• Steel and Composite Structures
• /
• v.42 no.1
• /
• pp.107-121
• /
• 2022

Past studies have shown that the aspect ratio (width-to-height) of a steel plate shear wall (SPSW) can significantly affect its seismic response. SPSWs with lower aspect ratio (narrow SPSW) may experience low lateral stiffness and flexure dominated drift response. As the height of the frame increases, the narrow SPSWs prove to be uneconomical and demonstrate inferior seismic response than their wider counterparts. Moreover, the thicker web plates required for narrow SPSWs exerts high inward pull on the VBEs. The present study suggests the limiting values of the aspect ratio for an SPSW system by evaluating the seismic collapse performance of 3-, 6- and 9-story SPSW systems using FEMA P695 methodology. For this purpose, nonlinear models are developed. These models are validated with the past quasi-static experimental results. Non-linear static analyses and Incremental dynamic analyses are then carried. The results are then utilized to conservatively suggest the limiting values of aspect ratios for SPSW system. In addition to the conventional-SPSW (Conv-SPSW), the collapse performance of staggered-SPSW (S-SPSW) is also explored. Its performance is compared with the Conv-SPSW and the use of S-SPSW is suggested in the cases where SPSW with lower than recommended aspect ratio is desired.

• Steel and Composite Structures
• /
• v.47 no.3
• /
• pp.339-353
• /
• 2023

The primary objective of the current study is to optimize and evaluate the seismic performance of steel momentresisting frame (MRF) structures considering soil-structure interaction (SSI) effects. The structural optimization is implemented in the context of performance-based design in accordance with FEMA-350 at different confidence levels from 50% to 90% by taking into account fixed- and flexible-base conditions using an efficient metaheuristic algorithm. Nonlinear response-history analysis (NRHA) is conducted to evaluate the seismic response of structures, and the beam-on-nonlinear Winkler foundation (BNWF) model is used to simulate the soil-foundation interaction under the MRFs. The seismic performance of optimally designed fixed- and flexible-base steel MRFs are compared in terms of overall damage index, seismic collapse safety, and interstory drift ratios at different performance levels. Two illustrative examples of 6- and 12-story steel MRFs are presented. The results show that the consideration of SSI in the optimization process of 6- and 12-story steel MRFs results in an increase of 1.0 to 9.0 % and 0.5 to 5.0 % in structural weight and a slight decrease in structural seismic safety at different confidence levels.

• Earthquakes and Structures
• /
• v.25 no.2
• /
• pp.99-112
• /
• 2023

This paper investigates the influences of Soil-Structure Interaction (SSI) on the seismic behavior of two-dimensional reinforced concrete moment-resisting frames subjected to Far-Field Ground Motion (FFGM) and Near-Field Ground Motion (NFGM). For this purpose, the nonlinear modeling of 7, 10, and 15-story reinforced concrete moment resisting frames were developed in Open Systems for Earthquake Engineering Simulation (OpenSees) software. Effects of SSI were studied by simulating Beam on Nonlinear Winkler Foundation (BNWF) and the soil type as homogenous medium-dense. Generally, the building resistance to seismic loads can be explained in terms of Incremental Dynamic Analysis (IDA); therefore, IDA curves are presented in this study. For comparison, the fragility evaluation is subjected to NFGM and FFGM as proposed by Quantification of Building Seismic Performance Factors (FEMA P-695). The seismic performance of Reinforced Concrete (RC) buildings with fixed and flexible foundations was evaluated to assess the probability of collapse. The results of this paper demonstrate that SSI and NFGM have significantly influenced the probability of failure of the RC frames. In particular, the flexible-base RC buildings experience higher Spectral acceleration (Sa) compared to the fixed-base ones subjected to FFGM and NFGM.

