Material BehaviorIn the past, UHPC carried high material and construction costs, hindering wide-scale adoption in structural applications. Developments in the past decade have led to open-source formulations that are more economical than proprietary versions and perform just as well. One of the earliest open-source mixes in the United States was published by Wille et al. (2011a, b, c). This was subsequently followed by a number of related and other mixes documented in Wille et al. (2012), Wille and Boisvert-Cotulio (2013), Alkaysi et al. (2016), Berry et al. (2017), El-Tawil et al. (2018), Alsalman et al. (2018), Tai and El-Tawil (2020), Mendonca et al. (2020), and El-Tawil et al. (2020). These mixes are generally made of components readily available on the US open market and do not require any special mixing or placing equipment.When properly formulated and reinforced with fibers, UHPC can display compressive and direct tensile strengths as high as 255 MPa and 37 MPa, respectively (Wille et al. 2011b, 2014). Changes in the type and quantity of fibers directly affect the ductility and strength of the material (Pyo and El-Tawil 2015; Pyo et al. 2016). UHPC also exhibits exceptional toughness prior to crack localization and self-consolidation properties (Pyo and El-Tawil 2015), and generally develops a high early strength in the range of 70–95 MPa within 24 h (Karmacharya and Chao 2019).The compressive and tensile responses of UHPC are quite different from those of regular concrete, and must be adequately modeled for realistic analysis or design. In general, UHPC exhibits an almost linear compressive stress–strain response up to the strain at the peak stress. Strain softening usually commences right after the peak is reached and the descending slope is controlled by the amount and type of fiber reinforcement. Fig. 1(a) shows a compressive stress–strain curve proposed by Sritharan et al. (2003) for analysis and design purposes, compared with the experimentally measured response in Acker and Behloul (2004).As a fiber-reinforced cementitious material, UHPC resists tensile stress through composite action between the matrix and embedded fibers. The transmission of forces between these two components occurs through interfacial bond. After cracking, fibers bridge the cracks, providing resistance to crack opening and enhancing structural behavior and durability. As shown in Fig. 1(b), UHPC’s tensile response can be generally characterized by an elastic portion, followed by strain-hardening, a plateau, and then a long strain-softening phase. Aaleti et al. (2013) proposed the idealized tensile response shown in Fig. 1(b) for analysis and design purposes.The linear portions of the tensile and compressive regimes are characterized by an elastic modulus, E. Several equations have been proposed to link the elastic modulus to compressive stress. For example, Sritharan et al. (2003) proposed E (MPa)=4,150fc′(MPa) [E (psi)=50,000fc′(psi)], while Garcia and Graybeal (2007) used a similar equation but with a slightly reduced coefficient (3,835 instead of 4,150 or 46,200 instead of 50,000). Rather than providing an explicit equation, ACI 239R (ACI 2018) just lists a range of values from 6,000–7,200 Ksi (40–50 MPa).The ACI 318 (ACI 2019) and AASHTO codes (AASHTO 2020) use a strain of 0.003 as the crushing strain (or maximum design compressive strain), εcu, at a postpeak compressive stress of 0.8fc′ for plain concrete. Chao et al. (2019) observed εcu of 0.015 and 0.003 for UHPC with 3% microsteel fiber by volume and plain concrete, respectively, in large-scale beam testing, where the strains were measured by a digital image correlation (DIC) system. The high compressive strain capacity of UHPC is not unusual for a high-performance fiber-reinforced cementitious material, as noted by Naaman (2018). The discrepancy between the response depicted in Fig. 1(a) and values noted in Chao et al. (2019) is attributed to the differences in UHPC fiber content. Further research is needed to specify values suitable for design.Longitudinal reinforcement is typically used in UHPC structural members subjected to bending. Previous research shows that, because of their tension-stiffening effect, reinforcing bars or prestressing strands used in structural members enhance the cracking distribution and tensile ductility of fiber-reinforced concrete. Fig. 2 illustrates the results of an investigation by Aghdasi et al. (2016), which provides the total (UHPC + #10M rebar) and pure (UHPC only) tensile stress–strain curves, as well as the tensile