• Earthquakes and Structures
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• v.10 no.3
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• pp.629-643
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• 2016

Among all the natural disasters, earthquakes are the most destructive calamities since they cause a plenty of injuries and economic losses leaving behind a series of signs of panic. The present study highlights the moment-curvature relationships for the structural elements such as beam and column elements and Non-Linear Static Pushover Analysis of RC frame structures since it is a very simplified procedure of non-linear static analysis. The highly popular model namely Mander's model and Kent and Park model are considered and then, seismic risk evaluation of RC building has been conducted using SAP 2000 version 17 treating uncertainty in strength as a parameter. From the obtained capacity and demand curves, the performance level of the structure has been defined. The seismic fragility curves were developed for the variations in the material strength and damage state threshold are calculated. Also the comparison of experimental and analytical results has been conducted.

• Journal of the Earthquake Engineering Society of Korea
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• v.18 no.4
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• pp.181-191
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• 2014

This research presents the nonlinear analysis model for reinforced concrete shear wall systems with special boundary elements as proposed by the Korean Building Code (KBC, 2009). In order to verify the analysis model, analytical results were compared with the experimental results obtained from previous studies. Established analytical model was used to perform nonlinear static and dynamic analyses. Analytical results showed that the semi-special shear wall improved significantly the performance in terms of ductility and energy dissipation as expected based on previous test results. Furthermore, nonlinear incremental dynamic analysis was performed using 20 ground motions. Based on computer analytical results, the ordinary shear wall, special shear wall and newly proposed semi-special shear wall systems were evaluated based on the methods in FEMA P965. The results based on the probabilistic approaches accounting for inherent uncertainties showed that the semi-special shear wall systems provide a high capacity/demand (ACMR) ratio owing to their details, which provide enough capacity to sustain large inelastic deformations.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2002.09a
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• pp.266-273
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• 2002

Pushover analysis is frequently used for evaluation of seismic performance and determination of seismic demand of a building structure in the current structural engineering practice field. However, pushover analysis has a advantage for estimation of seismic demands, which cannot account for the contributions of higher modes to response or for a redistribution of inertia forces because of structural yielding and the associated changes in the vibration properties of the structures. Recently, Chopra and Coel(2001) derived uncoupled inelastic dynamic equation of motion with several assumptions in the pushover analysis. By using this approach, pushover analysis for each mode is carried out and modal pushover analysis method, which can consider higher mode effects of the building, was suggested. The principle objective of this study is to introduced the modal pushover analysis by Chopra et al.(2001) and investigated the applicability and validity of this method for the steel moment frames subjected to various earthquake ground motions.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2002.03a
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• pp.349-356
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• 2002

There has been an increasing trend toward the use of pushover analysis as a tool for evaluating the seismic resistant and safety of a building structure in the performance based earthquake engineering field. The ATC-40 document proposed a nonlinear static procedure based on the Capacity Spectrum Method to determine earthquake-induced demand given the structure pushover curve, which a curve representing base shear versus roof displacement. However, the procedure is conceptually simple, iterative and time consuming method and may sometimes lead to no solution or multiple solutions. A new improved method of seismic performance evaluation for moment frame building, which take into account the previously mentioned deficiencies of currently used elastic design procedures, is presented in this paper. The results of nonlinear static and nonlinear time history analysis of an example high-rise steel moment frame designed by the proposed method are presented and discussed.

• Magazine of the Korean Society of Agricultural Engineers
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• v.43 no.5
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• pp.116-123
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• 2001

This paper represents results of an effort to seismically rehabilitate a 12-story nonductile reinforced concrete frame building. The frame located in the most severe seismic area, zone 4, is assumed to be designed and detailed for gravity load requirements only. Both pushover and nonlinear time-history analyses are carried out to determine strength, deformation capacity and the vulnerability of the building. The analysis indicates a drift concentration at the $1^{st}$ floor level due to inadequate strength and ductility capacity of the ground floor columns. The capacity curve of the structure, when superimposed on the average demand response spectrum for the ensemble of scaled earthquakes indicates that the structure is extremely weak and requires a major retrofit. The retrofit of the building is attempted using viscoelastic (VE) dampers. The dampers at each floor level are sized in order to reduce the elastic story drift ratios to within 1%. It is found that this requires substantially large dampers that are not practically feasible. With practical size dampers, the analyses of the viscoelastically damped building indicates that the damper sizes provided are not sufficient enough to remove the biased response and drift concentration of the building. The results indicate that VE-dampers alone are not sufficient to rehabilitate such a concrete frame. Concrete buildings, in general, being stiffer require larger dampers. The second rehabilitation strategy uses concrete shearwalls. Shearwalls increased stiffness and strength of the building, which resulted in reducing the drift significantly. The effectiveness of VE-dampers in conjunction with stiff shearwalls was also studied. Considering the economy and effectiveness, it is concluded that shearwalls were the most feasible solution for seismic rehabilitation of such buildings.

