• Title/Summary/Keyword: nonlinear deformation

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Porous Structures with Negative Poisson's Ratio using Pattern Transformation Triggered by Deformation (변형에 의한 패턴변화를 활용한 음의 포아송비 다공성 구조)

  • Oh, Myung-Hoon;Choi, Myung-Jin;Byun, Tauk;Cho, Seonho
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.30 no.4
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    • pp.275-282
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    • 2017
  • In this paper, using a pattern transformation triggered by deformation, we propose a porous structure that exhibits the characteristic of negative Poisson's ratio in both tension and compression. Due to the lack of torque for rotational motion of ligaments, the existing porous structure of circular holes shows positive Poisson's ratio under tension loading. Also, the porous structure of elliptic holes has a drawback of low durability due to stress concentration. Thus, we design curved ligaments to increase the rotational torque under tension and to alleviate the stress concentration such that strain energy is uniformly distributed in the whole structure. The developed structure possesses better stiffness and durability than the existing structures. It also exhibits the negative Poisson ratio in both compression and tension of 10% nominal strain. Through nonlinear finite element analysis, the performance of developed structure is compared with the existing structure of elliptic holes. The developed structure turns out to be significantly improved in terms of stiffness and durability.

STRESS DISTRIBUTION OF THREE NITI ROTARY FILES UNDER BENDING AND TORSIONAL CONDITIONS USING 3-DIMENSIONAL FINITE ELEMENT ANALYSIS (세가지 니켈 티타늄 파일의 휨과 비틀림 조건에서의 응력 분포에 관한 3차원 유한요소 연구)

  • Kim, Tae-Oh;Lee, Chan-Joo;Kim, Byung-Min;Park, Jeong-Kil;Hur, Bock;Kim, Hyeon-Cheol
    • Restorative Dentistry and Endodontics
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    • v.33 no.4
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    • pp.323-331
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    • 2008
  • Flexibility and fracture properties determine the performance of NiTi rotary instruments. The purpose of this study was to evaluate how geometrical differences between three NiTi instruments affect the deformation and stress distributions under bending and torsional conditions using finite element analysis. Three NiTi files (ProFile .06 / #30, F3 of ProTaper and ProTaper Universal) were scanned using a Micro-CT. The obtained structural geometries were meshed with linear, eight-noded hexahedral elements. The mechanical behavior (deformation and von Mises equivalent stress) of the three endodontic instruments were analyzed under four bending and rotational conditions using ABAQUS finite element analysis software. The nonlinear mechanical behavior of the NiTi was taken into account. The U-shaped cross sectional geometry of ProFile showed the highest flexibility of the three file models. The ProTaper, which has a convex triangular cross-section, was the most stiff file model. For the same deflection, the ProTaper required more force to reach the same deflection as the other models, and needed more torque than other models for the same amount of rotation. The highest von Mises stress value was found at the groove area in the cross-section of the ProTaper Universal. Under torsion, all files showed highest stresses at their groove area. The ProFile showed highest von Mises stress value under the same torsional moment while the ProTaper Universal showed the highest value under same rotational angle.

Evaluation of Reinforced Concrete Beam's Inelastic Behavior Characteristics using Beam-column Fiber Finite Element considering Shear Deformation Effect (전단변형 효과가 고려된 보-기둥 섬유유한요소를 이용한 철근콘크리트 보의 비탄성 거동특성 평가)

  • Cheon, Ju-Hyun;Hwang, Cheol-Seong;Park, Kwang-Min;Shin, Hyun-Mock
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.21 no.3
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    • pp.130-137
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    • 2017
  • The purpose of this study is to provide a reasonable analytical method for the reinforced concrete beams which shows failure mode of shear and flexure-shear by proposing a modified formulation to consider the effect of shear deformation on the beam-column fiber element based on the flexibility method and a new constitutive law of inelastic shear response history for the section. A total of 6 specimens of reinforced concrete beams which is designed to cause shear failure before yielding longitudinal reinforcement to investigate the influence of the main experimental variables on the shear behavior characteristics and the analysis was performed by using a non-linear finite element analysis program (RCAHEST) applying the newly modified constitutive equation by the authors. The failure mode and the overall behavior characteristics until fracture are predicted appropriately for all specimens and the results are expected to be useful enough for the 3 - D analysis to carry out reliable results of large-scale and complicated structures in the future.

