• Earthquakes and Structures
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• 제7권3호
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• pp.295-315
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• 2014

This paper presents the results of an analytical study on seismic reliability of viscoelastically damped frame systems in comparison with that of conventional moment resisting frame systems. In order to exhibit the reliability of the frame systems with viscoelastic dampers, seismic reliability analyses were carried out for steel framed buildings, 5 and 12 storeys in height, designed as: (a) Case 1: Conventional moment resisting frame, (b) Case 2: Frame with viscoelastic dampers providing supplemental effective damping ratio of 10%, and (c) Case 3: Frame with viscoelastic dampers providing supplemental effective damping ratio of 20%. Nonlinear time history analyses were utilized to develop seismic fragility curves whilst monitoring various performance objectives. To obtain robust estimators of the seismic reliability, a database including 15 natural earthquake ground motion records with markedly different characteristics was employed in the fragility analysis. The results indicate that depending upon the supplemental effective damping ratio, frames designed with viscoelastic dampers have considerably lower annual probability of exceedance of performance limit states for structural components, showing up to a five-fold reduction in comparison to conventionally designed moment resisting frame system.

• 콘크리트학회논문집
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• 제17권5호
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• pp.673-678
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• 2005

ACI 318(1999) 규준에서는 모멘트골조를 특수모멘트골조, 중간모멘트골조, 보통모멘트골조의 3가지로 구분하고 있다. 이중 중 약 지진 지역에서는 대부분의 구조물이 보통모멘트골조로 설계되고 있다. 이러한 보통모멘트골조는 현행 규준에서 가장 엄격하지 않은 상세와 요구사항이 적용되는 골조 형식이다 본 연구는 중력하중으로만 설계되고 ACI 318(1999) 기준의 보통모멘트골조의 상세만을 가지는 3층의 사무소 건물의 내진 성능 평가를 그 목표로 한다 실험적 연구를 위하여 1/3 축소 모델을 제작하여 준정적 실험을 실시하였다. 보통모멘트골조의 전체적인 거동은 갑작스러운 강도의 저감 없이 안정적인 거동을 하였다 실험결과, 중력하중으로만 설계된 3층의 사무소건물은 UBC 1997 규준의 지진 지역 1, 2A, 2B에서의 요구하는 설계 밑면전단력보다 더 큰 횡력 저항 능력을 가지고 있는 것으로 나타났다.

• 한국자동차공학회논문집
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• 제12권3호
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• pp.91-100
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• 2004

This study presents the development of a new aluminum seat frame for the commercial bus. Back moment and seat belt anchorage analysis of the conventional steel seat frame was conducted as a base model. Effective aluminum section dimensions for aluminum pipe were calculated from equivalent stiffness and equivalent weight study. Back moment and seat belt anchorage strength with the developed aluminum seat frame were compared to those of the base model. Additionally, to pass the fatigue test, shape modification of side frame assembly was conducted. From this study we could reduce the weight of seat frame more than 5 kg. And the current analysis model and procedure can provide useful informations in designing a new commercial car seat and can reduce the overall design cost and time.

• Structural Engineering and Mechanics
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• 제27권6호
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• pp.671-682
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• 2007

The probability and the reliability-based seismic performance evaluation procedure proposed in the FEMA-355F was applied to a reinforced concrete moment frame building in this study. For the FEMA procedure, which was originally developed for steel moment frame structures, to be applied to other structural systems, the capacity should be re-defined and the factors reflecting the uncertainties related to capacity and demand need to be determined. To perform the evaluation procedure a prototype building was designed per IBC 2003, and inelastic dynamic analyses were conducted applying site-specific ground motions to determine the parameters for performance evaluation. According to the analysis results, distribution of the determined capacities turned out to be relatively smaller than that of the demands, which showed that the defined capacity was reasonable. It was also shown that the prototype building satisfied the target performance since the determined confidence levels exceeded the objectives for both local and global collapses.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2001년도 봄 학술발표회 논문집
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• pp.565-570
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• 2001

Base shear and roof drift relation was acquired from experiment of 3 story ordinary moment resisting frame which was designed using gravity loads. To evaluate the dynamic behavior of the frame, analytical model was generated from experimental result. Dynamic analysis was performed using the analytical model subjected to earthquake ground motions with 500, 1000, and 2400 years of return period. And capacity spectrum method was adopted to find the performance points of the frame. Both dynamic analysis and CSM showed that the performance of the frame meet the life safety objectives suggested by FEMA 273 and ATC 40.

• Earthquakes and Structures
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• 제15권3호
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• pp.243-251
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• 2018

The dynamic responses of a rocking wall-moment frame (RWMF) with a post-tensioned cable are investigated. The nonlinear equations of motions are developed, which can be categorized as a single-degree-of-freedom (SDOF) model. The model is validated through comparison of the rocking response of the rigid rocking wall (RRW) and displacement of the moment frame (MF) against that obtained from Finite Element analysis when subjected ground motion excitation. A comprehensive parametric analysis is carried out to determine the seismic performance factors of the RWMF systems under near-fault trigonometric pulse excitation. The horizontal displacement of the RWMF system is compared with that of MF structures without RRW, revealing the damping effect of the RRW. Frame displacement spectra excited by trigonometric pulses and recorded earthquake ground motions are constructed. The effects of pulse type, mass ratio, frame stiffness, and wall slenderness variations on the displacement spectra are presented. The paper shows that the coupling with a RRW has mixed results on suppressing the maximum displacement response of the frame.