• Earthquakes and Structures
• /
• v.27 no.3
• /
• pp.209-226
• /
• 2024

The susceptibility of Reinforced Concrete (RC) buildings to earthquake-induced damage is a critical concern, primarily attributed to their inadequate seismic performance. The existing earthquake-resistant design code of India prescribes guidelines to minimize seismic damage but does not provide any means for evaluating the actual seismic performance and damage. To ascertain the seismic performance of the structures quantitatively, it is crucial to classify damage into measurable damage states. Damage Index (DI) acts as an important tool for this purpose. Among various procedures for computation of DI, the modified Park and Ang Damage Index appears to be highly accurate. However, the major drawback of this method is that it is lengthy and time-consuming. On the other hand, structural performances can be evaluated using various performance parameters such as interstory drift ratio (IDR), inelastic deformation, etc., as described in FEMA-356 and ASCE-41 17. The present study explores the correlation between seismic DI and structural performance in RC frame buildings designed according to IS code. Sixteen building models, incorporating diverse configurations, are examined using nonlinear static and time history analyses. A simplified equation is developed by regression analysis to predict DI based on IDR, offering a computationally efficient alternative. Validation tests are done to confirm the equation's accuracy. Furthermore, a unified damage scale integrating DI and seismic performance is also proposed for seismic damage evaluation of buildings designed by IS code.

• Earthquakes and Structures
• /
• v.27 no.4
• /
• pp.285-302
• /
• 2024

Conducting nonlinear pushover analysis typically demands intricate and resource-intensive computational efforts, involving a highly iterative process necessary for meeting both design-defined and requirements of codes in performance-based design. This study presents a computer-based technique for reinforced concrete (RC) buildings, incorporating optimization numerical approaches, optimality criteria and pushover analysis to automatically enhance seismic design performance. The optimal design of concrete beams, columns and shear walls in concrete frames is presented using the artificial bee colony optimization algorithm. The methodology is applied to three frames: a 4-story, an 8-story and a 12-story. These structures are designed to minimize overall weight while satisfying the levels of performance including Life Safety (LS), Collapse Prevention (CP), and Immediate Occupancy (IO). The process involves three main steps: first, optimization codes are implemented in MATLAB software, and the OpenSees software is used for nonlinear static analysis. By solving the optimization problem, several top designs are obtained for each frame and shear wall. Pushover analysis is conducted considering the constraints on relative displacement and plastic hinge rotation based on the nonlinear provisions of the FEMA356 nonlinear provisions to achieve each level of performance. Subsequently, convergence, pushover, and drift history curves are plotted for each frame, and leading to the selection of the best design. The results demonstrate that the algorithm effectively achieves optimal designs with reduced weight, meeting the desired performance criteria.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.24 no.6
• /
• pp.629-636
• /
• 2011

It has been suggested that buildings designed for strong ground motions will also have improved resistance to air blast loads. As an initial attempt to quantify this behavior, the responses of a ten story steel building, designed for the 1994 building code, with lateral resistance provided by perimeter moment frames, is considered. An analytical model of the building is developed and the magnitude and distribution of blast loads on the structure are estimated using available computer software that is based on empirical methods. To obtain the relationship between pressure, time duration, and standoff distance, these programs are used to obtain an accurate model of the air blast loading. A hemispherical surface burst for various explosive weights and standoff distances is considered for generating the air blast loading and determining the structural response. Linear and nonlinear analyses are conducted for these loadings. Air blast demands on the structure are compared to current seismic guidelines. These studies present the displacement responses, story drifts, demand/capacity ratio and inelastic demands for this structure.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2009.05a
• /
• pp.1739-1743
• /
• 2009

