By Linda Fresques and Mark Cramer
NMSU civil engineers apply bridge safety expertise
Travelers in New Mexico driving across bridges have good reason to be assured of their safety: The state’s bridges are routinely inspected by engineers and technicians who have been trained by nationally renowned experts from New Mexico State University’s Bridge Inspection Program. In fact, transportation professionals trained at NMSU have inspected many bridges throughout the United States and abroad.
The Bridge Evaluation Research Center is an important resource for bridge assessment, bridge inspection training, smart-bridge technology development and broad-based research and development. Although other training opportunities exist, the center offers the only university-based Bridge Safety Inspection training program in the nation whose focus is educating future civil engineers in the field of bridge inspection.
Faculty members of the civil engineering department have conducted comprehensive bridge inspection training for the New Mexico Department of Transportation since 1972, and since 1986 they also have conducted two-week training courses for the Federal Highway Administration through the National Highway Institute. All bridge inspectors in the United States are required to have this training according to the National Bridge Inspection Standards.
The department of civil engineering collaborates with the NMDOT to perform structural bridge inspections in the state, providing students with on-the-job training and experience. Inspections are conducted on six-month, one- or two-year intervals, depending on the bridge’s 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) as well as culverts and channels.
NMSU has a 40-year history of research and collaboration with industry through the Bridge Evaluation Research Center, working to improve the safety and serviceability of the nation’s bridges. This program fostered the university’s world-renowned research in “smart bridge” technology that incorporates fiber optics to monitor bridge performance. The research extends to new non-destructive testing techniques for evaluating and ensuring the safety and performance of transportation infrastructure.
“NMSU inspects numerous pre-stressed concrete girder, reinforced concrete slab and steel girder bridges throughout the state which provides a wide range of bridge inspection experience to our students,” said David Jauregui, civil engineering associate professor and director of the Bridge Inspection Program. “We also inspect some special structures, some of which are fracture-critical, including the bridges at Nogal Canyon, Rio Grande Gorge, Canadian River and Interstate 40 over the Rio Grande.”
NMSU’s department of civil engineering also collaborates with Los Alamos National Laboratory and the United States Army Corp of Engineers to conduct special, in-depth safety inspections of bridges owned by those agencies.
Undergraduate students in civil engineering assist professional engineers in the field, where they conduct visual inspections of the structures for signs of corrosion, indications of overload and impact damage, among other things. NMSU engineers use ultrasonic testing equipment to evaluate the internal condition of bridge components, such as steel pins and connection plates that cannot be visually inspected. The students document the inspection results and the professional engineer reviews preliminary reports.
“Quality control is paramount in the work we do,” Jauregui said. “If inconsistencies or questionable inspection results are found, students go back to the professional engineer for clarification. Inspection reports are reviewed thoroughly by a professional engineer before final submission to the district where the bridge is located, and to the NMDOT general office. This information is used to determine the bridge’s sufficiency to remain in service and also the extent of repairs needed, if any.”
NMSU students also participate in NMDOT internships in the Bridge Design Bureau 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 also are 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 and field visits. 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 more than 160 highway bridges and nearly 80 railroad bridges on portions of the Burlington Northern Santa Fe rail line that extends some 300 miles between Belen, N.M., and Trinidad, Colo.
“Load rating can be challenging because some of our railroad bridges were constructed in the late 1800s,” Jauregui said. “The design drawings are very old and difficult to interpret. A significant amount of engineering judgment is involved.”
The NMSU bridge research team also has developed methods incorporating the use of field testing and computer analysis methods to capture the three-dimensional behavior of bridges. This non-destructive 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 in Spain to develop automated inspection tools using close-range photogrammetry for vertical clearance and crack-size measurements. Belen Riverio Rodriguez, a Ph.D. student at the University of Vigo, recently completed a two-month appointment as a visiting scholar under Jauregui’s supervision.
The bridge program’s international collaborative efforts also are under way with the University of Chihuahua in Mexico. A Ph.D. student from that university will join the NMSU program in January to conduct research on the use of ultra-high-performance concrete for pre-stressed concrete girder bridges.
The bridge inspection program has made its mark even in the Far East. In September a delegation from China’s Ministry of Transportation visited NMSU as part of a three-week tour of the United States, organized by members of the department of engineering technology and surveying engineering, to gain expertise from the Bridge Evaluation Research Center.
“Tied altogether, a student who graduates from NMSU with a master’s degree in structural engineering can accumulate many years of practical bridge-related experience,” Jauregui said. “There are very few engineers right out of college that 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 ensure the safety of the traveling public.”