• Earthquakes and Structures
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• v.19 no.5
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• pp.395-409
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• 2020

With verifications through many relevant researches in the past few decades, adopting the equivalent lateral force procedure for designing seismically isolated structures as a preliminary or even final design approach has become considerably mature and publicly acceptable, especially for seismic isolation systems that mechanically exhibit bilinear hysteretic behavior. During the design procedure, in addition to a given seismic demand, structural designers still need to previously determine three parameters, such as mechanical properties of seismic isolation systems or design parameters and performance indices of seismically isolated structures. However, an arbitrary or improper selection of given parameters might cause diverse or even unacceptable design results, thus troubling structural designers very much. In this study, first, based on the criterion that at least either two design parameters or two performance indices of seismically isolated structures are decided previously, the rationality and applicability of design results obtained from different conditions are examined. Moreover, to consider variations of design parameters of seismically isolated structures attributed to uncertainties of mechanical properties of seismic isolation systems, one of the conditions is adopted to perform bounding analysis for seismic isolation design. The analysis results indicate that with a reasonable equivalent damping ratio designed, considering a specific variation for two design parameters (the effective stiffness and equivalent damping ratio) could present more conservative bounding design results (in terms of isolation displacement and acceleration transmissibility) than considering the same variation but for two mechanical properties (the characteristic strength and post-yield stiffness).

• Journal of the Earthquake Engineering Society of Korea
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• v.6 no.2
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• pp.1-7
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• 2002

A procedure for determination of performance point was developed based on the concept of the direct displacement-based design method. Using the proposed procedure, parametric study has been performed for various natural periods of the structure, yield strength, and the stiffness after the first yield. The proposed method was also applied to a 10-story steel frame, and the results were compared to those from the capacity spectrum method and the time history analysis. It was found from the comparison that there were good agreement between the results.

• Structural Engineering and Mechanics
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• v.83 no.2
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• pp.195-206
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• 2022

Significant structural damages due to earthquakes reveal the importance of seismic design provisions. This paper presents a comparison between the seismic design provisions of Albania, Croatia, Iran, and Turkey for the design of mid-rise reinforced-concrete (RC) frames. Information on the historical development of the considered provisions are given. The code provisions are compared, illustrating the main differences in the minimum requirements for column and beam detailing and analysis for mid-rise RC frames. 4-story, 5-story, and 6-story buildings are designed according to each design code, and their performance is evaluated comparatively by using a displacement-based adaptive pushover procedure and eigenvalue analysis. It is observed that recent Turkish code has the highest and Albanian code has the lowest level of requirements in terms of member size and reinforcement detailing. The considered models indicate 15%, 20% and 50%, lower period values than the Croatia, Iran and Albania buildings, respectively. Additionally, building models per Croatia, Iran and Albania codes have 30%, 35% and 65% less base shear capacity when compared to Turkish building codes. Building models per Croatia and Iran codes indicate similar properties both in terms of strength and stiffness.

• Earthquakes and Structures
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• v.27 no.4
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• pp.285-302
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• 2024

Conducting nonlinear pushover analysis typically demands intricate and resource-intensive computational efforts, involving a highly iterative process necessary for meeting both design-defined and requirements of codes in performance-based design. This study presents a computer-based technique for reinforced concrete (RC) buildings, incorporating optimization numerical approaches, optimality criteria and pushover analysis to automatically enhance seismic design performance. The optimal design of concrete beams, columns and shear walls in concrete frames is presented using the artificial bee colony optimization algorithm. The methodology is applied to three frames: a 4-story, an 8-story and a 12-story. These structures are designed to minimize overall weight while satisfying the levels of performance including Life Safety (LS), Collapse Prevention (CP), and Immediate Occupancy (IO). The process involves three main steps: first, optimization codes are implemented in MATLAB software, and the OpenSees software is used for nonlinear static analysis. By solving the optimization problem, several top designs are obtained for each frame and shear wall. Pushover analysis is conducted considering the constraints on relative displacement and plastic hinge rotation based on the nonlinear provisions of the FEMA356 nonlinear provisions to achieve each level of performance. Subsequently, convergence, pushover, and drift history curves are plotted for each frame, and leading to the selection of the best design. The results demonstrate that the algorithm effectively achieves optimal designs with reduced weight, meeting the desired performance criteria.

• International Journal of Concrete Structures and Materials
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• v.10 no.3
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• pp.355-371
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• 2016

In this study seismic performance of reinforced concrete staggered wall system structures were investigated and their behavior factors such as overstrength factors, ductility factors, and the response modification factors were evaluated from the overstrength and ductility factors. To this end, 5, 9, 15, and 25-story staggered wall system (SWS) structures were designed and were analyzed by nonlinear static and dynamic analyses to obtain their nonlinear force-displacement relationships. The response modification factors were computed based on the overstrength and the ductility capacities obtained from capacity envelopes. The analysis results showed that the 5- and 9-story SWS structures failed due to yielding of columns and walls located in the lower stories, whereas in the 15- and 25-story structures plastic hinges were more widely distributed throughout the stories. The computed response modification factors increased as the number of stories decreased, and the mean value turned out to be larger than the value specified in the design code.

