Abstract An ultra‐high‐performance concrete (UHPC) shell wrapped around a reinforced‐concrete (RC) column forms a UHPC–RC composite column. As UHPC–RC composite columns are increasingly used in practice, their performance under varying ambient temperatures and moisture conditions must be clarified. This study performed axial compression tests on UHPC–RC short columns under five temperatures (−20, 0, 20, 60, 100°C), three saturation states (dry, natural, fully saturated), and three stirrup spacings (35, 70, 105 mm). Results showed no debonding between the UHPC shell and core concrete after failure. The UHPC shell enhanced the peak load of RC columns by 67.4% (1129–1890 kN) and ductility coefficient by 26.4% (4.28–5.63). Under natural moisture, the peak load dropped 19.8% as temperature rose, while the ductility coefficient rose 74.8%. Saturation exerted temperature‐dependent effects on ductility. A peak‐load prediction model was established for −20°C ≤ T ≤ 100°C and different saturations, with a prediction‐test deviation within 5%, laying a theoretical and experimental foundation for UHPC–RC column design.
Gao et al. (Mon,) studied this question.