• Title/Summary/Keyword: mass irregularity

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A study on the effects of vertical mass irregularity on seismic performance of tunnel-form structural system

  • Mohsenian, Vahid;Nikkhoo, Ali
    • Advances in concrete construction
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    • v.7 no.3
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    • pp.131-141
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    • 2019
  • Irregular distribution of mass in elevation is regarded as a structural irregularity by which the modes with high energy levels are excited and in addition, it can lead the structure to withstanding concentration of nonlinear deformations and consequently, suffer from unpredictable local or global damages. Accordingly, with respect to the lack of knowledge and insight towards the performance of concrete buildings making use of tunnel-form structural system in seismic events, it is of utmost significance to assess seismic vulnerability of such structures involved in vertical mass irregularity. To resolve such a crucial drawback, this papers aims to seismically assess vulnerability of RC tunnel-form buildings considering effects of irregular mass distribution. The results indicate that modal responses are not affected by building's height and patterns of mass distribution in elevation. Moreover, there was no considerable effect observed on the performance levels under DBE and MCE hazard scenarios within different patterns of irregular mass distribution. In conclusion, it appears that necessarily of vertical regularity for tunnel-form buildings, is somehow drastic and conservative at least for the buildings and irregularity patterns studied herein.

Seismic evaluation of vertically irregular building frames with stiffness, strength, combined-stiffness-and-strength and mass irregularities

  • Nezhad, Moosa Ebrahimi;Poursha, Mehdi
    • Earthquakes and Structures
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    • v.9 no.2
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    • pp.353-373
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    • 2015
  • In this paper, the effects of different types of irregularity along the height on the seismic responses of moment resisting frames are investigated using nonlinear dynamic analysis. Furthermore, the applicability of consecutive modal pushover (CMP) procedure for computing the seismic demands of vertically irregular frames is studied and the advantages and limitations of the procedure are elaborated. For this purpose, a special moment resisting steel frame of 10-storey height was selected as reference regular frame for which the effect of higher modes is important. Forty vertically irregular frames with stiffness, strength, combined-stiffness-and-strength and mass irregularities are created by applying two modification factors (MF=2 and 4) in four different locations along the height of the reference frame. Seismic demands of irregular frames are computed by using the nonlinear response history analysis (NL-RHA) and CMP procedure. Modal pushover analysis (MPA) method is also carried out for the sake of comparison. The effect of different types of irregularity along the height on the seismic demands of vertically irregular frames is investigated by studying the results obtained from the NL-RHA. To demonstrate the accuracy of the enhanced pushover analysis methods, the results derived from the CMP and MPA are compared with those obtained by benchmark solution, i.e., NL-RHA. The results show that the CMP and MPA methods can accurately compute the seismic demands of vertically irregular buildings. The methods may be, however, less accurate especially in estimating plastic hinge rotations for weak or weak-and-soft top and middle storeys of vertically irregular frames.

Identifying stiffness irregularity in buildings using fundamental lateral mode shape

  • Vijayanarayanan, A.R.;Goswami, Rupen;Murty, C.V.R.
    • Earthquakes and Structures
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    • v.12 no.4
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    • pp.437-448
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    • 2017
  • Soft or extreme soft storeys in multi-storied buildings cause localized damage (and even collapse) during strong earthquake shaking. The presence of such soft or extremely soft storey is identified through provisions of vertical stiffness irregularity in seismic design codes. Identification of the irregularity in a building requires estimation of lateral translational stiffness of each storey. Estimation of lateral translational stiffness can be an arduous task. A simple procedure is presented to estimate storey stiffness using only properties of fundamental lateral translational mode of oscillation (namely natural period and associated mode shape), which are readily available to designers at the end of analysis stage. In addition, simplified analytical expressions are provided towards identifying stiffness irregularity. Results of linear elastic time-history analyses indicate that the proposed procedure captures the irregularity in storey stiffness in both low- and mid-rise buildings.

