• Structural Engineering and Mechanics
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• 제50권3호
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• pp.287-304
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• 2014

A computer based iterative numerical procedure has been developed to analyse reinforced high strength concrete columns subjected to horizontal wave loads and eccentric vertical load by taking the material, geometrical and wave load non-linearity into account. The behaviour of the column has been assumed, to be represented by Moment-Thrust-Curvature relationship of the column cross-section. The formulated computer program predicts horizontal load versus deflection behaviour of a column up to failure. The developed numerical model has been applied to analyse several column specimens of various slenderness, structural properties and axial load ratios, tested by other researchers. The predicted values are having a better agreement with experimental results. A simplified user friendly hydrodynamic load model has been developed based on Morison equation supplemented with a wave slap term to predict the high frequency non-linear impulsive hydrodynamic loads arising from steep waves, known as ringing loads. A computer program has been formulated based on the model to obtain the wave loads and non-dimensional wave load coefficients for all discretised nodes, along the length of column from instantaneous free water surface to bottom of the column at mud level. The columns of same size and material properties but having different slenderness ratio are analysed by the developed numerical procedure for the simulated wave loads under various vertical thrust. This paper discusses the results obtained in detail and effect of slenderness in resisting wave loads under various vertical thrust.

• 대한안전경영과학회지
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• 제26권1호
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• pp.9-14
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• 2024

Restraints of Branch Lines are used as earthquake-resistant support devices for fire-fighting pipes along with sway brace devices. The central types are aligned and fixed in a straight line with center of the pipe, but the eccentric types are fixed to on side of the pipe, so a bending moment occurs. In this study, three specimens each of central type and eccentric type were installed at an angle of 45° from the vertical and a monotonic compression load of 1340N was applied. All central type samples satisfied 17.8mm of the allowable displacement, but all eccentric type samples failed to meet the target load and buckled. Therefore, when considering the performance of eccentric type restraints, both compressive load and bending moment must be considered. Even through material mechanics calculations, the yield stress of eccentric type - 3/8 inch all threaded steel bolt - exceeds 320Mpa of the allowable stress. A experiment standards need to be established for eccentric type restraints.

• Earthquakes and Structures
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• 제17권6호
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• pp.623-633
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• 2019

A large number of available concrete buildings designed only considering gravity load that require seismic rehabilitation because of failure to meet plasticity criteria. Using steel bracings are a common type of seismic rehabilitation. The eccentric bracings with vertical link reduce non-elastic deformation imposed on concrete members as well as elimination of probable buckling problems of bracings. In this study, three concrete frames of 10, 15, and 20 stories designed only for gravity load have been considered for seismic improvement using performance-based plastic design. Afterwards, nonlinear time series analysis was employed to evaluate seismic behavior of the models in two modes including before and after rehabilitation. The results revealed that shear link can yield desirable performance with the least time, cost and number of bracings of concrete frames. Also, it was found that the seismic rehabilitation can reduce maximum relative displacement in the middle stories about 40 to 80 percent. Generally, findings of this study demonstrated that the eccentric bracing with vertical link can be employed as a suitable proxy to achieve better seismic performance for existing high rise concrete frames.

• 한국터널지하공간학회 논문집
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• 제9권3호
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• pp.219-228
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• 2007

본 연구에서는 축소모형실험을 통하여 편토압 및 측압이 터널 거동에 미치는 영향을 연구하였다. 모형실험 결과의 타당성은 수치해석을 통하여 검토하였다. 터널에 작용하는 편토압을 감소시킬 수 있는 방안으로 편향 배치된 지보구조를 제안하고 이 방안의 적용성을 검토하였다. 실험 결과, 편향 배치된 지보구조를 적용함으로서 발생되는 변위가 전체적으로 줄어들었고, 초기 균열이 발생되는 하중도 증가되었다. 또한 터널의 안정성에 크게 문제가 되는 최대 편압 수직하중 역시 증가함을 알 수 있었다. 터널에 작용하는 측압의 영향을 검토한 결과, 측압계수의 변화에 따라 변위 발생 양상 및 균열 발생 양상이 매우 변화함을 알 수 있었다. 또한, 안정성 측면에서 취약점을 나타내는 부분도 변화함을 알 수 있었다.

• Steel and Composite Structures
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• 제27권3호
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• pp.285-295
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• 2018

In this paper, the bearing capacity of a non-eccentric and eccentric tubular, concrete-filled, steel bridge pier was studied through the finite element method. Firstly, to verify the validity of the numerical analysis, the finite element analysis of four steel tube columns with concrete in-fill was carried out under eccentric loading and horizontal cyclic loading. The analytical results were compared with experimental data. Secondly, the effects of the eccentricity of the vertical loading on the seismic performance of these eccentrically loaded steel tubular bridge piers were considered. According to the simulated results, with increasing eccentricity ratio, the bearing capacity on the eccentric side of a steel tubular bridge pier (with concrete in-fill) is greatly reduced, while the capacity on the opposite side is improved. Moreover, an empirical formula was proposed to describe the bearing capacity of such bridge piers under non-eccentric and eccentric load. This will provide theoretical evidence for the seismic design of the eccentrically loaded steel tubular bridge piers with concrete in-fill.