• Advances in concrete construction
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• 제13권4호
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• pp.339-347
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• 2022

Retrofitting in reinforced concrete structures has been one of the most important research topics in recent years. There are several methods for retrofitting RC moment-resisting frames. the most important of which is the use of steel bracing systems with yielding dampers. With a proper design of yielding dampers, the stiffness of RC frame systems can be increased to the required extent so that the ductility of the structure is not significantly reduced. In the present study, two experimental samples of a one-third scale RC moment-resisting frame were loaded in the laboratory. In these experiments, the retrofitting effect of RC frames was investigated using Non-uniform Slit Dampers (NSDs). Based on the experimental results of the samples, seismic parameters, i.e., stiffness, ductility, ultimate strength, strength reduction coefficient, and energy dissipation capacity, were compared. The results demonstrated that the retrofitted frame had very significant growth in terms of stiffness, ultimate strength, and energy dissipation capacity. Although the strength reduction factor and ductility decreased in the retrofitted sample. In general, the behavior of the frame with NSDs was evaluated better than the bare frame.

• 한국건축시공학회지
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• 제15권6호
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• pp.569-577
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• 2015

구조물 내진설계에 대한 개념이 사양중심설계에서 성능기반설계로 변화하고 있다. 구조물 목표성능을 직접 부여하여 설계하는 성능기반설계를 위해서는 구조물 실제 거동을 정확히 예측하기 위한 비탄성 구조해석이 필요하다. 이에 본 연구에서는 KBC2009 기준으로 설계한 5층 철근콘크리트 모멘트-저항골조 시스템 구조물을 대상으로 푸쉬오버해석을 수행하여 내진성능을 평가한 후 직접공사비를 산출하여 경제성을 분석하였다. 분석 결과 보통 및 중간모멘트골조는 요구성능설계기준을 만족하며 직접공사비 또한 유사한 것으로 평가되었다. 하지만, 강 기둥-약 보 기준이 적용되는 특수모멘트골조는 요구성능설계기준을 만족하나 다른 골조시스템 보다 비경제적인 것으로 평가되었다. 따라서 IBC2012에서는 내진설계범주 D 중간모멘트골조 적용을 제한하고 있지만 5층 철근콘크리트 모멘트-저항골조 구조물의 경우, 특수모멘트골조 보다 보통 및 중간모멘트골조로 설계하는 것이 합리적이라고 판단된다.

• Steel and Composite Structures
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• 제28권2호
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• pp.139-147
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• 2018

Moment frames have considerable ductility against cyclic lateral loads and displacements; however, sometimes this feature causes the relative displacement to exceed the permissible limits. This issue can bring unfavorable hysteretic behavior on the frame due to the reduction in the stiffness and resistance against lateral loads. Most of common bracing systems usually control lateral displacements through increasing stiffness while result in decreasing the capacity for energy absorption. This has direct effect on hysteresis curves of moment frames. Therefore, a system that is capable of both having the capacity of energy absorption as well as controlling the displacements without a considerable increase in the stiffness is quite important. This paper investigates retrofitting of a single-storey steel moment frame using a delayed wire-rope bracing system equipped with the ductile middle steel plate. The steel plate is considered at the middle intersection of wire ropes, where it causes cables to be continuously in tension. This integrated system has the advantage of reducing considerable stiffness of the frame compared to cross bracing systems as a result of which it could also preserve the frame's energy absorption capacity. In this paper, FEM models of a delayed wire-rope bracing system equipped by steel plates with different geometries have been studied, validated, and compared with other researchers' laboratory test results.

• Structural Engineering and Mechanics
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• 제49권1호
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• pp.95-110
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• 2014

The study deals with physical modeling of space frame-pile foundation and soil system using finite element models. The superstructure frame is analyzed using complete three-dimensional finite element method where the component of the frame such as slab, beam and columns are descretized using 20 node isoparametric continuum elements. Initially, the frame is analyzed assuming the fixed column bases. Later the pile foundation is worked out separately wherein the simplified models of finite elements such as beam and plate element are used for pile and pile cap, respectively. The non-linear behaviour of soil mass is incorporated by idealizing the soil as non-linear springs using p-y curve along the lines similar to that by Georgiadis et al. (1992). For analysis of pile foundation, the non-linearity of soil via p-y curve approach is incorporated using the incremental approach. The interaction analysis is conducted for the parametric study. The non-linearity of soil is further incorporated using iterative approach, i.e., secant modulus approach, in the interaction analysis. The effect the various parameters of the pile foundation such as spacing in a group and configuration of the pile group is evaluated on the response of superstructure owing to non-linearity of the soil. The response included the displacement at the top of the frame and bending moment in columns. The non-linearity of soil increases the top displacement in the range of 7.8%-16.7%. However, its effect is found very marginal on the absolute maximum moment in columns. The hogging moment decreases by 0.005% while sagging moment increases by 0.02%.