• Steel and Composite Structures
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• 제27권4호
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• pp.417-426
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• 2018

This paper presents the seismic behaviors and restoring force model of ring beam joints of steel tube-reinforced concrete column structure under cyclic loading. First, the main failure mode, ultimate bearing capacity, stiffness degradation and energy dissipation capacity are studied. Then, the effects of concrete grade, steel grade, reinforcement ratio and radius-to-width ratios are discussed. Finally, the restoring force model is proposed. Results show that the ring beam joints of steel tube-reinforced concrete column structure performs good seismic performances. With concrete grade increasing, the ultimate bearing capacity and energy dissipation capacity increase, while the stiffness degradation rates increases slightly. When the radius-width ratio is 2, with reinforcement ratio increasing, the ultimate bearing capacity decreases. However, when the radius-to-width ratios are 3, with reinforcement ratio increasing, the ultimate bearing capacity increases. With radius-to-width ratios increasing, the ultimate bearing capacity decreases slightly and the stiffness degradation rate increases, but the energy dissipation capacity increases slightly.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2008년도 추계학술대회 논문집
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• pp.1012-1017
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• 2008

In this study, We examine closely the capacity spectrum method which a kind of displacement-based method evaluated by displacement of structure as an alternative to the load-based analysis method. The displacement-based method can easily review the strength of structure, seismic performance, ductility. Seismic performance by using capacity spectrum method is divided into design response spectrum and capacity spectrum. We can diagram design response spectrum by deciding the design seismic factor depending on performance target, site classification, seismic level, return period as UBC-97. Capacity spectrum is a load-displacement curve obtained by Push-over analysis considering the geometric parameter and the material parameter. We execute the seismic performance evaluation by using the capacity spectrum method to reinforced concrete pier which has been seismic design. As a result, We confirmed that there is a yield point and a ultimate point close by design response spectrum of UBC-97.

• Earthquakes and Structures
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• 제26권4호
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• pp.311-326
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• 2024

Transmission tower structures are particularly susceptible to damage and even collapse under strong seismic ground motions. Conventional seismic analyses of transmission towers are usually performed by considering only ground motion uncertainty while ignoring structural uncertainty; consequently, the performance evaluation and failure prediction may be inaccurate. In this context, the present study numerically investigates the seismic responses and failure mechanism of transmission towers by considering multiple sources of uncertainty. To this end, an existing transmission tower is chosen, and the corresponding three-dimensional finite element model is created in ABAQUS software. Sensitivity analysis is carried out to identify the relative importance of the uncertain parameters in the seismic responses of transmission towers. The numerical results indicate that the impacts of the structural damping ratio, elastic modulus and yield strength on the seismic responses of the transmission tower are relatively large. Subsequently, a set of 20 uncertainty models are established based on random samples of various parameter combinations generated by the Latin hypercube sampling (LHS) method. An uncertainty analysis is performed for these uncertainty models to clarify the impacts of uncertain structural factors on the seismic responses and failure mechanism (ultimate bearing capacity and failure path). The numerical results show that structural uncertainty has a significant influence on the seismic responses and failure mechanism of transmission towers; different possible failure paths exist for the uncertainty models, whereas only one exists for the deterministic model, and the ultimate bearing capacity of transmission towers is more sensitive to the variation in material parameters than that in geometrical parameters. This research is expected to provide an in-depth understanding of the influence of structural uncertainty on the seismic demand assessment of transmission towers.

• Earthquakes and Structures
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• 제10권5호
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• pp.1111-1123
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• 2016

To study seismic performance of steel frame-bent structure, one specimen with one-tenth scale, three-bay, and five-story was tested under reversed cyclic lateral load. The entire loading process and failure mode were observed, and the seismic performance indexes including hysteretic loops, skeleton curve, ductility, load bearing capacity, drift ratio, energy dissipation capacity and stiffness degradation were analyzed. The results show that the steel frame-bent structure has good seismic performance. And the ductility and the energy dissipation capacity were good, the hysteresis loops were in spindle shape, which shape were full and had larger area. The ultimate elastic-plastic drift ratio is larger than the limit value specified by seismic code, showing the high capacity of collapse resistance. It can be helpful to design this kind of structure in high-risk seismic zone.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 추계 학술발표회 제17권2호
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• pp.93-96
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• 2005

Since the columns with flexure-shear failure have lower ductility than those with flexural failure, shear capacity curve models shall be applied as well as flexural capacity curve in order to determine ultimate displacement for seismic design or performance evaluation. In this paper, a modified shear capacity curve model is proposed and compared with the other models such as the CALTRANS model, Aschheim et al.'s model, and Priestley et al.'s model. Four shear capacity curve models are applied to the 4 full scale circular bridge column test results and the accuracy of each model is discussed. It may not be fully adequate to drive a final decision from the application to the limited number of test results, however the proposed model provides the better prediction of failure mode and ultimate displacement than the other models for the selected column test results.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 춘계학술발표회 논문집(I)
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• pp.186-189
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• 2006

Since the columns with flexure-shear failure have lower ductility than those with flexural failure, shear capacity curve models shall be applied as well as flexural capacity curve in order to determine ultimate displacement for seismic design or performance evaluation. In this paper, a proposed modified shear capacity curve model is compared with the other models such as the CALTRANS model, Aschheim et al.'s model, and Priestley et al.'s model. Four shear capacity curve models are applied to the 4 full scale and 7 small scale circular bridge column test results and the accuracy of each model is discussed. It may not be fully adequate to drive a final decision from the application to the limited number of test results, however the proposed model provides the better prediction of failure mode and ultimate displacement than the other models for the selected column test results.

