Railway Track & Structures - November 2007 - (Page 21)

a similar system of hook bolts with spring lock washers and locking nuts. On the second girder, however, locking clips were used as well (Figure 5a). This system has performed satisfactorily, accumulating nearly 500 mgt of HAL traffic with no maintenance required. The addition of locking clips has been particularly effective in this case. Another commonly used bridge deck fastening system consists of bridge deck bolts with spring clips to engauge the bottom of the flange (Figure 7a). Several sizes of spring clips are available, depending primarily on the thickness of the girder top flange. The HCP-25 model was recommended for the steel bridge at FAST with a flange thickness of about 2.5 inches. On one girder, this system was installed and tightened per the manufacturer’s recommendation. When properly installed, the spring clip remains in contact with the bottom of the flange at all times. The spring clip provides a toe load in the same fashion as does an elastic rail fastener on a rail base. Ears on the spring clip engage the ties to prevent rotation. After about 35 mgt, the nuts on about a third of the fasteners had come loose, and several of the spring clips rotated, requiring maintenance. Figure 7b shows a rotated spring clip. The top flange experienced some gouging caused by the spring clips. This resulted from longitudinal movement between deck ties and girder (Figures 7ac). Note that the top flanges of the FAST steel bridge are smooth. On spans with no protruding rivet heads in the top cover plate, the rivet heads become embedded in ties, and would likely prevent such movement in conjunction with this type of fastening system. On one girder, the HCP-25 spring clips were installed using double nuts and threaded fastener adhesive (Figure 7c). This system has performed satisfactorily, accumulating over 300 mgt of HAL traffic with no maintenance required. The comment regarding gouging also applies to this configuration. This test is ongoing with additional accumulated tonnage. When the original spring clip installation required maintenance, the hardware was realigned and tightened using threaded fastener adhesive. This single-nut installation in comparison with the double-nut installation will help distinguish the benefits provided by double www.rtands.com nuts and threaded fastener adhesive. This system has performed satisfactorily, accumulating nearly 300 mgt of HAL traffic with no maintenance required. The previous comment regarding gouging also applies to this fastener configuration. This test is ongoing with additional tonnage being accumulated. These tests are ongoing. An advisory group of railroad chief bridge engineers and AREMA bridge committee chaimen provides technical oversight. References 1. Sasaoka, Charity, David Davis, Duane Otter, and Brian Doe. July 2002. “Evaluation of Specialized Rail Joints for Moveable Bridges under HAL Traffic.” Technology Digest TD-02-016. Association of American Railroads, Transportation Technology Center, Inc., Pueblo, Colo. 2. Sasaoka, Charity, David Davis, Duane Otter, and Brian Doe. September 2003. “Testing Rail Joints for Moveable Bridges.” Railway Track & Structures. pp. 21-25. Railway Track & Structures November 2007 21 http://www.rtands.com

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Railway Track & Structures - November 2007

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