Innovative Bridge Designs for Rapid Renewal (2014) / Chapter Skim
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269 UHPC Lab Testing Report This report was written in conjunction with Hartwell (2011)
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270 literature and past work regarding UHPC in bridge design. Subsequent sections discuss the different test methods and materials used in this research, the qualitative and quantitative results, and the conclusions and recommendations from the testing program.
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271 Source: Iowa Department of Transportation, 2011a. Figure C.2.
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272 Relevant UHPC Material Background As the United States faces the challenge of renewing its aging highway infrastructure, the longevity and durability of new structures are of particular interest. Research into many different materials and techniques to achieve durability has taken place.
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273 Current Bridge Applications UHPC has been used in many different bridge components. Applications range from UHPC I-girders and complete redecking systems to UHPC joint closures and precast concrete piles.
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274 joints of the Route 31 Bridge in Lyons. However, unlike the current demonstration project, the transverse deck joints in the Oneonta bridge were located in the positive bending moment region, placing the UHPC joint in compression.
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275 in an Imer Mortarman 750 mixer to batch the UHPC mix design (Lafarge Batching Procedure)
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276 0.1 g. This process was repeated two additional times for each individual specimen.
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277 To replicate the proposed demonstration bridge UHPC placement technique, acrylic glass bulkheads, which aimed to prevent the formation of cold joints, were fabricated and installed (Figure C.15)
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278 placement and eliminate a horizontal cold joint in the transverse joint, the first batch was agitated in the mold to disrupt the drying "skin" that began to form within 5 min of placement. The remaining UHPC from the second batch was then used to place one side of the longitudinal joint.
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279 CV-HPC-D mix, an Iowa DOT high-performance concrete bridge deck mix specific for the western region of Iowa, was used for the specimen's deck slab. The mix (Table C.5)
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280 permanent, then the two modules were connected via four steel angle plates (Figure C.20 and Figure C
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281 embedded bonded strain gauges were used on the upper and lower legs of the hairpins at locations directly over the steel beams and at midspan of the deck between the beams on both superstructure modules. In addition, eight surfacemounted strain gauges (three on the top surface of the deck and one on the bottom for each module)
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282 Figure C.23. Connection instrumentation locations, plan view.
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283 module-to-module transverse connection was -2,016 kip-ft. Because of the possibility of an HS-20 load on the other spans of the continuous bridge deck, a +74-kip-ft live-load moment was also possible.
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284 Conducting Service-Level Testing with Connection Retrofit After analyzing results from the initial service-level load testing and observing the formation of undesirable cracks, HNTB, the design engineer, designed a retrofit for the transverse moduleto-module connection (Figure C.30 and Figure C.31)
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285 Material Property Tests UHPC Quality Control Tests Quality control testing during the UHPC batching process in the laboratory at Iowa State University included temperature readings as well as static and dynamic flow testing. The testing was done according to Lafarge's flow testing procedure based on ASTM C230.
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286 Table C.6. Joint Constructability: UHPC Quality Control Test Results Batch Time Mix Temp Finish (F)
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287 The compressive strengths varied for the curing temperatures of 40°F, 70°F, and 100°F. The 28-day compressive strengths ( f ′c)
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288 Figure C.35. Compressive strength of UHPC Mix Design 2 (strength and serviceability)
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289 Flexural Strength Test TranSverSe JoInT STrenGTh and ServIceaBIlITy TeSTInG BaTch Three beams were tested to determine the modulus of rupture of the HPC used in the prefabricated deck modules. The beams tested had nominal cross-sectional dimensions of 6 in.