stress–strain curve of UHPC specimen with no rebar. The results indicate that, while the tensile strength remained nearly the same (7.7 MPa), the presence of rebar considerably enhanced the tensile ductility of the UHPC. In the UHPC specimen, tensile strain-hardening was maintained up to a strain of 1.3%, nearly 7.5 times larger than the specimen with no rebar.To date, most of the studies on UHPC material response have focused on monotonic behavior. There is a marked scarcity of data on high- and low-cycle fatigue loading. Although initial indications are that the high-cycle fatigue resistance of UHPC is extremely high (Ocel and Graybeal 2007; Fitik et al. 2008, 2010; Carlesso et al. 2019), future research studies are needed to confirm this finding and fully characterize the tensile and compressive response of fatigue-loaded UHPC, especially in high-demand applications such as wind towers and bridges. To the knowledge of the authors, there are no studies that have developed models of the low-cycle response of UHPC, and therefore research into this area is urgently needed.In addition, unlike plain concrete, because UHPC’s tensile capacity may be largely utilized in the strength design of a UHPC structural member, its long-term behavior can have an impact on the performance of the member. It has been shown that UHPC can experience tensile creep under long-term loading; however, tensile creep of UHPC can be decreased approximately 65% when thermal treatment of 60°C (140°F) for 72 h or 90°C (194°F) for 48 h is applied, respectively, prior to loading (Garas et al. 2010). Further research is warranted to investigate this effect on the long-term performance of UHPC members. In compression, UHPC is known to have much less creep than conventional concrete. As in tension, the use of heat treatment appears to decrease creep even further (Russell and Graybeal 2013).References Aaleti, S., B. Petersen and S. Sritharan. 2013. Design guide for precast UHPC waffle deck panel system, including connections. Rep. No. FHWA-HIF-13-032. Washington, DC: USDOT. Aaleti, S., and S. Sritharan. 2017. Investigation of a suitable shear friction interface between UHPC and normal strength concrete for bridge deck applications. Rep. No. InTrans Project 10-379. Ames, IA: Iowa DOT. AASHTO. 2008. LRFD bridge design specifications. 4th ed. Washington, DC: AASHTO. AASHTO. 2020. LRFD bridge design specifications. 9th ed. Washington, DC: AASHTO. ACI (American Concrete Institute). 2003. Bond and development of straight reinforcing bars in tension (ACI 408R-03). ACI 408. Detroit: ACI. ACI (American Concrete Institute). 2007. Report on structural design and detailing for high-strength concrete in moderate to high seismic applications. ACI ITG-4.3 R-07. Detroit: ACI. ACI (American Concrete Institute). 2014. Building code requirements for structural concrete (ACI 318-14) and commentary (ACI 318-14). ACI Committee 318. Farmington Hills, MI: ACI. ACI (American Concrete Institute). 2018. Ultra-high-performance concrete: An emerging technology report. ACI 239R. Detroit: ACI. ACI (American Concrete Institute). 2019. Building code requirements for structural concrete (ACI 318-19) and commentary (ACI 318-19). ACI Committee 318. Farmington Hills, MI: ACI. Acker, P., and M. Behloul. 2004. “Ductal® technology: A large spectrum of properties, a wide range of applications.” In Proc., Int. Symp. on UHPC, 11–23. Kassel, Germany: Kassel University Press. AFGC (French Association of Civil Engineering–French Authorities of Civil Engineering Structure Design, and Control). 2002. Ultra high performance fibre-reinforced concretes. Bagneux, France: AFGC. AFGC (French Association of Civil Engineering–French Authorities of Civil Engineering Structure Design, and Control). 2013. Ultra high performance fibre-reinforced concretes. Bagneux, France: AFGC. AFNOR (Association Française de Normalisation). 2016. National addition to Eurocode 2—Design of concrete structures: Specific rules for ultra-high performance fibre reinforced concrete (UHPFRC). NF P 18-710. France: AFNOR. Aghdasi, P., A. E. Heid, and S. H. Chao. 2016. “Developing ultra-high-performance fiber-reinforced concrete for large-scale structural applications.” ACI Mater. J. 113 (5): 559–570. https://doi.org/10.14359/51689103. Ahlborn, T. T. M., D. K. Harris, D. L. Misson, and E. J. Peuse. 2011. “Characterization of strength and durability of ultra-high-performance concrete under variable curing conditions.” Transp. Res. Rec. 2251 (1): 68–75. https://doi.org/10.3141/2251-07. Alkaysi, M., and S. El-Tawil. 