• Journal of the Earthquake Engineering Society of Korea
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• v.20 no.5
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• pp.301-310
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• 2016

There are differences in seismic behavior between non-skewed bridges and skewed bridges due to in-plane rotations caused by pounding between the skewed deck and its abutments during strong earthquake. Many advances have been made in developing design codes and guidelines for dynamic analyses of non-skewed bridges. However, there remain significant uncertainties with regard to the structural response of skewed bridges caused by unusual seismic response characteristics. The purpose of this study is performing non-linear time history analysis of the bridges using abutment-soil interaction model considering pounding between the skewed deck and its abutments, and analyzing global seismic behavior characteristics of the skewed bridges to assess the possibility of unseating. Refined bridge model with abutment back fill, shear key and elastomeric bearing was developed using non-linear spring element. In order to evaluate the amplification of longitudinal and transverse displacement response, non-linear time history analysis was performed for single span bridges. Far-fault and near-fault ground motions were used as input ground motions. According to each parameter, seismic behavior of skewed bridges was evaluated.

• Journal of the Society of Naval Architects of Korea
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• v.43 no.2 s.146
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• pp.197-205
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• 2006

In general, brackets found at tank boundary are design according to the Classification Society Rule. Since much man power is needed in manufacturing the brackets stiffened by flange, it is necessary to suggest alternative designs, of which flanges are removed, through the rigorous structural analysis. In this paper non-linear structural analysis for brackets with and/or without flange have been carried out to examine their structural behavior and ultimate strengths. Alternative designs for brackets are suggested based on the results of ultimate strength analysis so that the alternative brackets have the similar level of strength and stiffness to the original brackets. It has been seen that the structural safety of alternative brackets proposed in this paper are beyond the appropriate level. The primary benefit of replacing the original brackets by the alternatives is the reduction of man power in manufacturing brackets and 10 to 15% weight saving can be expected in additional. This paper ends with some comments about the extension of the present study.

• Computers and Concrete
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• v.14 no.1
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• pp.41-57
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• 2014

Modern trend in structural design is to use smaller elements in order to ensure several purposes such as economy, functionality and aesthetic in appearance. However, because of decreasing rigidity of the structural elements, the system displacements increases and displacements become an important subject in this kind of structures takes into account both geometrical changes and the carrying capacity of the material after linear-elastic boundary. In this study, a method is proposed to calculate the failure loads and to analyse the reinforced concrete space frame systems. The numerical examples gathered from the literature survey are solved with this method utilising the prepared computer program and the comparable results are presented. The results show that the method is sufficiently accurate.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2002.04a
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• pp.107-114
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• 2002

This paper deals with the non-linear analysis of cantilever beams with constant volume. Numerical methods are developed for solving the elastica of cantilever ben subjected to a tip Point load and a tip couple. The linear, parabolic and sinusoidal tapers with the regular polygon cross-section are considered, whose material volume and span length are always held constant. The Runge-Kutta and Regula-Falsi methods, respectively, are used to integrate the governing differential equations and to compute the unknown value of the tip deflection. The numerical results obtained herein are shown in tables and figures. Also the shapes of strongest beams are determined by reading the minimum values form the deflection versus section ratio curves.

• Journal of the Architectural Institute of Korea Structure & Construction
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• v.36 no.3
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• pp.121-128
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• 2020

In this paper, the ASCE 7 equivalent static approach for seismic design of non-structural elements is critically evaluated based on the measured floor acceleration data, theory of structural dynamics, and linear/nonlinear dynamic analysis of three-dimensional building models. The analysis of this study on the up-to-date database of the instrumented buildings in California clearly reveals that the measured database does not well corroborate the magnitude and the profile of the floor acceleration as proposed by ASCE 7. The basic flaws in the equivalent static approach are illustrated using elementary structural dynamics. Based on the linear and nonlinear dynamic analyses of three-dimensional case study buildings, it is shown that the magnitude and distribution of the PFA (peak floor acceleration) can significantly be affected by the supporting structural characteristics such as fundamental period, higher modes, structural nonlinearity, and torsional irregularity. In general, the equivalent static approach yields more conservative acceleration demand as building period becomes longer, and the PFA distribution in long-period buildings tend to become constant along the building height due to the higher mode effect. Structural nonlinearity was generally shown to reduce floor acceleration because of its period-lengthening effect. Torsional floor amplification as high as 250% was observed in the building model of significant torsional irregularity, indicating the need for inclusion of the torsional amplification to the equivalent static approach when building torsion is severe. All these results lead to the conclusion that, if permitted, dynamic methods which can account for supporting structural characteristics, should be preferred for rational seismic design of non-structural elements.

