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

• Earthquakes and Structures
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• 제14권1호
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• pp.21-32
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• 2018

Prefabricated structures are constructed by bolted connections of separated members. The design and analysis of these structures are generally performed by defining fully hinges for the connection of separated members at the joint of junction. In practice, these connections are not fully hinged. Therefore, the assumption of semi-rigid connections (restrained or partially fixity) instead of fully hinge connections is a more realistic approach for bolted connections used in the prefabricated elements. The aim of this study is to investigate the effects of semi-rigid connections on seismic performance of prefabricated structures. Nonlinear static analysis (pushover analysis) of a selected RC prefabricated structure is performed with SAP2000 structural analysis program by considering various partially fixity percentages for bolted connections. The target values of roof displacements obtained from the analyses according to ATC-40, FEMA-356, FEMA-440, and TEC-2007 codes are compared each other. The numerical results are given in tables and figures comparatively and discussed. The results show that the effects of semi-rigid connections should be considered in design and analysis of the prefabricated structures.

• Earthquakes and Structures
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• 제8권6호
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• pp.1435-1452
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• 2015

The performance of masonry infilled frames during the past earthquakes shows that the infill panels play a major role as earthquake-resistant elements. Experimental observations regarding the influence of infill panels on increasing stiffness and strength of reinforced concrete structures reveal that such panels can be used in order to strengthen reinforced concrete frames. The present study examines the influence of infill panels on seismic behavior of RC frame structures. For this purpose, several low- and mid-rise RC frames (two-, four-, seven-, and ten story) were numerically investigated. Reinforced masonry infill panels were then placed within the frames and the models were subjected to several nonlinear incremental static and dynamic analyses. In order to determine the acceptance criteria and modeling parameters for frames as well as reinforced masonry panels, the Iranian Guideline for Seismic Rehabilitation of Existing Masonry Buildings (Issue No. 376), the Iranian Guideline for Seismic Rehabilitation of Existing Structures (Issue No. 360) and FEMA Guidelines (FEMA 273 and 356) were used. The results of analyses showed that the use of reinforced masonry infill panels in RC frame structures can have beneficial effects on structural performance. It was confirmed that the use of masonry infill panels results in an increment in strength and stiffness of the framed buildings, followed by a reduction in displacement demand for the structural systems.

• Steel and Composite Structures
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• 제24권2호
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• pp.239-248
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• 2017

Friction dampers are displacement dependent energy dissipation devices which dissipate earthquake energy through friction mechanism and widely used in improving the seismic behavior of new structures and rehabilitation of existing structures. In this paper, the cyclic behavior of a friction damper with different friction materials is investigated through experimental tests under cyclic loading. The damper is made of steel plates, friction pads, preloaded bolts and hard washers. The paper aims at investigating the hysteretic behavior of three friction materials under cyclic loading to be utilized in friction damper. The tested friction materials are: powder lining, super lining and metal lining. The experimental results are studied according to FEMA-356 acceptance criteria and the most appropriate friction material is selected by comparing all friction materials results.

• 한국지진공학회논문집
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• 제16권6호
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• pp.13-20
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• 2012

In this study, 5-story structures were designed in accordance with KBC2009 for inelastic time history analysis of RC IMRF. Bending moment-curvature relationship for beam and column was identified with fiber model and bending moment-rotation relationship for beam-column joint was calculated with simple and unified joint shear behavior model and moment equilibrium relationship for the joint. The hysteretic behavior was simulated with three-parameter model suggested in IDARC program. The analytical results showed that the inelastic shear behavior of the joint could be neglected in the structural design for seismic design category C but the structure of category D did not satisfy the criteria of FEMA 356 for collapse prevention performance level.

• Structural Engineering and Mechanics
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• 제56권5호
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• pp.855-870
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• 2015

In this paper the effects of fling-step and forward-directivity on the seismic performance of steel eccentrically braced frames (EBFs) are addressed. Four EBFs with various numbers of stories (4-, 8-, 12- and 15-story) were designed for an area with high seismic hazard. Fourteen near-fault ground motions including seven with forward-directivity and seven with fling-step effects are selected to carry out nonlinear time history (NTH) analyses of the frames. Furthermore, seven more far-field records were selected for comparison. Findings from the study reveal that the median maximum links rotation of the frames subjected to three set of ground motions are in acceptable range and the links completely satisfy the requirement stated in FEMA 356 for LS performance level. The arrival of the velocity pulse in a near-fault record causes few significant plastic deformations, while many reversed inelastic cycles result in low-cycle fatigue damage in far-fault records. Near-fault records in some cases are more destructive and the results of these records are so dispersed, especially the records having fling-step effects.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2010년도 정기 학술대회
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• pp.2-5
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• 2010

