• Journal of the Earthquake Engineering Society of Korea
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• v.8 no.6 s.40
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• pp.13-22
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• 2004

Ductiluty factor has played an important role in seismic design as it is key component of response modification factor(R). In this stuty, ductility factors() are calculated by multiplying ductility factor for SDOF systems() and MDOF modification factors(). Ductility factors() for SDOF systems are computed from nonlinear dynamic analysis undergoing different level of displacement ductiluty demands and period when subjected to a large number of recorded earthquake ground motions. The MDOF modification factors() are proposed to account for the MDOF systems, based on previous studies. A total of 108 prototype steel frames are designed to investigate the ductility factors considering the number of stories(4, 8 and 16-stories), framing system(Perimeter Frames, PF and Distributed Frames, DF), failure mechanism(Strong-Column Weak-Beam, SCWB and Weak-Column Strong-Beam, WCSB), soil profiles(SA, SC and SE in UBC 1997) and seismic zone factors(Z=0.075, 0.2 and 0.4 in UBC 1997). It is shown that the number of stories, failure mechanisms (SCWB, WCSB), and soil profiles have great influence on the ductility factors, however, the structural system(Perimeter frames, Distributed frames), and seismic zones have no influence on the ductility factors.

• Journal of the Korea Institute of Building Construction
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• v.15 no.6
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• pp.569-577
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• 2015

Recently, the concept of seismic design has changed from prescriptive to performance based design. For the performance based design with the specified target performance of the structure, it is necessary to execute the inelastic structural analysis to predict precisely the actual behavior of the structure. To address this issue, the seismic performance of the 5-story RC moment-resisting frames designed in accordance with KBC2009 is evaluated through push-over analysis and economic analysis is conducted focused on the direct construction costs. The results show that the ordinary and the intermediate moment-resisting frame are evaluated to meet the required performance design criteria and that the direct construction costs of the two frames are similar. However, although the special moment-resisting frame designed with strong column-weak girder philosophy satisfies the required performance design criteria, the direct construction cost is uneconomical compared with other frames. Therefore, although the intermediate moment-resisting frame of design category D is prohibited in IBC2012, the ordinary and the intermediate moment-resisting frame are estimated to be more reasonable than the special moment-resisting frame for the design of 5-story RC moment-resisting frame.

• Steel and Composite Structures
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• v.50 no.3
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• pp.249-263
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• 2024

This article presents a comparative analysis of seismic behavior in steel-beam reinforced concrete column (RCS) frames versus steel and reinforced concrete frames. The study evaluates the seismic response and collapse behavior of RCS frames of varying heights through nonlinear modeling. RCS, steel, and reinforced concrete special moment frames are considered in three height categories: 5, 10, and 20 stories. Two-dimensional frames are extracted from the three-dimensional structures, and nonlinear static analyses are conducted in the OpenSEES software to evaluate seismic response in post-yield regions. Incremental dynamic analysis is then performed on models, and collapse conditions are compared using fragility curves. Research findings indicate that the seismic intensity index in steel frames is 1.35 times greater than in RCS frames and 1.14 times greater than in reinforced concrete frames. As the number of stories increases, RCS frames exhibit more favorable collapse behavior compared to reinforced concrete frames. RCS frames demonstrate stable behavior and maintain capacity at high displacement levels, with uniform drift curves and lower damage levels compared to steel and reinforced concrete frames. Steel frames show superior strength and ductility, particularly in taller structures. RCS frames outperform reinforced concrete frames, displaying improved collapse behavior and higher capacity. Incremental Dynamic Analysis results confirm satisfactory collapse capacity for RCS frames. Steel frames collapse at higher intensity levels but perform better overall. RCS frames have a higher collapse capacity than reinforced concrete frames. Fragility curves show a lower likelihood of collapse for steel structures, while RCS frames perform better with an increase in the number of stories.

• Journal of the Earthquake Engineering Society of Korea
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• v.9 no.5 s.45
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• pp.11-19
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• 2005

Seismic design of a building is usually performed by using the linear static procedure. However, the actual behavior of the building subjected to earthquake is inelastic and dynamic in nature. Therefore, inelastic dynamic analysis is required to evaluate the safety of the structure designed by the current design codes. For the validation, a RC special moment resisting frame building was chosen and designed by IBC 2003 representing new codes. Maximum plastic rotation and dissipated energy of some selected members were calculated for examining if the inelastic behavior of the building follows the intention of the code, and drift demand were calculated as well for checking if the building well satisfies the design drift limit. In addition, the effect of including internal moment resisting frames (non lateral resisting system) on analyses results was investigated. As a result of this study, the building designed by IBC 2003 showed the inelastic behavior intended in the code and satisfied the design drift limit. Furthermore, the internal moment resisting frames should be included in the analytical model as they affect the results of seismic analyses significantly.

