• Steel and Composite Structures
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• v.11 no.4
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• pp.273-290
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• 2011

In current ductility-based earthquake-resistant design, the estimation of design forces continues to be carried out with the application of response modification factors on elastic design spectra. It is well-known that the response modification factor (R) takes into account the force reduction, strength, redundancy, and damping of structural systems. The key components of the response modification factor (R) are force reduction ($R_{\mu}$) and strength ($R_S$) factors. However, the response modification and strength factors for structural systems presented in design codes were based on professional judgment and experiences. A numerical study has been accomplished to evaluate force reduction, strength, and response modification factors for special steel moment resisting frames. A total of 72 prototype steel frames were designed based on the recommendations given in the AISC Seismic Provisions and UBC Codes. Number of stories, soil profiles, seismic zone factors, framing systems, and failure mechanisms were considered as the design parameters that influence the response. The effects of the design parameters on force reduction ($R_{\mu}$), strength ($R_S$), and response modification (R) factors were studied. Based on the analysis results, these factors for special steel moment resisting frames are evaluated.

• Steel and Composite Structures
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• v.14 no.6
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• pp.621-636
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• 2013

Response modification factor is one of the seismic design parameters to consider nonlinear performance of building structures during strong earthquake, in conformity with the point that many seismic design codes led to reduce the loads. In the present paper it's tried to evaluate the response modification factors of dual moment resistant frame with buckling restrained braced (BRB). Since, the response modification factor depends on ductility and overstrength; the nonlinear static analysis, nonlinear dynamic analysis and linear dynamic analysis have been done on building models including multi-floors and different brace configurations (chevron V, invert V, diagonal and X bracing). The response modification factor for each of the BRBF dual systems has been determined separately, and the tentative value of 10.47 has been suggested for allowable stress design method. It is also included that the ductility, overstrength and response modification factors for all of the models were decreased when the height of the building was increased.

• Journal of the Earthquake Engineering Society of Korea
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• v.8 no.3
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• pp.53-62
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• 2004

In this paper the overstrength factors, ductility factors, and response modification factors of ordinary concentric braced frames designed in accordance with a current seismic design code are determined by performing pushover analysis. According to the analysis results, the overstrength and the response modification factors turn out to be larger than the values regulated in the codes in most model structures. However if the braces are reinforced by BRB or zipper columns, the overstrength factors and response modification factors turn out to increase significantly.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2005.03a
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• pp.372-379
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• 2005

The earthquake resistant design concept allows the nonlinear behavior of structures under the design earthquake. Therefore the response spectrum method provided in most codes introduces the response modification factors to consider the nonlinear behavior in the design process. For bridges, the response modification factors are given according to the ductility as well as the redundancy of piers. In this study, among influence factors on the nonlinear seismic behavior, the randomness of artificial accelerograms simulated with different durations, the pier ductility represented by the inelastic behavior characteristic curve and the regularity represented by pier heights are selected. The influence of such factor on the seismic behavior is investigated by comparing response modification factors calculated with the nonlinear time step analysis.

• Journal of the Earthquake Engineering Society of Korea
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• v.23 no.4
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• pp.201-209
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• 2019

Response modification factors of school facilities for non-seismic RC moment frames with partial masonry infills in 'Manual for Seismic Performance Evaluation and Retrofit of School Facilities' published in 2018 were investigated in the preceding study. However, since previous studies are based on 2D frame analysis and limited analysis conditions, additional verification needs to be performed to further apply various conditions including orthogonal effect of seismic load. Therefore, this study is to select appropriate response modification factors of school facilities for non-seismic RC moment frames with partial masonry infills by 3D frame analysis. The results are as follows. An appropriate response modification factor for non-seismic RC moment frames with partial masonry infills is proposed as 2.5 for all cases if the period is longer than 0.6 seconds. Also if the period is less than 0.4 seconds and the ratio of shear-controlled columns is less than 30%, 2.5 is chosen too. However, if the period is less than 0.4 seconds and the ratio of shear-controlled columns is higher than 30%, the response modification factor shall be reduced to 2.0. If the period is between 0.4 and 0.6 seconds, then linearly interpolates the response correction factor.

• 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.

