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| Outstanding technical and professional engineering accomplishments and contributions |
The nominee has made fundamental contributions to structural engineering research, teaching and design with structural concrete. He co-founded the highly successful consulting firm Tadros Associates, LLC, with two of his former students. The firm has already received several awards for outstanding bridges and other structures. He is the principal author of the first comprehensive, authoritative design guide of concrete bridges, the Precast/prestressed Concrete Institute Bridge Design Manual. Dr. Tadros along with one of his partners, Karen Bexten, designed the first high performance concrete bridge to open to traffic in the US in 1996, in Sarpy County, Nebraska. The theories developed by Dr. Tadros on design of prestressed concrete have received wide acclaim and are being used throughout the world. They include strength design for prestress transfer (developed jointly with Robert Mast), prestress loss in high performance concrete, analysis of cracked prestressed concrete flexural members, and theory of creep restraint of continuous members made of precast concrete units.
Dr. Tadros has invented several products that are widely used in practice. Perhaps his most popular product is the NU (Nebraska University) precast prestressed concrete I-girder, NU-girder. Introduced in the early 1990s, the NU-girder was initially adopted by his home state of Nebraska as the standard I-girder product, replacing the previously used AASHTO girders. With the introduction of the NU-girder, it has been possible to design alternates to steel plate girders using the same girder depth and girder spacing for a give span configuration. Gradually, concrete span capacities have grown from about 120 ft to about 280 ft over a period of 15 years. Several other states and other countries have adopted the NU-girder without modification or with slight modification, reaping similar benefits. They include New England states, Michigan, Washington, Wisconsin, Iowa, Alberta (Canada), India, Panama, Mexico, and Brazil. Similarly successful was the Inverted Tee Bridge System for short span bridges, which is now used in Nebraska, Kansas, Iowa, Florida, North Carolina and Australia. Most recently, Dr. Tadros has introduced the NUDECK precast prestressed full depth full width bridge deck system. Its novelty has earned the Skyline Bridge where it was first applied two PCI Awards, including the Harry Edward Award for innovation. Another product of note is the fully composite, energy efficient concrete sandwich panels. A patented fiberglass connector between the exterior concrete wythes allow for a high degree of composite action while preventing the nagging problem of thermal bridging in the type of construction.
Dr. Tadros is an outstanding teacher. He gives generously to his profession in the form of committee activities, uncompensated consulting, and organization of continuing education activities. The Highly successful Annual Structural Conference, which attracts structural engineers in the Midwest, has just celebrated its 25th anniversary. It was initiated by Dr. Tadros and two of his friends, against the recommendations of others who had previously attempted and failed to have a consistently successful training program for structural engineers in the area.
Dr. Tadros was once asked to state the accomplishment he was most proud of. His answer was not the 250 plus papers or the millions of research dollars or the award winning structures he designed. He was most proud of the highly successful engineers and professors he had mentored.
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| Impact of Work (technical, Commercial, national, etc.) |
The impact of the nominee’s work has been profound in the above categories. The company he co-founded has had tremendous influence not only in Nebraska but also nationwide. The award winning railroad bridge #59, in Nebraska City, had uniquely connected concrete boxes. It is frequently cited in designs in Oregon, Maryland and Florida. Clarks Bridge, another award winner, introduced for the first time the creation of continuity for deck weight without use of post-tensioning. This allowed a modified NU1100 (50” deep) I-girder to span 151 feet at a spacing of 10’-9”. This “threaded rod” continuity system has since been used on a number of other bridges in Nebraska, Illinois and Iowa. It has been used as a powerful value engineering tool saving the owners millions of dollars over the originally designed plate girder alternates. The about-to-be-completed Arbor Road Bridge is the first precast prestressed concrete girder bridge that is precast curved in plan and then post-tensioned in the field for continuity. The contractor saved time and several hundred thousand dollars despite the fact that the system was new.
Spliced concrete girder bridges, stretching the concrete girder spans to over 300 ft were made popular through the 1992 state of the art publication by Dr. Tadros and one of his former students. The sandwich panel system invented by Dr. Tadros has resulted in a new line of products marketed by large companies throughout the US.
Dr. Tadros’ research has resulted in a number of building and bridge code changes, significantly impacting structural design in the US. Prestress loss, compression limits, welded wire reinforcement fatigue limits, modulus of elasticity, creep and shrinkage are just examples.
Most significantly, Dr. Tadros has been the mentor of company executives such as Scott Gilliland, President of Tadros Associates, Mark Lafferty, General Manager of Concrete Industries, and Todd Culp, Marketing Director of Core Slab. He has mentored and has continued to be in touch with former students who now professors: Terry Wipf of Iowa State, Sharon Huo of Tennessee Technological University, John Ma of University of Tennessee and Sameh Badie of George Washington University.
Dr. Tadros service activities and his vision for his profession and community have produced results that benefit the profession and community on a daily basis. The Ravenna Arch Bridge he conceived and helped design without compensation is now the source of pride of the entire city of Ravenna, Nebraska. The PCI Bridge Design Manual took 10 years to develop, but is now in the library of virtually every designer of concrete bridges. The $22 million funding for the 3000 ft long with 600 ft mail span Missouri River Pedestrian Bridge between Omaha and Council Bluffs, Iowa, was made possible through the various civic organization presentations by Dr. Tadros of his vision for that bridge.
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