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22 1/2" 1/2" 1/2" 1/2" #4(401A) #4(401A) #8 C-bar 1 1/2" (VA2R only) 1 1/2" (2) #5(504A) (2) #5(501A) or #6(604A) #4(402A) #4(402A) 1" clear 1" clear Cross Section Cross Section Reinforcement Detail Reinforcement Detail at Ends at Midsection 3 1/2" 4'-0" 8" 3" 8 5/8" 6" 8" 4" 1 1/2" #4 (404) 2" 1'-6" 4 1/2" 2" 3'- 6 3/4" 4' 4' 2'-0" 8" 1'- 1 3/8" 1' - 9" 3 1/2" 13 /4" 3 1/2" 4 1/2" 3" 7" 2" 5'- 4 1/4" 2'-2" 3 1/2" #5 (504) 2'-9" #4 (401) #4 (402) #4 (403) #6 (604) Cross Section Figure 3.9. Cross section details of the Virginia specimens. reached as the failure load was beyond the capacity of the 3.2.4 Test Results loading frame. The failure load was calculated using the mea- A summary of test results is given in Table 3.2. The table sured material properties of the concrete cylinders made gives the failure mode and failure moment including those during fabrication of the specimens and the coupons taken calculated based on the specified and measured material of the reinforcing bars. properties and those obtained from the test. A summary dis- cussion related to each set of specimens is given in the follow- ing sections. More details about all fabrication and testing of 7 1/2" pairs of #4(401A) bars @ 12" spacing all specimens are given in Appendix C. pairs of #5(501A) bars @ 4" spacing 1 1/2" (1" clear) 3.2.4.1 Tennessee Specimens Upon inspection after the release of the strands, neither girder appeared to have experienced any visible end zone cracking. The research team believes that the lack of end zone cracking is due to the limited amount of prestressing force, the presence of end zone reinforcement, and the size (9) #4(402A) and shape of the girder. The girders contained thirty 0.5-in. diameter strands. This amount was the largest available to the producer at the time the specimens were made. The relatively 3 1/2" (9) #4(402A) @ 4" #4(402A) bars @ 12" small girder size and amount of prestressing, compared to the Figure 3.10. End zone reinforcement details depths, spans, and levels of prestress in other states, has been of VA1L (no EZR) and VA1R (no EZR). a challenge to the research team. This is because the research

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23 6 1/2" #4(401A) bars @ 12" #4(401A) bars @ 12" 7 1/2" 5 spa @ 2" pairs of #5(501A) bars @ 4" pairs of #5(501A) bars @ 4" 2 spa. @ 2" 1 1/2" (1" Clear) 1 1/2"(1" clear) #8 C-bar 6 pairs of #6(604A) @ 2" spacing (12) (10) #4(402A) #4(402A) 1 3/4" 4 3" 6 spa #4(402A) #4(402A) 2 1/2" 2 1/2" spa @ 4" @12" @12" 7 spa @ 4" = 2" @ 2" 28" 3" Figure 3.11. End zone reinforcement details of VA2L (LRFD) and VA2R (proposed). 6 1/2" 4" 2" 6 #6 bars @2 in. 6'-7 1/2" #5(5K1A) 3'-10" 5'-0"" 36- 0.6 in. strands @2 in. 6 1/2" 7 1/2" #3(3D1) 6" 3" 2'-4"" 1'-1" Figure 3.12. Cross section details of Florida specimens.

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24 #5(5K1A) 22 spaces @3" #5(5K1A) #5(5K1A) 22 spaces @3" spaced at 4" 6#6 bars full length Bars 4L Bars #3(3D1)@ 6" 1 1/2" Bars Bars Bars Bars 1 1/2" #3(3D1) #3(3D1) #3(3D1) #3(3D1) @ 3" @ 6" @ 6" @ 3" NOTE: PROVIDE A TOE PLATE 2'-2" BY 12" BY 1/2" WITH 6 STUDS AT EACH END Figure 3.13. End zone reinforcement details of FL1L (FL) and FL1R (modified FL). #5(5K1A) #5(5K1A) #5(5K1A) 5 spaces @3" 5 spaces @ 2" 5 spaces @ 4" 6#6 bars full length 1 1/2" 1.5" Bars #3(3D1) @ 6" Bars #3(3D1) @ 8" Bars #3(3D1) @ 2" 1 1/2" 1 1/2" 7'-6" 6' - 0" Figure 3.14. End zone reinforcement details of FL2L (LRFD) and FL2R (proposed).

