Structural responses of reinforced concrete columns subjected to uniaxial bending and restraint at elevated temperatures

• New experimental programme on RC columns at elevated temperatures.
• Combined action of eccentric load and restraint on heated columns is investigated.
• Eccentricity and initial load level adversely affect lateral deflection of columns.
• Normalised restraint forces increase when uniaxial eccentricity increases.
• Numerical analyses ignoring concrete spalling overpredict normalised restraint forces.

A total of six specimens were tested to failure to investigate the effects of uniaxial bending, axial restraint, and initial load level on the structural responses of reinforced concrete columns at elevated temperatures. The full-scale column specimens (nominal height of 3.3 m and square cross-section of 300 mm) were cast with concrete of 55 MPa compressive strength and reinforcing steel of 550 MPa yield strength, and were tested with different levels of initial load and uniaxial eccentricity. Temperature-dependent axial deformations, lateral deflections, thermal-induced restraint forces, failure modes, and failure times of the test specimens are compared with those obtained from numerical analyses using SAFIR program. It is experimentally shown that the lateral deflection at elevated temperatures is adversely affected by uniaxial eccentricity and initial load level. Besides, the development of thermal-induced restraint forces increases with eccentricity but decreases with initial load level, and can be overpredicted by the numerical analysis that ignores concrete spalling and implicitly accounts for concrete transient strain at elevated temperatures.