• Title/Summary/Keyword: nonlinear failure

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Numerical Analysis of Load Carrying Capacity of RC Structures Based on Concrete Damage Model (콘크리트 손상 모델을 적용한 콘크리트 구조물 구조내력 해석)

  • Woo, Sang Kyun;Lee, Yun;Yi, Seong Tae
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.16 no.5
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    • pp.121-128
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    • 2012
  • In this paper, nonlinear analysis for reinforced concrete structure for power transmission line is performed by considering the characteristics of the failure, which are depend on loading conditions and concrete material models. On the numerical evaluation for the failure behavior, the finite element analysis is applied. For the concrete material model, microplane model based on concrete damage is introduced. However, to describe the crack bridging effect of long and short fiber of steel fiber reinforced concrete (SFRC), tensile softening model is suggested and applied for SFRC. An numerical results by finite element technique are compared with the experiment results for box culvert specimen. Comparing on the experimental and analytical results, validity and reliability of numerical analysis are investigated.

Seismic Performance of Square RC Column Confined with Spirals (나선철근으로 횡구속된 정사각형 RC 기둥의 내진성능)

  • Ko, Seong Hyun
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.16 no.5
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    • pp.88-97
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    • 2012
  • The objective of this research is to investigate the seismic performance and flexure-shear behavior of square reinforced concrete bridge piers with solid and hollow cross section. Test specimens were nonseismically designed with the aspect ratio 4.5 Two reinforced concrete columns were tested under constant axial load while subjected to lateral load reversals with increasing drift levels. Longitudinal steel ratio was 2.217 percent. The transverse reinforcement ratio As/($s{\cdot}h$), corresponding to 58 percent of the minimum lateral reinforcement required by Korean Bridge Design Specifications for seismic detailing, which represent existing columns not designed by the current seismic design specifications or designed by limited ductility concept. This study are to provide quantitative reference data for the limited ductility design concept and tendency for performance or damage assessment based on the performance levels such as cracking, yielding, collapse, etc. Failure behavior, ultimate displacement/drift ratio, displacement ductility, response modification factor, equivalent viscous damping ratio, residual deformation, effective stiffness, plastic hinge length, strain of reinforcements and nonlinear analysis are investigated and discussed in this paper.

A mechanical model of vehicle-slab track coupled system with differential subgrade settlement

  • Guo, Yu;Zhai, Wanming;Sun, Yu
    • Structural Engineering and Mechanics
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    • v.66 no.1
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    • pp.15-25
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    • 2018
  • Post-construction subgrade settlement especially differential settlement, has become a key issue in construction and operation of non-ballasted track on high-speed railway soil subgrade, which may also affect the dynamic performance of passing trains. To estimate the effect of differential subgrade settlement on the mechanical behaviors of the vehicle-slab track system, a detailed model considering nonlinear subgrade support and initial track state due to track self-weight is developed. Accordingly, analysis aiming at a typical high-speed vehicle coupled with a deteriorated slab track owing to differential subgrade settlement is carried out, in terms of two aspects: (i) determination of an initial mapping relationship between subgrade settlement and track deflections as well as contact state between track and subgrade based on a semi-analytical method; (ii) simulation of dynamic performance of the coupled system by employing a time integration approach. The investigation indicates that subgrade settlement results in additional track irregularity, and locally, the contact between the concrete track and the soil subgrade is prone to failure. Moreover, wheel-rail interaction is significantly exacerbated by the track degradation and abnormal responses occur as a result of the unsupported areas. Distributions of interlaminar contact forces in track system vary dramatically due to the combined effect of track deterioration and dynamic load. These may not only intensify the dynamic responses of the coupled system, but also have impacts on the long-term behavior of the track components.

Experimental and numerical study on large-curvature curved composite box girder under hogging moment