Energy Dissipation Capacity of the T-stub Fastened by SMA bars (SMA 강봉으로 체결된 T-stub의 에너지소산능력)

  • Yang, Jae Guen;Baek, Min Chang;Lee, Jae Yun;Lee, Hyung Dong
    • Journal of Korean Society of Steel Construction
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    • v.26 no.3
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    • pp.231-240
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    • 2014
  • The T-stub subjected to an axial tensile force shows various behavior characteristics according to the changes in the diameter and tightening force of the fastener, the geometric shape of the T-stub, and the material properties of the T-stub and fastener. Due to the influence of these changes, the T-stub shows three failure modes: plastic failure after the flexural yielding of the T-stub flange, flexural yielding of the T-stub fillet, and fracture of the fastener. In general, a T-stub with a thin flange and where the gauge distance of the fastener is long has a larger energy dissipation capacity than a T-stub with a thick flange and where the gauge distance of the fastener is short, due to the plastic deformation after flexural yielding. In this study, three-dimensional nonlinear finite element analysis was carried out to determine the effect of the fastener used for fastening the T-stub on the energy dissipation capacity of the T-stub. For the fastener of the T-stub analysis model, F10T-M20 high-tension bolts and ${\varnothing}19.05-mm$ (3/4-inch) SMA bars were modeled, and the geometric shape of the T-stub was selected to represent the flexural yielding of the T-stub fillet and the axial tensile failure of the fastener.

Surgical Planning in Deformity Correction Osteotomies using Forward Kinematics and Inverse Kinematics (정기구학 및 역기구학을이용한하지 교정절골술 계획 생성)

  • Jeong, Jiwon;Lee, Seung Yeol;Youn, Kibeom;Park, Moon Seok;Lee, Jehee
    • Journal of the Korea Computer Graphics Society
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    • v.20 no.1
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    • pp.1-11
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    • 2014
  • Patients with cerebral palsy or arthritis have deformities in lower limb which cause unstable gait or posture and pains. Surgeons perform a deformity correction osteotomy with surgical plan. But sometimes they find the unexpected angular or rotational deformation after surgery. The problems are that there is no method to predict the result of a surgical plan and also there are so many factors to must consider in surgical planning step such as clinical measurements, rotation angle, wedge angle, morphology of lower limb, etc. This paper presents new methods for planning the deformity correction osteotomy efficiently. There are two approaches based on the 3D mesh model and the accurate assessment of the patient's lower limb. One is the manual pre-simulation of surgery using forward kinematics. And the other is the automatic surgical planning using inverse kinematics and nonlinear optimization. Using these methods, we can predict and verify the results of various surgical treatments and also we can find a more effective surgical plan easily compared to conventional methods.

Performance-based wind design of tall buildings: concepts, frameworks, and opportunities

  • Bezabeh, Matiyas A.;Bitsuamlak, Girma T.;Tesfamariam, Solomon
    • Wind and Structures
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    • v.31 no.2
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    • pp.103-142
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    • 2020
  • One of the next frontiers in structural wind engineering is the design of tall buildings using performance-based approaches. Currently, tall buildings are being designed using provisions in the building codes and standards to meet an acceptable level of public safety and serviceability. However, recent studies in wind and earthquake engineering have highlighted the conceptual and practical limitations of the code-oriented design methods. Performance-based wind design (PBWD) is the logical extension of the current wind design approaches to overcome these limitations. Towards the development of PBWD, in this paper, we systematically review the advances made in this field, highlight the research gaps, and provide a basis for future research. Initially, the anatomy of the Wind Loading Chain is presented, in which emphasis was given to the early works of Alan G. Davenport. Next, the current state of practice to design tall buildings for wind load is presented, and its limitations are highlighted. Following this, we critically review the state of development of PBWD. Our review on PBWD covers the existing design frameworks and studies conducted on the nonlinear response of structures under wind loads. Thereafter, to provide a basis for future research, the nonlinear response of simple yielding systems under long-duration turbulent wind loads is studied in two phases. The first phase investigates the issue of damage accumulation in conventional structural systems characterized by elastic-plastic, bilinear, pinching, degrading, and deteriorating hysteretic models. The second phase introduces methods to develop new performance objectives for PBWD based on joint peak and residual deformation demands. In this context, the utility of multi-variate demand modeling using copulas and kernel density estimation techniques is presented. This paper also presents joined fragility curves based on the results of incremental dynamic analysis. Subsequently, the efficiency of tuned mass dampers and self-centering systems in controlling the accumulation of damage in wind-excited structural systems are investigated. The role and the need for explicit modeling of uncertainties in PBWD are also discussed with a case study example. Lastly, two unified PBWD frameworks are proposed by adapting and revisiting the Wind Loading Chain. This paper concludes with a summary and a proposal for future research.