2016a. “Bond between ultra-high performance concrete and steel bars.” In Proc., First Int. Interactive Symp. on UHPC. Ames, IA: Iowa State Univ. Digital Press. Alkaysi, M., and S. El-Tawil. 2016b. “Effects of variations in the mix constituents of ultra high performance concrete (UHPC) on cost and performance.” Mater. Struct. 49 (10): 4185–4200. https://doi.org/10.1617/s11527-015-0780-6. Alkaysi, M., S. El-Tawil, Z. Liu, and W. Hansen. 2016. “Effects of silica powder and cement type on long term durability of ultra high performance concrete (UHPC).” Cem. Concr. Compos. 66 (Feb): 47–56. https://doi.org/10.1016/j.cemconcomp.2015.11.005. Al-Osta, M. A., M. N. Isa, M. H. Baluch, and M. K. Rahman. 2017. “Flexural behavior of reinforced concrete beams strengthened with ultra-high performance fiber reinforced concrete.” Constr. Build. Mater. 134 (Mar): 279–296. https://doi.org/10.1016/j.conbuildmat.2016.12.094. Aoude, H., F. P. Dagenais, R. P. Burrell, and M. Saatcioglu. 2015. “Behavior of ultra-high performance fiber reinforced concrete columns under blast loading.” Int. J. Impact Eng. 80 (Jun): 185–202. https://doi.org/10.1016/j.ijimpeng.2015.02.006. ASCE. 2016. Minimum design loads for buildings and other structures. ASCE/SEI 7-16. Reston, VA: ASCE. ASTM. 2017. Standard practice for fabricating and testing specimens of ultra-high performance concrete. ASTM C1856/C1856M. West Conshohocken, PA: ASTM. Baby, F., J. Billo, J. C. Renaud, C. Massotte, P. Marchand, F. Toutlemonde, A. Simon, and P. Lussou. 2010. “Shear resistance of ultra high performance fibre-reinforced concrete I-beams.” In Proc., FraMCoS7, 1411–1417. Dresden, Germany: IA-FraMCoS. Baby, F., P. Marchand, and F. Toutlemonde. 2014b. “Shear behavior of ultrahigh performance fiber-reinforced concrete beams. II: Analysis and design provisions.” J. Struct. Eng. 140 (5): 04013112. https://doi.org/10.1061/(ASCE)ST.1943-541X.0000908. Baby, F., P. Marchand, and F. Toutlemonde. 2017. “Analytical modeling of ultra-high-performance fiber-reinforced concrete behavior in ribbed plates.” ACI Struct. J. 114 (1): 3–13. Bandelt, M. J., and S. L. Billington. 2016. “Bond behavior of steel reinforcement in high-performance fiber-reinforced cementitious composite flexural members.” Mater. Struct. 49 (1–2): 71–86. https://doi.org/10.1617/s11527-014-0475-4. Bermudez, M., and C. C. Hung. 2019. “Shear behavior of ultra-high performance hybrid fiber reinforced concrete beams.” In Proc., 2nd Int. Interactive Symp. on UHPC. Ames, IA: Iowa State Univ. Digital Press. Berry, M., R. Snidarich and C. Wood. 2017. Development of non-proprietary ultra-high performance concrete. FHWA/MT-17-010/8237-001. Helena, MT: Montana DOT. Brühwiler, E., and E. Denarié. 2013. “Rehabilitation and strengthening of concrete structures using ultra-high performance fibre reinforced concrete.” Struct. Eng. Int. 23 (4): 450–457. https://doi.org/10.2749/101686613X13627347100437. Carbonell Muñoz, M. A., D. K. Harris, T. M. Ahlborn, and D. C. Froster. 2014. “Bond performance between ultrahigh-performance concrete and normal-strength concrete.” J. Mater. Civ. Eng. 26 (8): 04014031. https://doi.org/10.1061/(ASCE)MT.1943-5533.0000890. Carlesso, D. M., A. De la Fuente, and S. H. P. Cavalaro. 2019. “Fatigue of cracked high performance fiber reinforced concrete subjected to bending.” Constr. Build. Mater. 220 (Sep): 444–455. https://doi.org/10.1016/j.conbuildmat.2019.06.038. CEN (European Committee for Standardization). 2004. Eurocode 2: Design of concrete structures—Part 1. Brussels, Belgium: CEN. Chan, T., K. R. Mackie, and Z. B. Haber. 2020. “Precast seismic bridge column connection using ultra-high-performance concrete lap splice.” ACI Struct. J. 117 (1): 217–229. https://doi.org/10.14359/51718021. Chao, S. H. 2020. “Size effect on ultimate shear strength of steel fiber-reinforced concrete slender beams.” ACI Struct. J. 117 (1): 145–158. https://doi.org/10.14359/51718018. Chao, S. H., V. Kaka, G. Palacios, J. Kim, Y. J. Choi, P. Aghdasi, A. Nojavan, and A. E. Schultz. 2016. “Seismic behavior of ultra-high-performance fiber-reinforced concrete moment frame members.” In Proc., 1st Int. Interactive Symp. on UHPC–2016. Ames, IA: Iowa State Univ. Digital Press. Chao, S. H., A. E. Naaman, and G. J. Parra-Montesinos. 2009. “Bond behavior of reinforcing bars in tensile strain-hardening fiber-reinforced cement composites.” ACI Struct. J. 106 (6): 897–906. Chao, S.-H., V. Kaka, and M. Shamshiri. 2019. “Toward a non-prestressed precast long-span bridge girder using UHP-FRC.” In Proc., 2nd Int. Interactive Symp. On UHPC. Ames, IA: Iowa State Univ. Digital Press. Chao, S.