현재 국내에는 하천시설물의 인증과 관련한 제도와 법령이 마련되어 있지 않다. 하천시설물과 관련된 인증 제도는 효율적인 하천시설물의 유지관리를 가능하게 하고, 치수 안전성 증대에 기여할 수 있다. 본 연구는 미국의 제방 인증(levee accreditation) 제도를 분석하여 국내에 적용하는 방안에 관한 것이다. 미국의 연방 재난 관리국(Federal Emergency Management Agency; FEMA)은 국가 홍수 보험 프로그램(National Flood Insurance Program; NFIP)을 관리하고 있는데, 그의 일환으로 제방 인증 제도를 시행하고 있다. 제방의 인증은 제내지를 보호하는 제방 시스템이 100년 빈도의 홍수에 대한 방어 능력이 있는지를 기술적으로 검토하는 것이다. 여기서 제방 시스템이란, 제방, 홍수벽, 수문 장치, 펌프시설, 암거, 내수 배제 시설 등 홍수로부터 제내지를 보호하기 위한 모든 시설을 포함한다. 미국은 제방 인증을 위한 제도로서 연방 규정 조례(code of federal regulation; CFR)를 두어 제방 시스템의 설계, 운영, 유지관리의 기준을 마련하였다. 제방 인증을 신청하는 기관은 연방 규정 조례에서 정의된 제방 시스템의 운영 및 유지관리에 관한 문서를 갖추어야하고, 공학적인 설계 기준에 대하여 면밀히 검토되어야 한다. 운영 및 유지관리에 관한 사항은 수문과 내수배제 시스템을 포함한 제방 시스템의 홍수 시 운영 지침과 운영실적, 유지보수 지침과 점검 보고서 등이다. 공학적인 설계 기준에 대한 검토사항은 제방의 여유고, 수문, 호안, 제방과 기초의 안정성, 침하, 내수배제에 관한 분석 결과이다. 이러한 제방의 인증에 필요한 기술적인 검토 자료와 관련 문서는 등록된 전문 기술자나 제방의 설계와 시공능력을 갖춘 연방 기관을 통해 보증(certification) 되어야 한다. 현재, 미국에서 제방의 보증을 결정하는 대표적인 기관은 미 공병단(U.S. Army Corps of Engineers; USACE)이다. 제방 보증의 유효기간은 최대 10년이지만 검사와 평가가 지속되고, 유효 기간 만료 전이라도 언제든지 재검토될 수도 있다. 또한, 제방 시스템 전체에 대하여 보증 여부를 결정하고, 개별 시설에 대한 보증이나 조건부 보증은 수행하지 않는다. 국내에 제방 인증 제도를 도입하기 위해서는 제방 인증에 관한 절차, 수행 기관, 수행 방법 등에 대한 규정과 제도가 마련되어야 하고, 현재 국내에서 수행되고 있는 하천시설물의 안전도 검사 방법을 포함한 평가 지표와 평가 기술에 대한 인증 표준화가 요구된다.

• International Journal of Concrete Structures and Materials
• /
• v.6 no.4
• /
• pp.209-220
• /
• 2012

Post-earthquake fire (PEF) can lead to a rapid collapse of buildings that have been partially damaged as a result of a prior earthquake. Almost all standards and codes for the design of structures against earthquake ignore the risk of PEF, and thus buildings designed using those codes could be too weak when subjected to a fire after an earthquake. An investigation based on sequential analysis inspired by FEMA356 is performed here on the immediate occupancy (IO), life safety (LS) and collapse prevention (CP) performance levels of two portal frames, after they are pushed to arrive at a certain level of displacement corresponding to the mentioned performance level. This investigation is followed by a fire analysis of the damaged frames, examining the time taken for the damaged frames to collapse. As a point of reference, a fire analysis is also performed for undamaged frames and before the occurrence of earthquake. The results indicate that while there is minor difference between the fire resistances of the fire-alone situation and the frames pushed to the IO level of performance, a notable difference is observed between the fire-alone analysis and the frames pushed to arrive at LS and CP levels of performance and exposed to PEF. The results also show that exposing only the beams to fire results in a higher decline of the fire resistance, compared to exposing only the columns to fire. Furthermore, the results show that the frames pushed to arrive at LS and CP levels of performance collapse in a global collapse mode laterally, whereas at the IO level of performance and fire-alone situation, the collapse mechanism is mostly local through the collapse of beams. Whilst the investigation is conducted for a certain class of portal frames, the results confirm the need for the incorporation of PEF into the process of analysis and design, and provide some quantitative measures on the level of associated effects.