Estimation of track irregularity using NARX neural network (NARX 신경망을 이용한 철도 궤도틀림 추정)

  • Kim, Man-Cheol;Choi, Bai-Sung;Kim, Yu-Hee;Shin, Soob-Ong
    • Proceedings of the KSR Conference
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    • 2011.10a
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    • pp.275-280
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    • 2011
  • Due to high-speed of trains, the track deformation increases rapidly and may lead to track irregularities causing the track stability problem. To secure the track stability, the continual inspection on track irregularities is required. The paper presents a methodology for identifying track irregularity using the NARX neural network considering non-linearity in the train structural system. A simulation study has been carried out to examine the proposed method. Acceleration time history data measured at a bogie were re-sampled to every 0.25m track irregularity. In the simulation study, two sets of measured data were simulated. The second data set was obtained by a train with 10% more mass than the one for the first data set. The first set of simulated data was used to train the series-parallel mode of NARX neural network. Then, the track irregularities at the second time period are identified by using the measured acceleration data. The closeness of the identified track irregularity to the actual one is evaluated by PSD and RMSE.

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Influence of track irregularity on train and track behaviours on high speed rail (차량고속주행시 차량 및 궤도거동에 미치는 궤도틀림의 영향)

  • 이진욱;양신추;홍진완
    • Proceedings of the KSR Conference
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    • 1998.05a
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    • pp.307-314
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    • 1998
  • In this paper, a numerical method for analyzing the interactions between train and track is presented. The effect of track irregularity on high speed running trains and track is examined by parametric studies. Two types of vertical track irregularity are considered. The first one is ideally assumed to a sine wave to investigate train and track behaviors with the change of its shape feasibly, The second one is artificially generated from PSD of track irregularity which was established from the measured data on real railways. In the track dynamic model, rail is considered to have a distributed mass and to be supported discretely at sleepers above ballast divided into three layers. Then, the contact between wheel and rail is modeled by a nonlinear Hertzian spring.

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Seismic Behavior of High-rise Steel Moment-resisting Frames with Vertical Mass Irregularity (수직질량 비정형이 존재하는 고층 강 모멘트-저항골조의 지진 거동)

  • Park, Byong-Jeong;Song, In-Hawn
    • Journal of the Earthquake Engineering Society of Korea
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    • v.8 no.1
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    • pp.1-15
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    • 2004
  • Dynamic analyses were carried out to study the seismic response of high-rise steel moment-resisting frames in sixteen story buildings. The frames are intentionally designed by three different design procedures; strength controlled design. strong column-weak beam controlled design. and drift controlled design. The seismic performances of the so-designed frames with vertical mass irregularities were discussed in view of drift ratio. plastic hinge rotation, hysteretic energy input and stress demand. A demand curve of hysteretic energy inputs was also presented with two earthquake levels in peak ground accelerations for a future design application.

Theoretical formulation for vehicle-bridge interaction analysis based on perturbation method

  • Tan, Yongchao;Cao, Liang;Li, Jiang
    • Structural Engineering and Mechanics
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    • v.82 no.2
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    • pp.191-204
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    • 2022
  • A three-mass vehicle model including one rigid mass and two unsprung masses is adopted to predict the vehicle-bridge interaction (VBI) and to establish the nonlinear coupled governing equations. To overcome the numerical instability and large computation problems concerning the vehicle-bridge system, the perturbation method is used to convert the nonlinear coupled governing equations into a set of linear uncoupled equations. Formulas for bridge's natural frequencies considering both the VBI and the dynamic responses of bridge and vehicle are proposed. Compared with the numerical results obtained by the Newmark-β method, the theoretical solutions for natural frequencies and dynamic responses are validated. The effects of the important factors of unsprung mass, vehicle damping, surface irregularity on the natural frequencies and dynamic responses of bridge and vehicle are discussed, based on the theoretical solutions.

A Study on the Types of the Organic-Form Design Expression Characteristics in the Interior Design (실내디자인에 나타난 유기적 형태 디자인의 표현특성 유형에 관한 연구 -2000년대 이후 인테리어디자인 잡지에 게재된 작품을 중심으로-)

  • Lee, Jong-Sook;Park, Hyun-Ok;Lee, Han-Na
    • Journal of The Korean Digital Architecture Interior Association
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    • v.5 no.1
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    • pp.17-23
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    • 2005
  • To begin with, this research arranged this concepts by analyzing paper a reference paper. So, the theory was arranged by approaching the ideal, formative and contemporary side. In order to type characteristics expression of organic design, after year 2000 printed in "Interiors" journal analyzed the contents based on interior works. 1. A type of metaphorical expression, order and the imitations of animals and plants. 2. A type of non liner, and dynamical balance and irregularity. 3. A type of mass of indeterminate form. 4. A type of fluidity by a curved line and a curved surface.