-H., M. Shamshiri, X. Liu, G. Guillermo Palacios, A. E. Schultz, and A. Nojavan. 2021. “Seismically resilient robust ultra-high-performance fiber-reinforced concrete columns.” ACI Struct. J. 118 (2): 17–32. Chen, S., R. Zhang, L. J. Jia, and J. Y. Wang. 2018a. “Flexural behaviour of rebar-reinforced ultra-high-performance concrete beams.” Mag. Concr. Res. 70 (19): 997–1015. https://doi.org/10.1680/jmacr.17.00283. Chen, S., R. Zhang, L. J. Jia, J. Y. Wang, and P. Gu. 2018b. “Structural behavior of UHPC filled steel tube columns under axial loading.” Thin-Walled Struct. 130 (Sep): 550–563. https://doi.org/10.1016/j.tws.2018.06.016. Čítek, D., J. Kolísko, S. Řeháček, and T. Mandlík. 2016. “Concrete cover effect on bond behaviour of UHPC.” In Vol. 249 of Solid state phenomena, 273–277. Bäch SZ, Switzerland: Trans Tech Publications. De la Varga, I., Z. B. Haber, and B. A. Graybeal. 2018. “Enhancing shrinkage properties and bond performance of prefabricated bridge deck connection grouts: Material and component testing.” J. Mater. Civ. Eng. 30 (4): 04018053. https://doi.org/10.1061/(ASCE)MT.1943-5533.0002235. El-Tawil, S., Y.-S. Tai, and J. A. Belcher. 2018. Field application of non-proprietary ultra-high performance concrete: Practical experiences gained and lessons learned.” Concr. Int. 40 (1): 36–42. El-Tawil, S., Y.-S. Tai, J. A. Belcher, and D. Rogers. 2020. “Open-recipe ultrahigh performance concrete (UHPC): Busting the cost myth.” Concr. Int. 42 (6): 33–38. Farhat, F. A., D. Nicolaides, A. Kanellopoulos, and B. L. Karihaloo. 2007. “High performance fiber-reinforced cementitious composite (CARDIFRC)—Performance and application to retrofitting.” Eng. Fract. Mech. 74 (1–2): 151–167. https://doi.org/10.1016/j.engfracmech.2006.01.023. Fehling, E., P. Lorenz, and T. Leutbecher. 2012. “Experimental investigations on anchorage of rebars in UHPC.” In Proc., Hipermat 2012 3rd Int. Symp. on UHPC and Nanotechnology for High Performance Construction Materials, 533–540. Kassel, Germany: Kassel Univ. Press. Fitik, B., R. Niedermeier, and K. Zilch. 2008. “Fatigue behaviour of ultra high-performance concrete under cyclic stress reversal loading.” In Proc., Second Int. Symp. on Ultra High Performance Concrete, edited by E. Fehling, M. Schmidt, and S. Stürwald, 529–536. Kassel, Germany: Kassel Univ. Press. Fitik, B., R. Niedermeier, and K. Zilch. 2010. “Fatigue behaviour of ultra-high performance concrete under cyclic stress reversal loading.” In Proc., Third Int. Fib Congress and Exhibition Incorporating the PCI Annual Convention and National Bridge Conf. Lausanne, Switzerland: International Federation for Structural Concrete. Garas, V. Y., L. F. Kahn, and K. E. Kurtis. 2010. “Tensile creep test of fiber-reinforced ultra-high performance concrete.” J. Test. Eval. 38 (6): 674–682. Garcia, H., and B. A. Graybeal. 2007. Analysis of an ultra-high performance concrete two-way ribbed bridge deck slab. Rep. No. FHWA-HRT-07-055. Washington, DC: Federal Highway Administration. Graybeal, B. A. 2006. Structural behavior of ultra-high performance concrete prestressed I-girders. Rep. No. FHWA-HRT-06-115. Washington, DC: Federal Highway Administration. Graybeal, B. A. 2010. Field-cast UHPC connections for modular bridge deck elements. Rep. No. FHWA-HRT-11-022. Washington, DC: Federal Highway Administration. Graybeal, B. A., and F. Baby. 2013. “Development of direct tension test method for ultra-high-performance fiber-reinforced concrete.” ACI Mater. J. 110 (2): 117–186. Graybeal, B. A., and J. Yuan. 2014. Bond behavior of reinforcing steel in ultra-high performance concrete. Rep. No. FHWA-HRT-14-089; HRDI-40/11-14 (300) E. Washington, DC: Federal Highway Administration. Habel, K., E. Denarié, and E. Brühwiler. 2007. “Experimental investigation of composite ultra-high-performance fiber-reinforced concrete and conventional concrete members.” ACI Struct. J. 104 (1): 93–101. Haber, Z. B., I. De la Varga, B. A. Graybeal, B. Nakashoji, and R. El-Helou. 2018. Properties and behavior of UHPC-class materials. Rep. No. FHWA-HRT-18-036. Washington, DC: Federal Highway Administration. Hasgul, U., K. Turker, T. Birol, and A. Yavas. 2018. “Flexural behavior of ultra-high-performance fiber reinforced concrete beams with low and high reinforcement ratios.” Struct. Concr. 19 (6): 1577–1590. https://doi.org/10.1002/suco.201700089. Hidalgo, P. A., C. A. Ledezma, and R. M. Jordan. 