JEC COMPOSITES MAGAZINE - Issue #33 - June 2007 - 48

installed near Fond du Lac, Wisconsin in 2004. The present panel system utilizing pultruded plate as the SIP formwork was installed on a Greene County, Missouri bridge in November 2005. The Missouri system was the first to provide a fullyintegrated reinforcement and SIP formwork. To complement the deck reinforcement and develop a steel-free system, a new Modified Kansas Corral Rail (MKCR) reinforced with prefabricated glass FRP rebar cages was also developed. Advantages of composites In addition to the structural (static and fatigue) strength guaranteed by FRP reinforced concrete (RC) decks, the key features of the GRIDFORM® solution presented herein are: • easier and faster construction – over 70% reduction in construction time from reinforcement installation to deck casting and finishing; • higher productivity – the rate of concrete placement is increased by 50% compared to traditional steel reinforced decks with similar dimensions; • reduced labour cost – over 75% reduction in deck construction labour cost; • Improved safety – very lightweight FRP panels make handling easier and the design of the reinforcing profiles facilitates walking over the top mat; • enhanced durability – extensive research has demonstrated the superior corrosion resistance and durability of internal FRP reinforcement for concrete when compared to steel rebar. JEC Composites Magazine / No33 June 2007 Detailing of FRP SIP panels for Greene County bridge deck FEATURE “Construction” g…/… Rapid bridge deck construction with FRP reinforcing grids Five-day installation Fig. 2: Detailing of FRP SIP panels: longitudinal section with staggered grating layers. The GRIDFORM® reinforcement system was used in the construction of the new Bridge 1482301 in Greene County, Missouri, completed in November 2005. The County opted for the replacement of the 73-year old posted bridge due to the severe deterioration of the concrete deck, safety appurtenances, and steel girders that reduced the load rating from the original 10 tons to only 4.3 tons. The new bridge raised the load rating to AASHTO HS-20. It has the same total length of 44 m of the old structure, and consists of four symmetric spans, the exterior ones with a length of 11.3 m, and the interior ones of 10.7 m. The 178-mm-thick RC deck sits on four W24 x 84 rolled steel girders spaced at 1.8 m on-centre and running continuously along the bridge two-span half-length portions, with a closed expansion joint at the central support. The out-to-out deck and clear roadway width is 7.3 m. The bridge “redecking” operations took only five days to complete, instead of the two to three weeks normally required for similar steel reinforced decks with open-post railings built by the contractor (figure 3). The construction phases were as follows: • Day 1: All the 18 deck panels were set in place and anchored to the steel girders by six workers in a total of six hours. • Day 2: The prefabricated rail post cages were inserted into the cut-out pockets in the SIP panels; the deck details were formed in a traditional manner using plywood, including expansion joints, chamfers, and drip edges; the finishing machine was finally set. Fig. 3a: Five-day bridge redecking: installation of FRP SIP panels. The panel details and deck construction solutions were devised with the main objective of improving constructability, taking advantage of valuable inputs from contractors and practitioners. Full continuity of the main reinforcement elements was preserved by adopting a panel width that replicates that of the bridge deck. An acceptable degree of continuity in the secondary reinforcement was also ensured by the panel-to-panel overlap connection, as allowed by the 0.3-m offset between the top and bottom layers (figure 2). The end panels are designed to accommodate the expansion joints, and can be easily adjusted on-site due to the ease of saw-cutting the FRP components. Glass FRP strips with 3-mm thickness were inserted between the bottom-layer cross-rods and the form to cover the butt joints between adjacent form plates, thus preventing leaking of concrete during the casting operations. Each SIP unit can be anchored to the top flanges of steel I-girders by means of stainless steel threaded bolts and FRP washers; however, in case composite action is required between deck and girders, automatic welded shear studs can be accommodated in holes pre-drilled in the form plates. Mounting of the very lightweight (about 16 kg), prefabricated FRP rail post cages at the correct spacing is facilitated by the presence of pockets cut out in the reinforcing grids.

JEC COMPOSITES MAGAZINE - Issue #33 - June 2007

Table of Contents for the Digital Edition of JEC COMPOSITES MAGAZINE - Issue #33 - June 2007