Concrete Products covers the issues that attract producers of ready mixed and manufactured concrete focusing on equipment and material technology, market development and management topics.
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www.concreteproducts.com April 2014 • 39 www.hydronix.com 692 West Conway Rd, Suite 24, Harbor Springs, MI 49740 Tel: (231) 439-5000 Fax: (231) 439-5001 30 Years and Going Strong! STILL The Original STILL The Leader STILL THE BEST! Microwave Moisture Measurement for the Concrete Industry After a strong showing in January 2013, glass and polymer fiber-reinforced polymer hybrid precast girders again dominated the technical presentations on precast technol- ogy and accelerated bridge construction at the 93rd annual meeting of the Transpor- tation Research Board earlier this year in Washington, D.C. The TRB event kicked off the year for the surface transportation community, drawing nearly 12,000 to Washington from around the world. The program covered all transportation modes, with more than 4,500 presentations in nearly 800 sessions and workshops addressing topics of interest to stakeholders in government, industry and academia. For nearly 60 years TRB has been held among a cluster of hotels along Connecticut Avenue near Woodley Park and the Nation- al Zoo, but in 2015 it will move to bigger digs at the Walter E. Washington Conven- tion Center. Following are summaries of technical papers at TRB addressing precast applications. Next month we will look at ready-mixed concrete and cast-in-place technology at TRB. For more information, visit www.trb.org. Perspective view of a typical hybrid FRP-concrete truss girder, along with spec- imen dimensions and reinforcing details. Lighter-Weight Bridge System Relies on FRP-Concrete Girders Glass fber reinforced polymer (GFRP) tubes flled with concrete play an important part in a new-design bridge system, say Mo- hammad Aghahassani, Mamdouh Elbadry, Ph.D., P.Eng., and Mohammad Moravvej, Department of Civil Engineering, Univer- sity of Calgary, in their 2014 TRB paper, Experimental Fatigue Evaluation of Hybrid FRP-Concrete Bridge Truss Girders. "A novel hybrid bridge system compris- ing transversely spaced precast prestressed concrete truss girders, and a concrete deck cast or placed on top, has been developed," the authors say. "The girders have top and bottom concrete fanges connected by pre- cast vertical and diagonal truss members made of glass fber reinforced polymer tubes flled with concrete." The vertical members, predominantly in compression, are connected to the concrete fanges by means of dowels, they write, add- ing: "The diagonals, mainly in tension, are connected to the fanges using single-head- ed bars. The concrete fanges provide the fexural capacity of the girder, while the truss members resist the shear forces." The fanges are pretensioned during fabri- cation, and the girders may be post-tensioned by external tendons after erection to balance the slab weight and to provide continuity in multi-span bridges. All reinforcement and prestressing can be made of corrosion-resis- tant steel or glass and carbon FRP. "The proposed truss girder is thus light in weight and durable," the authors say. "The light weight allows for longer spans and reduces the initial cost. The potential enhancement in durability reduces the maintenance cost and extends the struc- ture's life span." The writers describe an experimental evaluation of the behavior of two-panel truss girders under static and fatigue loading. The fatigue tests under different service load levels and amplitudes showed that the truss girders satisfed the bridge code fatigue re- quirements. Post-fatigue monotonic loading tests showed considerable residual load-car- rying capacity of the girders following fatigue failure. "The test results have shown excel- lent performance of the truss girders under both static and fatigue loading," Aghahas- sani, Elbadry and Moravvej conclude. Accelerated Design Weds Hybrid Girders, Precast Slabs TECHNICAL TALK BY TOM KUENNEN FRP HYBRIDS MAKE ENCORE APPEARANCE AT TRB 2014 PHOTOS: Aghahassani, Elbadry and Moravvej Pedestrian bridge composed of two HFRP I-girders topped with a bridge deck made up of GFRP gratings constructed in Japan in 2011 replaced corroded steel bridge at right. Authors provide details of girders' cross-sec- tions (units are in mm). Composite crossings of hybrid fber rein- forced polymer (HFRP) I-girders topped with precast ultra-high performance fber rein- forced concrete (UHPFRC) slabs offer prom- ise for accelerated bridge construction, say Dr. Hai Nguyen and Dr. Wael Zatar, Marshall University, Huntington, W. Va., and Dr. Hi- roshi Mutsuyoshi, Saitama University, Japan, in their paper, Hybrid FRP Girders Topped with Segmental Precast Concrete Slabs for Accelerat- ed Bridge Construction. "Fiber reinforced polymer composites can be considered as an alternative to conven- tional materials in bridge construction, as they provide the following advantages: high PHOTOS: Nguyen, Zatar and Mutsuyoshi Concrete Products April 2014.indd 39 4/1/2014 11:39:30 AM