• Journal of the Earthquake Engineering Society of Korea
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• v.10 no.3 s.49
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• pp.1-11
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• 2006

This paper presents a seismic fragility analysis method for a cable-stayed bridge with energy dissipation devices. Model uncertainties represented by random variables include input ground motions, characteristics of energy dissipation devices and the stiffness of cable-stayed bridge. Using linear regression, we established demand models for the fragility analysis from the relationship between maximum responses and the intensity of input ground motions. For capacity models, we considered the moment and shear force of the main tower, longitudinal displacement of the girder, deviation of the stay cables tension and the local buckling of the main steel tower as the limit states for cable-stayed bridge. As a numerical example, fragility analysis results for the 2nd Jindo bridge are presented. The effect of energy dissipation devices is also briefly discussed.

• Structural Engineering and Mechanics
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• v.59 no.3
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• pp.455-473
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• 2016

Methods for the seismic demands evaluation of structures require iterative procedures. Many studies dealt with the development of different inelastic spectra with the aim to simplify the evaluation of inelastic deformations and performance of structures. Recently, the concept of inelastic spectra has been adopted in the global scheme of the Performance-Based Seismic Design (PBSD) through Capacity-Spectrum Method (CSM). For instance, the Modal Pushover Analysis (MPA) has been proved to provide accurate results for inelastic buildings to a similar degree of accuracy than the Response Spectrum Analysis (RSA) in estimating peak response for elastic buildings. In this paper, a simplified nonlinear procedure for evaluation of the seismic demand of structures is proposed with its applicability to multi-degree-of-freedom (MDOF) systems. The basic concept is to write the equation of motion of (MDOF) system into series of normal modes based on an inelastic modal decomposition in terms of ductility factor. The accuracy of the proposed procedure is verified against the Nonlinear Time History Analysis (NL-THA) results and Uncoupled Modal Response History Analysis (UMRHA) of a 9-story steel building subjected to El-Centro 1940 (N/S) as a first application. The comparison shows that the new theoretical approach is capable to provide accurate peak response with those obtained when using the NL-THA analysis. After that, a simplified nonlinear spectral analysis is proposed and illustrated by examples in order to describe inelastic response spectra and to relate it to the capacity curve (Pushover curve) by a new parameter of control, called normalized yield strength coefficient (${\eta}$). In the second application, the proposed procedure is verified against the NL-THA analysis results of two buildings for 80 selected real ground motions.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05a
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• pp.135-138
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• 2005

Since a ductile coupled shear wall system is the primary seismic load resisting systems of many structures, a coupling beams of these system must exhibit excellent ductility and energy absorption capacity. In this paper, the seismic response of coupled shear wall system is discussed. It includes that the evaluation of the degree of coupling between the shear walls and the coupling beams. It is demonstrated through a review of experimental investigations of coupling beam behavior that often the coupling beam ductility demand exceeds the expected available ductility. As a result, it is possible that coupled shear wall system will not behave as desired in the course of a significant seismic event. Limits to the allowable degree of coupling are proposed as a remedy to this apparent deficiency.

• Structural Engineering and Mechanics
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• v.31 no.5
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• pp.545-566
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• 2009

Bridge columns are subjected to combined actions of axial force, shear force and bending moment during earthquakes, caused by spatially-complex earthquake motions, features of structural configurations and the interaction between input and response characteristics. Combined actions can have significant effects on the force and deformation capacity of RC columns, resulting in unexpected large deformations and extensive damage that in turn influences the performance of bridges as vital components of transportation systems. This paper evaluates the seismic response of three prototype reinforced concrete bridges using comprehensive numerical models that are capable of simulating the complex soil-structural interaction effects and nonlinear behavior of columns. An analytical approach that can capture the shear-flexural interacting behavior is developed to model the realistic nonlinear behavior of RC columns, including the pinching behavior, strength deterioration and stiffness softening due to combined actions of shear force, axial force and bending moment. Seismic response analyses were conducted on the prototype bridges under suites of ground motions. Response quantities of bridges (e.g., drift, acceleration, section force and section moment etc.) are compared and evaluated to identify the effects of vertical motion, structural characteristics and the shear-flexural interaction on seismic demand of bridges.

• Earthquakes and Structures
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• v.24 no.5
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• pp.317-331
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• 2023

The buckling-restrained braced frames with eccentric configurations (BRBFECs) are stable cyclic behavior and high energy absorption capacity. Furthermore, they have an architectural advantage for creating openings like eccentrically braced frames (EBFs). In the present study, it has been suggested to use the performance-based plastic design (PBPD) method to calculate the design base shear of the BRBFEC systems. Moreover, in this study, to reduce the required steel material, it has been suggested to use the performance-based practical design (PBPD) method instead of the force-based design (FBD) method for the design of this system. The 3-, 6-, and 9-story buildings with the BRBFEC system were designed, and the finite element models were modeled. The seismic performance of the models was investigated using two suits of ground motions representing the maximum considered earthquake (MCE) and design basis earthquake (DBE) seismic hazard levels. The results showed that the models designed with the suggested method, which had lower weights compared to those designed with the FBD method, had a desirable seismic performance in terms of maximum story drift and ductility demand under earthquakes at both MCE and DBE seismic hazard levels. This suggests that the steel weights of the structures designed with the PBPD method are about 13% to 18% lesser than the FBD method. However, the residual drifts in these models were higher than those in the models designed with the FBD method. Also, in earthquakes at the DBE hazard level, the residual drifts in all models except the PBPD-6s and PBPD-9s models were less than the allowable reparability limit.