• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.20 no.4
• /
• pp.435-442
• /
• 2007

Since the Ronan Point apartment collapsed in 1968, researches on the progressive collapse have been intermittently conducted, and the collapse of the World Trade Center twin towers made the researches active again. In the United States guidelines such as GSA (2003) and DoD (2005) were provided for design and analysis of building structures against the progressive collapse. In this study the progressive collapse-resisting capacity of steel moment resisting frames designed by KBC-2005 was investigated using linear elastic static analysis and linear dynamic analysis procedures suggested in the guidelines. The results showed that in accordance with the GSA guideline the moment frame designed only for gravity load turned out to be vulnerable to the progressive collapse, whereas the lateral load resisting frame designed for earthquake load satisfied the criteria for progressive collapse. However both systems sailed to satisfy the criteria of the DoD-2005 guideline.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.32 no.3
• /
• pp.149-154
• /
• 2019

The structural system of domestic high-rise apartments can be divided into two parts; the core wall system, which is composed of walls concentrated in the center and the shear wall system, which comprises a great number of walls distributed in the plan. In order to analyze the lateral behavior of each system, buildings with typical domestic high-rise apartment plans were selected and nonlinear static analysis was performed to investigate the their collapse mechanism. From the force-displacement relation derived from nonlinear static analysis, response modification factor was evaluated by calculating the overstrengh and ductility factor, which are important in the seismic response. The ductility of core wall system is small, but as it is governed by wind load, its overstrength is greatly estimated, and its response modification factor is calculated by the overstrengh factor. Due to a large number of walls, shear wall system has a large ductility, making the response modification factor considerably large.

• Journal of the Korea Concrete Institute
• /
• v.23 no.2
• /
• pp.245-252
• /
• 2011

Currently, the design guidelines for the prevention of progressive collapse are not available in Korea due to the lack of study efforts in progressive collapse resistance evaluation of RC flat plate system. Therefore, in this study, three types of analysis were conducted to evaluate the progressive collapse resistance of a RC flat plate system. A linear static analysis was carried out by comparing the demand-capacity ratio (DCR) differences of the systems using the alternate load path method, which is the guideline of GSA. A dynamic behavior was investigated by checking the vertical deflection after removal of the column using the linear dynamic analysis. Lastly, a maximum load factor was investigated using the nonlinear static analysis. The finite element (FE) analyses were conducted using various parameters to analyze the results obtained using effective beam width (EB) model and plate element FEM (PF) model. This study results showed that the strength contributions of the slab in the EB models are underestimated compared to those obtained from the PF models. Therefore, a detailed FE analysis considering the slab element is required to thoroughly estimate the progressive collapse resisting capacity of flat plate system. The scenario of the corner column (CC) removal is the most dangerous conditions where as the scenario of the inner column (IC) removal is the least dangerous conditions based on the consideration of various parameters. The analysis results will allow more realistic evaluations of progressive collapse resistance of RC flat plate system.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.7 no.1
• /
• pp.9-16
• /
• 2003

To evaluate the seismic performance of multistory building structures use an equivalent SDOF model to represent the resistance of the structure to deformation as it respond in its predominant mode. This paper presents a method of converting a MDOF system into an equivalent SDOF model. The principal objective of this investigation is to evaluate appropriateness of converting method through perform nonlinear time history analysis of a multistory building structures and an equivalent SDOF model. The hysteresis rules to be used an equivalent SDOF model is obtained from the pushover analysis. Comparing the peak inelastic response of a moment resisting reinforced concrete frames and an equivalent SDOF model, the adequacy and the validity of the converting method is verified. The conclusion of this study is following; A method of converting a MDOF system into an equivalent SDOF model through the nonlinear time history response analysis is valid. The representative lateral displacement of a moment resisting reinforced concrete frames is close to the height of the first modal participation vector \ulcorner$_1{\beta}$${_1{\mu}}=1$. It can be found that the hysteresis rule of an equivalent SDOF model have influence on the time history response. Therefore, it necessary for selecting hysteresis rules to consider hysteresis characteristics of a moment resisting reinforced concrete frames.

• Proceedings of the KSME Conference
• /
• 2000.04a
• /
• pp.339-344
• /
• 2000

Newton-Raphson 기법은 구조물의 비선형 해석에 널리 쓰이는 반복계산기법이다. 비선형 해석을 위한 반복계산기법은 컴퓨터의 발달을 감안해도 상당한 계산시간이 소요된다. 본 논문에서는 신경회로망 예측을 사용한 Predicted Newton-Raphson 반복계산기법을 제안하였다. 통상적인 Newton-Raphson 기법은 이전스텝에서 수렴된 점으로부터 현재 스텝의 반복계산을 시작하는 반면 제시된 방법은 현재 스텝 수렴해에 대한 예측점에서 반복계산을 시작한다. 수렴해에 대한 예측은 신경회로망을 사용하여 이전 스텝 수렴해의 과거경향을 파악한 후 구한다. 반복계산 시작점이 수렴점에 보다 근접하여 위치하므로 수렴속도가 빨라지게 되고 허용되는 하중스텝의 크기가 커지게 된다. 또한 반복계산의 시작점으로부터 이루어지는 계산과정은 통상적인 Newton-Raphson 기법과 동일하므로 기존의 Newton-Raphson 기법과 정확히 일치하는 수렴해를 구할 수 있다. 구조물의 정적 비선형 거동에 대한 수치해석을 통하여 modified Newton-Raphson 기법과 제시된 Predicted Newton=Raphson 기법의 정확성과 효율성을 비교하였다. 제시된 Predicted Newton-Raphson 기법은 modified Newton-Raphson 기법과 동일한 해를 산출하면서도 계산상의 효율성이 매우 큼을 확인할 수 있었다.