2002. “Seismic behavior of squat reinforced concrete shear walls.” Earthquake Spectra 18 (2): 287–308. https://doi.org/10.1193/1.1490353. Hognestad, E. 1951. Study of combined bending and axial load in reinforced concrete members. Urbana, IL: Univ. of Illinois at Urbana Champaign. Hsiao, H.-J. 2020. “Effectiveness of ultra-high performance fiber reinforced concrete for retrofitting beam-column joints.” Masters thesis, National Cheng Kung Univ., Dept. of Civil Engineering. Hung, C. C., Y. T. Chen, and C. H. Yen. 2020a. “Workability, fiber distribution, and mechanical properties of UHPC with hooked end steel macro-fibers.” Constr. Build. Mater. 260 (Nov): 119944. https://doi.org/10.1016/j.conbuildmat.2020.119944. Hung, C. C., and S. El-Tawil. 2010. “Hybrid rotating/fixed-crack model for high-performance fiber-reinforced cementitious composites.” ACI Mater. J. 107 (6): 569–577. Hung, C. C., and P. L. Hsieh. 2020. “Comparative study on shear failure behavior of squat high-strength steel reinforced concrete shear walls with various high-strength concrete materials.” Structures 23 (Feb): 56–68. https://doi.org/10.1016/j.istruc.2019.11.002. Hung, C. C., C. W. Kuo, and C. I. Huang. 2020b. “Effectiveness of ultra-high performance concrete jacketing for retrofitting non-ductile RC columns.” J. Chin. Inst. Civ. Hydraul. Eng. 32 (8): 693–699. Hung, C. C., H. S. Lee, and S. N. Chan. 2019. “Tension-stiffening effect in steel-reinforced UHPC composites: Constitutive model and effects of steel fibers, loading patterns, and rebar sizes.” Composites, Part B 158 (Feb): 269–278. https://doi.org/10.1016/j.compositesb.2018.09.091. Hung, C. C., and K.-W. Wen. 2020. “Investigation of shear strength of ultra-high performance concrete beams without stirrup.” In Proc., 17th World Conf. on Earthquake Engineering, 17WCEE. Tokyo: International Association for Earthquake Engineering. Hung, C. C., W. M. Yen, and K. H. Yu. 2016. “Vulnerability and improvement of reinforced ECC flexural members under displacement reversals: Experimental investigation and computational analysis.” Constr. Build. Mater. 107 (Mar): 287–298. https://doi.org/10.1016/j.conbuildmat.2016.01.019. Hussein, H. H., K. K. Walsh, S. M. Sargand, and E. P. Steinberg. 2016. “Interfacial properties of ultrahigh-performance concrete and high-strength concrete bridge connections.” J. Mater. Civ. Eng. 28 (5): 04015208. https://doi.org/10.1061/(ASCE)MT.1943-5533.0001456. Hwang, H. H., D. M. Yoo, S. Y. Park, and B. S. Kim. 2009. “Optimized design of UHPC bridge deck slab for hybrid cable-stayed girder bridge.” In Proc., 13th REAAA Conf., 4–19. Selangor, Malaysia: Road Engineering Association of Asia and Australasia. Ichikawa, S., H. Matsuzaki, A. Moustafa, M. A. ElGawady, and K. Kawashima. 2016. “Seismic-resistant bridge columns with ultrahigh-performance concrete segments.” J. Bridge Eng. 21 (9): 04016049. https://doi.org/10.1061/(ASCE)BE.1943-5592.0000898. JSCE (Japanese Society of Civil Engineering). 2008. Recommendations for design and construction of high performance fiber reinforced cement composites with multiple fine cracks (HPFRCC), concrete engineering series 81. Tokyo: JSCE. Kahanji, C., F. Ali, and A. Nadjai. 2017. “Structural performance of ultra-high-performance fiber-reinforced concrete beams.” Struct. Concr. 18 (2): 249–258. https://doi.org/10.1002/suco.201600006. Karmacharya, A., and S.-H. Chao. 2019. “Precast ultra-high-performance fiber-reinforced concrete (UHP-FRC) for fast and sustainable pavement repair.” In Proc., Transportation Consortium of South Central States Conf. Baton Rouge, LA: LSU Digital Commons. KCI (Korea Concrete Institute). 2012. Design recommendations for ultra-high performance concrete K-UHPC. KCI-M-12-003. Seoul: KCI. Khalil, W. I., and Y. R. Tayfur. 2013. “Flexural strength of fibrous ultra high performance reinforced concrete beams.” ARPN J. Eng. Appl. Sci. 8 (3): 200–214. Khan, M. I., M. A. Al-Osta, S. Ahmad, and M. K. Rahman. 2018. “Seismic behavior of beam-column joints strengthened with ultra-high performance fiber reinforced concrete.” Compos. Struct. 200 (Sep): 103–119. https://doi.org/10.1016/j.compstruct.2018.05.080. Koo, I. Y., and S. G. Hong. 2016. “Strengthening RC columns with ultra high performance concrete.” In Proc., 2016 Structures Congress. Jeju Island, Korea: International Association of Structural Engineering and Mechanics. Lee, S. C., J. Y. Cho, and F. J. Vecchio. 2013. “Tension-stiffening model for steel fiber-reinforced concrete containing conventional reinforcement.” ACI Struct. J. 112 (4): 639–648. https://doi.org/10.14359/51687657. Le Hoang, A., E. Fehling, B. Lai, D. K. Thai, and N. Van Chau. 2019. “Experimental study on structural performance of UHPC and UHPFRC columns confined with steel tube.” Eng. Struct. 