• Journal of the Korean Society of Safety
• /
• v.30 no.3
• /
• pp.52-58
• /
• 2015

As sudden rainfall has happened, the debris flow has occurred in the mountain area. Recently sudden rainfall occurred so frequently caused by abnormal climate. Thus debris flow hazard had consecutively increased damage because of debris flow. Recently, Enormous damage due to debris flow have occurred in Korea. Various studies have been conducted to prevent search debris flow hazard. This study was carried out for debris flow behavior according to the land slope on propagation. It is the important one among factors that are related to the propagation over the city with respect to debris flow discharge and depth. For the numerical simulations in this study, the land slope was varied of 5, 0, $-5^{\circ}$ to investigate the debris flow behavior with the FLO-2D, often recommended by FEMA to simulate debris flow. To verify the performance of FLO-2D, comparison with the USGS experiments (Iverson et al, 2010) was conducted. From numerical results the propagation length of the debris flow was found the most sensitive one. Maximum of debris flow thickness and velocity and structural vulnerabilities were investigated to the effect of land slope. They was became smaller according to land slope of 5, -5, $0^{\circ}$ in the order. As a result, debris flow behavior analysis about the effect of the land slope could contribute to understand the vulnerability of city for debris flow hazards.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
• /
• 2016.05a
• /
• pp.191-193
• /
• 2016

인적오류 예방은 해양사고 예방에 가장 중요한 이슈로 현재 인식되고 있다. 현재 이러한 인적오류를 예방하기 위한 다양한 과학적인 기법들이 등장하고 있으나, 실제 인적오류를 예방할 수 있는 기법은 아직 개발되어 있지 못한 실정이다. 그 이유는 인적오류의 발생 원인과 특징이 사람을 대상으로 하기 때문에 실로 방대하고 원인식별이 어려우며, 원인과 결과 사이의 인과관계 구축에는 한계가 있기 때문이다. 기존 개발된 다양한 기법들은 이론적으로는 완벽할 수 있으나, 실제 방대한 원인과 결과 사이에 형성된 연계체인을 모두 흡수하기가 곤란하기 때문이다. 현재 IMO의 공식안전성평가(FSA) 기법이 해상분야에 널리 적용되고 있으나 구체적으로 어떠한 기법을 적용하여 인적오류를 적용할 수 있는지에 대해서는 아직도 애매모호한 실정이다. FTA, ETA, FEMA, SWIFT 등 다양한 분석기법의 등장과 AI, Fuzzy, MMC, Kalman 등 기초과학분야의 기본적인 이론과 기술을 적용할 수 있으나 인간의 인적오류 식별과 분석 및 평가와 예측에는 한계가 있는 것이 현재의 실정이다. 한편 최근에는 기존에 많은 문제점을 내포하고 있는 것으로 고려되었던 베이지안 네트워크(Bayesian Network, BN)가 다시 분석과 예측 분야에 등장하고 있는데, BN의 장점을 수용하고 단점을 해결할 수 있는 방법들이 연구되고 있기 때문이다. BN의 장점은 전방추론과 후방추론을 적용하여 사고의 원인과 결과를 분석한 후, 이에 대한 해결 방안을 식별할 수 있기 때문이다. BN의 단점은 이진(binary) 구조의 데이터만을 수용할 수 있기 때문에 상관 변수들이 방대한 경우 계산시간이 방대해지고 이를 모두 수용할 수 있는 방법이 없기 때문이다. 따라서 BN 구조를 어떻게 설계하는냐가 최근의 이수로 등장하고 있다. 본 연구에서는 이러한 제 문제점을 고찰하고 인적오류 모델 개발에 최적인 방법 또는 기술을 모색하는데 있다.