• Earthquakes and Structures
• /
• 제6권6호
• /
• pp.665-687
• /
• 2014

This paper presents a framework for analytical seismic vulnerability assessment of substandard reinforced concrete (RC) structures in developing countries. Amodified capacity-demand diagram method is used to predict the response of RC structures with degrading behaviour. A damage index based on period change is used to quantify the evolution of damage. To demonstrate the framework, a class of substandard RC buildings is examined. Abrupt accumulation of damage is observed due to the brittle failure modes and this is reflected in the developed vulnerability curves, which differ substantially from the curves of ductile structures.

• Structural Engineering and Mechanics
• /
• 제29권6호
• /
• pp.689-707
• /
• 2008

This study presents a method to evaluate the seismic risk of an extradosed bridge with seismic isolators of lead rubber bearings (LRBs), and also to show the effectiveness of the LRB isolators on the extradosed bridge, which is one of the relatively flexible and lightly damped structures in terms of seismic risk. Initially, the seismic vulnerability of a structure is evaluated, and then the seismic hazard of a specific site is rated using an earthquake data set and seismic hazard maps in Korea. Then, the seismic risk of the structure is assessed. The nonlinear seismic analyses are carried out to consider plastic deformation of bridge columns and the nonlinear characteristics of soil foundation. To describe the nonlinear behaviour of a column, the ductility demand is adopted, and the moment-curvature relation of a column is assumed to be bilinear hysteretic. The fragility curves are represented as a log-normal distribution function for column damage, movement of superstructure, and cable yielding. And the seismic hazard at a specific site is estimated using the available seismic hazard maps. The results show that in seismically-isolated extradosed bridges under earthquakes, the effectiveness of the isolators is much more noticeable in the columns than the cables and girders.

• Structural Engineering and Mechanics
• /
• 제10권4호
• /
• pp.405-426
• /
• 2000

Two approximate methods based on mechanism analysis suitable for seismic assessment/design of structural concrete are reviewed. The methods involve use of equal energy concept or equal displacement concept along with appropriate patterns of inelastic deformations to relate structure's maximum lateral displacement to member and plastic deformations. One of these methods (Clough's method), defined here as a ductility-based approach, is examined in detail and a modification for its improvement is suggested. The modification is based on estimation of maximum inelastic displacement using inelastic design response spectra (IDRS) as an alternative to using equal energy concept. The IDRS for demand displacement ductilities are developed for a single degree of freedom model subjected to several accelerograms as functions of response modification factor (R), damping ratios, and strain hardening. The suggested revised methodology involves estimation of R as the ratio of elastic strength demand to code level demand, and determination of design base shear using $R_{design}{\leq}R$ and maximum displacement, determination of plastic displacement using IDRS and subsequent local plastic deformations. The methodology is demonstrated for the case of a 10-story precast wall panel building.

• 한국전산구조공학회:학술대회논문집
• /
• 한국전산구조공학회 2006년도 정기 학술대회 논문집
• /
• pp.741-748
• /
• 2006

Seismic performance evaluation was conducted for four wind-designed concentrically braced steel highrise buildings in order to check the feasibility of designing steel highrise buildings per elastic seismic design criterion (or strength and stiffness solution) in the regions of strong wind and moderate seismicity. The pushover analysis results revealed that the wind-designed highrise buildings possess significantly increased elastic seismic capacity due to the overstrength resulting from the wind serviceability criterion. The strength demand-to-capacity study showed that, due to the wind-induced overstrength, highrise buildings with a slenderness ratio of larger than four or five can withstand elastically even the maximum considered earthquake at the performance level of immediate occupancy. Based on the analytical results of this study, practical elastic seismic design procedure for steel highrise buildings in the regions of moderate seismicity is proposed.

• 대한건축학회논문집:구조계
• /
• 제35권10호
• /
• pp.127-133
• /
• 2019

Damage to high-rise buildings caused by earthquakes is less frequency due to small distribution of high-rise buildings and low transmissibility of seismic motion to high-rise buildings. However, demand for high-rise buildings is increasing for development of construction technology and efficient land use. In addition, if high-rise buildings are constructed on soft ground such as landfill, transmissibility of seismic motion due to long-periodization of seismic waves is likely to increase. Thus, with development of technology, buildings are required to expand range of seismic design such as safety for long-period seismic waves. Therefore, in this study, dynamic experiments were performed to evaluate response characteristics of high-rise buildings according to period characteristics of seismicwaves and time history analysis was performed to verify them.

• 콘크리트학회논문집
• /
• 제20권2호
• /
• pp.193-202
• /
• 2008

현행 도로교설계기준의 내진설계기준은 완전연성 설계 개념을 채택함으로써, 과도하게 배근되는 횡구속철근으로 인하여 현장 시공에 어려움을 겪는 사례가 많이 있다. 이것은 한반도와 같은 중 약진직역에서 완전연성이 필요하지 않는 경우가 일반적임에도 불구하고 완전연성을 확보하기 위한 심부 구속철근량이 배근되기 때문이다. 이와 같은 문제점을 해결하기 위한 방안으로 한정연성 설계개념을 도입한 연성도 내진설계법이 제안된 바 있다. 연성도 내진설계법에서는 재료강도와 함께 소요연성도와 형상비를 변수로 하여 횡구속철근량을 결정하는 산정식을 사용하고 있다. 본 논문은 횡구속철근 산정식을 중심으로 연성도 내진설계법의 안전성을 검증함을 목적으로 한다. 국내 외에서 수행된 89개의 원형단면 기둥 실험 결과를 대상으로 변위연성도 안전율을 검토한 결과 1.11$\sim$3.98 사이의 값을 보였으며, 평균 변위연성도 안전율은 1.90으로 충분한 안전율을 보였다. 이 논문에서는 또한 연성도 내진설계법의 구체적인 설계절차도 소개하였으며, 횡구속철근의 설계에 고려되는 주요 변수들이 변위연성도 안전율에 주는 영향도 분석하였다.

