• Title, Summary, Keyword: lateral stiffness

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Stiffness Reduction Factor for Flat-Plate Structures under Combined Load (조합하중을 받는 무량판 구조의 강성 감소 계수에 관한 고찰)

  • 송진규;최정욱;윤정배
    • Proceedings of the Earthquake Engineering Society of Korea Conference
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    • pp.302-310
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    • 2003
  • Cracking of slabs will be caused by applied load and volume changes during the life of a structure and thus it reduces flexural stiffness of slabs. The effect of slab cracking must be considered for appropriate modeling of the flexural stiffness for frame members used in structural analysis. Analytical and experimental study was undertaken to estimate the stiffness reduction of slabs. In the analytical approach, the trend of slab stiffness reduction related to gravity and lateral loads is found and the stiffness reduction factor ranged from a half to a quarter in ACI building code is reasonable when defining range. Analyzing results of the test by Hwang and Moehle for 0.5% drift show that the differences of rotational stiffness on the connection types is found and good results of lateral stiffness using the value of one-third is obtained.

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Storey-based stability analysis of multi-storey unbraced frames

  • Liu, Y.;Xu, L.
    • Structural Engineering and Mechanics
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    • v.19 no.6
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    • pp.679-705
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    • 2005
  • This paper presents a practical method to evaluate the effective length factors for columns in multi-storey unbraced frames based on the concept of storey-based elastic buckling by means of decomposing a multi-storey frame into a series of single-storey partially-restrained (PR) frames. The lateral stiffness of the multi-storey unbraced frame is derived and expressed as the product of the lateral stiffness of each storey. Thus, the stability analysis for the multi-storey frame is conducted by investigating the lateral stability of each individual storey, which is facilitated through decomposing the multi-storey frame into a series of single-storey PR frames and applying the storey-based stability analysis proposed by the authors (Xu and Liu 2002) for each single-storey PR frame. Prior to introducing decomposition approaches, the end rotational stiffness of an axially load column is derived and rotational stiffness interaction between the upper and lower columns is investigated. Three decomposition approaches, characterized by means of distributing beam-to-column rotational-restraining stiffness between the upper and lower columns, are proposed. The procedure of calculating storey-based column effective length factors is presented. Numerical examples are then given to illustrate the effectiveness of the proposed procedure.

Stiffness Reduction Factor for Post-Tensioned Flat Plate Slabs under Lateral Loads (횡하중하의 포스트 텐션 플랫 플레이트 해석을 위한 강성감소계수)

  • Park, Young-Mi;Park, Jin-Ah;Han, Sang-Whan
    • Journal of the Korea Concrete Institute
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    • v.21 no.5
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    • pp.661-668
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    • 2009
  • Effective beam width model(EBWM) has been used for analysis of post-tensioned(PT) flat plate slab frames under lateral loads. The accuracy of this model in predicting lateral drifts and unbalanced moments strongly depends on the estimated effective stiffness of PT flat plate slabs. As moments on the slab due to lateral loads increases, cracks occur which leads to stiffness reduction in slabs. For analyzing PT flat plate slab structure under lateral loads with good precision, reduction in slab stiffness has to be accurately estimated for EBWM. For this purpose, this study collected test results of PT flat plate system conducted by former researches. And this study reduced the width of slab so that the stiffness of the EBWM converged into the lateral stiffness of each test specimens by trial and error. By conducting nonlinear regression analysis using the stiffness ratio of the reduced width of slab to the effective width of EBWM with respect to the level of slab moments, an equation for calculating stiffness reduction factor for slab is proposed. For verifying the accuracy of the proposed equation, this study compared with the test result of the PT flat plate frame. It is shown that the EBWM with the proposed equation predicts the actual stiffness of the PT specimen which varied according to the level of applied moment.