• Earthquakes and Structures
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• 제22권3호
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• pp.319-330
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• 2022

Retrofit of soft-story buildings due to seismic loads using Gap-Inclined-Brace (GIB) system is considered a new retrofit technique that aims to maintain both strength and stiffness of structure. In addition, it provides more ductility and less P-delta effect, and subsequently better performance is observed. In this paper, the effect of the eccentricity between GIB and the retrofitted column due to installation on the efficiency of the retrofitting system is studied. In addition, a modification in the determination method of GIB properties is introduced to reduce the eccentricity effect. Also, the effect of GIB system on the seismic response of mid-rise buildings with different heights considering soft-story at various heights has been studied. A numerical model is developed to study the impact of such system on the response of retrofitted soft-story buildings under the action of seismic loads. To achieve that goal, this model is used to perform a numerical investigation, by considering five case study scenarios represent several locations of soft-story of two mid-rise reinforced concrete buildings. At first, Non-linear static pushover analysis was carried out to develop the capacity curves for case studies. Then, Non-linear time history analyses using ten earthquake records with five peak ground accelerations is performed for each case study scenario before and after retrofitting with GIB. The results show that large GIB eccentricity reduce the ultimate lateral resistance and deformation capacity of the retrofitting system. Moreover, the higher the retrofitted building, the more deformation capacity is observed but without significant increase in ultimate lateral resistance.

• Structural Engineering and Mechanics
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• 제24권1호
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• pp.91-105
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• 2006

In this paper, post-earthquake capacity evaluation method of reinforced concrete buildings was studied. Substructure pseudo-dynamic test and static loading test of first story column in a four-story R/C building was carried out in order to investigate the validity of the evaluation method proposed in the Damage Assessment Guideline (JBDPA 2001). In pseudo-dynamic test, different levels of damage were induced in the specimens by pre-loading, and input levels of seismic motion, at which the specimens reached to the ultimate stage, were examined. From the experimental result, no significant difference in damage levels such as residual crack width between the specimens under static and pseudo-dynamic loading was found. It is shown that the seismic capacity reduction factors ${\eta}$ can provide a reasonable estimation of post-earthquake seismic capacity of R/C buildings suffered earthquakes.

• 한국지진공학회논문집
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• 제10권2호
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• pp.1-10
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• 2006

형상비가 상대적으로 작은 철근콘크리트 교각에 지진작용으로 인한 반복 횡하중이 작용하면 초기단계와 중간단계의 변위에서는 휨 거동을 보이다가 최종변위단계에서는 전단에 의해 파괴되는 휨-전단 거동을 보인다. 휨-전단 파괴거동을 보이는 교각은 휨 파괴거동을 보이는 교각에 비하여 연성능력이 저하되므로, 내진설계 또는 내진성능평가에서 극한변위를 해석적으로 결정하기 위해서는 휨성능곡선과 함께 전단성능곡선 모델을 적용하여야 한다. 본 논문에서는 원형교각에 대한 기존 모델을 수정한 전단성능곡선 모델을 제안하였고, CALTRANS 모델, Aschheim등의 모델, Priestley 등의 모델, 제안모델의 특징을 비교하였다. 또 국내에서 수행된 실물크기 기둥 실험체를 대상으로 전단성능곡선 모델을 평가하였다. 제한된 범위의 소수 실험결과에 대한 적용으로서 일반화하기는 어려울 것이지만, 실험결과와 비교 검토한 결과 제안모델이 파괴형태의 예측과 변위성능 예측의 정확도에서 매우 우수한 것으로 평가되었다.

• Geomechanics and Engineering
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• 제30권2호
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• pp.123-138
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• 2022

Present study computes the ultimate bearing capacity of an embedded strip footing situated on the rock slope subjected to seismic loading. Influences of embedment depth of strip footing, horizontal seismic acceleration coefficient, rock slope angle, Geological Strength Index, normalized uniaxial compressive strength of rock mass, disturbance factor, and Hoek-Brown material constant are studied in detail. To perform the analysis, the lower bound finite element limit analysis method in combination with the semidefinite programming is utilized. From the results of the present study, it can be found that the magnitude of the bearing capacity factor reduces quite substantially with an increment in the seismic loading. In addition, with the increment in slope angle, further reduction in the value of the bearing capacity factor is observed. On the other hand, with an increment in the embedment depth, an increment in the value of the bearing capacity factor is found. Stress contours are presented to describe the combined failure mechanism of the footing-rock slope system in the presence of static as well as seismic loadings for the different embedment depths.