• Journal of the Earthquake Engineering Society of Korea
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• v.8 no.1
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• pp.29-37
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• 2004

The overstrength factor and the ductility factor are the two important factors that determine response modification factors used in current seismic codes, In this paper the overstrength and ductility factors of special concentric braced frames are determined by performing pushover analysis of model structures with various stories and span lengths. and by using those factors the response modification factors are obtained. According to the analysis results. the overstrength and the ductility factors are larger than the values proposed by the codes in low-rise structures. and the opposite is true in medium to high-rise structures, It is also found that the factors increase as the height of structures decreases and the span length increases.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.30 no.2
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• pp.185-189
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• 2017

The purpose of earthquake resistant design for typical bridges is the 'No Collapse Design' allowing emergency vehicles just after earthquakes. The Roadway Bridge Design Code provides design provisions to carry out such 'No Collapse Design' with a ductile mechanism and response modification factors given for connections and substructure play key role in this procedure. In case of response modification factors for substructure, the Roadway Bridge Design Code provides values considering ductility and redundancy. On the other hand, 'AASHTO LRFD Bridge Design Specifications' provides values considering additionally an artificial factor according to the bridge importance categories divided into critical, essential and others. In this study, a typical bridge with steel bearing connections and reinforced concrete piers is selected and different response modification factors for substructure are applied with design conditions given in the Roadway Bridge Design Code. Based on the comparison study of the design results, supplementary measures are suggested required by applying different response modification factors for substructure.

• Structural Engineering and Mechanics
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• v.68 no.2
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• pp.159-170
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• 2018

This paper aims to develop response modification factors for stiffness degrading structures by incorporating soil-structure interaction effects. A comprehensive parametric study is conducted to investigate the effects of key SSI parameters, natural period of vibration, ductility demand and hysteretic behavior on the response modification factor of soil-structure systems. The nonlinear dynamic response of 6300 soil-structure systems are studied under two ensembles of accelograms including 20 recorded and 7 synthetic ground motions. It is concluded that neglecting the stiffness degradation of structures can results in up to 22% underestimation of inelastic strength demands in soil-structure systems, leading to an unexpected high level of ductility demand in the structures located on soft soil. Nonlinear regression analyses are then performed to derive a simplified expression for estimating ductility-dependent response modification factors for stiffness degrading soil-structure systems. The adequacy of the proposed expression is investigated through sensitivity analyses on nonlinear soil-structure systems under seven synthetic spectrum compatible earthquake ground motions. A good agreement is observed between the results of the predicted and the target ductility demands, demonstrating the adequacy of the expression proposed in this study to estimate the inelastic demands of SSI systems with stiffness degrading structures. It is observed that the maximum differences between the target and average target ductility demands was 15%, which is considered acceptable for practical design purposes.

• Journal of the Earthquake Engineering Society of Korea
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• v.11 no.4
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• pp.53-63
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• 2007

Seismic design codes are developed mainly based on the observation of the behavior of structures in the high seismicity regions where structures may experience significant amount of inelastic deformations and major earthquakes may result in structural damages in a vast area. Therefore, seismic loads are reduced in current design codes for building structures using response modification factors which depend on the ductility capacity and overstrength of a structural system. However, structures in low seismicity regions, subjected to a minor earthquake, will behave almost elastically because of the larger overstrength of structures in low seismicity regions such as Korea. Structures in low seismicity regions may have longer periods since they are designed to smaller seismic loads and main target of design will be minor or moderate earthquakes occurring nearby. Ground accelerations recorded at stations near the epicenter may have somewhat different response spectra from those of distant station records. Therefore, it is necessary to verify if the seismic design methods based on high seismicity would he applicable to low seismicity regions. In this study, the adequacy of design spectra, period estimation and response modification factors are discussed for the seismic design in low seismicity regions. The response modification factors are verified based on the ductility and overstrength of building structures estimated from the farce-displacement relationship. For the same response modification factor, the ductility demand in low seismicity regions may be smaller than that of high seismicity regions because the overstrength of structures may be larger in low seismicity regions. The ductility demands in example structures designed to UBC97 for high, moderate and low seismicity regions were compared. Demands of plastic rotation in connections were much lower in low seismicity regions compared to those of high seismicity regions when the structures are designed with the same response modification factor. Therefore, in low seismicity regions, it would be not required to use connection details with large ductility capacity even for structures designed with a large response modification factor.