with assessing the condition state of major bridge systems — deck, superstructure or substructure. Soon, these same inspectors will be expected to extend their qualitative judgment to individual bridge elements, including bearings, stringers, joints; in an effort to improve diagnostics, supporting asset management programs. The medical analogy is distressing — expecting your doctor to diagnose a serious illness by observing your skin texture, posture and muscle tone.
A Federal Highway Administration (FHWA) study published over ten years ago concluded that visual inspection is a subjective process that produces highly variable results. Follow-on publications explained the inability of visual inspection protocols to properly support optimal spending programs by federal, state and local governments. In essence, the taxpayers are being asked to accept bridge condition assessments, diagnosis, and treatment plans developed from using the bridge equivalents of reflex hammers and tongue depressors. Again, given the advanced condition assessment technology at our fingertips, why is this process acceptable for sick bridges?
About the same time, the FHWA study on bridge inspection effectiveness was published, a group of pioneering engineers recognized the opportunity to bring much-needed condition assessment technology to bridge owners; allowing them to more accurately diagnose bridge condition and develop cost effective alternatives for treatment. This industry is comprised of a variety of fully commercialized product and service suppliers that refer to the offerings as Advanced Condition Assessment Technologies to differentiate them from the NBIS visual inspection processes.
Over the past ten years, a significant number of projects have experienced successful outcomes using advanced condition assessment technologies. Our company has documented millions of dollars in capital savings for repairs or replacements that were either not necessary or could safely be deferred. These include the delay of a $70 million dollar superstructure repair in the Northeast; $800,000 in savings each for two bridges in that had severe corrosion and millions more for bridges in the Western U.S. where repair techniques were proven effective instead of the initially planned bridge replacements. Other firms report similar positive results. Our industry estimates that 30-40% of bridges analyzed using advanced condition assessment technologies are in better to much better condition than visual inspection indicated.
The Bridge Preservation Imperative
We all want to live long lives in good health. Bridges are no different. But when we start experiencing symptoms of aging or have specific medical issues, we meet with our doctor and expect him to conduct whatever tests are necessary to accurately diagnose our condition and develop a realistic treatment plan, preserving our health and extending our life span.
We believe bridges should follow the same process. Yet, by not using the most advanced condition assessment technologies when and as warranted, bridge practitioners may not be able to make an accurate diagnosis or develop an optimal treatment plan; interfering with the bridge preservation imperative so popular today with the Association of American State Highway and Transportation Officials (AASHTO), State DOTs, and other transportation agencies.
Adopting New Developments
Medicine is replete with innovative developments whose impact was substantial, including Marie Curie and x-rays, Karl Landsteiner’s blood testing, Alexander Fleming’s discovery of antibiotics. Fortunately, it didn’t take long for these powerful tools to be included in a doctor’s arsenal to diagnose and treat adverse medical conditions, allowing patients to rapidly regain health and extend their life span.
Unlike medicine, bridge management developments are often the result of tragedy. Examples include the collapse of the Silver Bridge in Ohio (resulting in visual inspection standards); the partial collapse of the Hoan Bridge in Milwaukee (resulting in more emphasis on fatigue and fracture analysis); the Schoharie Creek Bridge in New York (resulting in emphasis on scour assessment) and the I-35W collapse in Minneapolis, leading the FHWA and Congress to place increased emphasis on asset management, risk assessment, and data-driven decision making.
Another recent and powerful development was the acknowledgment by AASHTO that conventional diagnostics and analytical techniques may be too conservative. Supported by a long list of positive results from advanced condition assessment technologies to determine safe load capacities, superstructure condition, deck de-lamination, impact of concrete shear cracking, AASHTO included this statement in the 2011 edition of theirManual for Bridge Evaluation(MBE):
“The actual performance of most bridges is more favorable than conventional theory dictates. When a structure’s computed theoretical safe load capacity or remaining fatigue life is less than desirable, it may be beneficial to the Bridge Owner to take advantage of some of the bridge’s inherent extra capacity that may have been ignored in conventional calculations.”
The MBE goes on to explain how to utilize maximum strain values obtained from sensing devices to calculate a correction factor that can substantially increase the safe load rating and potentially defer bridge replacement for decades. This acknowledgment has enormous implications for bridge management, but also impacts the perceived need for funding to repair or replace bridges with low ratings.
While organizations such as the American Society of Civil Engineers (ASCE) and Transportation for America (T4America) continue to stress spending more and more money, AASHTO’s statement and approved alternative methods calls into question the way we are developing and using visual inspection data as the very foundation of everyday bridge management, and subsequent determination of required funding to achieve a state of good repair.
Data Trumps Analysis
In an AASHTO sponsored conference earlier this year, several well respected bridge management practitioners made presentations about how optimal decisions to maintain, repair or replace bridges can be made. Equations were presented to calculate system value; how bridges deteriorate and move to lower condition states over time in the context of Markov chain analysis; and finally, a sophisticated statistical analytical technique using probability distributions for determination of system reliability.
These analytical techniques were offered as realistic methods to support more optimal financial decisions in the context of DOT asset management programs. However, there was a major disconnect between what statistical techniques should be used and the data quality produced by NBIS visual inspection. Objective, definitive data is the essential foundation for use of sophisticated statistical analysis methods.
The Need for Objective, Definitive Condition Data
At this time, Congress is formulating a Transportation Bill that will replace a series of continuing resolutions. The Senate recently released its version, called MAP-21. The House is expected to release its version this month and then negotiate differences in language for passage and the President’s signature. Importantly, both the House and Senate have decided to focus attention on some key issues that relate to improved transportation management; asset management programs, optimal spending, lowering system risk, and data driven decision making.
For some time, FHWA has been advocating the widespread adoption of an asset management programs for state DOTs and other transportation agencies. The three major components of an asset management program include: (1) cataloging what you own, (2) periodic assessment of condition, then (3) use of condition data to develop and analyze options to achieve a state of good repair. Finally, selection of the optimal decision to maintain, repair or replace an asset should be made with due consideration for public safety and available funds. Unfortunately, a number of bridge owners have not yet fully adopted asset management programs, spurring Congress to specifically emphasize the use of this process to measure and improve management performance.
State DOTs and other transportation agencies that don’t use data-driven, risk-adjusted decision making for bridge management and financial optimization may face loss of funding just when infrastructure funding needs are becoming more apparent. But, the biggest remaining hurdle for implementing this enhanced management process is the availability of objective, definitive condition data. With objective, precise and timely data State DOTs and other transportation agencies can achieve what Congress expects. Without such data, they will not meet the intent of Congress.
Owners can continue relying solely on visual condition assessment processes that return subjective and highly variable data, believing that this is the most effective means to reach the multiple objectives Congress intends owners to achieve.
Or they can recognize those shortcomings and deploy, where technically appropriate and cost effective, a variety of advanced condition assessment technologies that will support the multiple Congressional objectives of data driven, risk-adjusted and financially optimized bridge management in the context of a comprehensive asset management program.
One thing for certain, actions taken today can make a big difference in how we shape our transportation future.
For more information, contact LifeSpan Technologies on the Web at www.lifespantechnologies.com,
or by calling 770-234-9494.