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17 3. For each bridge project, the research team designed two were shipped to the structures laboratory in Omaha, 42-ft-long specimens using the same number of strands Nebraska, within a month from their production date. used in the actual bridge. At least one of the four ends of the Concrete cylinders made during production and coupons specimens had to have the same end zone reinforcement of rebars were also sent to the structures laboratory with details used on the actual bridge. the specimens. 4. The precast concrete girder companies reviewed the details of the specimens and tried to find the right time to cast them 3.2.2 Description of the Test Specimens next to some of the girders of the actual bridge project. and Test Setup Therefore, the specimens were fabricated using the same material in the production of the girder of the actual bridge Table 3.1 summarizes the details of the eight specimens. The and received the same level of treatment regarding curing details in this table include the specimen type, type of end zone and strand release technique. reinforcement (EZR) details, material properties, number of 5. The precast concrete girder companies in Washington, prestress strands, and type of failure. Specimens are listed in Virginia, and Florida allowed the research team to be the order in which they were fabricated and tested. present at time of prestress release and to record any end The "proposed" detail was developed by the research team zone cracking that might appear. Most of the specimens based on the research that was conducted at the University Table 3.1. Design criteria of the full-scale specimens. Girder #1 Girder #2 State Left End Right End Left End Right End Girder Type EZR Type EZR Type EZR Type EZR Type Repair Repair Repair Repair TN1L TN1R TN2L TN2R LRFD 2007 EZR Proposed EZR TN DOT EZR Proposed EZR* No repair No repair No repair No repair Tennessee Construction Products, Inc., Jackson, Tennessee Designed to fail in flexure Type III ' AASHTO f ci = 6,000 psi, f c' = 7,000 psi Beams Bottom: 30 straight 0.5 in., 270 ksi, low relaxation strands stressed to 33.8 kips Top: 2 straight 0.5 in., 270 ksi, low relaxation strands stressed to 5 kips 7.5 in. thick CIP slab was added in the lab, f c' = 9,000 psi WA1L WA1R WA2L WA2R Proposed EZR* LRFD 2007 EZR NO EZR NO EZR Washington No repair No repair No repair Epoxy Injection State Concrete Technology Corporation (CTC), Tacoma, Washington Designed to fail in shear WF58G ' f ci = 6,000 psi, f c' = 8,000 psi (Wide Flange Super Girder) Bottom: 38 straight 0.6 in., 270 ksi, low relaxation strands jacked to 43.9 kips Top: 20 straight 0.6 in., 270 ksi, low relaxation strands jacked to 43.9 kips + 4 "temporary" post-tension 0.6 in. diameter strands VA1L VA1R VA2L VA2R No EZR No EZR LRFD 2007 Proposed EZR* No repair No repair EZR No repair Virginia No repair Bayshore Concrete Products, Cape Charles, Virginia PCEF45 Designed to fail in flexure (VA new ' f ci = 6,000 psi, f c' = 8,500 psi Bulb-Tee) Bottom: 38 straight 0.6 in., 270 ksi, low relaxation strands jacked to 43.9 kips Top: 14 straight 0.6 in., 270 ksi, low relaxation strands jacked to 43.9 kips 4-in. thick, 47-in. wide deck slab was cast monolithically with the top flange FL1L FL1R FL2L FL2R FL DOT EZR Mod. FL DOT LRFD 2007 Proposed EZR* No repair EZR EZR No repair Florida No repair No repair Standard Concrete Products, Tampa, Florida 60-in. deep Designed to fail in flexure inverted T ' beams f ci = 6,000 psi, f c' = 8,500 psi Bottom: 36 straight 0.6 in., 270 ksi, low relaxation strands jacked to 43.9 kips 10-in. thick, 24-in. wide CIP deck was added in the lab, f c' = 10,000 psi * Proposed EZR is the end zone reinforcement recommended by Tuan et al. (16) and discussed in Section 1.2.3 of this report.

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18 of Nebraska (16). As explained in Chapter 2, the LRFD Spec- 3.2.2.1 Tennessee Specimens ifications (18) and University of Nebraska proposed detail (16), Construction Products, Inc. of Jackson, Tennessee, fab- recommend that the end zone reinforcement should be ricated two 42-ft-long Type III AASHTO I-girders for the designed to resist 4% of the total prestressing force at trans- project. Each specimen had thirty 0.5-in. diameter, 270 ksi, fer, and that the reinforcement should be designed for a ser- low relaxation prestressing strands, stressed to 33.8 kips per vice stress not exceeding 20 ksi. However, the LRFD Specifi- strand. They also contained two partially stressed 0.5-in. cations states that this reinforcement should be distributed diameter strands in the top flange, stressed to 5 kips per strand. within h/4 (one-fourth of the depth of the girder) from the The specimens were designed to fail in flexure. Of the four ends, end of the girder, while the University of Nebraska proposed two had the end zone reinforcement designed to the proposed detail recommends that 50% of this reinforcement should be design; one was designed using LRFD specifications, and one placed within h/8 (one-eighth of the depth of the girder) from contained the same end zone reinforcement existing on the the end of the beam and the remainder should be placed be- typical Tennessee production girders. Figures 3.2 through 3.5 tween h/8 and h/2 from the end. show the details of the Tennessee specimens. 1'-4" Strands pulled to 5 kips 7" 2#6 (A601) #6 (A601) 2 1/2" 4 1/2" 41'-10" 8" 2#5 (A500) each end, projecting 6" (only appears on End TN2L) 1'-7" 7" 3'-9" 8" #5(A500) 6" 5'-6" 7 1/2" 8" 1'-4" 7" 6" 1'-10" (a) Longitudinal Reinforcement 5" #5(H500) or #6(H600) H500 or H600 10" 4'-0" 90 #3(HA310) HA301 #3 (HA300) 10" 7 1/8" HA300 5 1/2" 11" 1'-8" (b) Shear and Confinement Reinforcement Figure 3.2. Cross section details of Tennessee specimens.

