Earthquake-induced damage updating for remaining-life assessment of steel frame substructure systems

This paper presents a framework combining theoretical, numerical, and experimental approaches for evaluating the remaining-life of high-rise steel buildings based on earthquake-induced fatigue damage propagation in local beam-to-column connections. A mesh-independent finite element model is developed and implemented using the concept of lumped damage mechanics to estimate the fatigue-induced life loss associated with the extent of crack propagation until complete rupture failure occurred in beam-to-column connection substructure of high-rises. In this framework, a damage state variable is introduced at each end of beam elements and can be linked to the extension of the fatigue fracture in real frame building joints. Then, the damage evolution law is developed by extending the conventional Manson–Coffin law and a new crack-driving parameter to quantify the extent of damage states and predict the remaining life of the associated components in high-rises buildings. The proposed model is validated by a damage index measured from the local wireless sensors in substructure tests of ductile steel beam-to-column connections subjected to ultra-low cycle fatigue loadings. The residual resistance can be quantified by updating the damage curve with the identified damaged conditions.