• 한국구조물진단유지관리공학회 논문집
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• 제18권2호
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• pp.1-8
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• 2014

본 연구의 목적은 경계요소를 갖는 철근콘크리트 전단벽의 잠재소성힌지길이를 합리적으로 평가할 수 있는 단순모델의 제시이다. 전단벽의 높이에 따른 이상화된 곡률분포로부터, 기본방정식은 항복모멘트와 최대모멘트 그리고 사인장균열에 의한 부가모멘트의 함수로 일반화되었다. 전단벽의 항복모멘트와 최대모멘트는 변형률 적합조건과 힘의 평형조건을 기반하여 산정하였다. 사인장균열 발생의 여부는 ACI 318-11에서 제시된 콘크리트의 전단력으로부터 검토되었으며, 부가모멘트는 Park and Paulay에 의해 제시된 트러스기구를 이용하여 산정하였다. 이들 모멘트식들은 다양한 변수범위에서 변수연구를 수행하였다. 결과적으로 등가소성힌지길이는 주철근 및 수직철근지수와 축력지수의 함수로 제시될 수 있었다. 제시된 등가소성힌지길이의 모델은 실험결과의 비교에서 평균 및 표준편차가 각각 1.019와 0.102로 실험 결과를 정확하게 예측하였다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2008년도 추계 학술발표회 제20권2호
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• pp.221-224
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• 2008

할선강성을 이용하여 모멘트저항골조의 모멘트재분배를 수행하는 선형해석법을 연구하였다. 제안된 방법에서는 모멘트재분배가 요구되는 부재의 소성힌지에 회전스프링을 모델링한 후, 이 스프링의 할선 강성을 조정하여 비탄성변형으로 인해 저감된 부재의 휨강성을 반영한다. 회전스프링의 할선강성을 조정하여 선형해석한 결과, 해당 부재와 전체 구조물에서 힘의 평형이 만족될 때까지 계산을 반복한다. 할선강성해석을 통해, 소성힌지의 비탄성변형에 의한 하중의 재분배가 고려될 수 있으며, 해당 소성힌지에서의 요구회전변형이 변형능력을 초과하지 않는지 비교함으로써 안전성을 평가할 수 있다. 검증을 위해, 제안된 방법은 기존의 연속보에 대한 실험연구와 비교되었으며, 기존건물의 평가에 적용되었다.

• 대한조선학회논문집
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• 제47권6호
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• pp.843-849
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• 2010

This paper presents definition of symmetry of a ship section where three symmetries are proposed: material, geometric, and load symmetries. Precise terminologies of centroid, moment plane, and neutral axis plane are also defined. It is suggested that force vector equilibrium as well as force equilibrium are necessary condition to determine new position of neutral axis due to translational and rotational mobility. It is also stated that new reference datum of ENMP(elastic neutral moment plane), PNMP(fully plastic moment plane), ENAP(elastic neutral axis plane), and INAP(inelastic neutral moment plane) are required to define asymmetric section properties such as second moment of area, elastic section modulus, yield moment, fully plastic moment, and ultimate moment. Since collision-induced damage and flooding-induced biaxial bending moment produce typical asymmetry of section, the section properties are calculated for a typical VLCC. Geometry asymmetry is determined from ABS and DNV rules and two moment planes of 0/30 degs are assumed for load asymmetry. It is proved that the property reduction ratios directly calculated from second moment of area are usually larger than area reduction ratio. Reduction ratio of ultimate moment capacity shows almost linearly proportional to area reduction ratio. Mobility of elastic and inelastic neutral axis planes is visually provided.

• Steel and Composite Structures
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• 제32권1호
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• pp.79-90
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• 2019

This study introduces new connections that connect the beam to the column with slit dampers. Plastic deformations and damages concentrate on slit dampers. The slit dampers prevent plastic damages of column, beam, welds and panel zone and act as fuses. The slit dampers were prepared with IPE profiles that had some holes in the webs. In this paper, two experimental specimens were made. In first specimen (SDC1), just one slit damper connected the beam to the column and one IPE profile with no holes connected the bottom flange of the beam to the column. The second specimen (SDC2) had two similar dampers which connected the top and bottom flange of the beam to the column. Cyclic loading was applied on Specimens. The cyclic displacements conditions continued until 0.06 radian rotation of connection. The experimental observations showed that the bending moment of specimen SDC2 increased until 0.04 story drift. In specimen SDC1, the bending moment decreases after 0.03 story drift. Test results indicate the high performance of the proposed connection. Based on the results, the specimen with two slit damper (SDC2) has higher seismic performance and dissipates more energy in loading process than specimen SDC1. Theoretical formulas were extended for the proposed connections. Numerical studies have been done by ABAQUS software. The theoretical and numerical results had good agreements with the experimental data. Based on the experimental and numerical investigations, the high ductility of connection is obtained from plastic damages of slit dampers. The most flexural moment of specimen SDC1 occurred at 3% story drift and this value was 1.4 times the plastic moment of the beam section. This parameter for SDC2 was 1.73 times the plastic moment of the beam section and occurred at 4% story drift. The dissipated energy ratio of SDC2 to SDC1 is equal to 1.51.

