• Structural Engineering and Mechanics
• /
• 제75권3호
• /
• pp.295-309
• /
• 2020

The construction of Reinforced Concrete (R/C) buildings with unreinforced masonry infills is part of the traditional building practice in many countries with regions of high seismicity throughout the world. When these buildings are subjected to seismic motions the presence of masonry infills and especially their configuration can highly influence the seismic damage state. The capability to avoid configurations of masonry infills prone to seismic damage at the stage of initial architectural concept would be significantly definitive in the context of Performance-Based Earthquake Engineering. Along these lines, the present paper investigates the potential of instant prediction of the damage response of R/C buildings with various configurations of masonry infills utilizing Artificial Neural Networks (ANNs). To this end, Multilayer Feedforward Perceptron networks are utilized and the problem is formulated as pattern recognition problem. The ANNs' training data-set is created by means of Nonlinear Time History Analyses of 5 R/C buildings with a large number of different masonry infills' distributions, which are subjected to 65 earthquakes. The structural damage is expressed in terms of the Maximum Interstorey Drift Ratio. The most significant conclusion which is extracted is that the ANNs can reliably estimate the influence of masonry infills' configurations on the seismic damage level of R/C buildings incorporating their optimum design.

• Earthquakes and Structures
• /
• 제4권3호
• /
• pp.299-324
• /
• 2013

The current research focuses on the seismic vulnerability assessment of typical Southern Europe buildings, based on processing of a large set of observational damage data. The presented study constitutes a sequel of a previous research. The damage statistics have been enriched and a wider damage database (178578 buildings) is created compared to the one of the first presented paper (73468 buildings) with Damage Probability Matrices (DPMs) after the elaboration of the results from post-earthquake surveys carried out in the area struck by the 7-9-1999 near field Athens earthquake. The dataset comprises buildings which developed damage in several degree, type and extent. Two different parameters are estimated for the description of the seismic demand. After the classification of damaged buildings into structural types they are further categorized according to the level of damage and macroseismic intensity. The relative and the cumulative frequencies of the different damage states, for each structural type and each intensity level, are computed and presented, in terms of damage ratio. Damage Probability Matrices (DPMs) are obtained for typical structural types and they are compared to existing matrices derived from regions with similar building stock and soil conditions. A procedure is presented for the classification of those buildings which initially could not be discriminated into structural types due to restricted information and hence they had been disregarded. New proportional DPMs are developed and a correlation analysis is fulfilled with the existing vulnerability relations.

• 한국지진공학회:학술대회논문집
• /
• 한국지진공학회 2003년도 춘계 학술발표회논문집
• /
• pp.93-100
• /
• 2003

Seismic isolation systems can improve the seismic safety of nuclear power plants by decreasing seismic force transmitted to structures and equipment. This study evaluates the effectiveness of equipment seismic isolation systems by the comparison of core damage frequencies in non-isolated and isolated cases. It can be found that the seismic isolation systems increase seismic capacity of nuclear equipment and decrease core damage frequencies significantly. The effect of equipment isolation is more significant in the PGA range of 0.3g to 0.5g.

• Earthquakes and Structures
• /
• 제15권3호
• /
• pp.307-317
• /
• 2018

The current study explores the soil-structure interaction (SSI) effect on the potential seismic damage of mid-rise non-seismically designed reinforced concrete frames retrofitted by Fibre Reinforced Polymer (FRP). An 8-storey reinforced concrete frame poorly-confined due to transverse reinforcement deficiency is selected and then retrofitted by FRP wraps to provide external confinement. The poorly-confined and FRP retrofitted frames with/without SSI are modelled using hysteretic nonlinear elements. Inelastic time history and damage analyses are performed for these frames subjected to different seismic intensities. The results show that the FRP confinement significantly reduces one or two damage levels for the poorly-confined frame. More importantly, the SSI effect is found to increase the potential seismic damage of the retrofitted frame, reducing the effectiveness of FRP retrofitting. This finding, which is contrary to the conventionally beneficial concept of SSI governing for decades in structural and earthquake engineering, is worth taking into account in designing and evaluating retrofitted structures.