• 한국구조물진단유지관리공학회 논문집
• /
• 제15권3호
• /
• pp.195-206
• /
• 2011

역량스펙트럼방법은 구조물의 내진성능을 평가하는 도구로서 점점 더 이용 빈도가 증가하고 있다. 강도감소계수는 역량스펙트럼방법에서 정의하는 비탄성요구스펙트럼을 생성하기 위해 사용되며 다양한 강도감소계수 공식들이 제안되고 있다. 이 연구는 강도감소계수의 공식이 비탄성요구스펙트럼의 형상에 미치는 영향과 아울러 교량의 지진응답변위에 미치는 영향을 평가하였다. 연구 목적에 따라, 기존에 제안된 몇 가지 강도감소계수 공식들이 조사되고, 예제연구를 통하여 분석되었다. 서로 다른 원호각을 갖는 곡선교를 선정하여 서로 다른 강도감소계수 공식을 적용하여 역량스펙트럼방법으로 교각의 변위를 평가하였다. 역량스펙트럼의 결과를 검증할 목적으로 비선형시간이력해석도 함께 수행되었다. 연구결과에 의하면, 역량스펙트럼방법은 더 큰 원호각을 갖는 교량일수록 실제보다 더 큰 교각의 변위를 산출한다. 비탄성요구스펙트럼을 작성하는 많은 방법이 제안되어 있음에도 불구하고, 각 방법들이 산출하는 교각의 비탄성변위응답은 큰 차이가 없다.

• Structural Monitoring and Maintenance
• /
• 제5권3호
• /
• pp.325-343
• /
• 2018

This study aims to propose a performance-based design method of a novel passive base isolation system, BIO isolation system, which is inspired by an energy dissipation mechanism called 'sacrificial bonds and hidden length'. Fragility functions utilized in this study are derived, indicating the probability that a component, element, or system will be damaged as a function of a single predictive demand parameter. Based on PEER framework methodology for Performance-Based Earthquake Engineering (PBEE), a systematic design procedure using performance and fragility objectives is presented. Base displacement, superstructure absolute acceleration and story drift ratio are selected as engineering demand parameters. The new design method is then performed on a general two degree-of-freedom (2DOF) structure model and the optimal design under different seismic intensities is obtained through numerical analysis. Seismic performances of the biologically inspired (BIO) isolation system are compared with that of the linear isolation system. To further demonstrate the feasibility and effectiveness of this method, the BIO isolation system of a 4-storey reinforced concrete building is designed and investigated. The newly designed BIO isolators effectively decrease the superstructure responses and base displacement under selected earthquake excitations, showing good seismic performance.

• Earthquakes and Structures
• /
• 제9권4호
• /
• pp.911-936
• /
• 2015

This work evaluates the performance of a number of seismic assessment procedures when applied to a case study reinforced concrete (RC) wall building. The performance of each procedure is evaluated through its ability to accurately predict deformation demands, specifically, roof displacement, inter-storey drift ratio and wall curvatures are considered as the key engineering demand parameters. The different procedures include Direct Displacement-Based Assessment, nonlinear static analysis and nonlinear dynamic analysis. For the latter two approaches both lumped and distributed plasticity modelling are examined. To thoroughly test the different approaches the case study building is considered in different configurations to include the effects of unequal length walls and plan asymmetry. Recommendations are made as to which methods are suited to different scenarios, in particular focusing on the balance that needs to be made between accurate prediction of engineering demand parameters and the time and expertise required to undertake the different procedures. All methods are shown to have certain merits, but at the same time a number of the procedures are shown to have areas requiring further development. This work also highlights a number of key aspects related to the seismic response of RC wall buildings that may significantly impact the results of an assessment. These include the influence of higher-mode effects and variations in spectral shape with ductility demands.

• Steel and Composite Structures
• /
• 제37권5호
• /
• pp.571-587
• /
• 2020

In this article the seismic demand and performance of two recent braced steel frames named steel moment frames with the elliptic bracing (ELBRFs) are assessed through a laboratory program and numerical analyses of FEM. Here, one of the specimens is without connecting bracket from the corner of the frame to the elliptic brace (ELBRF-E), while the other is with the connecting brackets (ELBRF-B). In both the elliptic braced moment resisting frames (ELBRFs), in addition to not having any opening space problem in the bracing systems when installed in the surrounding frames, they improve structure's behavior. The experimental test is run on ½ scale single-story single-bay ELBRF specimens under cyclic quasi-static loading and compared with X-bracing and SMRF systems in one story base model. This system is of appropriate stiffness and a high ductility, with an increased response modification factor. Moreover, its energy dissipation is high. In the ELBRF bracing systems, there exists a great interval between relative deformation at the yield point and maximum relative deformation after entering the plastic region. In other words, the distance from the first plastic hinge to the collapse of the structure is fairly large. The experimental outcomes here, are in good agreement with the theoretical predictions.