• Computers and Concrete
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• v.7 no.4
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• pp.303-315
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• 2010

In this paper, we present a new finite Timoshenko beam element with a model for ultimate load computation of reinforced concrete frames. The proposed model combines the descriptions of the diffuse plastic failure in the beam-column followed by the creation of plastic hinges due to the failure or collapse of the concrete and or the re-bars. A modified multi-scale analysis is performed in order to identify the parameters for stress-resultant-based macro model, which is used to described the behavior of the Timoshenko beam element. The micro-scale is described by using the multi-fiber elements with embedded strain discontinuities in mode 1, which would typically be triggered by bending failure mode. A special attention is paid to the influence of the axial force on the bending moment - rotation response, especially for the columns behavior computation.

• Earthquakes and Structures
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• v.10 no.6
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• pp.1405-1428
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• 2016

Besides the complex instructions of guidance documents for seismic rehabilitation of existing buildings, some institutions have provided simple criteria in terms of simplified rehabilitations. ASCE 41-06 is one of documents that introduced a simple method for assessment of certain buildings that do not require advanced analytical procedures. Furthermore the New Zealand guideline has presented a simple lateral mechanism analysis that is a hand static analysis for determining the probable collapse mechanism, lateral strength and displacement capacity of the structure. The present study is focused on verifying the results of the simplified methods which is used by NZSEE and ASCE 41-06 in assessment of existing buildings. For this, three different special steel moment and braced frames are assessed under these two guidelines and the accuracy of the results is checked with the results of nonlinear static and dynamic analysis. After comparison of obtained results, suggestions are presented to improve seismic retrofit criteria.

• Steel and Composite Structures
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• v.28 no.6
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• pp.767-778
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• 2018

The purpose of this study is to investigate how a fully restrained bolted beam splice affects the connection behavior as a column-tree connection in steel special moment frames under cyclic loading when located within the plastic hinge zone. The impacts of this attachment in protected zone are observed by using nonlinear finite element analyses. This type of splice connection is designed as slip-critical connection and thereby, the possible effects of slippage of the bolts due to a possible loss of pretension in the bolts are also investigated. The 3D models with solid elements that have been developed includes three types of connections which are the connection having fully restrained beam splice located in the plastic hinge location, the connection having fully restrained beam splice located out of the plastic hinge and the connection without beam splice. All connection models satisfied the requirement for the special moment frame connections providing sufficient flexural resistance, determined at column face stated in AISC 341-16. In the connection model having fully restrained beam splice located in the plastic hinge, due to the pretension loss in the bolts, the friction force on the contact surfaces is exceeded, resulting in a relative slip. The reduction in the energy dissipation capacity of the connection is observed to be insignificant. The possibility of the crack occurrence around the bolt holes closest to the column face is found to be higher for the splice connection within the protected zone.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.21 no.5
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• pp.429-437
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• 2008

In this study the progressive collapse potential of braced frames were investigated using the nonlinear static and dynamic analyses. All of nine different brace types were considered along with a special moment-resisting frame for comparison. According to the pushdown analysis results, most braced frames designed per current design codes satisfied the design guidelines for progressive collapse initiated by loss of a first story mid-column; however most model structures showed brittle failure mode. This was caused by buckling of columns after compressive braces buckled. Among the braced frames considered, the inverted- V type braced frames showed superior ductile behavior during progressive collapse. The nonlinear dynamic analysis results showed that all the braced frame model structures remained in stable condition after sudden removal of a column, and their deflections were less than that of the moment-resisting frame.

• Journal of the Earthquake Engineering Society of Korea
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• v.27 no.1
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• pp.13-24
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• 2023

In this study, alternative seismic force-resisting systems for plant structure supporting equipment were designed, and the seismic performance thereof was compared using nonlinear dynamic analysis. One alternative seismic force-resisting system was designed per the requirement for ordinary moment-resisting and concentrically braced frames but with a reduced base shear. The other seismic force-resisting system was designed by accommodating seismic details of intermediate and unique moment-resisting frames and special concentrically braced frames. Different plastic hinge models were applied to ordinary and ductile systems based on the validation using existing test results. The control model obtained by code-based flexible design and/or reduction of base shear did not satisfy the seismic performance objectives, but the alternative structural system did by strengthened panel zones and a reduced effective buckling length. The seismic force to equipment calculated from the nonlinear dynamic analysis was significantly lower than the equivalent static force of KDS 41 17 00. The comparison of design alternatives showed that the seismic performance required for a plant structure could be secured economically by using performance-based design and alternative seismic-force resisting systems adopting minimally modified seismic details.

• Journal of the Earthquake Engineering Society of Korea
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• v.11 no.5
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• pp.1-9
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• 2007

This study summarizes the results of a research project aimed at investigating the inelastic rotation capacity of beam-column connections of reinforced concrete moment frames. A total of 91 test specimens for beam-column joint connections were examined in detail, and 28 specimens were classified as special moment frame connections based on the design and detailing requirements in the ACI 318-02 Provisions. Then the acceptance criteria, originally defined for steel moment frame connections in the AISC-02 Seismic Provisions, were used to evaluate the joint connections of concrete moment frames. Twenty-seven out of 28 test specimens that satisfy the design requirements for special moment frame structures provide sufficient strength and are ductile up to a plastic rotation of 0.03 rad. without any major degradation in strength. Joint shear stress, column-to-beam flexural strength ratio, and transverse reinforcement ratio in a joint all play a key role in good performance of the connections.