• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2003.09a
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• pp.271-279
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• 2003

The objective of this study is to evaluate the damage of the reinforced concrete bridge piers. For the purpose of this research, twelve reinforced concrete specimens were fabricated and experimented with quasi-static test method. The selected test parameters are lap splice, axial load ratio, confinement steel ratio and number of loading cycle. The method of evaluate of damage index is the model proposed by Park and Ang. In accordance with this research, the most effective test parameter is lap splice of longitudinal steel. Therefore, the retrofit scheme of reinforced concrete bridge piers with lap splice of longitudinal steel, which was constructed before 1992, must be settled without delay. Otherwise, the effect of axial force is trivial. The more confinement steel is less damage index and more loading cycle lead to raise damage. The damage statement proposed Park and Ang is the same with experimental results.

• Structural Engineering and Mechanics
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• v.72 no.1
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• pp.83-97
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• 2019

In this research, the vulnerability of some reinforced concrete frames with different stories are studied based on the Park-Ang Damage Index. The damages of the frames are investigated under various earthquakes with nonlinear dynamic analysis in IDARC software. By examining the most important characteristics of earthquake parameters, the damage index and vulnerability of these frames are investigated in this software. The intensity of Erias, velocity spectral intensity (VSI) and peak ground velocity (PGV) had the highest correlation, and root mean square of displacement ($D_{rms}$) had the lowest correlation coefficient among the parameters. Then, the particle swarm optimization (PSO) algorithm was used, and the sinusoidal waves were equivalent to the used earthquakes according to the most influential parameters above. The damage index equivalent to these waves is estimated using nonlinear dynamics analysis. The comparison between the damages caused by earthquakes and equivalent sinusoidal waves is done too. The generations of sinusoidal waves equivalent to different earthquakes are generalized in some reinforced concrete frames. The equivalent sinusoidal wave method was exact enough because the greatest difference between the results of the main and artificial accelerator damage index was about 5 percent. Also sinusoidal waves were more consistent with the damage indices of the structures compared to the earthquake parameters.

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

• Advances in concrete construction
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• v.10 no.3
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• pp.271-278
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• 2020

Quantifying the amount of damage of structures under earthquakes is an interesting issue that researchers have attended on and have presented some damage indices. Whereas a lot of damage indices have been introduced based on nonlinear dynamic analysis, computational effort, the calculus complicacy and time-consuming of this analysis are the main drawbacks to widespread use of these indices. The objective of this study is to quantify the damage of Shear Wall Reinforced Concrete Frames (SWRCFs) based on pushover analysis as a procedure that can reflect the behavior of structures from elastic to collapse. For this purpose, firstly, several SWRCFs are designed and the capacity spectrum of each one is achieved via pushover analysis. After that, the static damage indices of the designed frames are obtained. Then, nonlinear dynamic analyses are performed on these frames and the Park and Ang damage index as the basis damage criterion is achieved. Afterward, some relations are presented to predict the dynamic damage of these frames via pushover analysis. Eventually, to confirm the validity of the proposed relations, the values of Park and Ang damage index of three new SWRCFs are acquired once utilizing nonlinear dynamic analysis and again applying the introduced relations. Outcomes prove the validity of some presented damage indices.

• Earthquakes and Structures
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• v.16 no.2
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• pp.197-208
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• 2019

The objective of this study is to propose new seismic intensity parameters based on the Hilbert spectrum and to associate them with the seismic damage potential. In recent years the assessment of even more seismic features derived from the seismic acceleration time-histories was associated with the structural damage. For a better insight into the complex seismic acceleration time-history, Hilbert-Huang Transform (HHT) analysis is utilized for its processing, and the Hilbert spectrum is obtained. New proposed seismic intensity parameters based on the Hilbert spectrum are derived. The aim is to achieve a significant estimation of the seismic damage potential on structures from the proposed new intensity parameters confirmed by statistical methods. Park-Ang overall structural damage index is used to describe the postseismic damage status of structures. Thus, a set of recorded seismic accelerograms from all over the word is applied on a reinforced concrete frame structure, and the Park-Ang indices through nonlinear dynamic analysis are provided and considered subsequently as reference numerical values. Conventional seismic parameters, with well-known seismic structural damage interrelation, are evaluated for the same set of excitations. Statistical procedures, namely correlation study and multilinear regression analysis, are applied on the set of the conventional parameters and the set of proposed new parameters separately, to confirm their interrelation with the seismic structural damage. The regression models are used for the evaluation of the structural damage indices for every set of parameters, respectively. The predicted numerical values of the structural damage indices evaluated from the two sets of seismic intensity parameters are inter-compared with the reference values. The numerical results confirm the ability of the proposed Hilbert spectrum based new seismic intensity parameters to approximate the postseismic structural damage with a smaller Standard Error of Estimation than this accomplished of the conventional ones.