• Steel and Composite Structures
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• 제28권6호
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• pp.767-778
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• 2018

The purpose of this study is to investigate how a fully restrained bolted beam splice affects the connection behavior as a column-tree connection in steel special moment frames under cyclic loading when located within the plastic hinge zone. The impacts of this attachment in protected zone are observed by using nonlinear finite element analyses. This type of splice connection is designed as slip-critical connection and thereby, the possible effects of slippage of the bolts due to a possible loss of pretension in the bolts are also investigated. The 3D models with solid elements that have been developed includes three types of connections which are the connection having fully restrained beam splice located in the plastic hinge location, the connection having fully restrained beam splice located out of the plastic hinge and the connection without beam splice. All connection models satisfied the requirement for the special moment frame connections providing sufficient flexural resistance, determined at column face stated in AISC 341-16. In the connection model having fully restrained beam splice located in the plastic hinge, due to the pretension loss in the bolts, the friction force on the contact surfaces is exceeded, resulting in a relative slip. The reduction in the energy dissipation capacity of the connection is observed to be insignificant. The possibility of the crack occurrence around the bolt holes closest to the column face is found to be higher for the splice connection within the protected zone.

• Steel and Composite Structures
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• 제45권2호
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• pp.249-261
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• 2022

This paper presents a numerical study to develop a guideline for estimating the plastic strength of elliptical steel slit damper with reasonable accuracy. The strut width increases from middle to end in elliptical steel slit damper and it is observed from the past studies that variation of the width is not considered for calculating the plastic strength of the damper. It is also noticed that the existing formulas for predicting plastic strength of this kind of damper may not be accurate and further refinement is warranted. Study is then carried on elliptical steel slit damper made of mild steel and having different geometry to find out equivalency of it with oblong steel slit damper having similar plastic strength. A few three-dimensional finite element models of seismic moment connection system with steel slit damper are developed and validated against past experiments for carrying the present study considering both the material nonlinearity as well as geometric nonlinearity. The results of the parametric studies have been compared with energy quantities and presented graphically to better understand the effects of different parameters on the system. Based on the pattern of parametric study results, closed-form semi-empirical algebraic expression of damper plastic strength is developed for elliptical steel slit damper which shows very good agreement with finite element analysis as well as experiments. This developed expression can now be used for elliptical steel slit damper in replacement with any type of damper in the design of moment connection.

• 국제초고층학회논문집
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• 제2권4호
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• pp.355-365
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• 2013

The paper reports results of recent studies on the effects of column support conditions on the lateral displacements of moment frames at incipient collapse. The article presents a number of exercises in the plastic theory of structures that lead to useful design formulae. It has been shown that Drift Shifting (DS) is caused due to differences in the stiffnesses of adjoining columns, and that changes in drift ratios are more pronounced at first level column joints in both fixed as well as pinned base frames. In well proportioned moment frames, DS in the upper levels could be minimized, even reduced to zero. It has been demonstrated that DS can be eliminated in properly designed fixed and grade beam supported (GBS) moment frames. Several examples, including symbolic P-delta effects, have been provided to demonstrate the validity and the applications of the proposed ideas to the design and drift control of moment frames. The proposed methodology is exact within the bounds of the theoretical assumptions and is well suited for preliminary design and teaching purposes.

• 국제강구조저널
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• 제18권5호
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• pp.1772-1783
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• 2018

Nowadays, the researches about composite structure system are being implemented in various fields, and many steel structures are designed based on that. In this study, the bending and seismic performance of the newly developed high-performance cold forming composite beam are evaluated by several experiments. As a result of the bending performance test, the bending moment of beam was increased stably depending on the depth and plate thickness of beam, and it is considered that the bending moment can be evaluated by the equation of a composite beam design. As a result of the seismic performance test, it was verified that sufficient seismic performance was obtained despite the increase of a negative moment rebar and depth of beam. In addition, the nominal bending moment has obtained the strength above the plastic bending moment, and also the plastic rotation angle has satisfied the requirement of composite intermediate moment frame.

• Steel and Composite Structures
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• 제1권1호
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• pp.145-158
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• 2001

An experimental study was conducted to evaluate the effects of loading sequence and lateral bracing on the behavior of reduced beam section (RBS) steel moment frame connections. Four full-scale moment connections were cyclically tested-two with a standard loading history and the other two with a near-fault loading history. All specimens reached at least 0.03 radian of plastic rotation without brittle fracture of the beam flange groove welds. Two specimens tested with the nearfault loading protocol reached at least 0.05 radian of plastic rotation, and both experienced smaller buckling amplitudes at comparable drift levels. Energy dissipation capacities were insensitive to the types of loading protocol used. Adding a lateral bracing near the RBS region produced a higher plastic rotation; the strength degradation and buckling amplitude were reduced. A non-linear finite element analysis of a one-and-a-half-bay beam-column subassembly was also conducted to study the system restraint effect. The study showed that the axial restraint of the beam could significantly reduce the strength degradation and buckling amplitude at higher deformation levels.

• 콘크리트학회논문집
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• 제23권6호
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• pp.731-740
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• 2011

KCI 2007, ACI 318-08에 제시된 모멘트재분배 방법은 등분포 중력하중을 받는 연속 휨재에 대하여 검증된 방법이다. 횡하중에 의한 모멘트재분배 및 비탄성 거동은 중력하중과 전혀 다른 메커니즘을 발생된다. 이 연구에서는 기초역학에 근거하여 중력하중과 횡하중을 받는 철근콘크리트 모멘트골조의 보에 발생되는 모멘트재분배와 소성변형의 관계를 정량화하고, 이로부터 보의 소성변형능력에 근거한 모멘트재분배 설계법을 제안하였다. 제안된 모멘트재분배비는 KCI 2007, ACI 318-08 등 기존 설계기준과 마찬가지로 극한한계상태의 단면해석으로 결정되는 철근의 인장변형률로 정의된다. 또한 모멘트재분배비는 경간, 철근비, 단면강성, 변형경화 거동에 의하여 영향을 받는다. 제안된 방법을 사용하여 탄성해석으로 구한 설계모멘트를 재분배시키는 설계 가이드라인 및 예제를 제시하였다.