  • Zhu, Li;Wang, Jia J.;Zhao, Guan Y.;Huo, Xue J.;Li, Xuan
    • Steel and Composite Structures
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    • v.37 no.2
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    • pp.117-136
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    • 2020
  • Curved steel-concrete composite box girder has been widely adopted in urban overpasses and ramp bridges. In order to investigate its mechanical behavior under complicated and combined bending, shear and torsion load, two large-curvature composite box girders with interior angles of 25° and 45° were tested under static hogging moment. Based on the strain and deflection measurement on critical cross-sections during the static loading test, the failure mode, cracking behavior, load-displacement relationship, and strain distribution in the steel plate and rebar were investigated in detail. The test result showed the large-curvature composite box girders exhibited notable shear lag in the concrete slab and steel girder. Also, the constraint torsion and distortion effect caused the stress measured at the inner side of the composite beam to be notably higher than that of the outer side. The strain distribution in the steel web was approximately linear; therefore, the assumption that the plane section remains plane was approximately validated based on strain measurement at steel web. Furthermore, the full-process non-linear elaborate finite element (FE) models of the two specimens were developed based on commercial FE software MSC.MARC. The modeling scheme and constitutive model were illustrated in detail. Based on the comparison between the FE model and test results, the FE model effectively simulated the failure mode, the load-displacement curve, and the strain development of longitudinal rebar and steel girder with sufficient accuracy. The comparison between the FE model and the test result validated the accuracy of the developed FE model.

The Comparative Study of Software Optimal Release Time of Finite NHPP Model Considering Property of Nonlinear Intensity Function (비선형 강도함수 특성을 이용한 유한고장 NHPP모형에 근거한 소프트웨어 최적방출시기 비교 연구)

  • Kim, Kyung-Soo;Kim, Hee-Cheul
    • Journal of Digital Convergence
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    • v.11 no.9
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    • pp.159-166
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    • 2013
  • In this paper, make a study decision problem called an optimal release policies after testing a software system in development phase and transfer it to the user. When correcting or modifying the software, finite failure non-homogeneous Poisson process model, presented and propose release policies of the life distribution, half-logistic property model which used to an area of reliability because of various shape and scale parameter. In this paper, discuss optimal software release policies which minimize a total average software cost of development and maintenance under the constraint of satisfying a software reliability requirement. In a numerical example, the parameters estimation using maximum likelihood estimation of failure time data, make out estimating software optimal release time. Software release time is used as prior information, potential security damages should be reduced.

Evaluation of Ductility Factors for MDOF Systems in Special Steel Moment Resisting Frames (철골 연성 모멘트 골조에 대한 다자유도 시스템의 연성계수 평가)

  • Kang, Cheol-Kyu;Han, Young-Cheol
    • Journal of the Earthquake Engineering Society of Korea
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    • v.8 no.6 s.40
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    • pp.13-22
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    • 2004
  • Ductiluty factor has played an important role in seismic design as it is key component of response modification factor(R). In this stuty, ductility factors() are calculated by multiplying ductility factor for SDOF systems() and MDOF modification factors(). Ductility factors() for SDOF systems are computed from nonlinear dynamic analysis undergoing different level of displacement ductiluty demands and period when subjected to a large number of recorded earthquake ground motions. The MDOF modification factors() are proposed to account for the MDOF systems, based on previous studies. A total of 108 prototype steel frames are designed to investigate the ductility factors considering the number of stories(4, 8 and 16-stories), framing system(Perimeter Frames, PF and Distributed Frames, DF), failure mechanism(Strong-Column Weak-Beam, SCWB and Weak-Column Strong-Beam, WCSB), soil profiles(SA, SC and SE in UBC 1997) and seismic zone factors(Z=0.075, 0.2 and 0.4 in UBC 1997). It is shown that the number of stories, failure mechanisms (SCWB, WCSB), and soil profiles have great influence on the ductility factors, however, the structural system(Perimeter frames, Distributed frames), and seismic zones have no influence on the ductility factors.

Failure Study for Knee Joint Through 3D FE Modeling Based on MR Images (자기공명영상 기반 3차원 유한요소모델링을 통한 무릎관절의 파손평가)

  • Bae, Ji-Yong;Park, Jin-Hong;Song, Seong-Geun;Park, Sang-Jin;Jeon, In-Su;Song, Eun-Kyoo
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.22 no.6
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    • pp.533-539
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    • 2009
  • In this study, the femur, the tibia, the articular cartilage and the menisci are three dimensionally reconstructed using MR images of healthy knee joint in full extension of 26-year-old male. Three dimensional finite element model of the knee joint is fabricated on the reconstructed model. Also, the FE models of ligaments and tendons are attached on the biologically suitable position of the FE model. Bones, articular cartilages and menisci are considered as homogeneous, isotropic and linear elastic materials, and ligaments and tendons are modeled as truss element and nonlinear elastic springs. The numerical results show the contact pressure and the von Mises stress distribution in the soft tissues such as articular cartilages and menisci which can be regarded as important parameters to estimate the failure of the tissues and the pain of the patients.