• Computational Structural Engineering
• /
• v.11 no.4
• /
• pp.383-390
• /
• 1998

0.93m/sec의 평균속도는 변위제어 삼점휨 실험된 콘크리트 보의 하중-변위 측정결과를 선형탄성파괴역학모델과 가상균열모델에 기초한 유한요소법으로 분석하였다. 두 모델 모두 실험결과와 잘 일치하며, 균열성장길이가 약 60∼70㎜가 될 때까지 안전된 균열성장을 보이다 불안정한 균열성장에 의해 파손되었다. 선형탄성파괴역학모델에 의한 수치해석 결과 에너지해방률은 균열성장길이에 비례해서 증가하였으며, 최대값(202N/m)에 이르게 되면 일정한 값을 유지하였다. 가상균열모델에 기초한 수치해석결과 이 연구에 사용된 하중속도와 시험편의 크기에 대해 70㎜의 완전한 파괴진행대가 평성되었으며, 이는 기존의 정적 실험결과에 대한 수치해석 결과보다 상당히 작은 값이었다.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.20 no.5
• /
• pp.543-550
• /
• 2007

As an emerging materials in construction fields, FRP(fiber reinforced polymer) has been used in many area of civil engineering for its light weight and high strength. In this study we chose the 2nd Jindo-Bridge as a prototype, and evaluate effect of replacing steel components to FRP components through simplified 3D linear analysis. Static and modal analysis are done and the analysis results are compared with steel case analysis. From the static analysis results, the maximum stress of each component and maximum displacement of middle span are compared. Due to the reduction of deadload, the FRP structure causes less deflection than the original steel structure and from the reduced section (cable) analysis we confirmed the previous result. The occurrence wind velocity of flutter is compared by the frequency ratio.

• International Journal of Highway Engineering
• /
• v.5 no.4 s.18
• /
• pp.13-22
• /
• 2003

Several design methods from overseas are employed without considering different conditions such as material properties, climate, and traffic condition in this country. Therefore, there are limitations in application. Therefore, new pavement analysis system which is able to design a pavement efficiently and economically should be set up. In this study, 243 probable sections are classified depending on values of layer thickness and elastic modulus, and the effect of load types for the probable sections are analyzed. The section showing larger load distribution is chosen for analysis. As a result of sensitivity, a layer thickness has more influence on pavement than an elastic modulus does. The stress distribution of FWD test load is larger than that of circular load. This study compares outputs between nonlinear elastic model and linear elastic model. Based on the result, this study finds nonlinear elastic model considering stress condition in the ground is recommended for subbase.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.6 no.1
• /
• pp.55-62
• /
• 2002

The upper wall-lower frame structures(mixed building structures) are usually composed of shear wall structure in the upper part of structure which is used as residential space and frame structure in the lower part of structure which is used as commercial space centering around the transfer system in the lower part of structure. These structures are characteristics of stiffness irregularity, mass irregularity, and vertical geometric irregularity. The purpose of this study is to investigate the nonlinear response characteristics and the seismic capacity of mixed building structures when the number of stories in the lower frame is varied. The conclusions of this study are following. 1) As the result of push-over analysis of structure such as roof drift(i.e. roof displacement/structural height) and base shear coefficient, when the stories of lower frame system are increased, base shear coefficient is decreased, but roof drift is increased. 2) According to an increase in stories of the lower fame, story drift and ductility ratio of upper wall system are decreased and behavior of upper wall system is closed to elastic. 3) When the stories of lower frame system are increased, the excessive story drift is concentrated on the lower frame system.

• Composites Research
• /
• v.14 no.6
• /
• pp.9-15
• /
• 2001

In the present work, a linear static analysis is presented for thin-walled prismatic box-beams made of generally anisotropic materials. A mixed beam theory has been used to model and carry out the analysis. Several different constitutive assumptions for the shell-wall of the beam section are assessed into the beam formulation. Simple layup cases of box-beams representing bending-torsion or extension-torsion coupled configuration have been considered and tested to clearly show the effects of elastic couplings of the beam. A detailed finite element structural analysis using the MSC/NASTRAN has been carried out to validate the current analytical results. Numerical results show that appropriate assumptions for the constitutive relations are important and crucial for the accurate prediction of beam stiffness constants and also thor the beam behavior.