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290 Table C.10. 28-Day Abrasion Test Results: Day 2 Specimen Age: 2 Days ASTM C 944: Abrasion Resistance of Concrete Surfaces by Rotating Cutter Method Test Date: 2/24/2011 Specimen ID Surface Initial Mass Mass 1 Mass 2 Final Mass Wear Depth Loss of Mass Additional Notesg g g g mm g % A2-1 NA 0.00 0.00% *
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291 Table C.13. 28-Day Abrasion Test Results: Day 28 Specimen Age: 28 Days ASTM C 944: Abrasion Resistance of Concrete Surfaces by Rotating Cutter Method Test Date: 3/22/2011 Specimen ID Surface Initial Mass Mass 1 Mass 2 Final Mass Wear Depth Loss of Mass Additional Notesg g g g mm g % A28-1 rough 1700.7 1699.1 1698.8 1698.5 2.20 0.13% A28-2 cut 1698.5 1698.4 1698.2 1698.1 0.40 0.02% A28-3 cut 1855.3 1855.2 1855.1 1854.9 0.40 0.02% A28-4 form 1854.9 1854.5 1853.9 1853.4 1.50 0.08% B28-1 rough 1959.8 1959 1958.6 1958.3 1.50 0.08% B28-2 cut 1958.3 1958.1 1958 1957.9 0.40 0.02% B28-3 cut 2020.6 2020.4 2020.3 2020.2 0.40 0.02% B28-4 form 2020.2 2019.1 2017.8 2016.4 3.80 0.19% C28-1 rough 1985.4 1984.7 1984.4 1983.7 1.70 0.09% C28-2 cut 1803.7 1803.3 1803.2 1803.1 0.60 0.03% C28-3 cut 2054.1 2053.7 2053.3 2053.1 1.00 0.05% C28-4 form 2053.1 2053 2052.9 2052.6 0.50 0.02% SHRP 2 Project No R04 - Phase III - Task 10C: Test 2 Table C.12.
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292 the bridge to traffic, will likely be reached 4 days after placement. Thus, the contractor will have roughly 2 days to perform grinding of the joints from the time the 10,000-psi threshold is reached until opening of the bridge to traffic at 14,000-psi compressive strength.
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293 one transverse UHPC deck joint was constructed to investigate issues relating to casting sequence, material mixing and placement rates, effects of ambient temperature on construction, flow characteristics of the UHPC, and consolidation of material at congested locations. Testing of the UHPC joints for constructability was completed at Iowa State University in April 2011.
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294 The test also validated the use of top forms and chimneys at the high end of the 2% cross slope of the bridge deck at transverse joints. The top forms were applied sequentially as the joint was filled from the lowest elevation to the highest.
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295 placement sequence of the UHPC (Figure C.43) will be controlled, starting at the lowest elevations through the transverse joints over the piers up to the bulkheads.
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296 Figure C.46. Applied moment versus actuator displacement.
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297 Figure C.47. Top-of-deck surface mounted strain gauges over the joint interface.
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298 Later, inspection during fatigue testing further confirmed the interfacial debonding and opening occurring below servicelevel conditions. In addition to joint interface debonding and substantial opening, strain levels in the embedded strain gauges registered above the expected HPC cracking strain as well.
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299 Figure C.50. Embedded strain gauge location and identification.
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300 Figure C.52. Row 2, top-of-deck embedded strain gauges (static)
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301 Figure C.53. Row 3, top-of-deck embedded strain gauges (static)
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302 Figure C.54. Row 1, bottom-of-deck embedded strain gauges (static)
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303 Figure C.55. Row 2, bottom-of-deck embedded strain gauges (static)
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304 The groupings of embedded strain gauges on the bottomof-deck reinforcement were located within the UHPC joint and near the joint interface only (Figure C.54 through Figure C.56)
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305 the high strains at the termination of the hairpin reinforcement in the top of deck means cracking of the HPC is expected. These data suggest that the transverse connection detail was not satisfying the original project aim to avoid cracking in the deck over the pier.
