Behaviours of concrete stub columns confined by steel tubes at cold-region low temperatures

Abstract

This paper evaluates the axial compressive behaviour of concrete stub columns confined by steel tubes (CSC-CSTs) at low temperatures of 30 ~ −80 °C relevant to cold regions. Experiments including ten circular and ten square CSC-CSTs subjected to axial compression at four low temperatures were carried out. The studied parameters included low temperature (T), different grades of NWC (fc), wall-thickness of the steel tube (t), and height of the CSC-CSTs (L). The test results revealed that bulge of steel tubes, concrete crushing, and vertical fracture in steel tube (only in square CSC-CSTs) occurred to CSC-CSTs. The load-shortening (PS) behaviour of CSC-CSTs exhibits similar manner in the first elastic and nonlinear working stage, but varies at their recession stages due to different confinement ratio by steel tube. Low temperatures improved axial compressive behaviours of CSC-CSTs. Increasing concrete strength improved the compressive strength of CSC-CSTs at low temperatures, but reduced their ductility. Thicker steel tube improved the PS behaviour of CSCCSTs at low temperatures whilst the height of CSC-CSTs exhibited marginal influences on their low-temperature compressive behaviours. Theoretical models were developed to estimate PS behaviours of CSC-CSTs, and validations against 20 test results confirmed their accuracy.