详情

District 3-0 Investigation of Fiber Wrap Technology for Bridge Repair and Rehabilitation

项目名称：	District 3-0 Investigation of Fiber Wrap Technology for Bridge Repair and Rehabilitation
摘要：	Pennsylvania Department of Transportation (PennDOT) District 3-0 owns and maintains approximately 300 concrete T-beam bridges throughout their nine counties. The number, age and condition of these bridges are representative of PennDOT's T-beam bridges statewide. The District 3-0 bridges range in age from the early 1900's through the early 1970's. Inspection records indicate NBIS condition ratings varying from 3 (serious) to 7 (good). Deterioration of the superstructures is primarily due to age but also due to water damage deteriorating the inside faces and bottom flanges of fascia beams adjacent to drains. Construction practices in those years were primarily to form holes through the deck along the inside face of parapets, thereby allowing water from the deck to drain directly onto the fascia beams. Where feasible, the District has plugged these drains on short span (<30') structures; for longer structures, PVC or metal downspouts have been installed to extend below the bottoms of beams. In addition, the District utilizes concrete jackets to encase previously deteriorated fascia beams and/or bottom flanges. Major rehabilitation of damaged beams is often beyond the capabilities of the District's county maintenance forces, and conventional repair methods are expensive and typically do not address loss of load carrying capacity. With limited funding, un-repaired structures typically deteriorate to the extent where replacement becomes the only alternative. Best management practices dictate finding innovative repair methodologies that extend the structure's service life and restore load carrying capacity to minimize current and future economic impact to the public. For this reason in recent years the District has considered using innovative materials such as FRP systems as a viable method to extend service life and maintain or restore load capacity. In previous District studies, both the technical and economic feasibility of externally bonded FRP for concrete bridge repair and retrofit were extensively evaluated. This was done through a comprehensive literature review and an effective survey of state DOTs; the analysis of findings conclusively showed favorable attributes and advantages of applying FRP technology for repairing concrete T-beam bridges in lieu of conventional repair methods. Based partly on National Cooperative Highway Research Program (NCHRP) studies, the District developed a system for ranking concrete T-beam bridges into three categories as candidates for possible FRP repair: Level 1 showing extensive damage and with all work to be completed by contract forces; Level 2 showing moderate damage and the repair work to be implemented by a combined approach of contract and District forces; and finally Level 3 with minor damage and all repair work to be performed by District forces. A cost analysis was performed for District-3 bridges for the 3 levels of proposed repair indicated above. In relation to conventional repair methods, the FRP technology was shown to be significantly more cost effective for Level 1, particularly in relation to total bridge replacement, and either less or equally costly for Levels 2 and 3, depending on the scenarios considered. Thus, it was concluded that District-3 would significantly benefit from the implementation of FRP technology for repair of concrete T-beam bridges, with potential application to over 50 percent of the bridges considered in the study. Moreover, design and construction guidelines to be developed through a District-3 field demonstration project can serve PennDOT statewide for future applications of FRP repair and retrofit to various types of concrete bridges. The District is following a phased sequence for developing design and construction standards for the rehabilitation of concrete T-beam bridge projects beginning with a Level 1 repair to be followed by Levels 2 and 3. This proposed approach will provide the best possible transfer of technology, allowing District personnel to oversee a contract repair; participate in a hands-on repair; and finally, to complete repairs utilizing county maintenance forces with oversight by District bridge personnel. The scope of work of this project will include assisting and documenting the rehabilitation of bridge no. 49-4012-0250-1032 through its planned contract repairs; performing follow-up lab and field testing to validate design, analysis, and construction techniques; and developing design and construction guidelines and specifications. The candidate bridge for a Level 1 repair was selected corresponding to level of overall visual damage as noted in NCHRP Report 514 and various factors based on previous District studies, including age, level of service, deficient load capacity, global damage, ADTT and accessibility. The selected single-span T-beam bridge is no. 49-4012-0250-1032, which is a 48-ft (45-ft ctr. to ctr. bearings) bridge located near Elysburg, Northumberland County, PA. During design, the assessment of this bridge included visual inspection, coring of samples from the deck, obtaining concrete samples from the beams, and removing a section of main steel rebar. The field and laboratory evaluations of material samples included in-situ NDT techniques such as ultrasonic pulse velocity and rebound hammer tests. Laboratory tests served to obtain structural properties of concrete and steel, and also to characterize concrete samples through various chemical tests (carbonation, cement content, soluble chloride) and microstructure evaluations (SEM and EDX). The bridge was then load-tested to evaluate static and dynamic responses, and results were used to validate analysis methods for load-rating (using both PennDOT's BAR-7 program and AASHTO methods) and extensive Finite Element modeling. Finally, the calibrated analytical models were used to design the FRP repair for the bridge, including flexure and shear of girders, and checking the adequacy of the slab design. Bid documents and requirements to implement the retrofit of this bridge are based upon NCHRP guidelines and ACI specifications, combined with current PennDOT specifications and results and recommendations from previous District studies.
状态：	Completed
资金：	315804.00
资助组织：	Mid-Atlantic Universities Transportation Center<==>Pennsylvania Department of Transportation
项目负责人：	Karavage, Lisa
执行机构：	West Virginia University, Morgantown
开始时间：	20080115
实际结束时间：	20100114
主题领域：	Bridges and other structures；Highways；Maintenance and Preservation