187 (May): 457–477. https://doi.org/10.1016/j.engstruct.2019.02.063. Li, H.-S. 2016. “Tension stiffening behavior and structural flexural behavior of steel reinforced UHPFRC members.” Master thesis, National Cheng Kung Univ., Dept. of Civil Engineering. Lim, W. Y., and S. G. Hong. 2016. “Shear tests for ultra-high performance fiber reinforced concrete (UHPFRC) beams with shear reinforcement.” Int. J. Concr. Struct. Mater. 10 (2): 177–188. https://doi.org/10.1007/s40069-016-0145-8. Liu, J., C. Wu, Y. Su, J. Li, R. Shao, G. Chen, and Z. Liu. 2018. “Experimental and numerical studies of ultra-high performance concrete targets against high-velocity projectile impacts.” Eng. Struct. 173 (Oct): 166–179. https://doi.org/10.1016/j.engstruct.2018.06.098. Maguire, M., G. Morcous, K. Hanna, and M. K. Tadros. 2009. “Ultra-high-performance concrete in standard precast/prestressed concrete products.” In Proc., PCI National Bridge Conf. Chicago: Precast/Prestressed Concrete Institute. Magureanu, C., I. Sosa, C. Negrutiu, and B. Heghes. 2012. “Mechanical properties and durability of ultra-high-performance concrete.” ACI Mater. J. 109 (2): 177–183. Makita, T., and E. Brühwiler. 2014. “Tensile fatigue behaviour of ultra-high performance fibre reinforced concrete combined with steel rebars (R-UHPFRC).” Int. J. Fatigue 59 (Feb): 145–152. https://doi.org/10.1016/j.ijfatigue.2013.09.004. Mao, L., S. J. Barnett, A. Tyas, J. Warren, G. K. Schleyer, and S. S. Zaini. 2015. “Response of small scale ultra high performance fibre reinforced concrete slabs to blast loading.” Constr. Build. Mater. 93 (Sep): 822–830. https://doi.org/10.1016/j.conbuildmat.2015.05.085. Meade, T., and B. Graybeal. 2010. “Flexural response of lightly reinforced ultra-high performance concrete beams.” In Proc., Third Int. Fib Congress and Exhibition Incorporating the PCI Annual Convention and National Bridge Conf. Chicago: Precast/Prestressed Concrete Institute. Mendonca, F., M. Abo El-Khier, G. Morcous, and J. Hu. 2020. Feasibility study of development of ultra-high performance concrete (UHPC). Rep. No. SPR-P1(18) M072. Omaha, NE: Nebraska DOT. Naaman, A. E. 2018. Fiber reinforced cement and concrete composites. 1st ed. Sarasota, FL: Techno Press. Noshiravani, T., and E. Brühwiler. 2013. “Experimental investigation on reinforced ultra-high-performance fiber-reinforced concrete composite beams subjected to combined bending and shear.” ACI Struct. J. 110 (2): 251–261. Ocel, J., and B. Graybeal. 2007. “Fatigue behavior of an ultra-high performance concrete I-girder.” In Proc., PCI National Bridge Conf. Chicago: Precast/Prestressed Concrete Institute. Park, J. J., D. Y. Yoo, S. W. Kim, and Y. S. Yoon. 2012a. “An evaluation on the restrained shrinkage of ultra-high performance concrete.” In Key engineering materials, 449–452. Bäch SZ, Switzerland: Trans Tech Publications. https://doi.org/10.4028/www.scientific.net/KEM.525-526.449. Park, S. H., D. J. Kim, and S. W. Kim. 2016. “Investigating the impact resistance of ultra-high-performance fiber-reinforced concrete using an improved strain energy impact test machine.” Constr. Build. Mater. 125 (Oct): 145–159. https://doi.org/10.1016/j.conbuildmat.2016.08.027. Paschalis, S. A., A. P. Lampropoulos, and O. Tsioulou. 2018. “Experimental and numerical study of the performance of ultra high performance fiber reinforced concrete for the flexural strengthening of full scale reinforced concrete members.” Constr. Build. Mater. 186 (Oct): 351–366. https://doi.org/10.1016/j.conbuildmat.2018.07.123. Paulay, T., M. J. N. Priestley, and A. J. Synge. 1982. “Ductility in earthquake resisting squat shear walls.” ACI J. 79 (4): 257–269. Pyo, S., S. El-Tawil, and A. E. Naaman. 2016. “Direct tensile behavior of ultra high performance fiber reinforced concrete (UHP-FRC) at high strain rates.” Cem. Concr. Res. 88 (Oct): 144–156. https://doi.org/10.1016/j.cemconres.2016.07.003. Randl, N., T. Mészöly, and P. Harsányi. 2018. “Shear behaviour of uhpc beams with varying degrees of fibre and shear reinforcement.” In High tech concrete: Where technology and engineering meet, 500–507. New York: Springer. Riedel, W., M. Nöldgen, E. Straßburger, K. Thoma, and E. Fehling. 2010. “Local damage to ultra high performance concrete structures caused by an impact of aircraft engine missiles.” Nucl. Eng. Des. 240 (10): 2633–2642. https://doi.org/10.1016/j.nucengdes.2010.07.036. RILEM (International Union of Laboratories and Experts in Construction Materials, Systems and Structures). 