A Damage Model for Predicting the Nonlinear Behavior of Rock (암석의 비선형 거동해석을 위한 손상모델 개발)

  • 장수호;이정인;이연규
    • Journal of the Korean Geotechnical Society
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    • v.18 no.5
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    • pp.83-97
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    • 2002
  • An experimental model which considers post-peak behaviors and pre-peak damage characteristics representing changes of elastic moduli in each damage level was developed. From experiments, some damage thresholds of rocks were determined, and regression analyses were carried out in order to represent changes of elastic moduli in each damage level as functions of confining pressure. In addition, it was intended to simulate post-peak behaviors with Hoek-Brown constants, $m_r\;and\;s_r$ for post-failure. The developed experimental model was implemented into $FLAC^{2D}$ by a FISH function. From results of parametric studies on Hoek-Brown constants for post-peak, it was revealed that uniaxial compressive strength more highly depends upon $s_r$, although it depends on both $m_r\;and\;s_r$. It was also shown that the post-peak slopes of stress-stain curves depend mainly on $m_r$. When the optimum models obtained from parametric studies were applied to numerical analysis, they predicted maximum strengths obtained from experiments and well simulated stiffness changes due to damage levels.

Failure Criteria of a 6-Inch Carbon Steel Pipe Elbow According to Deformation Angle Measurement Positions (변형각의 측정 위치에 따른 6인치 탄소강관엘보의 파괴 기준)

  • Yun, Da Woon;Jeon, Bub Gyu;Chang, Sung Jin;Park, Dong Uk;Kim, Sung Wan
    • Journal of the Earthquake Engineering Society of Korea
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    • v.26 no.1
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    • pp.13-22
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    • 2022
  • This study proposes a low-cycle fatigue life derived from measurement points on pipe elbows, which are components that are vulnerable to seismic load in the interface piping systems of nuclear power plants that use seismic isolation systems. In order to quantitatively define limit states regarding leakage, i.e., actual failure caused by low-cycle fatigue, in-plane cyclic loading tests were performed using a sine wave of constant amplitude. The test specimens consisted of SCH40 6-inch carbon steel pipe elbows and straight pipes, and an image processing method was used to measure the nonlinear behavior of the test specimens. The leakage lines caused by low-cycle fatigue and the low-cycle fatigue curves were compared and analyzed using the relationship between the relative deformation angles, which were measured based on each of the measurement points on the straight pipe, and the moment, which was measured at the center of the pipe elbow. Damage indices based on the combination of ductility and dissipation energy at each measurement point were used to quantitatively express the time at which leakage occurs due to through-wall cracking in the pipe elbow.

An algorithm for quantifying dynamic buckling and post-buckling behavior of delaminated FRP plates with a rectangular hole stiffened by smart (SMA) stitches

  • Soltanieh, Ghazaleh;Yam, Michael C.H.
    • Smart Structures and Systems
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    • v.28 no.6
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    • pp.745-760
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    • 2021
  • Dynamic buckling of structure is one of the failure modes that needs to be considered since it may result in catastrophic failure of the structure in a short period of time. For a thin fiber-reinforced polymer (FRP) plate under compression, buckling is an inherent hazard which will be intensified by the existence of defects like holes, cracks, and delamination. On the other hand, the growth of the delamination is another prime concern for thin FRP plates. In the current paper, reinforcing the plates against buckling is realized by using SMA wires in the form of stitches. A numerical framework is proposed to simulate the dynamic instability emphasizing the effect of the SMA stitches in suppressing delamination growth. The suggested algorithm is more accurate than the other methods when considering the transformation point of the SMA wires and the modeling of the cohesive zone using simple and yet reliable technique. The computational design of the method by producing the line by line orders leads to a simple algorithm for simulating the super-elastic behavior. The Lagoudas constitutive model of the SMA material is implemented in the form of user material subroutines (VUMAT). The normal bilinear spring model is used to reproduce the cohesive zone behavior. The nonlinear finite element formulation is programmed into FORTRAN using the Newmark-beta numerical time-integration approach. The obtained results are compared with the results obtained by the finite element method using ABAQUS/Explicit solver. The obtained results by the proposed algorithm and those by ABAQUS are in good agreement.