• Title/Summary/Keyword: perfect plasticity

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Inter-Rater and Intra-Rater Reliability of the Modified Ashworth Scale and the Modified Tardieu Scale: A Comparison Study (수정된 Ashworth 척도와 수정된 Tardieu 척도의 검사자간, 검사자내 신뢰도 비교 연구)

  • Choi, Yul-Jung;Lee, Jung-Ah;Shin, Hwa-Kyung
    • The Journal of Korean Physical Therapy
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    • v.22 no.4
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    • pp.29-33
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    • 2010
  • Purpose: The purpose of this study was to assess and compare the reliability of the Modified Tardieu Scale (MTS) with the Modified Ashworth Scale (MAS) in patients with hemiplegia. Methods: Two experienced physical therapists examined twenty six patients (17 male and 9 female) with an age range of 19-83 years (mean=51.9 SD=15.2). They assessed the elbow flexor/extensor muscle spasticity in the affected side. Interand intra-rater reliability of the MAS and the MTS were calculated using kappa statistics. Intraclass correlation coefficient (ICC) was calculated to determine the inter- and intra-rater reliability of the angle of muscle reactions (R2-R1). Results: The intra-rater reliability of the MAS (K=0.39-0.55) and MTS (K=0.33-0.55) was fair to moderate. The inter-rater reliability was significantly higheras measured with MTS (K=0.54-0.66) in comparison with MAS (K=0.52). Intra-rater reliability of R2-R1 was moderate to almost perfect (ICC=0.52-0.86), and inter-rater reliability was substantial (ICC=0.74-0.76). Conclusion: The MTS provides higher inter-rater reliability compared with the MAS in hemiplegia patient analysis, but intra-rater reliability of both scales was not significantly different. Thus further research is needed to examine not only reliability, but also validity of these measurement systems.

Foundation Analysis and Design Using CPT Results : Settlement Estimation of Shallow Foundation (CPT 결과를 이용한 기초해석 및 설계 : 얕은 기초의 침하량 산정)

  • 이준환;박동규
    • Journal of the Korean Geotechnical Society
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    • v.20 no.8
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    • pp.5-14
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    • 2004
  • The settlement of foundations under working load conditions is an important design consideration. Well-designed foundations induce stress-strain states in the soil that are neither in the linear elastic range nor in the range usually associated with perfect plasticity. Thus, in order to accurately predict working settlements, analyses that are more realistic than simple elastic analyses are required. The settlements of footings in sand are often estimated based on the results of in-situ tests, particularly the standard penetration test (SPT) and the cone penetration test (CPT). In this paper, we analyze the load-settlement response of vertically loaded footings placed in sands using both the finite element method with a non-linear stress-strain model and the conventional elastic approach. Based on these analyses, we propose a procedure for the estimation of footing settlement in sands based on CPT results.

New constitutive models for non linear analysis of high strength fibrous reinforced concrete slabs

  • Yaseen, Ahmed Asaad;Abdul-Razzak, Ayad A.
    • Structural Engineering and Mechanics
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    • v.82 no.1
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    • pp.121-131
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    • 2022
  • The main goal of this study is to prepare a program for analyzing High Strength Steel Fibrous Reinforced Concrete (HSSFRC) slabs and predict the response and strength of the slab instead of preparing a prototype and testing it in the laboratory. For this purpose, new equations are proposed to represent the material properties of High Strength Steel Fibrous Reinforced Concrete. The proposed equations obtained from performing regression analysis on many experimental results using statistical programs. The finite element method is adopted for non-linear analysis of the slabs. The eight-node "Serendipity element" (3 DoF) is chosen to represent the concrete. The layered approach is adopted for concrete elements and the steel reinforcement is represented by a smeared layer. The compression properties of the concrete are modeled by a work hardening plasticity approach and the yield condition is determined depending on the first two stress invariants. A tensile strength criterion is adopted in order to estimate the cracks propagation. many experimental results for testing slabs are compared with the numerical results of the present study and a good agreement is achieved regarding load-deflection curves and crack pattern. The response of the load deflection curve is slightly stiff at the beginning because the creep effect is not considered in this study and for assuming perfect bond between the steel reinforcement and the concrete, however, a great agreement is achieved between the ultimate load from the present study and experimental results. For the models of the tension stiffening and cracked shear modulus, the value of Bg and Bt (Where Bg and Bt are the curvature factor for the cracked shear modulus and tension stiffening models respectively) equal to 0.005 give good results compared with experimental result.

