The National Academies

NCHRP IDEA 20-30/IDEA 080 [Completed (IDEA)]

Development of a Generic Connector System for Attaching Conventional Bridge Rails to RFP Composite Bridge Decks
[ NCHRP 20-30 (NCHRP-IDEA) ]

  Project Data
Staff Responsibility: Dr. Inam Jawed

This NCHRP Project has achieved its goal of developing and testing a connector system that allows the attachment of standard steel post and rail as well as standard concrete barrier systems to most currently manufactured fiber reinforced polymer (FRP) composite bridge decks and superstructures. Current federal standards require that railing systems for rehabilitated bridges must: 1) be crash tested or 2) make small changes in designs that do not materially change a crash tested system if it passes the specified test level (TL-2) static tests. Prior to this project no bridge railing system had qualified under these two criteria and none were available. Therefore the use of FRP composite bridge decks for the rehabilitation of bridges has been limited to bridges on which the bridge rail can be connected to the supporting beams of the structure. The number of bridges that cannot currently be fitted with FRP composite decks because a tested railing system has not been available is estimated to be at least 50,000. Therefore the need for a generic bridge rail system of both steel post and concrete barrier designs for generic FRP composite bridge decks and superstructures is a critical requirement for expanding the use of rapid installation composite decks and superstructures. Since both steel post and concrete barrier railings have been crash tested, the strategy for this investigation utilized existing railing units and focused only on the development of an attachment system that does not compromise the strength of existing rails but focuses specifically on the direct connection of the railing to the deck. The initial research consisted of a simple analysis of the loads that are imposed on an FRP deck by existing railings at the time the railings fail. Thus if the tested rails fail without damage to the FRP composite deck the probability is that the full railing system will successfully pass a crash test. The stresses arising in the FRP deck could be absorbed using a top and bottom steel plate system that spreads the impact load over a sufficiently large area of the composite deck. The area of the plates and the size and number of bolts was determined to be small enough so that two plate clamping systems on the composite deck appeared to be feasible. Also the use of concrete barriers appeared to be feasible if six connection bolts were used in place of the standard four. Subsequently the plate/bolt connector design has been subjected to (TL-2) static testing and passed successfully. For the steel post railing, crash testing is not necessary since the railing system has not been materially altered. The plate connector design is now available for use on FRP decks. In the case of concrete barriers, the use of steel plates under the FRP decks has been statically tested to the TL-2 level. However, since no suitable crash test is available, it will be necessary to crash test the FRP deck connector system. As a compromise, a bogie test may be acceptable. This decision has not been made yet. In either the full-scale crash test or the bogie crash test there is a high probability that the connector system for concrete barrier bridge rails will successfully pass either mandatory crash test. All testing is currently being performed at the Midwest Roadside Safety Facility by the Civil Engineering Department, University of Nebraska at Lincoln. A steel framework has been designed by BG Consultants of Manhattan, Kansas. This FRP panel support system is of a general utility and will be available for all FRP manufacturers to use to test their panels. The diaphragms will need to be modified to accommodate various steel support beam spacings.  It is estimated that the development of the two bridge rail systems will double the use of FRP composite decks for both new and rehabilitated bridge decks. Given the lightweight and rapid installation features of FRP decks, this will allow them to be replaced overnight on a lane-bylane and section-by-section basis and will allow multi-lane commuter highways to maintain traffic. This procedure will provide greater flexibility in rebuilding failing bridges and greatly reduce commuter delay and frustration. KSCI has in the last few months actually demonstrated successfully the lane-by-lane closure feature, while the section-by-section feature is considered the easier requirement to meet for both FRP bridge decks and self-supporting superstructures. This payoff feature is hard to give an exact value to but is very important. A cooperative effort will be carried out between KSCI and the Market Development Alliance of the FRP Composite Industry to make these designs for the connectors easily and directly available to fabricators of railings and contractors. Two bridges with FRP superstructures in Missouri and New York have been built and installed after having successfully passed the required TL-2 static test. Two bridge decks on detour bridges with FRP composite decks were fabricated and installed in Kansas in the spring of 2005.

Final Report is not available.

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