2003. “Test and design methods for steel fibre reinforced concrete’-sigma-epsilon-design method.” Mater. Struct. 36 (262): 560–567. https://doi.org/10.1617/14007. Ronanki, V. S., D. B. Valentim, and S. Aaleti. 2016. “Development length of reinforcing bars in UHPC: An experimental and analytical investigation.” In Vol. 4 of Proc., First Int. Interactive Symp. on UHPC, 1–9. Ames, IA: Iowa State Univ. Digital Press. Russell, H. G., and B. A. Graybeal. 2013. Ultra-high performance concrete: A state-of-the-art report for the bridge community. Rep. No. FHWA-HRT-13-060. Washington, DC: Federal Highway Administration Office of Infrastructure Research and Development. Sarkar, J. 2010. Characterization of the bond strength between ultra high performance concrete bridge deck overlays and concrete substrates. Houghton, MI: Michigan Technological University. Shao, Y., and S. L. Billington. 2019. “Utilizing full UHPC compressive strength in steel reinforced UHPC beams.” In Proc., 2nd Int. Interactive Symp. on UHPC. Albany, NY: Iowa State Univ. Digital Press. Shin, H. O., K. H. Min, and D. Mitchell. 2018. “Uniaxial behavior of circular ultra-high-performance fiber-reinforced concrete columns confined by spiral reinforcement.” Constr. Build. Mater. 168 (Apr): 379–393. https://doi.org/10.1016/j.conbuildmat.2018.02.073. Sritharan, S., B. Bristow, and V. Perry. 2003. “Characterizing an ultra-high performance material for bridge applications under extreme loads.” In Proc., 3rd Int. Symp. on High Performance Concrete. Paris: International Union of Laboratories and Experts in Construction Materials, Systems and Structures. Stürwald, S. 2018. “Bending behaviour of UHPC reinforced with rebars and steel fibres.” In High tech concrete: Where technology and engineering meet, 473–481. New York: Springer. Tadros, M. K., A. Sevenker, and R. Berry. 2019. “Ultra-high-performance concrete: A game changer.” Structure Magazine 65 (3): 33–36. Tadros, M. K., and Y. L. Voo. 2016. “Taking ultra-high-performance concrete to new heights.” ASPIRE 10 (3): 36–38. Tai, Y. S., and S. El-Tawil. 2020. “Effect of component materials and mixing protocol on the short-term performance of generic ultra-high-performance concrete.” Constr. Build. Mater. 238 (Mar): 117703. https://doi.org/10.1016/j.conbuildmat.2019.117703. Tayeh, B. A., B. A. Bakar, M. M. Johari, and Y. L. Voo. 2012. “Mechanical and permeability properties of the interface between normal concrete substrate and ultra high performance fiber concrete overlay.” Constr. Build. Mater. 36 (Nov): 538–548. https://doi.org/10.1016/j.conbuildmat.2012.06.013. Tran, N. T., T. K. Tran, J. K. Jeon, J. K. Park, and D. J. Kim. 2016. “Fracture energy of ultra-high-performance fiber-reinforced concrete at high strain rates.” Cem. Concr. Res. 79 (Jan): 169–184. https://doi.org/10.1016/j.cemconres.2015.09.011. Turker, K., U. Hasgul, T. Birol, A. Yavas, and H. Yazici. 2019. “Hybrid fiber use on flexural behavior of ultra high performance fiber reinforced concrete beams.” Compos. Struct. 229 (Dec): 111400. https://doi.org/10.1016/j.compstruct.2019.111400. Valikhani, A., A. J. Jahromi, I. M. Mantawy, and A. Azizinamini. 2020. “Experimental evaluation of concrete-to-UHPC bond strength with correlation to surface roughness for repair application.” Constr. Build. Mater. 238 (Mar): 117753. https://doi.org/10.1016/j.conbuildmat.2019.117753. Verma, M., P. R. Prem, J. Rajasankar, and B. H. Bharatkumar. 2016. “On low-energy impact response of ultra-high performance concrete (UHPC) panels.” Mater. Des. 92 (Feb): 853–865. https://doi.org/10.1016/j.matdes.2015.12.065. Voo, Y. L., and S. J. Foster. 2010. “Characteristics of ultra-high performance ‘ductile’concrete and its impact on sustainable construction.” IES J. Part A: Civ. Struct. Eng. 3 (3): 168–187. Wang, D., Y. Ju, W. Zheng, and H. Shen. 2018a. “Seismic behavior and shear bearing capacity of ultra-high performance fiber-reinforced concrete (UHPFRC) beam-column joints.” Appl. Sci. 8 (5): 810. https://doi.org/10.3390/app8050810. Wang, Z., X. Nie, J. S. Fan, X. Y. Lu, and R. Ding. 2019b. “Experimental and numerical investigation of the interfacial properties of non-steam-cured UHPC-steel composite beams.” Constr. Build. Mater. 195 (Jan): 323–339. https://doi.org/10.1016/j.conbuildmat.2018.11.057. Wang, Z., J. Wang, Y. Tang, Y. Gao, and J. Zhang. 2019c. “Lateral behavior of precast segmental UHPC bridge columns based on the equivalent plastic-hinge model.” J. Bridge Eng. 24 (3): 04018124. https://doi.org/10.1061/(ASCE)BE.1943-5592.0001332. Wibowo, H., and S. Sritharan. 