• Computers and Concrete
• /
• 제21권1호
• /
• pp.55-66
• /
• 2018

A large main shock may consist of numerous aftershocks with a short period. The aftershocks induced by a large main shock can cause the collapse of a structure that has been already damaged by the preceding main shock. These aftershocks are important factors in structural damages. Furthermore, despite what is often assumed in seismic design codes, earthquakes do not usually occur as a single event, but as a series of strong aftershocks and even fore shocks. For this reason, this study investigates the effect and potential of consecutive earthquakes on the response and behavior of concrete structures. At first, six moment resisting concrete frames with 3, 5, 7, 10, 12 and 15 stories are designed and analyzed under two different records with seismic sequences from real and artificial cases. The damage states of the model frames were then measured by the Park and Ang's damage index. From the results of this investigation, it is observed that the sequences of ground motions can almost double the accumulated damage and increased response of structures. Therefore, it is certainly insufficient to ignore this effect in the design procedure of structures. Also, the use of artificial seismic sequences as design earthquake can lead to non-conservative prediction of behavior and damage of structures under real seismic sequences.

• Earthquakes and Structures
• /
• 제9권5호
• /
• pp.1091-1114
• /
• 2015

The adequacy of a number of advanced earthquake Intensity Measures (IMs) to predict the structural damage of earthquake resistant 3D R/C buildings is investigated in the present paper. To achieve this purpose three symmetric in plan and three asymmetric 5-storey R/C buildings are analyzed by nonlinear time history analysis using 74 bidirectional earthquake records. The two horizontal accelerograms of each ground motion are applied along the structural axes of the buildings and the structural damage is expressed in terms of the maximum and average interstorey drift as well as the overall structural damage index. For each individual pair of accelerograms the values of the aforementioned seismic damage measures are determined. Then, they are correlated with several strong motion scalar IMs that take into account both earthquake and structural characteristics. The research identified certain IMs which exhibit strong correlation with the seismic damage measures of the studied buildings. However, the degree of correlation between IMs and the seismic damage depends on the damage measure adopted. Furthermore, it is confirmed that the widely used spectral acceleration at the fundamental period of the structure is a relatively good IM for medium rise R/C buildings that possess small structural eccentricity.

• Smart Structures and Systems
• /
• 제16권1호
• /
• pp.1-26
• /
• 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.

• 한국지진공학회:학술대회논문집
• /
• 한국지진공학회 2005년도 학술발표회 논문집
• /
• pp.453-460
• /
• 2005

In this study, the seismic fragility analysis of a base isolated condensate storage tank installed in the nuclear power plant. The condensate storage tank is safety related structure in a nuclear power plant. The failure of this tank affect significantly to the core damage frequency of the nuclear power plants. The seismic analysis of the liquid storage tank was performed by the simple calculation method and the dynamic time storage analysis method. The convective and impulsive fluid mass is modeled as added masses proposed by several researchers. To evaluate the effectiveness of the isolation system, the comparison of HCLPF and core damage frequencies in non-isolated and isolated cases are carried out. It can be found from the results that the seismic isolation system increases the seismic capacity of a condensate storage tank and decreases the core damage frequency significantly.

• Earthquakes and Structures
• /
• 제3권3_4호
• /
• pp.231-248
• /
• 2012

In this study, a systematic investigation is carried out on the seismic behaviour of plane moment resisting steel frames (MRF) to repeated strong ground motions. Such a sequence of earthquakes results in a significant damage accumulation in a structure because any rehabilitation action between any two successive seismic motions cannot be practically materialised due to lack of time. In this work, thirty-six MRF which have been designed for seismic and vertical loads according to European codes are first subjected to five real seismic sequences which are recorded at the same station, in the same direction and in a short period of time, up to three days. Furthermore, the examined frames are also subjected to sixty artificial seismic sequences. This investigation shows that the sequences of ground motions have a significant effect on the response and, hence, on the design of MRF. Additionally, it is concluded that ductility demands, behaviour factor and seismic damage of the repeated ground motions can be satisfactorily estimated using appropriate combinations of the corresponding demands of single ground motions.

• Earthquakes and Structures
• /
• 제11권4호
• /
• pp.649-664
• /
• 2016

A seismic damaged bridge may be hit again by a strong aftershock or another earthquake in a short interval before the repair work has been done. However, discussions about the impact of the unrepaired damages on the residual earthquake resistance of a steel bridge are very scarce at present. In this paper, nonlinear time-history analysis of a steel arch bridge was performed using multi-scale hybrid model. Two strong historical records of main shock-aftershock sequences were taken as the input ground motions during the dynamic analysis. The strain response, local deformation and the accumulation of plasticity of the bridge with and without unrepaired seismic damage were compared. Moreover, the effect of earthquake sequence on crack initiation caused by low-cycle fatigue of the steel bridge was investigated. The results show that seismic damage has little impact on the overall structural displacement response during the aftershock. The residual local deformation, strain response and the cumulative equivalent plastic strain are affected to some extent by the unrepaired damage. Low-cycle fatigue of the steel arch bridge is not induced by the earthquake sequences. Damage indexes of low-cycle fatigue predicted based on different theories are not exactly the same.