The Effect of the flexural stiffness of Floor Slabs on The Seismic Response of Multi-story Building Structures (바닥판의 휨강성이 고층건물의 지진거동에 미치는 영향)

  • 김현수
    • Proceedings of the Earthquake Engineering Society of Korea Conference
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    • pp.170-177
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    • 2000
  • Recently many high-rise apartment buildings are constructed using the box system which is composed only of concrete walls and slabs. Commercial softwares such as ETABS used for the analysis of high-rise apartment buildings are employing the rigid diaphragm assumption for simplicity in the analysis procedure. In general the flexural stiffness of floor slabs are ignored in the analysis, This assumption may be reasonable for the estimation of seismic response of framed structures. But in the case of the box system used in the apartment buildings floor slabs has major effects on the lateral stiffness of the structure. So if the flexural stiffness of slabs in the box system is ignored the lateral stiffness may be significantly underestimated, For these reasons it is recommended to use plate elements to represent the floor slabs. In the study A typical frame structure and a box system structure are chosen as the example structure. When a 20 story frame structure is subjected to the static lateral loads the displacements of the roof are 15.33cm and 17.52cm for the cases with and without the flexural stiffness of the floor slabs. And in case of box system the roof displacement was reduced from 16.18cm to 8.61cm The model without the flexural stiffness of floor slabs turned out to elongate the natural periods of vibration accordingly.

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A Study on Characteristics of PRAT and Cornering due to the Belt Angle of Tire by the FEM (FEM을 이용한 타이어의 벨트각도에 따른 PRAT 및 코너링 특성 연구)

  • Sung, Ki-Deug;Kim, Seong-Rae;Kim, Ki-Hyun;Kim, Sun-Joo;Cho, Choon-Tack
    • Journal of the Korean Society for Precision Engineering
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    • v.23 no.2
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    • pp.104-112
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    • 2006
  • The influence of tire belt angle on the Plysteer Residual Aligning Torque(PRAT) and the cornering stiffness by the FEM has been studied. The PRAT is a performance factor of the tire about vehicle pull, and the cornering stiffness has relation to vehicle steering response of outdoor test. To validate FE model for analysis, simulation data for both the static stiffness(vertical, lateral) and the PRAT have been compared with the experimental data. In addition to the characteristics of the PRAT and the cornering stiffness due to the tire belt angle, rolling and cornering contact characteristics have been studied. The tendency of the PRAT and the cornering stiffness due to the belt angle can be used as a guide line for the tire design in relation to vehicle pull and vehicle steering response.

A Study on the Lateral Vibration Reduction of the High-speed Electric Multiple Unit (동력분산형 고속열차의 횡방향 진동저감에 관한 연구)

  • Jeon, Chang-Sung;Park, Joon-Hyuk;Kim, Sang-Soo;Kim, Seog-Won
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.20 no.12
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    • pp.797-803
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    • 2019
  • This study was carried out to reduce the lateral vibration of high-speed electric multiple units. In the study, the high-speed electric multiple unit prototype (HEMU-430X) has a high lateral vibration at low equivalent conicity regardless of the wheel profiles (XP55, GV40, S1002). As wheel wear progresses and the equivalent conicity increases, the lateral vibration tends to decrease. The reason is that a combination of the suspension characteristics causes the body and bogie to resonate at a frequency of 1.4 Hz when the equivalent conicity is low, resulting in body hunting. An investigation of the lateral vibration of overseas high-speed trains showed that a decrease in the hydraulic stiffness of the yaw damper could improve the vibration. The series stiffness of the yaw damper is a combination of the hydraulic stiffness and elastic joint. In this study, an attempt was made to improve the lateral vibration by lowering the stiffness of the elastic joint. The series stiffness of the adjusted yaw damper was approximately 60% compared to the original one. The on track test results showed improvement in the lateral vibration for both running directions. The vibration reduction method of this study can be used for EMU-250 and EMU-320 in future commercial operations.

Lateral Behavior in Outrigger System of Tall Building Considering Floor Diaphragm (바닥 격막을 고려한 초고층 아웃리거 구조시스템의 수평거동)

  • Kim, Hyong-Kee
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.22 no.6
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    • pp.45-52
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    • 2018
  • The paper aimed to find out the lateral behavior of outrigger system in high-rise building considering floor diaphragm. To achieve this goal, a structural schematic design of 80 stories building was conducted by utilizing MIDAS-Gen. In this research, the key parameters of the structure analysis were the outrigger location in plan, the slab stiffness, the outrigger stiffness and the kind of diaphragm. For the purpose of this study, we analyzed and studied the lateral displacement in top floor, the story drift and the stress in slab. The research results indicated that the outrigger location in plan, the slab stiffness, the outrigger stiffness and the kind of diaphragm had an effect on lateral behavior in outrigger system of tall building. And the results of this analysis research can provided the assistance in getting the basic data of structure design for looking for the lateral behavior of outrigger system in the high-rise building.

