Presenter: Loai F. El-Gazairly, Ph.D., P.E., Associate, Whitman, Requardt & Associates (WRA), Richmond, Virginia
Topic: Design and Construction of Post-Tensioned Straddle Bents for US 301 over SR 1 in Delawar
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The US 301, Section 1 project in New Castle County, Delaware includes the preliminary and final design of the 5.5 miles of limited-access toll highway. One of the most complex design elements of the project is the interchange of the new US 301 with the existing SR 1 and US 13. The structure design includes 11 new highway bridges, one bridge widening, eight major culverts, three retaining walls, and seven sign structures. The US 301 over SR 1 flyover includes two pre-cast post-tensioned straddle bents (the first in the State of Delaware) with maximum span length of 116 feet and total design weight of 750 tones. Due to the caps concrete volume a mass concrete provision is introduced along with a thermal control plan in order to constrain the core rate of hydration and to prevent the formation of potential cracks. The straddle bents were casted and partially post-tensioned while been supported on falsework within the median of SR 1 then transported, lifted and erected into their final position. A second stage of post-tensioning was performed after erection to provide the ultimate strength of the bents to support the anticipated superstructure loads. The presentation will discuss the cap design philosophy and its structural analysis during casting, construction staging, transporting and erection.
Loai El-Gazairly has more than 36 years of design and management experience and participated in the design and construction of landmark bridge projects both nationally and internationally. Project examples are Route 895 in VA, the John James Audubon Bridge in LA, the Indian River Inlet Bridge in DE and others. The typical construction cost for such projects exceeded $150M and some of them established the record in technical advancement for bridges in the USA. He acted as a senior manager and technical advisor for many transportation projects and delivered quality engineering projects on time and within budget. Loai received his B.Sc. and M.Sc. degrees in Civil Engineering from Alexandria University, Egypt as well as a Ph.D. degree in Structural Engineering from the Georgia Institute of Technology. He is a Professional Engineer (P.E.) in the States of Virginia, Georgia, Florida, South Carolina, New Jersey, Pennsylvania and Ohio. Loai is now serving as the President of the American Society of Civil Engineers (ASCE) in Richmond.