• 한국강구조학회 논문집
• /
• 제18권2호
• /
• pp.147-160
• /
• 2006

본 논문에서는 개선소성힌지해석과 유전자 알고리듬을 이용한 평면 강골조 구조물의 퍼지최적설계 방법을 제시하였다. 개선소성힌지해석에서는 강골조 구조물의 기하학적 비선형성을 고려하기 위해 보-기둥 요소의 안정함수를 사용하였으며, 재료적 비선형을 고려하기 위해 잔류응력, 소성힌지, 그리고 기하학적 불완전성 등에 의한 점진적인 강성감소모델을 사용하였다. 유전자 알고리듬에서는 토너먼트 선택방법과 마이크로 유전자 알고리즘을 사용하였다. 목적함수로는 구조물의 총중량을 사용하였으며, 제약조건으로는 하중-저항능력, 사용성, 연성도, 그리고 시공성에 관한 기준을 고려하였다. 퍼지최적설계에서는 명확한 목적함수와 퍼지제약을 가지는 경우에 한하여 허용 오차는 제한값의 5%로 선택하고 비소속함수와 레벨컷 방법을 이용하여 0에서 1까지 0.2간격으로 나누어 최적화하였다. 여러 평면 강골조 구조물의 최적설계를 수행하여 일반GA최적설계와 퍼지GA최적설계의 최적값을 비교하였다.

• Earthquakes and Structures
• /
• 제20권2호
• /
• pp.133-148
• /
• 2021

The paper presents a simplified force-based seismic design procedure for the preliminary design of steel haunch retrofitting for the seismic upgrade of deficient RC frames. The procedure involved constructing a site-specific seismic design spectrum for the site, which is transformed into seismic base shear coefficient demand, using an applicable response modification factor, that defines base shear force for seismic analysis of the structure. Recent experimental campaign; involving shake table testing of ten (10), and quasi-static cyclic testing of two (02), 1:3 reduced scale RC frame models, carried out for the seismic performance assessment of both deficient and retrofitted structures has provided the basis to calculate retrofit-specific response modification factor Rretrofitted. The haunch retrofitting technique enhanced the structural stiffness, strength, and ductility, hence, increased the structural response modification factor, which is mainly dependent on the applied retrofit scheme. An additional retrofit effectiveness factor (ΩR) is proposed for the deficient structure's response modification factor Rdeficient, representing the retrofit effectiveness (ΩR=Rretrofitted /Rdeficient), to calculate components' moment and shear demands for the retrofitted structure. The experimental campaign revealed that regardless of the deficient structures' characteristics, the ΩR factor remains fairly the unchanged, which is encouraging to generalize the design procedure. Haunch configuration is finalized that avoid brittle hinging of beam-column joints and ensure ductile beam yielding. Example case study for the seismic retrofit designs of RC frames are presented, which were validated through equivalent lateral load analysis using elastic model and response history analysis of finite-element based inelastic model, showing reasonable performance of the proposed design procedure. The proposed design has the advantage to provide a seismic zone-specific design solution, and also, to suggest if any additional measure is required to enhance the strength/deformability of beams and columns.

• Architectural research
• /
• 제25권1호
• /
• pp.1-9
• /
• 2023

Structural ageing influences the structural performance in a negative way by reducing the seismic resilience of the structure which makes it a major concern around the world. Retrofitting is considered to be a pragmatic and feasible solution to address this issue. Numerous retrofitting techniques are devised by researchers over the years. The viability of using steel bracings as retrofitting component is evaluated on a G+30 storied building model designed according to ACI318-14 and ASCE 7-16. Four different types of steel bracing arrangements (V, Inverted V/ Chevron, Cross/ X, Diagonal) are assessed in the model developed in commercial nu-merical analysis software while considering both material and geometric nonlinearities. Reducing displacement and cost in the structures indicates that the design is safe and economical. Therefore, the purpose of this article is to find the best bracing system that causes minimum displacement, which indicates maximum lateral stiffness. To evaluate the seismic vulnerability of each system, incremental dynamic analysis was conducted to develop fragility curves, followed by the formation of collapse margin ratio (CMR) as stipulated in FEMA P695 and finally, a cost estimation was made for each system. The outcomes revealed that the effects of ge-ometric nonlinearity tend to evoke hazardous consequences if not considered in the structural design. Probabilistic seismic and economic probes indicated the superior performance of V braced frame system and its competency to be a germane technique for retrofitting.