• Structural Engineering and Mechanics
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• v.48 no.6
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• pp.809-822
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• 2013

Base isolation is widely used in seismic resisting buildings due to its low construction cost, high reliability, mature theory and convenient usage. However, it is difficult to design the isolation layer in high-rise buildings using the available bearings because high-rise buildings are characterized with long period, low horizontal stiffness, and complex re-distribution of the internal forces under earthquake loads etc. In this paper, a simple and innovative isolation bearing, named Teflon-based lead rubber isolation bearing, is developed to address the mentioned problems. The Teflon-based lead rubber isolation bearing consists of friction material and lead rubber isolation bearing. Hence, it integrates advantages of friction bearings and lead rubber isolation bearings so that improves the stability of base isolation system. An experimental study was conducted to validate the effectiveness of this new bearing. The effects of vertical loading, displacement amplitude and loading frequency on the force-displacement relationship and energy dissipation capacity of the Teflon-based lead rubber isolation bearing were studied. An analytical model was also proposed to predict the force-displacement relationship of the new bearing. Comparison of analytical and experimental results showed that the analytical model can accurately predict the force-displacement relationship and elastic shear deflection of the Teflon-based lead rubber isolation bearings.

• Structural Engineering and Mechanics
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• v.87 no.4
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• pp.305-315
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• 2023

The idea of the combination of the fractional-order operators with the brain emotional learning-based intelligent controller (BELBIC) is developed for implementation in seismic-excited structures equipped with active mass damper (AMD). For this purpose, a new design framework of the mentioned combination namely fractional-order BEBIC (FOBELBIC) is proposed based on a modified-teaching-learning-based optimization (MTLBO) algorithm. The seismic performance of the proposed controller is then evaluated for a 15-story building equipped with AMD subjected to two far-field and two near-field earthquakes. An optimal BELBIC based on the MTLBO algorithm is also introduced for comparison purposes. In comparison with the structure equipped with a passive tuned mass damper (TMD), an average reduction of 44.7% and 42.8% are obtained in terms of the maximum absolute and RMS top floor displacement for FOBELBIC, while these reductions are obtained as 30.4% and 30.1% for the optimal BELBIC, respectively. Similarly, the optimal FOBELBIC results in an average reduction of 42.6% and 39.4% in terms of the maximum absolute and RMS top floor acceleration, while these reductions are given as 37.9% and 30.5%, for the optimal BELBIC, respectively. Consequently, the superiority of the FOBELBIC over the BELBIC is concluded in the reduction of maximum and RMS seismic responses.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2002.09a
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• pp.83-90
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• 2002

There are few earthquake records in Korea and the Japanese or American representative earthquake records have been generally used in the seismic design. In this study, some earthquake records which the range of earthquake magnitudes varies from 5.3 to 7.9 were collected and analyzed to assess which record can rationally reflect Korean seismic characteristics. In this assessment, each seismic energy and acceleration spectrum were analyzed with the unified maximum ground acceleration. Several numerical analyses on Korean representative caisson structures were also carried out to compare each dynamic displacement. In these numerical analyses, soil conditions and the dimension of structure such as height and width were changed. Through this assessment, it is found that the compatible earthquake magnitude in Korea is lower than 7. From the result of numerical analyses, it is shown that horizontal dynamic displacements corresponding to earthquake magnitudes over than 7 are quite larger than those below earthquake magnitude 7. Based on this study, it is necessary that Korean seismic design guideline will refer earthquake magnitude criteria for the construction of the economical aseismic structure.

• Steel and Composite Structures
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• v.37 no.3
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• pp.259-272
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• 2020

In this study a new hysteretic damper for seismic retrofit of soft-first story structures is proposed and its seismic retrofit effect is evaluated. The damper consists of one steel column member and two flexural fuses at both ends made of steel plates with reduced section, which can be placed right beside existing columns in order to minimize interference with passengers and automobiles in the installed bays. The relative displacement between the stories forms flexural plastic hinges at the fuses and dissipate seismic energy. The theoretical formulation and the design procedure based on plastic analysis is provided for the proposed damper, and the results are compared with a detailed finite-element (FE) model. In order to apply the damper in structural analysis, a macromodel of the damper is also developed and calibrated by the derived theoretical formulas. The results are compared with the detailed FE analysis, and the efficiency of the damper is further validated by the seismic retrofit of a case study structure and assessing its seismic performance before and after the retrofit. The results show that the proposed hysteretic damper can be used effectively in reducing damage to soft-first story structures.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.4A
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• pp.659-675
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• 2006

Recently, significant progress has been made in performance-based engineering methods that rely mainly on nonlinear static seismic analysis procedures. The Capacity Spectrum Method (CSM) and the Displacement Coefficient Method (DCM) are the representative nonlinear static seismic analysis procedures. In order to evaluate the applicability of the procedures to the seismic evaluation and design process of new and existing structures, the accuracy of both CSM and DCM should be evaluated in advance. The accuracy of seismic responses by the nonlinear static procedures is evaluated in comparison with the shaking table test results for the structural wall specimen subjected to the far field and near field earthquakes. Also conducted are comparative studies where the shaking table test results are compared with those from nonlinear dynamic analysis procedures, i.e., Single-Degree-of-Freedom (SDOF), equivalent SDOF and Multi-Degree-of-Freedom (MDOF) systems.