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25 Location of the clamping force P Test setup for the first end 30" 6" a = 11'-6" b = 29'-6" 6" L = 41'-0" Bending Moment Diagram (a*b/L) P = 8.274 P (k-ft) (b/L) P = 0.72 P Shear Force Diagram (a/L) P = 0.28 P Location of the clamping force P 30" Test setup for the second end a = 17'-6" b = 12'-0" 12'-0" L = 29'-6" 6" Bending Moment Diagram (a*b/L) P = 7.119 P (k-ft) (b/L) P = 0.41 P Shear Force Diagram (a/L) P = 0.59 P Figure 3.15. Support and loading arrangement of the full-scale specimens. 1" threaded rods (2) C12 x 20.7 1" threaded steel shapes rods jack locked 1'-0" in at 54k 12'-0" 7 1/4" 2'-6" 6" P 5'-5 1/4" 9' (2) C12 x 20.7 steel shapes 3'-9" 3/4" rubber pad 12" (2) C12 x 20.7 steel shapes 3'-0" Figure 3.17. Location of the point Figure 3.16. End clamping detail. load and clamping mechanism.

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26 Table 3.2. Summary of the test results of the full-scale specimens. Strength Calculated Using: % Difference Mode of State End Design Specified Measured Specified Measured Failure Test Data Values Values and Test and Test TN1L LRFD Flexure 4,204 k-ft 4,299 k-ft 4,539 k-ft 8.0 5.6 TN1R Proposed* Flexure 4,204 k-ft 4,299 k-ft 4,494 k-ft 6.9 4.5 Tennessee TN2L TN DOT Flexure 4,204 k-ft 4,299 k-ft 4,649 k-ft 10.6 8.1 TN2R Proposed* Flexure 4,204 k-ft 4,299 k-ft ** -- -- WA1L** Proposed* Shear 311.3 k 319.8 k 508.5 k 63.3 59.0 * Washington WA1R LRFD Shear 311.3 k 319.8 k *** -- -- State WA2L Non Shear 311.3 k 319.8 k 434.2 k 39.5 35.8 WA2R Non Shear 311.3 k 319.8 k 457.5 k 47.0 43.1 VA1L Non Flexure 7,471 k-ft 7,809 k-ft 7,852 k-ft 5.1 0.6 VA1R Non Bearing 7,471 k-ft 7,809 k-ft 7,593 k-ft 1.6 2.8 Virginia VA2L LRFD Flexure 7,471 k-ft 7,809 k-ft 8,215 k-ft 10.0 5.2 VA2R Proposed* Flexure 7,471 k-ft 7,809 k-ft 8,492 k-ft 13.7 8.7 FL1L FL DOT Flexure 10,039 k-ft 10,317 k-ft 9,890 k-ft 1.5 4.1 Mod. FL FL1R Flexure 10,039 k-ft 10,317 k-ft ** -- -- Florida DOT FL2L LRFD Flexure 10,039 k-ft 10,317 k-ft ** -- -- FL2R Proposed* Flexure 10,039 k-ft 10,317 k-ft ** -- -- * Proposed EZR detail is the end zone reinforcement recommended by Tuan et al. (16) and discussed in Section 1.2.3 of this report. ** The girder exceeded the setup capacity. *** Girder end was epoxy repaired. team wanted to have specimens with end zone cracking to see allowing them to form once the presence of reinforcing steel their effect on the girder capacity. To achieve this goal, deep decreases. This phenomenon is shown in Figure 3.21. The girders with a large number of strands should be used. How- figure also shows the end reinforcement for WA1L contain- ever, these large girders would be a challenge to load to fail- ing a C-shaped #8 bar 1.5 in. from the girder end. This bar was ure in the structures laboratory because they require a large placed in conjunction with the pairs of #6 bars to locate a amount of applied force that might be beyond the capacity of greater amount of steel close to the girder end. the testing facility. All four ends failed in shear and reached much higher capac- Reviewing the test results revealed that classical flexural ities than the estimated requirements. Figure 3.22 shows failure occurred in all specimens at a load higher than the how the shear cracks run in the opposite direction of the estimated load. The flexural failure was associated with loss end zone cracks. The load on the girder produces a force of bond between the strands and the concrete at the girder that works in a direction to close the end zone cracks. This end, as shown in Figure 3.18. demonstrates that even with excessive amounts of end zone Figure 3.19 shows the load-deflection relationship of end cracking, the structural capacity of the girders was not reduced TN1L, which clearly shows the elastoplastic behavior of the below acceptable limits. Both the repaired and unrepaired concrete section. girders reached capacities greater than the theoretical cal- culated capacities. It was also noted that the end that was 3.2.4.2 Washington State Specimens repaired by epoxy injection did not perform noticeably bet- As expected, upon release of the prestress force, the ends ter than the unrepaired end, having similar percent differ- without end zone reinforcement (WA2L and WA2R) expressed ences between the theoretical and actual results, as shown in much more end zone cracking than the ends that contained Table 3.2. This gives evidence that epoxy injection does not additional reinforcement (WA1L and WA1R). The comparison necessarily improve the structural capacity of girders with is shown in Figure 3.20. Both ends that contained additional end zone cracks. end reinforcement experienced similar widths and patterns of An example of the load-deflection relationship is presented end zone cracking. in Figure 3.23, which shows how the test data far exceeds In both of the reinforced ends, there was a delay in the loca- the estimated capacities. The curve is for End WA1R that was tion of the end zone cracks where they did not start until a few designed using LRFD specifications. In this case, the load inches into the girder. The responsible factor for this may be required to fail the girder in flexure was greater than the the concentrated amount of reinforcing steel located near the 800 kips capacity of the two hydraulic jacks in the test setup. end preventing cracks from starting at the very edge, but then The curve shows where loading was halted, but it can be

