Behaviour of thermally shocked RC columns internally confined by auxetic steel wire mesh

An experimental programme was designed to test 24 square columns (200 mm side and 1000 mm length) with different numbers of layers (one, two, three, four and five) of auxetic steel wire mesh (ASWM) as a substitute for stirrup reinforcement within the middle region of the column height. The effect of thermal shock was also assessed, with the tested columns divided into two sets of 12 damaged specimens and 12 undamaged specimens. Sufficient ties were provided at the column ends to prevent premature failure. The ASWM layers provided the columns with the required lateral confinement depending on the number of applied layers (N-ASWM) and the concrete compressive strength. Thermal shock was found to reduce the concrete compressive strength, thus degrading the column's performance in terms of ductility, strength and stiffness. The number of ASWM layers used significantly improved the ductility, energy absorption, and column axial capacity, but this improvement was limited to N-ASWM = 4 or 5, while the stiffness increased for all values of N-ASWM. The average enhancement in the column's axial capacity was 15% for the intact specimens, but this was reduced to approximately 10% under the effect of thermal shock.