• Journal of Korean Tunnelling and Underground Space Association
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• v.2 no.2
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• pp.72-85
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• 2000

Rock is a very complex and heterogeneous material, containing structural flaws due to geologic generation process. Because of those structural flaws, deformation and failure of rock when subjected to differential compressive stresses is non-linear. To simulate the non-linear behavior of rock, mechanical crack models, that is, sliding and shear crack models have been used in several studies. In those studies, non-linear stress-strain curves and various behaviors of rock including the changes of effective elastic moduli ($E_1$, $E_2$, ${\nu}_1$, ${\nu}_2$, $G_2$) due to crack growth were simulated (Kemeny, 1993; Jeon, 1996, 1998). Most of the studies have mainly focused on the verification of the mechanical crack model with relatively less attempt to apply it to practical purposes such as numerical analysis for underground and/or slope design. In this study, the validity of mechanical crack model was checked out by simulating the non-linear behavior of rock and consequently it was applied to a practical numerical analysis, finite element analysis commonly used.

• Journal of the Earthquake Engineering Society of Korea
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• v.17 no.6
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• pp.279-291
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• 2013

The seismic damage of non-structural components, such as communication facilities, causes direct economic losses as well as indirect losses which result from social chaos occurring with downtime of communication and financial management network systems. The current Korean seismic code, KBC2009, prescribes the design criteria and requirements of non-structural components based on their elastic response. However, it is difficult for KBC to reflect the dynamic characteristics of structures where non-structural components exist. In this study, both linear and nonlinear time history analyses of structures with various analysis parameters were carried out and floor acceleration spectra obtained from analyses were compared with both ground acceleration spectra used for input records of the analyses and the design floor acceleration spectrum proposed by National Radio Research Agency. Also, this study investigates to find out the influence of structural dynamic characteristics on the floor acceleration spectra. The analysis results show that the acceleration amplification is observed due to the resonance phenomenon and such amplification increases with the increase of building heights and with the decrease of structure's energy dissipation capacities.

• Earthquakes and Structures
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• v.14 no.3
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• pp.229-239
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• 2018

Under strong ground motion, pounding can be caused because of the different dynamic properties between two adjacent buildings. Using different structural systems in two adjacent structures makes a difference in the lateral stiffness and thus changes the pounding force between them. In this paper, the effect of the structural system of adjacent buildings on the amount of force applied by pounding effects has been investigated. Moment resisting frame systems (MRFs), lateral X-bracing system (LBS), shear wall system (SWS) and dual system (DS) have been investigated. Four different cases has been modelled using finite element (FE) method. The number of stories of the two adjacent buildings is different in each case: case 1 with 6 and 4 stories, case 2 with 9 and 6 stories, case 3 with 15 and 6 stories and case 4 with 10 and 10 stories. The structures have been modelled three-dimensionally. Non-linear time history analysis has been done on the structures using the finite element software SAP2000. In order to model pounding effects, the non-linear gap elements have been used.

• Structural Engineering and Mechanics
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• v.85 no.4
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• pp.485-500
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• 2023

The non-linear static analysis of reinforced concrete (RC) structures using the three-dimensional (3D) finite element method is a time-consuming and challenging task. Moreover, this type of analysis encounters numerical problems such as the lack of convergence of results in the stages of growth and propagation of cracks in the structure. The time integration analysis along with the mass scaling (MS) technique is usually used to overcome these limitations. Despite the use of this method in the 3D finite element analysis of RC structures, a comprehensive study has not been conducted so far to assess the effects of the MS method on the accuracy of results. This study aims to evaluate the accuracy of the MS method in the non-linear quasi-static finite element analysis of RC structures. To this aim, different types of RC structures were simulated using the finite element approach based on the implicit time integration method and the mass scaling technique. The influences of effective parameters of the MS method (i.e., the allowable values of increase in the mass of the RC structure, the relationship between the duration of the applied load and fundamental vibration period of the RC structure, and the pattern of applied loads) on the accuracy of the simulated results were investigated. The accuracy of numerical simulation results has been evaluated through comparison with existing experimental data. The results of this study show that the achievement of accurate structural responses in the implicit time integration analyses using the MS method involves the appropriate selection of the effective parameters of the MS method.

• Structural Engineering and Mechanics
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• v.78 no.2
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• pp.219-230
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• 2021

International seismic codes stipulate that adjacent buildings should be separated by a specified minimum distance, otherwise the pounding effect should be considered in the design. Recent researches proposed an alternative method (Double Difference Combination Rule) to estimate seismic gap between structures, as this method considers the cross relation of adjacent buildings behavior during earthquakes. Four different criteria were used to calculate the minimum separation distance using this method and results are compared to the international codes for five separation cases. These cases used four case study buildings classified by different heights, lateral load resisting systems and fundamental periods of vibrations to assess the consistency in results for the alternative methods. Non-linear analysis was performed to calculate the inelastic displacements of the four buildings, and the results were used to evaluate the relation between elastic and inelastic displacements due to the ductility of structural elements resisting seismic loads. A verification analysis was conducted to guarantee that the separation distance calculated is sufficient to avoid pounding. Results shows that the use of two out of the four studied methods yields separation distances smaller than that calculated by the code specified equations without under-estimating the minimum separation distance required to avoid pounding.