• Title/Summary/Keyword: lateral drift

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Pushover Analysis Considering Effects of Degradation of Shear Strength (전단강도 감소효과를 고려한 Pushover 해석)

  • Lee, Young-Wook
    • Proceedings of the Korea Concrete Institute Conference
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    • pp.514-517
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    • 2006
  • Nonseismic designed RC frame have a possibility of shear failure because of deficiencies of reinforcing details. To model the shear failure in numerical analysis, shear strength degradation models which include Moehle's and ATC 40 are compared and applied to push-over analysis. For numerical analysis, three storied building frame is selected and designed according to Korean Concrete Design Code(2003). From the numerical analysis, it is pointed out that there may be great difference in lateral drift capacity if a different shear strength model is used. And the capacity can be severely underestimated if the restraining model of plastic rotation of ATC 40 is used, compared to the use of shear spring for shear degradation.

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Application of the Direct Displacement Based Design Methodology for Different Types of RC Structural Systems

  • Malekpour, Saleh;Dashti, Farhad
    • International Journal of Concrete Structures and Materials
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    • v.7 no.2
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    • pp.135-153
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    • 2013
  • This study investigates the direct displacement based design (DDBD) approach for different types of reinforced concrete structural systems including single moment-resisting, dual wall-frame and dual steel-braced systems. In this methodology, the displacement profile is calculated and the equivalent single degree of freedom system is then modeled considering the damping characteristics of each member. Having calculated the effective period and secant stiffness of the structure, the base shear is obtained, based on which the design process can be carried out. For each system three frames are designed using DDBD approach. The frames are then analyzed using nonlinear time-history analysis with 7 earthquake accelerograms and the damage index is investigated through lateral drift profile of the models. Results of the analyses and comparison of the nonlinear time-history analysis results indicate efficiency of the DDBD approach for different reinforced concrete structural systems.

Study On Optimal Design Of Mega-Structure System For High-Rise Buildings (초고층 메가 구조시스템의 최적설계에 관한 연구)

  • Jung, Eun-Young;Park, Sung-Soo
    • Journal of the Architectural Institute of Korea Structure & Construction
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    • v.33 no.3
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    • pp.21-28
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    • 2017
  • According to these high-rise buildings under construction in Korea in recent years, core walls and mega structural system were introduced as a optimal structural system with a certain scale and plane form, what need to be done included the structural characteristics of this kind of system and the accurate results, and what's more, the study of simple optimization methods should also be investigated. In this paper, models of mega structural system were determined, Approximation concept of Stiffness-Based Optimal Design Technique based on optimal design technique of preceding research and displacement sensitivity analysis were formalized, lateral drift constraint equation was created, rate of change response of structures with the changing of design parameters was determined. The possibility of optimal selection and cross section calculation of mega structural members can be known through those processes.

An Experimental Study on the Structural Behavior of Concrete Columns Confined with Welded Reinforcement Grids (용접 띠철근 보강된 콘크리트 기둥의 역학적 거동에 관한 실험적 연구)

  • Choi, Chang-Sik;Saatcioglu, Murat
    • Magazine of the Korea Concrete Institute
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    • v.11 no.2
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    • pp.187-196
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    • 1999
  • An experimental investigation was conducted to study the structural behavior of concrete columns confined with welded grids. The full-scale columns with different volumetric ratio, spacing and arrangement of welded reinforcement grids were tested under simulated seismic loading. The columns were subjected to constant axial compression of approximately 20% or 40% of their capacities accompanied by incrementally increasing lateral deformation reversals. The results indicate that the welded reinforcement grid can be used effectively as confinement reinforcement provided that the steel used, have sufficient ductility and the welding process employed does not alter the strength and elongation characteristics of steel. The grids improved the structural performance of columns, which developed lateral drift ratios in excess of 3% with the spacing and volumetric ratio of transverse reinforcement similar to those required by the ACI 318-95 Building Code. Drift capacity further increased when grids with larger number of cells were used. Furthermore, the use of grids reduced congesting of reinforcement while the dimensional accuracy provided perfect support to longitudinal reinforcement.

