Aggie, Ingeniero September 2010

09/02/08: David Jauregui (photo by Darren Phillips)NMSU civil engineers apply bridge expertise

Travelers in New Mexico who drive across bridges have good reason to be assured of their safety:  the state’s bridges are routinely inspected by engineers who have been trained by nationally renowned experts from New Mexico State University’s Bridge Inspection Program. In fact, many bridges throughout the United States have been inspected by transportation professionals who have been trained at NMSU.

Over the past four decades, faculty members of the civil engineering department, in concert with the New Mexico Department of Transportation, have conducted comprehensive bridge inspection training for the NMDOT since 1972, as well as two-week training courses for the Federal Highway Administration through the National Highway Institute since 1986. All bridge inspectors in the United States are required to have this training.

The foundation for the bridge program at NMSU is undergraduate and graduate-level education, on-the-job experience and research focused on the transportation industry.  The department routinely graduates engineers whose education is supplemented with several years of experience in the field.

The civil engineering department collaborates with the NMDOT to perform structural bridge inspections in the state, providing civil engineering students with on-the-job training and experience.  They conduct bridge inspections on six-month, one- or two-year intervals, depending on the configuration and/or condition. Co-op students, working on six-month assignments under the supervision of professional engineers, inspect and rate several hundred bridges throughout the state including the deck, superstructure, and substructure components.

“We inspect many of the prestressed concrete girder, reinforced concrete slab, and steel girder bridges throughout the state,” said David Jáuregui, civil engineering associate professor and director of the Bridge Inspection Program. “We also inspect some special structures, including the bridges at Nogal Canyon, Rio Grande Gorge, Canadian River and Interstate 40 over the Rio Grande.”

NMSU’s civil engineering department also collaborates with the Los Alamos National Laboratory and the United States Army Corp of Engineers to conduct special, in-depth safety inspection of bridges owned by those agencies.

Undergraduate students specializing in structural engineering assist professional engineers in the field where they conduct visual inspections of the structures for things such as signs of corrosion, indications of overload and impact damage.  NMSU engineers use ultrasonic testing equipment to evaluate the internal condition of bridge components such as steel pins that cannot be visually inspected. The inspections involve evaluations and ratings on a scale of zero (failed condition) to nine (excellent condition) of the bridge deck, which receives the load; the superstructure (girders, trusses, and arches); and the substructure (piers and abutments). Bridges that receive ratings of four or lower are classified as “structurally deficient” and require more thorough inspections.

The inspection results are documented by undergraduate students and preliminary reports are reviewed by the professional engineer.

“This is where quality control comes in,” said Jáuregui. “If inconsistencies or questionable results are found, students go back to the professional engineer for clarification. Final reports are reviewed by a professional engineer before submission to the district where the bridge is located and to the NMDOT general office. This information is used to determine if any and to what extent repairs are needed.”

Students from NMSU also participate in NMDOT internships in the Bridge Design Division in Santa Fe. They are employed in the summer and are involved in the design, construction, inspection and load rating of bridges.

NMSU civil engineers are also involved in research to develop improved methods for structural health monitoring of bridges.

Graduate students are using state-of-the-art computer techniques to determine load ratings of bridges based on information derived from design plans. Information is entered to create a computer model of the bridge which then provides an estimate of bridge capacity. The system was adopted by NMDOT and NMSU has applied the approach to evaluate highway bridges and nearly 80 railroad bridges on portions of the Burlington Northern Santa Fe rail line that extends some 300 miles between Belen and Trinidad, Col.

“This can be challenging because some of our railroad bridges were constructed in the late 1800s,” said Jáuregui. “The design drawings are very old and difficult to interpret. A lot of engineering judgment is involved.”

The NMSU bridge research team has also developed methods that incorporate the use of field testing and computer analysis methods to capture the three-dimensional behavior of bridges. The new evaluation method could be applied to a significant percentage of the bridges in New Mexico.  At this time, NMSU is collaborating with the University of Vigo, Spain to develop automated inspection tools using close-range photogrammetry for vertical clearance and crack size measurements. Belen Riverio Rodríguez, a Ph.D. student at the University of Vigo, is currently serving a two-month appointment as a visiting scholar under Jáuregui’s supervision.

The advanced evaluation techniques have also been used in a Sandia National Laboratory structural health monitoring project.  Andrew Daumueller, a Ph.D. student working with Jáuregui in the NMSU civil engineering department, is using diagnostic field testing and finite element analysis to evaluate railroad bridges that are fracture critical and evaluating the remaining fatigue life of those structures.

Jáuregui said the new evaluation techniques could be used starting with the construction of a new bridge to create a baseline and track the bridge behavior over its service life to help engineers inspect, evaluate and better manage the state’s bridge inventory.

“It’s more quantitative—most bridge inspection is visual. This is a cost-effective application of technology to evaluate bridge performance and supplements visual data gathered during inspections,” said Jáuregui. “It’s a good investment to insure the safety and serviceability of our bridges in the long-term.”

“Tied all together, a student who graduates from NMSU with a master’s degree in structural engineering can accumulate many years of practical experience,” said Jáuregui. “There are very few people who are qualified to do this kind of work and there is a definite need in light of our failing infrastructure. This work often goes unnoticed, but it is very important to insure the safety of the traveling public.”

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