Tensile Strength Measurement on Compacted Sand-Bentonite Mixtures (다짐된 모래-벤토나이트 혼합토의 인장강도 측정)

  • Jung, Soo-Jung;Kim, Tae-Hyung;Kim, Chan-Kee
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.26 no.6C
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    • pp.377-384
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    • 2006
  • Theoretical and experimental study of the unconfined penetration (UP) test was conducted to suggest a new test method (referred to as IUP, Improved Unconfined Penetration) for determination of the tensile strength of compacted sand-bentonite mixtures. The tensile strength of compacted mixtures can be calculated from limit analysis based on the theory of perfect plasticity. The measurement errors in new test method were reduced by improving the UP device. Preliminary experiment results indicate that the tensile strength increases with increasing the disk size, loading rate and pH level. In addition, the disk diameter with 25.4 mm and the loading rate with 0.5%/min~1%/min are most suitable condition for the IUP test. The reliability of IPU test was verified by through the fact that good agreement between the IUP and conventional split tensile test results is observed.

Moment Resistance Performance Evaluation of Larch Glulam Joints using GFRP-reinforced Laminated Plate and GFRP Rod (GFRP 보강적층판 및 GFRP rod를 이용한 낙엽송 집성재 접합부의 모멘트저항 성능평가)

  • Jung, Hong-Ju;Song, Yo-Jin;Lee, In-Hwan;Hong, Soon-Il
    • Journal of the Korean Wood Science and Technology
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    • v.44 no.1
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    • pp.40-47
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    • 2016
  • Instead of metal connector generally used on the structural glued laminated timber rahmen joints, the GFRP reinforced laminated plates combining veneer and GFRP (Glass Fiber Reinforced Plastic) and bonded type GFRP rod were used as the connectors. As a result of moment resistance performance evaluation on the joint part applied with these connectors, the yield moment of specimen using the GFRP reinforced laminated plates and GFRP rod pin was measured 4 % lower in comparison to the specimen (Type-1) using the metal connectors, but the initial rotational stiffness was measured 29% higher. Also, the yield moment and rotational stiffness of the specimen using the GFRP-reinforced laminated plates and wood (Eucalyptus marginata) pin showed were measured 11% and 56% higher in comparison to the Type-1 specimen, showing the best performance. It was also confirmed through the failure shape and perfect elasto-plasticity analysis that it showed ductility behavior, not brittle fracture, from the shear resisting force by the pin and the bonding strength increased and the unification of member was carried out. On the other hand, in case of the specimen bonded with GFRP rod, it was impossible to measure the bonding performance or it was measured very low due to poor bonding.

Shear Friction Strength Model of Concrete considering Transverse Reinforcement and Axial Stresses (축응력 및 횡보강근을 고려한 콘크리트의 전단마찰내력 평가모델)

  • Hwnag, Yong-Ha;Yang, Keun-Hyeok
    • Journal of the Korea Concrete Institute
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    • v.28 no.2
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    • pp.167-176
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    • 2016
  • Shear friction strength model of concrete was proposed to explain the direct friction mechanism at the concrete interfaces intersecting two structural elements. The model was derived from a mechanism analysis based on the upper-bound theorem of concrete plasticity considering the effect of transverse reinforcement and applied axial loads on the shear strength at concrete interfaces. Concrete was modelled as a rigid-perfectly plastic material obeying modified Coulomb failure criteria. To allow the influence of concrete type and maximum aggregate size on the effectiveness strength of concrete, the stress-strain models proposed by Yang et al. and Hordijk were employed in compression and tension, respectively. From the conversion of these stress-strain models into rigidly perfect materials, the effectiveness factor for compression, ratio of effective tensile strength to compressive strength and angle of concrete friction were then mathematically generalized. The proposed shear friction strength model was compared with 91 push-off specimens compiled from the available literature. Unlike the existing equations or code equations, the proposed model possessed an application of diversity against various parameters. As a result, the mean and standard deviation of the ratios between experiments and predictions using the present model are 0.95 and 0.15, respectively, indicating a better accuracy and less variation than the other equations, regardless of concrete type, the amount of transverse reinforcement, and the magnitude of applied axial stresses.