• Earthquakes and Structures
• /
• v.15 no.3
• /
• pp.295-306
• /
• 2018

Reinforced concrete containment (RCC) building has long been considered as the last barrier for keeping the radiation from leaking into the environment. It is important to quantify the performance of these structures and facilities considering extreme conditions. However, the preceding research on evaluating nuclear power plant (NPP) structures, particularly considering mainshock-aftershock seismic sequences, is deficient. Therefore, this manuscript serves to investigate the seismic fragility of a typical RCC building subjected to mainshock-aftershock seismic sequences. The implementation of the fragility assessment has been performed based on the incremental dynamic analysis (IDA) method. A lumped mass RCC model considering the tri-linear skeleton curve and the maximum point-oriented hysteretic rule is employed for IDA analyses. The results indicate that the seismic capacity of the RCC building would be overestimated without taking into account the mainshock-aftershock effects. It is also found that the seismic capacity of the RCC building decreases with the increase of the relative intensity of aftershock ground motions to mainshock ground motions. In addition, the effects of artificial mainshock-aftershock ground motions generated from the repeated and randomized approaches and the polarity of the aftershock with respect to the mainshock on the evaluation of the RCC are also researched, respectively.

• Structural Engineering and Mechanics
• /
• v.72 no.3
• /
• pp.395-408
• /
• 2019

Engineered structures built in seismic-prone areas are affected by aftershocks in addition to mainshocks. Although aftershocks generally are lower in magnitude than that of the mainshocks, some aftershocks may have higher intensities; thus, structures should be able to withstand the effect of strong aftershocks as well. This seismic scenario arises for far-field mainshock along with near-field aftershocks. In this study, four 2D reinforced concrete (RC) frames with different numbers of stories were designed in accordance with the current Iranian seismic design code. As a way to evaluate the seismic response of the case-study RC frames, the inter-story drift ratio (IDR) demand, the residual inter-story drift ratio (RIDR) demand, the Park-Ang damage index, and the period elongation ratio can be useful engineering demand parameters for evaluating their seismic performance under mainshock-aftershock sequences. The frame models were analyzed under a set of far-field mainshock, near-fault aftershocks seismic sequences using nonlinear dynamic time-history analysis to investigate the relationship among IDR, RIDR, Park-Ang damage index and period ratio experienced by the frames. The results indicate that the growth of IDR, RIDR, Park-Ang damage index, and period ratio in high-rise and short structures under near-fault aftershocks were significant. It is evident that engineers should consider the effects of near-fault aftershocks on damaged frames that experience far-field mainshocks as well.

• Earthquakes and Structures
• /
• v.7 no.6
• /
• pp.1241-1258
• /
• 2014

This is paper presents the results of an analytical study aimed at evaluating the effect of narrow-banded mainshock/aftershock seismic sequences on the response of structures built on very soft soil sites. Due to the scarce availability of recorded seismic sequences in accelerographic stations located in the lake-bed of Mexico City, artificial narrow-banded sequences were employed. In the first part of this study, a parametric investigation was carried out to identify the mainshock/aftershock ground motion features that have detrimental effects in the seismic performance of equivalent single-degree-of-freedom systems representative of framed-buildings that house standard and essential facilities. In the second part of this work, the seismic response of two (8- and 18-story) steel-moment resisting frames that house essential facilities is examined. It is concluded that buildings with fundamental periods of vibration longer than the dominant period of the mainshock can experience a significant increment in their inter-story drift demands due to the occurrence of an aftershock.

• Earthquakes and Structures
• /
• v.16 no.4
• /
• pp.425-436
• /
• 2019

Successive ground motions having short time intervals have occurred in many earthquakes so far. It is necessary to investigate the effects of this phenomenon on different types of structures and to take these effects into consideration while designing or retrofitting structures. The effects of seismic sequences on the structures with combined reinforced concrete shear wall and moment resisting frame system have not been investigated in details yet. This paper has tried to analyse the seismic performance of structures with such structural systems subjected to mainshock-aftershock sequences. The effects of the seismic sequences on the investigated models are evaluated by strong measures such as IDA capacity and fragility and vulnerability curves. The results of this study show that the seismic sequences have a significant effect on the investigated models, which necessitates considering this effect on designing, retrofitting, decision making, and taking precautions.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.22 no.5
• /
• pp.291-298
• /
• 2018

Existing reinforced concrete building structures have seismic vulnerabilities under successive earthquakes (or mainshock-aftershock sequences) due to their inadequate column detailing, which leads to shear failure in the columns. To improve the shear capacity and ductility of the shear-critical columns, a fiber-reinforced polymer jacketing system has been widely used for seismic retrofit and repair. This study proposed a numerical modeling technique for damaged reinforced concrete columns repaired using the fiber-reinforced polymer jacketing system and validated the numerical responses with past experimental results. The column model well captured the experimental results in terms of lateral forces, stiffness, energy dissipation and failure modes. The proposed column modeling method enables to predict post-repair effects on structures initially damaged by mainshock.