Residual structural capacity evaluation of steel moment-resisting frames with dynamic-strain-based model updating method

This paper presents a method for evaluating the residual structural capacity of earthquake-affected steel structures. The method first quantifies the damage severity of a beam by computing the dynamic-strain-based damage index. Next, the model used to analyze the structure is updated based on the damage index, to reflect the observed damage conditions. The residual structural capacity is then estimated in terms of changes in stiffness and strength, which can be applied by structural engineers, via a nonlinear static analysis of the updated model. The main contributions of this paper are in performance evaluation of the dynamic-strain-based damage index for seismically induced damage using a newly developed substructure testing environment, consideration of various damage patterns in composite beams, and extension of a local damage evaluation technique to a residual capacity estimation procedure by incorporating the model-updating technique. In laboratory testing, the specimens were damaged quasi-statically, and vibration tests were conducted as the damage proceeded. First, a bare steel beam-column connection was tested, and then a similar one with a floor slab was used for a more realistic case. The estimated residual structural capacities for these specimens were compared with the static test results. The results verified that the proposed method can provide fine estimates of the stiffness and strength deteriorations within 10% for the specimen without the floor slab and within 30% for that with the floor slab. Copyright (c) 2017 John Wiley & Sons, Ltd.