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27 (a) Classical Flexural Cracking (b) Strand Rotation (c) Strand Slippage Figure 3.18. Typical flexural failure and loss of bond in the Tennessee specimens. 700000 600000 500000 Load (lb) 400000 300000 Capacity Using Estimated Values (590 K) 200000 Capacity Using Measured Values (604 K) 100000 Load vs. Deflection 0 0 0.2 0.4 0.6 0.8 1 1.2 1.4 Deflection (in) Figure 3.19. Load-deflection curve of TN1L.

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28 (a) WA2L (no EZR) Figure 3.21. Crack pattern of WA1L and WA2R. (b) WA1R (LRFD) Figure 3.20. End zone cracking of WA2L and WA1R. presumed that the girder would continue to take load until Figure 3.22. End WA1L after shear failure. flexural failure. cracks on the ends without end zone reinforcement were wider and more prevalent. The end designed using the AASHTO 3.2.4.3 Virginia Specimens LRFD specifications experienced the least amount of cracking. Upon release of the prestress force, all of the Virginia spec- See Figure 3.24. imens experienced cracking in the range of 0.004 to 0.010 in. End VA1R was the first Virginia end tested and it failed in width and extending no more than 3 ft from the end. The prematurely due to inadequate bearing area, as shown in

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29 800000 700000 600000 Load (lb) 500000 400000 300000 Capacity Using Estimated Values (510 k) 200000 Capacity Using Measured Values (524 k) System Capacity (800 k) 100000 Load vs. Deflection 0 0 0.1 0.2 0.3 0.4 0.5 0.6 Deflection (in) Figure 3.23. Load versus deflection curve for End WA1R. Figure 3.25. This occurrence prompted the team to devise than 3 ft into the specimens. The two ends designed using a pivoting support with a larger bearing area, shown in Fig- LRFD specifications and the proposed method had crack- ure 3.26. The three remaining ends failed in shear as designed, ing patterns of similar severity. However, the end designed where all ends held loads higher than their design capacities. using the LRFD experienced slightly more cracking than the This is further proof that end zone cracks, even in cases where proposed method. The two ends designed from Florida details the cracks are wider and longer than any typically reported, were similarly cracked as well. The end that had some of the do not reduce the structural capacity of girders below the end reinforcement removed experienced slightly more crack- design limits. ing than the end with more reinforcement, however, the improvement is not significant enough to justify using that amount of extra steel for reinforcement. Comparisons are 3.2.4.4 Florida Specimens shown in Figures 3.27 and 3.28. Upon release of the prestress force, all end zone cracks were The girders were originally designed to fail in flexure. How- around 0.004 to 0.006 in. in width and did not extend farther ever, a mix-up at the precasting plant caused one or both of (a) VA1R (No EZR) (b) VA2R (Proposed) Figure 3.24. End zone cracking of VA1R and VA2R.