A full-scale jointed plain concrete pavement (JPCP) with two different dowel bar arrangements, namely, standard and special method, was constructed and evaluated under actual traffic-environmental condition in Florida. November 2, 2011 2nd International Conference on Best Practices for Concrete Pavements Presentation Outline • Introduction • Benefits of dowel and tie bars • Dowel and tie bar design – Diameter – Length – Spacing • Construction • Summary November 2, 2011 2nd International Conference on Best Practices for Concrete Pavements Dowel Diameter Germany 25 mm USA Concrete … This technique provides for retrofitting dowel bars in a concrete pavement that was originally constructed as a non-dowel jointed pavement. 3D FEM is an e cient and accurate method to calculate the interaction characteristics in concrete pavements. – “Dowel Alignment Testing and Tolerances” – new tech brief, currently in review 021, “Best Practices for Dowel Placement Tolerances” FHWA 2016 – FHWA-HIF-16-003, “Dowel Basket Anchoring Methods - Best Practices for Jointed Concrete Pavements” FHWA (2018?) Results indicate that the radar system is capable of determining the location of dowel bars placed in concrete pavements. on concrete pavement construction in the United States: • Dowel placement tolerances that may not reflect field experience—The existing specifications are based on limited laboratory testing and ana-lytical investigations. Photo 22. Addition to dowel-bar baskets controls joint formation M any state departments of transportation set tolerances for the accuracy of dowel-bar placement in a concrete-pavement joint. The patch is then ready for concrete placement. The results of an investigation conducted to develop placement tolerances for dowels at concrete pavement joints are presented. 9 in. The paper addresses all forms and combinations of dowel misalignment. An Alternative to Traditional Round Dowel Bars Plate Dowel Innovations Driven by Industrial Concrete Paving Introduction Round dowel bars have long been the standard load transfer device for concrete pavements with thick-nesses of about 8 inches or greater. The purpose of the analysis was to compute restraint stresses induced in the concrete pavement for different levels of dowel misalignment. They are inserted at the mid-depth of slab and coated a bond breaking material to restrict bonding to the PCC. Holes are drilled in the existing pavement to accept the dowel bars. Dowel bars always inserted in the mid-depth of the slab. For standard dowel bar arrangement, dowel bars spaced at 304.8 mm (12 in), while three dowel bars spaced at 304.8 mm (12 in) only within the wheel paths were … 1-1/4 in. This guide specification is directly applicable to 18 in. dowel placement achieved by contractors using typical methods is not well known. The mechanical connection provided by dowels 08-db_retrofit_REV3_08-03-05.qxd 10/6/2005 1:22 PM Page 7 Dowel bar retrofit (DBR) is a load transfer restoration process that delivers a renewed level of structural strength to portland cement concrete pavement (PCCP). Between the initial milling and concrete placement, th e Inspector must recheck the slab to insure that all unsound concrete is removed. vStudy dowel and tie bars and know when and how to use them. Clean the area by sand blasting and air blasting. terms of load and to compare di erent types of structures and used dowels (dimensions, coating, placement, etc.). The improved load transfer reduces slab deflections relative to undowelled joints. Verify that dowels have been coated with an approved bond release compound to prevent bonding of dowel slot patch material to dowels. A dowel bar retrofit (DBR) is a method of reinforcing cracks in highway pavement by inserting steel dowel bars in slots cut across the cracks. Dowel bar retrofit has been in use in the US for about three decades now. They are placed across the transverse joint of the concrete pavement to allow the movement. The solution for semi-infinite dowel bar encased in concrete pavement can be obtained: (8) y = e-β x 2 β 3 EI [(P-M 0 β) cos (β x) + (M 0 β) sin (β x)] where β is relative stiffness of the dowel bar encased in concrete, P is shear force carried by the critical dowel, M 0 is bending moment carried by the critical dowel at joint face which is equal to the product of −P and half joint width. Dowels are used in jointed concrete pavements to provide load transfer and improve performance. Dowel placement along 16 transverse joints was evaluated with the radar system. The dowel bars are to be sized as follows: DOWEL BAR SIZES Pavement Thickness Minimum Dowel Bar Diameter Less than 9 in. maximum of the top of the dowel bars or 1/2 of the slab thickness. Dowels are needed at these locations for all pavements, regardless of thickness or truck traffic. With the improvement in quality standard and design of the national road projects, DPWH also considers current annual average daily traffic report and axle loading for trucks and trailers to determine the need for thicker pavement. 1-1/2 in. Photo 21. Improper placement (embedment) of dowel bars leads to decrease in load transfer efficiency, which can result in faulting and other pavement distresses. Scope, Background and Applicability . In DBR, slots are cut, concrete removed, dowel bars inserted, repair mortar is placed in the slots, the surface finished, cured, and, most often, diamond ground. By limiting the allowable misalignment of dowel bars, these tolerances are designed to improve bar placement … Holes are drilled on existing concrete pavement to install the dowels and tie bars and filled with epoxy resin or hardener grout. One of the most efficient ways to restore load transfer at the joints is dowel bar retrofit (DBR). For jointed plain concrete pavements, check that dowel bar baskets, tie bar baskets, and the bars themselves are not being displaced during the concrete placement and paving operations. Tie bars Tie bars are deformed rebars… Many of those retrofits have been in place for 20 plus years and performing well. Title: Effect of Dowel Bar Arrangements on Performance of Jointed Plain Concrete Pavement (JPCP) Author(s): Kukjoo Kim, Sanghyun Chun, Sangyoung Han, and Mang Tia Publication: IJCSM Volume: 12 Issue: Appears on pages(s): Keywords: dowel bar arrangement, concrete pavements, finite element analysis and long-term performance. Dowel Bar Alignment and Location for Placement by Mechanical Dowel Bar Insertion January 7, 2013 . 1. Dowel-Bar Retrofit 7 FIGURE 1.Dowel-bar retrofit schematic. Size. The rule of thumb for dowel size is: Dowel Diameter = 1/8 of the Pavement Thickness. 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