2018. Use of ultra-high-performance concrete for bridge deck overlays. Rep. No. IHRB Project TR-683. Ames, IA: Iowa State Univ. of Science and Technology. Wille, K., and C. Boisvert-Cotulio. 2013. Development of non-proprietary ultra-high performance concrete for use in the highway bridge sector. FHWA Publication No. FHWA-HRT-13-100. NTIS Accession No. PB2013-110587. Washington, DC: Federal Highway Administration. Wille, K., S. El-Tawil, and A. E. Naaman. 2014. “Properties of strain hardening ultra high performance fiber reinforced concrete (UHP-FRC) under direct tensile loading.” Cem. Concr. Compos. 48 (Apr): 53–66. https://doi.org/10.1016/j.cemconcomp.2013.12.015. Wille, K., A. E. Naaman, and S. El-Tawil. 2011b. “Optimizing ultra-high-performance fiber reinforced concrete.” Concr. Int. 33 (9): 35–41. Wille, K., A. E. Naaman, S. El-Tawil, and G. J. Parra-Montesinos. 2012. “Ultra-high performance concrete and fiber reinforced concrete: Achieving strength and ductility without heat curing.” Mater. Struct. 45 (3): 309–324. https://doi.org/10.1617/s11527-011-9767-0. Wille, K., A. E. Naaman, and G. J. Parra-Montesinos. 2011c. “Ultra-high performance concrete with compressive strength exceeding 150 MPa (22 ksi): A simpler way.” ACI Mater. J. 108 (6): 46–54. Xu, J., C. Wu, H. Xiang, Y. Su, Z. X. Li, Q. Fang, H. Hao, Z. Liu, Y. Zhang, and J. Li. 2016. “Behaviour of ultra high performance fibre reinforced concrete columns subjected to blast loading.” Eng. Struct. 118 (Jul): 97–107. https://doi.org/10.1016/j.engstruct.2016.03.048. Xu, S., C. Wu, Z. Liu, K. Han, Y. Su, J. Zhao, and J. Li. 2017. “Experimental investigation of seismic behavior of ultra-high performance steel fiber reinforced concrete columns.” Eng. Struct. 152 (Dec): 129–148. https://doi.org/10.1016/j.engstruct.2017.09.007. Xu, S., C. Wu, Z. Liu, and R. Shao. 2019. “Experimental investigation on the cyclic behaviors of ultra-high-performance steel fiber reinforced concrete filled thin-walled steel tubular columns.” Thin-Walled Struct. 140 (Jul): 1–20. https://doi.org/10.1016/j.tws.2019.03.008. Yang, I. H., J. Park, K. C. Kim, C. Joh, and H. Lee. 2020. “An experimental study on the ductility and flexural toughness of ultrahigh-performance concrete beams subjected to bending.” Materials (Basel) 13 (10): 2225. https://doi.org/10.3390/ma13102225. Yin, H., W. Teo, and K. Shirai. 2017. “Experimental investigation on the behaviour of reinforced concrete slabs strengthened with ultra-high performance concrete.” Constr. Build. Mater. 155 (Nov): 463–474. https://doi.org/10.1016/j.conbuildmat.2017.08.077. Yoo, D. Y., N. Banthia, and Y. S. Yoon. 2017a. “Experimental and numerical study on flexural behavior of ultra-high-performance fiber-reinforced concrete beams with low reinforcement ratios.” Can. J. Civ. Eng. 44 (1): 18–28. https://doi.org/10.1139/cjce-2015-0384. Yoo, D. Y., N. Banthia, and Y. S. Yoon. 2017b. “Impact resistance of reinforced ultra-high-performance concrete beams with different steel fibers.” ACI Struct. J. 114 (1): 113–124. https://doi.org/10.14359/51689430. Yoo, D. Y., S. T. Kang, and Y. S. Yoon. 2014. “Effect of fiber length and placement method on flexural behavior, tension-softening curve, and fiber distribution characteristics of UHPFRC.” Constr. Build. Mater. 64 (Aug): 67–81. https://doi.org/10.1016/j.conbuildmat.2014.04.007. Yoo, D. Y., and S. Kim. 2019. “Comparative pullout behavior of half-hooked and commercial steel fibers embedded in UHPC under static and impact loads.” Cem. Concr. Compos. 97 (Mar): 89–106. https://doi.org/10.1016/j.cemconcomp.2018.12.023. Yoo, D. Y., J. J. Park, S. W. Kim, and Y. S. Yoon. 2013. “Early age setting, shrinkage and tensile characteristics of ultra high performance fiber reinforced concrete.” Constr. Build. Mater. 41 (Apr): 427–438. https://doi.org/10.1016/j.conbuildmat.2012.12.015. Yousef, A. M., A. M. Tahwia, and N. A. Marami. 2018. “Minimum shear reinforcement for ultra-high performance fiber reinforced concrete deep beams.” Constr. Build. Mater. 184 (Sep): 177–185. https://doi.org/10.1016/j.conbuildmat.2018.06.022. Yu, R., L. Van Beers, P. Spiesz, and H. J. H. Brouwers. 2016. “Impact resistance of a sustainable ultra-high performance fibre reinforced concrete (UHPFRC) under pendulum impact loadings.” Constr. Build. Mater. 107 (Mar): 203–215. https://doi.org/10.1016/j.conbuildmat.2015.12.157. Zanuy, C., and G. S. Ulzurrun. 2019. “Bending model for composite UHPFRC-RC elements including tension stiffening and crack width.” Eng. Struct. 209 (Apr): 109958.