Evaluation of Earthquake-Induced Risks in Modern, Code-Conforming Reinforced Concrete Moment Frames

Abstract: The main objective of this study is to employ performance assessment procedure to evaluate earthquakeinduced risks in modern, code-conforming Reinforced Concrete (RC) moment frames in terms of collapse risk and possible financial losses. In order to accomplish this goal, a set of 15 archetype RC moment frames is evaluated in this study. The buildings are different regarding height and structural system ductility. The archetypes are assumed to be located in three zones with different levels of seismicity. The findings of the collapse assessment procedure indicate that the constraint of ASCE 7-05 for the lower limit of design base shear has the most significant impact and the ductility has the least influence on collapse risk. Also, it has been found that buildings located in the low seismicity zone have significantly lower levels of losses. Sensitivity analysis is employed to study the variations of earthquake consequences due to the variations in the design decisions

A Maximum Likelihood Prediction Model for Building Seismic Response

Earthquakes in seismically-active regions present a significant human and financial risk to communities. This study focuses on proposing a prediction model that could serve as a means for quantifying the impact of the main characteristics of earthquakes on the seismic risk of reinforced concrete moment frame structures. The seismic hazard due to sequential earthquakes is examined under mainshock-aftershock seismic sequences. A two-step maximum likelihood regression approach was adopted in order to propose a relationship that would link the seismic response of the studied buildings to the key characteristics of an earthquake. The accuracy of the proposed prediction equation was examined by comparing its outcomes with what was expected from physics-based models. Both the magnitude of an earthquake as well as the distance from the building's location to the rupture plane of the building were found to be among the parameters with the most notable impact on the buildings' seismic response

Stochastic Characterization of Aftershock Building Seismic Performance

The increase in seismic activity after a large-magnitude earthquake coupled with the reduction in the lateral load-carrying capacity of the affected structures presents a significant human and financial risk to communities. The focus of this study is placed on formulating a framework for quantifying the impact of both the elevated post-mainshock seismic hazard as well as the mainshock-induced structural damage on building seismic performance. The viability of the proposed framework is examined through its application to mainshock-aftershock seismic performance evaluation of a set of reinforced concrete frames. Additionally, discrepancies between the frequency content of mainshock and aftershock ground motions and their impact on the seismic performance of RC moment frames is investigated. Two metrics are used in evaluating the seismic performance; seismic risk and seismic-induced financial losses. Both metrics are evaluated in both pre- and post-mainshock environments. The time-dependent nature of seismic hazard in the post-mainshock environment is accounted for through the adoption of a Markov risk assessment framework. In the post-mainshock environment, the seismic risk is examined as a function of the time elapsed since the mainshock’s occurrence while in the pre-mainshock environment, the risk is investigated during an assumed lifespan of 50 years for the studied structures. For the buildings and the high-seismicity site used in this study, both the increased post-mainshock seismic hazard as well as the reduction in the structural capacity are found to have a great influence on the seismic risk. The application of the proposed frameworks for seismic performance under mainshock-aftershock ground motions to the reinforced concrete frame buildings in Los Angeles County is also demonstrated. The outcomes of the regional seismic performance analysis show that omitting aftershocks from the seismic performance steps would lead to underestimating annual expected seismic risk and loss by up to 50% and 15%