최근 공동주택 거주자의 공간변화 욕구에 대응하기 위하여 가변성 평면이 가능한 구조시스템에 대한 연구가 활발히 진행되고 있다. 이에 따라 건식벽체 구조시스템, 복합 무량 벽체 구조시스템, 격간벽 시스템 등 구조적으로 안정성이 확보되면서 공간가변성이 뛰어난 구조시스템이 대안으로 제시되었다. 본 연구에서는 격간벽 시스템의 지진해석을 통해 내진성능을 평가하였다. 비선형 정적해석 및 동적해석 결과 격간벽 시스템은 벽식 구조시스템에 비하여 초과강도가 작고, 연성이 다소 감소하지만 FEMA-356에서 정하는 붕괴 방지 수준을 만족하여 충분한 내진성능을 보유한 것으로 나타났다.

• 한국지진공학회논문집
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• 제23권5호
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• pp.249-259
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• 2019

To study the seismic resistance of the shear capacity of the RC beam-column joints of two-story and four-story RC buildings, sample buildings are designed with ordinary moment resisting frame. For the shear capacity of joints, the equations of FEMA 356 and NZ seismic assessment are selected and compared. For comparison, one group of buildings is designed only for gravity loads and the other group is designed for seismic and gravity loads. For 16 cases of the designed buildings, seismic performance point is evaluated through push-over analysis and the capacity of joint shear strength is checked. Not only for the gravity designed buildings but also for seismic designed buildings, the demand of joint shear is exceeding the capacity at exterior joints. However, for interior joint, the demand of joint shear exceeds the capacity only for one case. At exterior joints, the axial load stress ratio is lower than 0.21 for gravity designed buildings and 0.13 for seismic designed buildings.

• Earthquakes and Structures
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• 제24권1호
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• pp.11-20
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• 2023

"Performance-based design (PBD)" is based on designing a structure with choosing a performance target under design criteria to increase the structure's resistance against earthquake effect. The plastic hinge formation is determined as one of the fundamental data in finite elements nonlinear analysis to distinguish the condition of the structure where more significant potential damage could occur. If the number of plastic hinges in the structure is increased, the total horizontal load capability of the structure is increased, also. Theoretically, when the number of plastic hinges of the plane frame structure reaches "the degree of hyperstaticity plus one", the structure will reach the capability of the largest ultimate horizontal load. As the number of plastic hinges to be formed in the structure increases towards the theoretical plastic hinge number (TPHN), the total horizontal load capability of the structure increases, proportionally. In the previous studies of the authors, the features of examining the new performance criteria were revealed and it was formulated as follows "Increase the total number of plastic hinges to be formed in the structure to the number of theoretical plastic hinges as much as possible and keep the structure below its targeted performance with related codes". With this new performance criterion, it has been shown that the total lateral load capability of the building is higher than the total lateral load capability obtained with the traditional PBD method by the FEMA 440 and FEMA 356 design guides. In this study, PBD analysis results of structures with frame carrier systems are presented in the light of the Turkey Building Earthquake Code 2019. As a result of this study, it has been shown that the load capability of the structure in the examples of structures with frame carrier system increases by using this new performance criterion presented, compared to the results of the examination with the traditional PBD method in TBEC 2019.

• 공학기술논문지
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• 제5권1호
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• pp.11-18
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• 2012

Large scale earthquake was occurred in different parts of the world like Japan (in 1995), Republic of Pakistan (2005), in China (2008) etc and enormous structures were damaged. As a result of collapse of school buildings structures numerous students are died and it had a big impact on the international community. Therefore, the interest of preparing the seismic resistant school building structures in our country is increases as school building are used as emergency shelter for local residents. But the current standard of seismic design ratio of 3.7% is applied for school building in Korea which is only significant earthquake damage is expected. In order to overcome the current situation, seismic performance evaluation is carried out for the existing school building and an accurate and appropriate seismic retrofit is required based on performance evaluation to upgrade the existing school buildings. In this paper, nonlinear analysis on existing school buildings for ATC-40(Applied Technology Council, ATC) and FEMA-356(Federal Emergency Management Agency, FEMA) are carried out using the capacity spectrum method to evaluate seismic performance and to determine the need for retrofitting. In addition, after reinforcement to enhance the seismic performance is applied the seismic performance evaluation is carried out to verify the effectiveness of seismic retrofit.