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.

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PA R T N E R S P O T L I G H T 26 | ASPIRE Summer 2016 DYWIDAG is celebrating a special anniversary: 150 years. At this time, we are looking back at the beginnings of modern industrial construction and reflecting on the extraordinary achievements of DYWIDAG engineers. These achievements continue to motivate us to develop creative and technically innovative solutions for construction. Now, in the twenty-first century, more and more daring architectural designs are possible, and we know that this creative power would have been unthinkable had it not been for the development of new concrete construction methods, from precast concrete to post-tensioning. It is difficult to appreciate today how much technical knowledge and risk- taking was needed to begin using unreinforced concrete. This original concrete was compacted by pressure surges during pounding (compressed concrete) in structures for which safety had to be of the utmost importance. 1880—12-m (39 ft) Span in Dusseldorf One of the first concrete bridges in Germany using this technology was built by DYWIDAG in 1880. It was an exhibition bridge with a 12-m (39 ft) span that carried a pavilion and stood on the premises of Dusseldorf's trade and art exhibition. The demolition of the bridge at a later stage was extremely difficult due to the high compression of the concrete. For a quarter century thereafter, DYWIDAG built compressed concrete bridges. In 1922, DYWIDAG built a unique, 60-mm-thick (2.4 in.), 25-m-diameter (82 ft) dome structure. Still today, the construction material concrete is constantly proving its superiority around the world for shell construction and in post- tensioning. Both construction methods are inseparably connected with the name of Dyckerhoff & Widmann AG (DYWIDAG). 1927—Saale Bridge Alsleben In 1927, DYWIDAG was awarded the contract for construction of the Saale Bridge Alsleben, having designed an innovative dual pivot arch rib structure with stress ribbons. During construction, the stress ribbons were first connected with one side of the 68-m-long (223 ft) arches and loosely positioned above a recess in the middle of the longitudinal girders for the bridge deck. Afterwards, the stress ribbons were tensioned using a newly developed puller until they had reached their working load and were then concreted. This project represented the first important step towards post-tensioned concrete. The post-tensioning construction method developed by DYWIDAG introduced an innovative period for the construction industry. Thanks to this method, it may be said that concrete triumphed over the laws of gravity and it was used in new areas for the first time. Even major bridges could be built using post- tensioning and concrete instead of the steel construction method. 1965—Pioneer Work and a World Record A convincing example for this development is the Bendorf Bridge, which crosses the Rhine north of Koblenz, Germany. With a span of 208 m (682 ft), it was the world's widest concrete girder bridge when opened in 1965. Even today, it is still fully functional. Know-How for International Projects In the 1950s, in addition to its traditional business area of construction, DYWIDAG began signing license and consulting contracts for the application of the different DYWIDAG construction methods around the world. The success in post-tensioning was especially helpful for DYWIDAG in this process. This mainly applied to the following areas: • Bridges built using the DYWIDAG Post-Tensioning System • Construction of large bridges using the patented DYWIDAG Free Cantilever Method • DYWIDAG Prestressed Concrete Sleepers (Crossties) In Europe, the DYWIDAG Post- Tensioning System was mainly used in conjunction with the free cantilever method and the use of precast concrete elements. The first projects were the Freudenau Harbor Bridge and the Au-Leistenau Bridge in Austria. In Sweden, a large number of bridges were built using the free cantilever and precast concrete methods. Examples include the bridge leading over the Kallosund near Skagerrak with a main span of 94 m (308 ft), which was completed in 1957. Additional license agreements were signed in Denmark, Finland, Norway, and the Netherlands. 150 Years of Bruecke-aus-Stampfbeton made of high-compression concrete. by Dave Martin, DYWIDAG-Systems International USA Inc.

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