Axial Behavior of Reinforced UHPC-NSC Composite Column under Compression

Abstract

This paper proposes a novel reinforced ultra-high-performance concrete (UHPC)-normal strength concrete (NSC) composite column. The main feature of the reinforced UHPC-NSC composite column is the use of an exterior UHPC cover, which is helpful for improving the load-carrying capacity, deformability, and crack resistance. This study focused on the axial behavior of the reinforced UHPC-NSC composite column. A total of 12 specimens were designed to investigate the axial behavior of the composite column under compression. The thickness of the exterior UHPC cover, volumetric stirrup ratio, and construction method were considered as the main experimental parameters. The failure modes and strain–stress relationships are discussed in this paper. By introducing the exterior UHPC cover, the peak confined strength obviously improved. The compressive strain at the peak confined strength was mainly determined by the deformability of the plain UHPC material. The composite column resulted in a unique sudden drop immediately after the peak confined strength, owing to the rapid loss of the confining stress from the exterior UHPC cover. A trilinear model is proposed to describe the strain–stress relationship of the composite column. The results obtained by the modified model are in good agreement with the test results.

Effects of Freeze–Thaw Cycles on Axial Compression Behaviors of UHPC-RC Composite Columns

“…Lu et al (2021) [12] found that among the components of UHPC, the water-binder ratio had the greatest influence on frost resistance. Li et al (2020) [13] found that the damage of the chloride salt freeze-thaw cycle to reactive powder concrete (RPC) was greater than that of the freshwater freeze-thaw cycle. Zhang et al (2020) [14] found that freeze-thaw cycles accelerated the development of cracks in ordinary reinforced concrete (RC) columns, and the number of cracks increased with the increase of F-T times.…”

“…Xie [20] found that the axial compressive bearing capacity of UHPC-RC composite columns gradually increased with the increase in UHPC tube thickness. Li [21] found that the bearing capacity of the composite column of pouring the concrete core first and pouring the UHPC tube later is higher than that of pouring the UHPC tube first and pouring the core concrete later. Zhang [22] and Shan [23] found that increasing the steel fiber content and stirrup ratio of UHPC tubes can effectively improve the peak load and ductility of UHPC-RC composite columns.…”

Effect of ultra‐high performance concrete repair layer thickness on the behavior of concrete columns

“…The UHPFRC gains interest in research covering column strengthening due to the properties mentioned, providing superior resistance capacity for the original structure without a significant increase in the thickness of the system 23 . As a result, a series of investigations were conducted on the performance of column strengthened using the UHPFRC 23–26 …”

“…Li et al 26 studied 12 examples of columns with layers of high‐performance concrete with longitudinal and transverse reinforcement rebar. The authors investigated some parameters: the jacketing thickness, the volumetric ratio of stirrups, and the construction method.…”

“…23 As a result, a series of investigations were conducted on the performance of column strengthened using the UHPFRC. [23][24][25][26] Enami 23 investigated the influence of the confinement by ultra-high-performance concrete (UHPC) and UHPFRC in short reinforced concrete columns with circular and square sections through experimental analysis and numerical simulations, also evaluating the addition of reinforcement and CFRP. By analyzing 16 reinforced columns, the author concluded that small increments of the strengthening thickness provide high gains in the axial compressive strength.…”