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306 Figure C.58. Row 2, top-of-deck embedded strain gauges (1,000,000 cycles)
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307 Table C.14. Row 1, Top-of-Deck Strain Accrual Gauge S2-1-2T µe S2-1-1T µe J2-1-T µe J1-1-T µe S1-1-1T µe S1-1-2T µe 3,000 cycles 210 440 146 58 474 172 1,000,000 cycles 250 506 163 73 505 236 Strain increase 19.3% 15.0% 12.1% 27.4% 6.6% 37.6% Table C.15.
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308 Figure C.59. Row 3, top-of-deck embedded strain gauges (1,000,000 cycles)
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309 Figure C.61. Row 1, top-of-deck strain accrual.
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310 Figure C.62. Row 1, bottom-of-deck strain accrual.
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311 Figure C.63. Row 2, top-of-deck strain accrual.
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312 Figure C.64. Row 2, bottom-of-deck strain accrual.
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313 Figure C.65. Row 3, top-of-deck strain accrual.
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314 Figure C.66. Row 3, bottom-of-deck strain accrual.
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315 By contrast, applying 70 kips posttensioning force in each of the rods minimized or negated the tensile strain across the interface entirely when loaded to Service Level I All surface-mounted strain gauges spanning the interface registered below the HPC cracking strain until after the Service Level I conditions were applied (Figure C.74)
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316 Figure C.68. Row 1, top-of-deck embedded strain gauges (60-k retrofit)
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317 Figure C.69. Row 2, top-of-deck embedded strain gauges (60-k retrofit)
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318 Figure C.70. Row 3, top-of-deck embedded strain gauges (60-k retrofit)
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319 Figure C.71. Row 1, bottom-of-deck embedded strain gauges (60-k retrofit)
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320 Figure C.72. Row 2, bottom-of-deck embedded strain gauges (60-k retrofit)
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321 Figure C.73. Row 3, bottom-of-deck embedded strain gauges (60-k retrofit)
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322 Figure C.74. Top-of-deck surface-mounted strain gauges over interface (70-k retrofit)
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323 Figure C.75. Row 1, top-of-deck embedded strain gauges (70-k retrofit)
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324 Figure C.76. Row 2, top-of-deck embedded strain gauges (70-k retrofit)
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325 Figure C.77. Row 3, top-of-deck embedded strain gauges (70-k retrofit)
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326 Figure C.78. Row 1, bottom-of-deck embedded strain gauges (70-k retrofit)
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327 Figure C.79. Row 2, bottom-of-deck embedded strain gauges (70-k retrofit)
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328 Figure C.80. Row 3, bottom-of-deck embedded strain gauges (70-k retrofit)
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329 Figure C.81. Ultimate capacity moment versus deflection.
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330 Figure C.82. Row 1, top-of-deck embedded strain gauges (ultimate)
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331 Figure C.83. Row 2, top-of-deck embedded strain gauges (ultimate)
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332 Figure C.84. Row 3, top-of-deck embedded strain gauges (ultimate)
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333 Figure C.85. Row 1, bottom-of-deck embedded strain gauges (ultimate)
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334 Figure C.86. Row 2, bottom-of-deck embedded strain gauges (ultimate)
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335 Figure C.87. Row 3, bottom-of-deck embedded strain gauges (ultimate)
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336 this manner. This result corresponded to the specimen entering into inelastic deformation around the same applied moment in Figure C.81.
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337 hairpin reinforcement bars acted as the ultimate mode of failure for the transverse connection. Deformation in the bottom flange of the W30X99 girders was identified as the test progressed and the specimen underwent large deflections (Figure C.93)
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338 • Specimens with a formed surface finish exhibited less abrasion resistance than specimens with cut surfaces because the steel fibers in the UHPC lay parallel with the surface and tended to pull off easily. Fiber alignment was attributed to material flow on the bottom surface of the mold.
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339 Service-Level Fatigue Testing • Visual inspection at the onset of the 1,000,000-cycle servicelevel fatigue testing confirmed cracking in the precast HPC deck near the joint interface. • Strain accrual during fatigue testing suggested propagation of existing cracks in the specimen.
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