Effects of cyclic loading and high-temperature cooling on mechanical properties of Q450 weathering steel

The investigation of the mechanical properties of steel structures after cyclic loadings such as earthquakes, wind vibrations, and high-temperature cooling helps to study the stability of steel structures in extremely complex environments. Hence, this study investigates the mechanical characteristics of cyclically loaded Q450 weathering steel after high-temperature cooling. Before the tensile test, Q450 weathering steel was previously damaged by cyclic loading, and then the Q450 weathering steel specimens with different cyclic loading damages were heated and cooled. Based on the test results, the effect of the sequence of cyclic loading and high-temperature cooling on the mechanical characteristics of steel was also discussed. The failure model of cyclically loaded Q450 weathering steel after high-temperature cooling was observed. The residual mechanical characteristics of Q450 weathering steel after being subjected to extreme environments were discussed by comparing the mechanical characteristics of undamaged steel specimens. The test findings reveal that the cyclic loading pre-damage, heating temperature, and cooling method greatly impact the important parameters of Q450 weathering steel, such as strength, elastic modulus, and ductility. Comparing the sequence of cyclic loading, heating and cooling, Q450 weathering steel with cyclic loading pre-damage of 95 % was considerably influenced by the sequence of extreme environments. In contrast, the influence of the extreme environmental sequence was not significant when the pre-damage was 50 % and 75 %. In addition, the modulus of elasticity is indifferent to the extreme environmental sequences, whereas the elongation displays complicated change patterns under varied degrees of pre-damage. Finally, the stress-strain relationship considering the interactive effects of cyclic loading damage, temperature, and cooling method was proposed using a multi-component numerical model.