Selection of Optimal Structural System for Complex-shaped Super-tall Building Structural Systems Using Parametric Design Technique (파라메트릭 기법을 이용한 비정형 초고층 건물의 최적 구조시스템 선정)

  • Kim, Yeong-Min;Kim, Chee-Kyeong;Choi, Hyun-Chul
    • Journal of the Architectural Institute of Korea Structure & Construction
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    • v.28 no.1
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    • pp.77-84
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    • 2012
  • This study suggests the methodology for selection of optimal complex-shaped super-tall building structural systems using parametric design technique. The presented methodology include parametric modeler related structural analysis software, so that, geometry models generated using parametric technique can be analyzed and evaluated automatically in a integrated system. In extracting optimal alternative, target conditions can be considered in parametric modeler, so that, modeling and optimization can be carried out in a one integrated system and the optimal alternative according to the change of target conditions can be extracted dynamically. The applicability of the presented parametric methodology was checked by applying this technique to the complex-shaped super-tall buildings. Three structural systems, such as diagrid, braced tube and outrigger system were chosen as basic structural system and here, twist angle and section thickness of main structural members was parameterized. The target conditions was set as minimum weight satisfying lateral drift criteria. As the application results, the optimal alternative satisfying target conditions can be extracted automatically, and this showed the applicability of the proposed methodology.

Validity of Plastic-Hinge Models Related to Design Equation for Special Boundary Element (특수 경계요소 설계식에 반영된 소성 힌지 모델의 타당성에 대한 평가)

  • Lee, Sang-Sup;Bae, Kyu-Woong
    • Journal of the Architectural Institute of Korea Structure & Construction
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    • v.28 no.9
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    • pp.83-90
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    • 2012
  • The purpose of this paper is to assess the validity of simplified plastic-hinge model which was a background of the displacement-based design equation of boundary elements in ACI318-99 provisions. The plastic-hinge models that could describe the relationship between the top displacement and the curvature at the base of the wall were investigated including Wallace2002 model, Wallace2004 model and Englekirk model. Wallace2002 model is a basis of the displacement-based design equation of boundary elements, but Wallace2004 model and Englekirk model are known for making a more accurate estimation. To evaluate accuracy of Wallace2002 model, the results for the top displacement and the neutral axis depth of wall computing from each model were compared. In the process, it was found that the aspect ratio has effects on the results, so the influence of aspect ratio on Wallace2002 model and Wallace2004 model was examined. Then, the proper aspect ratio range for which Wallace2002 and Wallace2004 could be valid was presented. These analyses show that Wallace2002 model has a lower level of accuracy at large aspect ratio and large lateral drift ratio.

Repair and Strengthening Methods for Concrete Structures using Sprayed Fiber Reinforced Polymers - Strengthening performance of Reinforced Concrete Shear Columns - (Sprayed FRP 공법에 의한 콘크리트 구조물의 보수.보강법 개발에 관한 연구 - 철근콘크리트 전단기둥의 보강성능 평가 -)

  • Lee, Kang-Seok;Byeon, In-Hee;Son, Young-Sun;Lee, Moon-Sung;Li, Cheng-Hao;Lee, Li-Hyung
    • Proceedings of the Korea Concrete Institute Conference
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    • pp.137-140
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    • 2006
  • In this study, a seismic performance of reinforced concrete columns strengthened by a sprayed fiber reinforced polymer (SFRP) is investigated. For this purpose, six column specimens approximately scaled into 2/3, are designed and tested under a constant axial load, 10% of the nominal axial strength of column, and pseudo-static reversed cyclic lateral loading system. Four specimens are strengthened by Sprayed FRP using different combinations of short fibers (carbon or glass fiber) and resins (epoxy or vinyl esther). For comparison, the test investigated in this study also includes a specimen strengthened using carbon fiber reinforced polymer (CFRP), and also a control specimen without strengthening. The results revealed that specimens strengthened using SFRP showed a improved structure behavior, compared to control specimen, in terms of strength, ductility, lateral drift capacity, and energy-absorbtion capacity. In addition, compared to the specimen strengthened using CFRP, Sprayed FRP-strengthened specimens reasonably showed a equivalent seismic performance.