• Earthquakes and Structures
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• 제14권6호
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• pp.537-549
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• 2018

Using vertical links in eccentric braced frames is one of the best passive structural control approaches due to its effectiveness and practicality advantages. However, in spite of the subject importance there are limited studies which evaluate the seismic reliability and response reduction factor (R-factor) in this system. Therefore, the present study has been conducted to improve the current understanding about failure mechanism in the structural systems equipped with vertical links. For this purpose, following definition of demand and capacity response reduction factors, these parameters are computed for three different buildings (4, 8 and 12 stories) equipped with this system. In this regards, pushover and incremental dynamic analysis have been employed, and seismic reliability as well as multi-level response reduction factor according to the seismic demand and capacity of the frames have been derived. Based on the results, this system demonstrates high ductility and seismic energy dissipation capacity, and using the response reduction factor as high as 8 also provides acceptable reliability for the frame in the moderate and high earthquake intensities. This system can be used in original buildings as lateral load resisting system in addition to seismic rehabilitation of the existing buildings.

• 한국공간구조학회논문집
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• 제22권2호
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• pp.29-37
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• 2022

The collapse of reinforced concrete (RC) frame buildings is mainly caused by the failure of columns. To prevent brittle failure of RC column, numerous studies have been conducted on the seismic performance of strengthened RC columns. Concrete jacketing method, which is one of the retrofitting method of RC members, can enhance strength and stiffness of original RC column with enlarged section and provide uniformly distributed lateral load capacity throughout the structure. The experimental studies have been conducted by many researchers to analyze seismic performance of seismic strengthened RC column. However, structures which have plan and vertical irregularities shows torsional behavior, and therefore it causes large deformation on RC column when subjected to seismic load. Thus, test results from concentric cyclic loading can be overestimated comparing to eccentric cyclic test results, In this paper, two kinds of eccentric loading pattern was suggested to analyze structural performance of RC columns, which are strengthened by concrete jacketing method with new details in jacketed section. Based on the results, it is concluded that specimens strengthened with new concrete jacketing method increased 830% of maximum load, 150% of maximum displacement and changed the failure modes of non-strengthened RC columns.

• Structural Engineering and Mechanics
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• 제71권3호
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• pp.211-221
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• 2019

To study the eccentric compression behavior of ultra-high performance fiber reinforced concrete (UHPFRC) columns, six UHPFRC columns and one high-strength concrete (HSC) column were tested. Variation parameters include load eccentricity, volume of steel fibers and stirrup ratio. The crack pattern, failure mode, bearing capacity, and deformation of the specimens were studied. The results showed that the UHPFRC columns had different failure modes. The large eccentric compression failure mode was the longitudinal tensile reinforcements yielded and many horizontal cracks appeared in the tension zone. The small eccentric compression failure mode was the longitudinal compressive reinforcements yielded and vertical cracks appeared in the compressive zone. Because of the bridging effect of steel fibers, the number of cracks significantly increased, and the width of cracks decreased. The load-deflection curves of the UHPFRC columns showed gradually descending without sudden dropping, indicating that the specimens had better deformation. The finite element (FE) analysis was performed to stimulate the damage process of the specimens with monotonic loading. The concrete damaged plasticity (CDP) model was adopted to characterize the behaviour of UHPFRC. The contribution of the UHPFRC tensile strength was considered in the bearing capacity, and the theoretical calculation formulas were derived. The theoretical calculation results were consistent with the test results. This research can provide the experimental and theoretical basis for UHPFRC columns in engineering applications.

• Computers and Concrete
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• 제27권5호
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• pp.437-445
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• 2021

Retrofitting of structures has gained importance over the recent years. Particularly, Reinforced Cement Concrete (RCC) column strengthening has become a challenge to the structural engineers, owing to the risks and complexities involved in it. There are several methods of RCC column strengthening viz. RCC jacketing, steel jacketing and Fiber Reinforced Polymer (FRP) wrapping etc., FRP wrapping is the most promising alternative when compared to the others. The large research database shows FRP wrapping, through lateral confinement, improves the axial load carrying capacity of the columns under concentric loading. However, its confining efficiency reduces under eccentric loading. Hence a relative newer technique called Near Surface Mounting (NSM), in which Carbon FRP (CFRP) strips are epoxy grouted to the precut grooves in the cover concrete of the columns, has been thrust domain of research. NSM technique strengthens the column nominally under concentric load case while significantly under eccentric case. A novel configuration of NSM in which the vertical NSM (VNSM) strips are being connected by horizontal NSM (HNSM) strips was numerically investigated under both concentric and eccentric loading. It was found that the configuration with 6 HNSM strips performed better under eccentric loading than under concentric loading, while the configuration with 3 HNSM strips performed better under concentric loading than under eccentric loading. Hence an optimum of 4 HNSM strips is recommended as strengthening measure for the given column specifications. It was also found that Aluminum alloy cannot be used instead of CFRP in NSM applications owing to its lower mechanical properties.

• 한국터널지하공간학회 논문집
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• 제5권3호
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• pp.227-239
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• 2003

복개 터널구조물은 친환경적 건설을 위하여 성토체는 일정 구배를 갖는 경사시공을 하게되고, 이로 인하여 복개 터널구조물에는 편토압이 작용하게 된다. 현재 복개 터널구조물의 설계를 위하여 일반적으로 적용되고 있는 구조공학적 해석시 연직토압은 콘크리트 라이닝 상부 성토체를 상재하중으로 고려하여 산정하고, 좌 우측에 작용하는 횡방향 토압은 정지토압 분포를 적용하고 있다. 그러나 이러한 토압분포는 콘크리트 라이닝 좌 우측 측벽부 외측에서 성토체의 경사시공에 의한 편토압의 영향을 고려할 수 없다. 따라서, 본 연구에서는 성토사면에 의한 편토압을 고려한 합리적인 복개 터널구조물 해석 및 설계를 위한 기본연구로써, 지반공학적 모델링 기법을 이용하여 성토사면에 의한 편토압 고려 방안을 제안하였으며, 구조공학적 해석기법을 통하여 제안된 편토압 고려방안의 적용성을 검토하였다.