Structural Implications of the Synergistic Interactions between Steel Reinforcement and UHPC

  • Shih-Ho Chao (The University of Texas at Arlington)
  • Venkatesh Kaka (Armstrong-Douglass Structural Engineers)
  • Missagh Shamshiri (Aguirre & Fields)


The excellent mechanical properties of ultra-high-performance concrete (UHPC) can revolutionize the design of reinforced concrete structural members. However, UHPC material properties were typically measured without including longitudinal steel reinforcement while the synergistic interaction of UHPC and steel reinforcement can significantly alter UHPC material properties. Experimental studies indicates that UHPC’s tensile ductility can be significantly enhanced due to the presence of longitudinal reinforcement. In addition, while concrete’s cracking strength can hardly be considerably increased in a typical reinforced concrete member, increasing the longitudinal reinforcement ratio by a significant amount can enhance the cracking strength of UHPC up to five to eight times that of plain concrete. The reason behind this is that when the longitudinal reinforcement ratio surpasses a critical threshold, the longitudinal reinforcement can efficiently share tensile force and halt the growth of microcracks in concrete, preventing them from connecting and forming a percolation crack. Allowing a higher steel ratio also leads to smaller tensile and bond stresses in tensile reinforcement. Because crack widths in a flexural member are roughly proportional to the stress in steel reinforcement, the low stress will allow better control of the crack width and, hence, stiffness of the member. Notably, UHPC’s maximum compressive strain can reach about five times higher than that of plain concrete. This high compressive strain capacity allows a concrete member to maintain tension-controlled behavior even with a high amount of steel rebars. Neglecting the greater compressive ductility of UHPC can limit the maximum permissible quantity of longitudinal reinforcement, resulting in the early rupture of longitudinal reinforcement and restricted flexural capacity.

Keywords: UHPC, tension-controlled, maximum compressive strain, cracking strength

How to Cite:

Chao, S., Kaka, V. & Shamshiri, M., (2023) “Structural Implications of the Synergistic Interactions between Steel Reinforcement and UHPC”, International Interactive Symposium on Ultra-High Performance Concrete 3(1): 111. doi:

Rights: © 2023 The Author(s). All rights reserved.

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Published on
04 Jun 2023
Peer Reviewed