Assessment of collapse modes in reinforced concrete frames considering record-to-record and modeling uncertainties

Dominant Collapse Mechanisms (DCMs) have been reported to play an important role in collapse capacity of structural systems and the seismic losses consequent to it. Therefore, DCMs of Reinforced Concrete (RC) frames have been studied, in this article, considering Record-To-Record (RTR) and modeling uncertainties. Two sets of RC frames have been designed, in this regard, that share the design assumptions but contain different levels of over-strength. Each set contains 26, 4- to 20-story nonlinearly modeled frames. Initially, Incremental Dynamic Analysis (IDA) was used to identify frames DCMs. Then, the RTR variability reflected through IDA was combined with spectral shape and pulse effects of the ground motion records. Modeling uncertainties were finally introduced to the study using a response surface based Monte Carlo method. The study results revealed that the degree to which DCMs were affected by the associated uncertainties was a function of the over-strength provided to the frames. This effect is found to be generally important and particularly remarkable for especially detailed ductile structures.