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Experimental Investigation of The Shear Strengthening of Unreinforced Masonry Infilled RC Frames Using CFRP Sheet (CFRP Sheet를 이용한 철근콘크리트 프레임면내 조적벽체의 전단내력 평가에 관한 실험적 연구)

  • Lee, Young-Hak;Kim, Min-Sook;Byon, Eun-Hyuk;Kim, Hee-Cheul
    • Journal of the Earthquake Engineering Society of Korea
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    • v.14 no.1
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    • pp.63-70
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    • 2010
  • The purpose of this study is to investigate experimentally the behavior of unreinforced masonry RC frames strengthened by CFRP sheet under cyclic lateral loading. Four test specimens were constructed as one-story, one-bay, 1/2 scale unreinforced masonry infilled RC frames and differences in strength and stiffness were evaluated in specimens on which had been applied different retrofitting methods. Test results indicated that the CFRP sheets significantly increased the strength and stiffness of the specimens, and the specimens retrofitted in columns and masonry indicated the most adequate retrofitting methods.

Strength of Interior Post-Tensioned Flat Plate Slab-Column Connection based on Failure Mechanism (파괴 메커니즘을 고려한 내부 포스트텐션 플랫 플레이트 슬래브-기둥 접합부의 강도식 평가)

  • Kim, Min-Nam;Ha, Sang-Su;Lee, Li-Hyung
    • Proceedings of the Korea Concrete Institute Conference
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    • pp.126-129
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    • 2006
  • A bending moment $M_u$ transferred at slab-column connection is resisted at the slab critical section by flexure and shear. The ACI 318-05 Building Code(1) gives an empirical equation for the fraction ${\gamma}_{\upsilon}$ of the moment $M_u$ to be transferred by shear at the slab critical section at d/2 from the column face and also the effective wide(c+3h). The equation is based on tests of interior slab-column connections without shear reinforcement. In order to investigate the data eight test specimens were examined. The test shows that increased slab load substantially reduces both the unbalanced moment capacity and the lateral drift capacity of the connection. Especially, the specimens with the bottom reinforcement existence and nonexistence, appears remarkable differences. Studies also show that the code equation for ${\gamma}_{\upsilon}$ does not apply to all cases. The purpose of this study is to compare the test results with present ACI 318-05 Building Code provisions for design of slab-column connections and with the analysis of the experimental data for a new limitation of strength equation without shear reinforcement and bottom reinforcement.

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Occupant comfort evaluation and wind-induced serviceability design optimization of tall buildings

  • Huang, M.F.;Chan, C.M.;Kwok, Kenny C.S.
    • Wind and Structures
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    • v.14 no.6
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    • pp.559-582
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    • 2011
  • This paper presents an integrated wind-induced dynamic analysis and computer-based design optimization technique for minimizing the structural cost of general tall buildings subject to static and dynamic serviceability design criteria. Once the wind-induced dynamic response of a tall building structure is accurately determined and the optimal serviceability design problem is explicitly formulated, a rigorously derived Optimality Criteria (OC) method is to be developed to achieve the optimal distribution of element stiffness of the structural system satisfying the wind-induced drift and acceleration design constraints. The effectiveness and practicality of the optimal design technique are illustrated by a full-scale 60-story building with complex 3D mode shapes. Both peak resultant acceleration criteria and frequency dependent modal acceleration criteria are considered and their influences on the optimization results are highlighted. Results have shown that the use of various acceleration criteria has different implications in the habitability evaluations and subsequently different optimal design solutions. The computer based optimization technique provides a powerful tool for the lateral drift and occupant comfort design of tall building structures.