• Steel and Composite Structures
• /
• 제16권4호
• /
• pp.417-436
• /
• 2014

During an earthquake, steel frame columns can be subjected to high axial forces combined with inelastic rotation demand resulting from story drift. Generally, the whole beam or component can be represented with one element. In elasto-plastic analysis, subdivision is necessary if the plastic deformation occurs within two ends of beams. If effects of the joint panel are necessarily considered in the analysis, the joint panel should be represented with an independent element. It is a special element to represent the shear deformation of the joint panel in the beam-column connection zone. Several analytical models for panel zone (PZ) behavior exist, in terms of shear force-shear distortion relationships. Among these models, the Krawinkler PZ model is the most popular one which is used in the AISC code. Some studies have pointed out that Krawinkler's model gives good results for the range of thin to medium column flanges thickness. This paper, introduces a new model to estimate the response of shear force-shear distortion for the PZ including column axial force. The model is applicable to both thin and thick column flange. To achieve an appropriate PZ mathematical model first, the effects of PZ strength and stiffness on connection response are parametrically studied using finite element models. More than one thousand and four-hundred beam-column connections are included in the parametric study, with varied parameters; then based on analytical results a simple mathematical model is presented. A comparison between the results of proposed method herein with FE analyses shows the average error especially in thick column flange is significantly reduced which demonstrates the accuracy, efficiency, and simplicity of the proposed model.

• Smart Structures and Systems
• /
• 제25권2호
• /
• pp.241-254
• /
• 2020

Using confined shape memory alloy (SMA) bar or plate, this study proposes an innovative self-centering damper. The damper is essentially properly machined SMA core, i.e., bar or plate, that encased in buckling-restrained device. To prove the design concept, cyclic loading tests were carried out. According to the test results, the damper exhibited desired flag-shape hysteretic behaviors upon both tension and compression actions, although asymmetric behavior is noted. Based on the experimental data, the hysteretic parameters that interested by seismic applications, such as the strength, stiffness, equivalent damping ratio and recentering capacity, are quantified. Processed in the Matlab/Simulink environment, a preliminary evaluation of the seismic control effect for this damper was conducted. The proposed damper was placed at the first story of a multi-story frame and then the original and controlled structures were subjected to earthquake excitations. The numerical outcome indicated the damper is effective in controlling seismic deformation demands. Besides, a companion SMA damper which represents a popular type in previous studies is also introduced in the analysis to further reveal the seismic control characteristics of the newly proposed damper. In current case, it was found that although the current SMA damper shows asymmetric tension-compression behavior, it successfully contributes comparable seismic control effect as those having symmetrical cyclic behavior. Additionally, the proposed damper even shows better global performance in controlling acceleration demands. Thus, this paper reduces the concern of using SMA dampers with asymmetric cyclic behavior to a certain degree.

• 한국전산구조공학회논문집
• /
• 제18권4호통권70호
• /
• pp.395-404
• /
• 2005

본 논문에서는 동적하중 재하 시 공간 강뼈대 구조물의 비선형 시간이력 해석에 대한 간편하고 효율적인 수치해석 기법을 제시하였다. 뼈대의 강성행렬에 안정함수를 적용함으로서 기하학적 비선형성 즉 P-$\delta$ 및 P-$\Delta$ 효과를 고려하였다. 접선계수 개념 및 New Orbison 완전 소성면에 기초한 연화소성힌지를 적용하여 축방항력에 의한 부재의 점진적 항복 및 휨에 의한 부재의 부분 소성화를 고려하였다. 증분형태로 정식화된 뼈대 구조의 동적평형방정식의 해를 수치적으로 구하기 위하여 적분형태의 평균가속도법을 사용하여 컴퓨터 프로그램을 개발하였다. 검증 예제에 대하여 보요소 모델을 사용한 ABAQUS 및 개발된 프로그램에 의한 해석결과를 비교함으로서 개발된 프로그램의 정밀도와 해석시간에 대한 효율성을 입증하였다.

• 한국강구조학회 논문집
• /
• 제22권2호
• /
• pp.121-128
• /
• 2010

저층 장스팬 철골프레임에는 강재절감을 위해 휨모멘트 저항에 극대화한 판폭 두께비가 큰 변단면 부재를 사용하고 있다. 게다가, 밀착조임 볼트접합은 고장력 볼트조임에 비하여 공사비 절감과 시공용이성의 장점을 지니고 있다. 한편, 밀착조임 엔드플레이트 접합사용에 다수 장점을 가지고 있음에도 불구하고 구조적 거동 및 해석상의 복잡함이 존재한다. 이에 본 연구에서는 밀착조임 엔드플레이트 접합형 변단면 부재에 대한 실대형 실험을 행하였다. 변수로는 체결 토크치, 재하패턴, 볼트종류, 접합부 파괴형이다. Silva et al.과 AISC(2003)에서 제시한 강성 및 내력식을 이용한 예측결과를 실험결과와 비교하였다.

