ASPIRE is a quarterly magazine published by PCI in cooperation with the associations of the National Concrete Bridge Council. The editorial content focuses on the latest technology and key issues in the Concrete Bridge Industry.
Issue link: http://www.aspiremagazinebyengineers.com/i/622975
PERSPECTIVE A SILVER BULLET FOR U.S. PRECASTERS The time is ripe to make the investment in reusable segmental forms by Craig Finley Jr., Finley Engineering Group Inc. A combination of ingenuity, advanced planning, and open-minded teamwork among the owner, general contractor, and the engineer resulted in substantial construction cost savings and a much quicker schedule on the first (and three additional) bridge project as part of Israel’s major highway development projects. It also gave Danya Cebus, which was the general contractor and precaster, a significant competitive advantage to win additional work. The key component for this country’s developing infrastructure systems was designing numerous segmental bridges to the same cross section and erection method that best met the contractor’s expertise and available equipment. While not new to Europe and other parts of the world, the use of standard precast machines for multiple projects was a novel, and some considered risky, approach in Israel. Although designing to standard precast box cross sections had been proven to have limited interest in the United States in the past, the time may be ripe to reconsider. The Initial Challenge The precasting machines were originally designed for the $273 million Ein Ha’Kore Interchange on Highway 431, part of the Cross-Israel Highway, but now more than 1100 segments on three additional bridge projects have been built out of the same two precasting machines. The general contractor knew that efficient construction methods were a key element for success, and they were looking to apply innovative techniques to reach their goal. Finley Engineering Group brought their international experience to the project to provide a simple solution to a complex problem. All the involved entities—including governmental officials, the owner’s engineering representatives (who had completed the preliminary design), and the contractor’s ownership group— considered the alternatives and were open to the innovative idea. They agreed that precast concrete segmental bridges, using external tendons with diabolos, were a safe, cost-effective, and reliable long-term solution for this project. The use of external tendons provided simplified precasting details, rapid erection procedures, and improved long-term durability. They also added technical advantages in the bridge design, such as increased ductility for flexural moment resistance and a significant reduction in principle tensile stresses in the box-girder webs. These benefits allowed for longer, constant depth span lengths for the bridges, while still meeting the interchange design requirements. External tendons also provided savings on long-term maintenance costs allowing for simpler tendon replacement and periodic inspections. As a result, the general contractor, who was an experienced precaster but had no segmental bridge experience, was able to win the design-build operate- transfer project based on its low bid, and finish ahead of the ambitious schedule. This was critical to