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Association between Awareness of Nutrition Labels and Menstrual Cycle Irregularity in Korean Women: The Fifth Korea National Health and Nutrition Examination Survey (2010~2012)

  • Yoo, Hae Young;Ryu, Eunjung;Kim, Ji-Su;Han, Kyung-do
    • Journal of Korean Academy of Nursing
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    • v.47 no.1
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    • pp.133-141
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    • 2017
  • Purpose: The aim of this study was to identify the relationship between awareness of nutrition labeling and menstrual cycle irregularity in women from a nationally representative sample of the Korean population. Methods: A cross-sectional analysis was performed using hierarchical multi-variable logistic regression analysis models. A total of 4,324 women aged 19~54 years from the 2010~2012 Korean National Health and Nutrition Examination Survey participated in the study. The participants were classified into three groups based on self-report responses to a questionnaire about their awareness of nutrition labels: Reading, Not-Reading, and Not-Knowing Groups. Results: The Reading, Not-Reading, and Not-Knowing Groups comprised 46.4%, 44.9%, and 8.7% of the participants, respectively, and 53.6% of the participants had never used nutrition labels. In the Not-Knowing Group, irregular menstrual cycles for more than 3 months were significantly more common than women with irregular menstrual cycles for up to 3 months and women with regular menstrual cycles. Women in the Not-Knowing Group were more likely to exhibit menstrual cycle irregularity (adjusted odds ratio: 1.63, 95% confidence interval: 1.10~2.41) compared to women in the Reading Group after adjusting for age, body mass index, smoking status, alcohol intake, exercise regularity, stress, depression, suicidal ideation, metabolic syndrome, age at menarche, parity, and use of oral contraceptives. Conclusion: No awareness of nutrition labeling appears to be associated with a higher prevalence of menstrual cycle irregularity in a nationally representative group of Korean women.

The Importance of Interface Irregularity between the Tumor and Brain Parenchyma in Differentiating between Typical and Atypical Meningiomas: Correlation with Pathology

  • Lee, Jeongmin;Lee, Yeon Soo;Ahn, Kook-Jin;Lee, Song;Jang, Jinhee;Choi, Hyun Seok;Jung, So-Lyung;Kim, Bum-soo;Jeun, Sinsoo;Hong, Yongkil
    • Investigative Magnetic Resonance Imaging
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    • v.20 no.3
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    • pp.158-166
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    • 2016
  • Purpose: To understand clinical significance of irregular interface between meningioma and adjacent brain parenchyma in predicting histological grading of tumor, focusing on brain parenchymal invasion. Materials and Methods: Pathologically confirmed 79 cases with meningiomas with pathological reports about the presence of parenchymal invasion were included. We defined the presence of interface irregularity as either spiculations or fuzzy margins between the tumor and brain parenchyma. We counted number of spiculations and measured ratio of fuzzy margin length to whole length of mass with consensus of two neuroradiologists. We classified the patients into Present group and Absent group, and the two groups were compared by using the Mann-Whitney U test. Statistical correlations between the presence of an interface irregularity and brain parenchymal invasion by the tumor as well as meningioma histological grade were tested with chi-square test. The optimal cutoff values of spiculation numbers and the ratio of fuzzy margins were determined. The sensitivity and specificity of number of spiculations, ratio of fuzzy margin and the presence of irregular interface as combined parameters for predicting the parenchymal invasion were calculated using ROC curve analysis. Results: Statistically significant differences were noted between the Present and Absent groups for number of spiculations and ratio of fuzzy margin (P = 0.038 and P = 0.028, respectively). The optimal cutoff value for number of spiculations (> 4.5 with 61.1% sensitivity and 68.9% specificity) and the ratio of fuzzy margin (> 0.24 with 66.7% sensitivity and 65.6% specificity) were determined. The sensitivity and specificity of interface irregularity as the combined parameters were 72% and 59%, respectively. The interface irregularity between tumor and brain parenchyma significantly correlated with not only brain parenchymal invasion (P = 0.001) and but also histological grade (P < 0.001). Conclusion: The interface irregularity between tumor and brain parenchyma in MRI can be a strong predictive factor for brain parenchymal invasion and high grade meningioma.