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19 Double Projected Bars H500 @ 6" 2 spa @ 4 1/2" = 9" 5" 2 spa @ 3" = 6" 3 spa @ 2" = 6" 3 pairs of H600 4 pairs @ 3" of H600 @ @2 3" 1" 12 HA300 12 HA300 + + 12 HA301 12 HA301 @ 6" @ 6" 4.5" 1 1/2" Figure 3.3. End zone reinforcement details of TN1L (LRFD) and TN1R (proposed). 3.2.2.2 Washington State Specimens was more critical than having the strands draped. The force at Concrete Technology Corporation (CTC) of Tacoma, the top of the girder from the prestressed strands and the post- Washington, produced two 42-ft long, 58-in. deep Wash- tensioned strands created additional stresses in the girder web, ington Super Girders (Wide Flange Girders). Each spec- amplifying the end zone cracks. The top and bottom strands imen contained 38 straight 0.6-in. diameter, 270 ksi, low apply opposing flexural moments creating vertical tensile relaxation prestressing strands in the bottom portion of the forces in the web. girder, jacked to 43.9 kips per strand. At the top of the web, The specimens were designed to fail in shear. The first girder each specimen contains 20 additional straight 0.6-in diam- had one end designed using the AASHTO LRFD specifications eter prestressing strands and 4 "temporary" post-tension and the other using the proposed improved reinforcement 0.6-in diameter strands. The four "temporary" strands were design procedure. The other girder did not contain any addi- included in an attempt to amplify the end zone cracking as tional end zone reinforcement other than the typical shear much as possible. reinforcement. This was done to create the maximum amount The production girders that the Washington specimens of end zone cracking possible for the girder. The precast pro- were modeled after contained 20 draped prestressing strands. ducer stated that if they had a production girder that showed However, none of the girder specimens manufactured for the the extent of end cracking experienced by the test specimens, structural testing contained draped strands, so the top strands it would not be accepted. One of the ends that did not con- in the Washington specimens remained straight. Having the tain additional end reinforcement received an epoxy injec- prestressing strands remain straight at the top of the girder tion repair at the precast yard using the typical epoxy repair Double Projected Bars H500 @ 6" 5" Double Proj. 5 spa @ 3" = 1'-3" 3 spa @ 2" = 6" Bar H600 (typ) 3" 4 pairs of H600 @ 2" 6 pairs 1" of H601 12 HA300 5 HA300 + 12 HA301 @ 6" @ 3" 4.5" 4 pairs of H501 1 1/2" Figure 3.4. End zone reinforcement details of TN2L (TN) and TN2R (proposed).

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20 2" 1'-8" 2" 2" 2 1/2" (2) #4 bars 3 1/2" 2 1/2" 2" 2 1/2" (2) #3 bars (2) #4 threaded rods Figure 3.5. Girder TN1 decking cross section. procedure outlined in Manual for the Evaluation and Repair of Precast, Prestressed Concrete Bridge Products (11). The matching end was not repaired in any way. Figures 3.6 through 3.8 show the details of the Washington State specimens. 3.2.2.3 Virginia Specimens Bayshore Concrete Products of Cape Charles, Virginia, donated two 42-ft long, 45-in. high bulb-T girders with thirty- eight 0.6-in. diameter, 270 ksi, low relaxation prestressing strands in the bottom flange and fourteen 0.6-in. diameter, 270 ksi, low relaxation prestressing strands in the top flange of the girders, each tensioned to 44 kips. The straight pre- stressing strands in the top of the girder were designed to create additional vertical tensile stresses in the girder web, amplifying end zone cracks. These girders were designed to fail in flexure. Much like the Washington girders, two of the girder ends did not contain any additional end zone rein- Figure 3.6. Details of Washington specimens. forcement other than the typical shear reinforcement. The remaining ends were designed using the AASHTO LRFD Specification and the proposed improved details. In the end that was designed using the proposed details, a #8 C-shaped They had thirty-six 0.6-in. diameter, 270 ksi, low relaxation pre- bar was placed at 1 in. clear cover, in the same cross-sectional stressing strands in the bottom flange, tensioned to 43.94 kips plane as one of the pairs of #5 bars in order to get a larger each, and six #6 bars of mild steel reinforcement along the amount of steel closer to the girder end. None of the four ends top of the web. These six bars were placed to resist the top were repaired in any way. Figures 3.9 through 3.11 show the tensile forces produced by the prestressing strands. On spec- details of the Virginia specimens. imen FL1, one end contained the exact same configuration for end reinforcement as the Florida production girders, while the other end was designed to resemble the Florida 3.2.2.4 Florida Specimens end reinforcement design. On specimen FL2, one end was Standard Concrete Products of Tampa, Florida, produced designed using AASHTO LRFD specifications and the other two 42-ft long, 60-in. deep inverted-T girders for the project. was designed using the proposed detail. After receiving the