• 한국항해항만학회:학술대회논문집
• /
• 한국항해항만학회 2002년도 추계공동학술대회논문집
• /
• pp.89-93
• /
• 2002

선박에서 주요소중에 하나인 판요소는 해양구조물과 골조구조물에 비해 고차의 부정정 구조물로서 구성부재가 국부적으로 좌굴 붕괴하더라도 구조전체적인 붕괴에까지 곧바로 연결될 가능성은 일반적으로 많지 않다고 알려져 왔다. 그러나, 일단 구성부재가 좌굴붕괴하고 나면 국부적으로 구조강성이 저하하고, 그 결과 주변의 타 구조부재가 밟는 하중분담이 증가함으로써 연쇄적으로 구성부재가 소성붕괴하여 결국에는 구조전체적으로 붕괴할 위험성이 있다. 그래서, 이러한 현상을 정확하게 해석하기 위해서는 좌굴 및 좌굴후 거동에 대한 연구가 필요하며 본 논문에서는 면내하중을 받는 직사각형판에 대해서 판 주변 지지조건을 달리한 시리즈 해석을 범용유한요소 프로그램인 ANSYS를 사용하였다. 본 논문에서는 면내하중이 작용하는 판의 경계조건에 따른 시리즈 해석을 통하여 선체판의 탄소성 거동을 규명하였다.

• Smart Structures and Systems
• /
• 제31권4호
• /
• pp.421-436
• /
• 2023

This paper presents a vibration displacement measurement and damage identification method for a space truss structure from its vibration videos. Features from Accelerated Segment Test (FAST) algorithm is combined with adaptive threshold strategy to detect the feature points of high quality within the Region of Interest (ROI), around each node of the truss structure. Then these points are tracked by Kanade-Lucas-Tomasi (KLT) algorithm along the video frame sequences to obtain the vibration displacement time histories. For some cases with the image plane not parallel to the truss structural plane, the scale factors cannot be applied directly. Therefore, these videos are processed with homography transformation. After scale factor adaptation, tracking results are expressed in physical units and compared with ground truth data. The main operational frequencies and the corresponding mode shapes are identified by using Subspace Stochastic Identification (SSI) from the obtained vibration displacement responses and compared with ground truth data. Structural damages are quantified by elemental stiffness reductions. A Bayesian inference-based objective function is constructed based on natural frequencies to identify the damage by model updating. The Success-History based Adaptive Differential Evolution with Linear Population Size Reduction (L-SHADE) is applied to minimise the objective function by tuning the damage parameter of each element. The locations and severities of damage in each case are then identified. The accuracy and effectiveness are verified by comparison of the identified results with the ground truth data.

• Structural Engineering and Mechanics
• /
• 제25권1호
• /
• pp.53-73
• /
• 2007

In this study, an effective load increment method for multi modal adaptive non-linear static (pushover) analysis (NSA) for building type structures is presented. In the method, lumped plastisicity approach is adopted and geometrical non-linearties (second-order effects) are included. Non-linear yield conditions of column elements and geometrical non-linearity effects between successive plastic sections are linearized. Thus, load increment needed for formation of plastic sections can be determined directly (without applying iteration or step-by-step techniques) by using linearized yield conditions. After formation of each plastic section, the higher mode effects are considered by utilizing the essentials of traditional response spectrum analysis at linearized regions between plastic sections. Changing dynamic properties due to plastification in the system are used on the calculation of modal lateral loads. Thus, the effects of stiffness changes and local mechanism at the system on lateral load distribution are included. By using the proposed method, solution can be obtained effectively for multi-mode whereby the properties change due to plastifications in the system. In the study, a new procedure for determination of modal lateral loads is also proposed. In order to evaluate the proposed method, a 20 story RC frame building is analyzed and compared with Non-linear Dynamic Analysis (NDA) results and FEMA 356 Non-linear Static Analysis (NSA) procedures using fixed loads distributions (first mode, SRSS and uniform distribution) in terms of different parameters. Second-order effects on response quantities and periods are also investigated. When the NDA results are taken as reference, it is seen that proposed method yield generally better results than all FEMA 356 procedures for all investigated response quantities.