Thinking outside the concrete box

From left: Assistant Professor Ali Abolmaali, graduate student Anil Kumar Garg and Joe Lundy of Hanson Products examine cracks in a large section of concrete pipe following a full-scale test.

High-ranking transportation officials from across the United States visited The University of Texas at Arlington in June for a high-tech demonstration that could result in new design codes for roads and bridges.

Using laser instrumentation from UT Arlington’s Automation & Robotics Research Institute (ARRI), civil and environmental engineering Assistant Professor Sayed-ali “Ali” Abolmaali and a team of researchers tested the durability of large sections of concrete pipe used to channel water runoff below roadways. Dr. Abolmaali and his associates won a two-year grant from the American Concrete Pipe Association to investigate the shear capacity of precast concrete box culverts. Several nationally recognized research centers competed for the study.

“Traffic load can cause failure of box culverts,” Abolmaali said. “Studies have shown that the shear capacity has not been looked at closely enough.”

Assisting Abolmaali are civil and environmental engineering Professor John Matthys, Professor Raul Fernandez of ARRI, Yeol Choi from Kyungpook National University of South Korea and two graduate students. The team is conducting experimental studies in the College of Engineering’s Structural Engineering Laboratory, followed by numerical studies in the National Science Foundation-funded Structural Simulation Laboratory.

Structural members such as beams, rods and boxes are all normally subjected to bending, shear and axial loads. Shearing is especially critical at the slide joints where sections come together. Individual and joined sections of concrete box culverts—each weighing several tons—will be subjected to shear-type loading, simulating real-world conditions.

The project consists of three stages: lab with instrumentation on the steel-reinforcing cage and the finished concrete sections; developing finite element models for shear crack predictions; and calibrating the models with actual test results. During lab tests, hydraulic rams will exert pressure at several points along the culvert, and a variety of laser sensors—some mounted on a motorized rail that traverses the length of the section—will record the effects of the stress.

Thirty specimens will be tested to the point of failure. “The beauty of this is that we’re doing full-scale testing. We want to eliminate the errors associated with small-scale test models,” Abolmaali said. “This study may become part of transportation design codes across the country.”

The project integrates research and teaching for undergraduate and graduate students. In addition to the two graduate research assistants, a National Science Foundation-funded Research Experience for Undergraduates grant will support six students for two summers.

Industry support is so strong that Abolmaali is negotiating to establish a Center for Advanced Research in Underground Concrete Structures at UT Arlington where national standards would be set for concrete culverts and pressurized/nonpressurized pipe.

— Roger Tuttle