• Earthquakes and Structures
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• v.7 no.6
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• pp.1119-1139
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• 2014

A damage-based seismic design procedure for steel frame structures is formulated as an optimization problem, in which minimization of the initial construction cost is treated as the objective of the problem. The performance constraint of the design procedure is to achieve "repairable" damage state for earthquake demands that are less severe than the design ground motions. The Park-Ang damage index is selected as the seismic damage measure for the quantification of structural damage. The charged system search (CSS) algorithm is employed as the optimization algorithm to search the optimum solutions. To improve the time efficiency of the solution algorithm, two simplifying strategies are adopted: first, SDOF idealization of multi-story building structures capable of estimating the actual seismic response in a very short time; second, fitness approximation decreasing the number of fitness function evaluations. The results from a numerical application of the proposed framework for designing a twelve-story 3D steel frame structure demonstrate its efficiency in solving the present optimization problem.

• Earthquakes and Structures
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• v.18 no.4
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• pp.507-517
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• 2020

This study aims to present new frequency-related seismic intensity parameters (SIPs) based on the Hilbert-Huang Transform (HHT) analysis. The proposed procedure is utilized for the processing of several seismic accelerograms. Thus, the entire evaluated Hilbert Spectrum (HS) of each considered seismic velocity time-history is investigated first, and then, a delimited area of the same HS around a specific frequency is explored, for the proposition of new SIPs. A first application of the suggested new parameters is to reveal the interrelation between them and the structural damage of a reinforced concrete frame structure. The index of Park and Ang describes the structural damage. The fundamental frequency of the structure is considered as the mentioned specific frequency. Two statistical methods, namely correlation analysis and multiple linear regression analysis, are used to identify the relationship between the considered SIPs and the corresponding structural damage. The results confirm that the new proposed HHT-based parameters are effective descriptors of the seismic damage potential and helpful tools for forecasting the seismic damages on buildings.

• Smart Structures and Systems
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• v.16 no.1
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• pp.1-26
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• 2015

Minimizing construction cost and reducing seismic damage are two conflicting objectives in the design of any new structure. In the present work, we try to develop a framework in order to solve the optimum performance-based design problem considering the construction cost and the seismic damage of steel moment-frame structures. The Park-Ang damage index is selected as the seismic damage measure because it is one of the most realistic measures of structural damage. The non-dominated sorting genetic algorithm (NSGA-II) is employed as the optimization algorithm to search the Pareto optimal solutions. To improve the time efficiency of the proposed framework, three simplifying strategies are adopted: first, simplified nonlinear modeling investigating minimum level of structural modeling sophistication; second, fitness approximation decreasing the number of fitness function evaluations; third, wavelet decomposition of earthquake record decreasing the number of acceleration points involved in time-history loading. The constraints of the optimization problem are considered in accordance with Federal Emergency Management Agency's (FEMA) recommended seismic design specifications. The results from numerical application of the proposed framework demonstrate the efficiency of the framework in solving the present multi-objective optimization problem.

• Advances in concrete construction
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• v.5 no.4
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• pp.407-422
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• 2017

Evaluating seismic performance of urban structures for future earthquakes is one of the key prerequisites of rehabilitation programs. Irregular structures, as a specific case, are more susceptible to sustain earthquake damage than regular structures. The study here is to identify damage states of vertically irregular structures using the well-recognized Park-Ang damage index. For doing this, a regular 3-story reinforced concrete (RC) structure is first designed based on ACI-318 code, and a peak ground acceleration (PGA) of 0.3 g. Some known vertical irregularities such as setback, short column and soft story are then applied to the regular structure. All the four structures are subjected to seven different earthquakes accelerations and different amplitudes which are then analyzed using nonlinear dynamic procedure. The damage indices of the structures are then accounted for using the pointed out damage index. The results show that the structure with soft story irregularity sustains more damage in all the earthquake records than the other structures. The least damage belongs the regular structure showing that different earthquake with different accelerations and amplitudes have no significant effect on the regular structures.

• Earthquakes and Structures
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• v.14 no.2
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• pp.129-142
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• 2018

The current paper introduces a new approach for development of damage index to obtain the maximum damage in the reinforced concrete frames caused by as-recorded single and consecutive earthquakes. To do so, two sets of strong ground motions are selected based on maximum and approximately maximum peak ground acceleration (PGA) from "PEER" and "USGS" centers. Consecutive earthquakes in the first and second groups, not only occurred in similar directions and same stations, but also their real time gaps between successive shocks are less than 10 minutes and 10 days, respectively. In the following, a suite of six concrete moment resisting frames, including 3, 5, 7, 10, 12 and 15 stories, are designed in OpenSees software and analyzed for more than 850 times under two groups of as-recorded strong ground motion records with/without seismic sequences phenomena. The idealized multilayer artificial neural networks, with the least value of Mean Square Error (MSE) and maximum value of regression (R) between outputs and targets were then employed to generate the empirical charts and several correction equations for design utilization. To investigate the effectiveness of the proposed damage index, calibration of the new approach to existing real data (the result of Park-Ang damage index 1985), were conducted. The obtained results show good precision of the developed ANNs-based model in predicting the maximum damage of regular reinforced concrete frames.