Composite Behavior and Shear Strength of DH-Beams with Steel Deck Plates (무해체 데크플레이트 철판을 사용한 DH-beam의 합성거동과 전단강도)

  • Moon, Jeong-Ho;Oh, Young-Hun
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.20 no.3
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    • pp.1-9
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    • 2016
  • The purpose of this study is to examine the shear strength and structural performance of DH-Beams. The DH-Beam construction method uses thin steel plates as form-works and structural elements. Steel plates and rebars for DH-Beams were prefabricated at factory and then erected before casting concrete at construction sites. In this study, the contribution of steel plates to the shear strength of DH-Beam was evaluated since the plates were expected to work as reinforcements. Five test specimens were made for experimental and analytical studies. They consisted of two DH-Beams for the positive loading test and two DH-Beams for the negative loading test and a RC beam for the comparison purpose. Test results on DH-Beams were compared with design equations and the RC beam test result. It was proven that DH-Beams demonstrated the good shear behavior showing sufficient strengths and deformation capacities. Nonlinear analyses with test specimens were also used to evaluate the contribution of DH plates to strengths. Analytical models included various cases such as beams with lateral plates only or beams without any plates. These analyses also showed that steel plates can contribute to the enhancement of shear strength of DH-Beams. Based on experimental and analytical studies, it was concluded that steel plates of DH-Beams can be used as good shear reinforcements.

A Nonlinear Structural Analysis for a Composite Structure Composed of Spent Nuclear Fuel Disposal Canister and Bentonite Buffer: Symmetric Rock Movement (고준위폐기물 처분용기와 벤토나이트 버퍼로 이루어진 복합구조물에 대한 비선형 구조해석: 대칭 암반 전단력)

  • 권영주;최석호;최종원
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.16 no.4
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    • pp.369-376
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    • 2003
  • In this paper, a nonlinear structural analysis for the composite structure composed of the spent nuclear fuel disposal canister and the 50㎝ thick bentonite buffer is carried out to predict the collapse of the canister while the horizontal symmetric sudden rock movement of 10㎝ is applied on the composite structure. This sudden rock movement is anticipated by the earthquake etc. at a deep underground. Elastoplastic material model is adopted. Drucket-Prager yield criterion is used for the material yield prediction of the bentonite buffer and von-Mises yield criterion is used for the material yield prediction of the canister(cast iron, copper). Analysis results show that even though very large deformations occur beyond the yield point in the bentonite buffet, the canister structure still endures elastic small strains and stresses below the yield strength. Hence, the 50㎝ thick bentonite buffet can protect the canister safely against the 10㎝ sudden rock movement by earthquake etc.. Analysis results also show that bending deformations occur in the canister structure due to the shear deformation of the bentonite buffer.

p-Version Finite Element Analysis of Composite Laminated Plates with Geometric and Material Nonlinearities (기하 및 재료비선형을 갖는 적층평판의 p-Version 유한요소해석)

  • 홍종현;박진환;우광성
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.15 no.3
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    • pp.491-499
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    • 2002
  • A p-version finite element model based on degenerate shell element is proposed tot the analysis of orthotropic laminated plates. In the nonlinear formulation of the model, the total Lagrangian formulation is adopted with large deflection and moderate rotation being accounted tot in the sense of yon Karman hypothesis. The material model is based on the Huber-Mises yield criterion and Prandtl-Reuss flow rule in accordance with the theory of strain hardening yield function, which is generalized lot anisotropic materials by introducing the parameters of anisotropy. The model is also based on extension of equivalent-single layer laminate theory(ESL theory) with shear deformation, leading to continuous shear strain at the interface of two layers. The integrals of Legendre polynomials are used for shape functions with p-level varying from 1 to 10. Gauss-Lobatto numerical quadrature is used to calculate the stresses at the nodal points instead of Gauss points. The validity of the proposed P-version finite element model is demonstrated through several comparative points of iew in terms of ultimate load, convergence characteristics, nonlinear effect, and shape of plastic tone.

Swelling behavior Simulation Study of KJ-II Bentonite Buffer Blocks under Various Experimental Conditions (다양한 실험조건에 따른 경주 벤토나이트 완충재 블록의 팽윤 거동 해석)

  • Lee, Deuk-Hwan;Go, Gyu-Hyun;Lee, Gi-Jun;Yoon, Seok
    • Journal of the Korean Geotechnical Society
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    • v.40 no.2
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    • pp.29-40
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    • 2024
  • This study aimed to evaluate the swelling behavior characteristics of KJ-II buffer blocks by performing numerical analysis of swelling pressure measurement experiments using the nonlinear elasticity model of COMSOL Multiphysics. The analysis was conducted under boundary conditions that included isotropic constraints and water injection pressure, mirroring the experimental settings. Validation of the numerical model was achieved by comparing its outputs with experimental results. The validated model was then used to simulate swelling deformations under unconfined conditions and to analyze swelling pressure as influenced by dry density and the geometric shape of the buffer material. The results accurately represented the swelling deformation observed during the saturation process and demonstrated that swelling pressure increases with higher dry density. Moreover, simulations concerning the geometric shape of the buffer material indicated a markedly faster rate of pressure increase in U-shaped samples compared to cylindrical ones. Analysis suggested that stress manifested preemptively near the internal edges of U-shaped samples during saturation. To enhance the simulation's fidelity to actual buffer material behavior, further refinement of the analysis model using a nonlinear elasticity model is recommended.