Prediction of the Ratios of Increase in Lateral Stiffness for Preliminary Structural Design of Tall Buildings (초고층건물의 초기 구조설계를 위한 횡강성 증가율 예측)

  • Jung, Jong-Hyun
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.20 no.4
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    • pp.453-462
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    • 2007
  • The purpose of this study is to predict the ratios of increase in lateral stiffness for preliminary structural design of tall buildings. For this, the basic models of tall buildings with 60 stories are generated. The basic models have typical floor plan of Box or T type. And the factors for increase in lateral stiffness are selected as follows; the addition of outriggers, increase in material strength, and increase in member size of core walls, outrigger columns, and outrigger walls. Then these factors are applied to the basic models and their effects are investigated using the results of structural analysis. Finally, based on the investigation, the ratios of increase in lateral stiffness for preliminary structural design of tall buildings are proposed and applied to examples of tall building for verification of the ratios.

Three dimensional analysis of reinforced concrete frames considering the cracking effect and geometric nonlinearity

  • Kara, Ilker Fatih;Dundar, Cengiz
    • Structural Engineering and Mechanics
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    • v.31 no.2
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    • pp.163-180
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    • 2009
  • In the design of tall reinforced concrete (R/C) buildings, the serviceability stiffness criteria in terms of maximum lateral displacement and inter-story drift must be satisfied to prevent large second-order P-delta effects. To accurately assess the lateral deflection and stiffness of tall R/C structures, cracked members in these structures need to be identified and their effective member flexural stiffness determined. In addition, the implementation of the geometric nonlinearity in the analysis can be significant for an accurate prediction of lateral deflection of the structure, particularly in the case of tall R/C building under lateral loading. It can therefore be important to consider the cracking effect together with the geometric nonlinearity in the analysis in order to obtain more accurate results. In the present study, a computer program based on the iterative procedure has been developed for the three dimensional analysis of reinforced concrete frames with cracked beam and column elements. Probability-based effective stiffness model is used for the effective flexural stiffness of a cracked member. In the analysis, the geometric nonlinearity due to the interaction of axial force and bending moment and the displacements of joints are also taken into account. The analytical procedure has been demonstrated through the application of R/C frame examples in which its accuracy and efficiency in comparison with experimental and other analytical results are verified. The effectiveness of the analytical procedure is also illustrated through a practical four story R/C frame example. The iterative procedure provides equally good and consistent prediction of lateral deflection and effective flexural member stiffness. The proposed analytical procedure is efficient from the viewpoints of computational effort and convergence rate.

Lateral Stiffness of Steel Moment Frames Having Dogbone Seismic Connection (독본(dogbone) 내진접합부를 갖는 철골 모멘트골조의 횡강성 평가)

  • 이철호
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.15 no.4
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    • pp.639-647
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    • 2002
  • A simplified analytical procedure is presented to estimate the reduction of elastic lateral stiffness of steel moment frames arising from the radius-cut dogbone weakening. With the original radius-cut dogbone shape, it is almost impossible or too complicated to integrate analytically the mathematical expressions encountered when applying the conjugate beam method to compute the beam deflection component. In this study, the problem is circumvented by replacing the original radius-cut dogbone with an equivalent dogbone of constant width. The equivalence between the two is established by imposing an equal dogbone elongation criterion. This approach is justified by using a calibrated finite clement analysis. Then, the elastic lateral deflection components from the column, panel zone, and beam are derived for a typical beam-column subassembly. The derived results can be used to evaluate the reduction of the frame lateral stiffness. Case studies conducted within some practical ranges of frame configurations show that the reduction in frame lateral stiffness due to the presence of dogbone cut is on the order of 1 to 2 percent and is reasonably negligible in practical sense.