• Title/Summary/Keyword: Strain-based design

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Ductility-based seismic design of precast concrete large panel buildings

  • Astarlioglu, Serdar;Memari, Ali M.;Scanlon, Andrew
    • Structural Engineering and Mechanics
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    • v.10 no.4
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    • pp.405-426
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    • 2000
  • Two approximate methods based on mechanism analysis suitable for seismic assessment/design of structural concrete are reviewed. The methods involve use of equal energy concept or equal displacement concept along with appropriate patterns of inelastic deformations to relate structure's maximum lateral displacement to member and plastic deformations. One of these methods (Clough's method), defined here as a ductility-based approach, is examined in detail and a modification for its improvement is suggested. The modification is based on estimation of maximum inelastic displacement using inelastic design response spectra (IDRS) as an alternative to using equal energy concept. The IDRS for demand displacement ductilities are developed for a single degree of freedom model subjected to several accelerograms as functions of response modification factor (R), damping ratios, and strain hardening. The suggested revised methodology involves estimation of R as the ratio of elastic strength demand to code level demand, and determination of design base shear using $R_{design}{\leq}R$ and maximum displacement, determination of plastic displacement using IDRS and subsequent local plastic deformations. The methodology is demonstrated for the case of a 10-story precast wall panel building.

Analysis of implant strain value exerted using different screw tightening protocols in screw-retained 3-unit prostheses (3본 나사 유지형 임플란트 보철물의 고정 방식에 따른 임플란트 고정체 치경부에 발생하는 변형율 비교분석)

  • Kim, Sang-Beom;Lee, Du-Hyeong;Lee, Cheong-Hee
    • The Journal of Korean Academy of Prosthodontics
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    • v.58 no.4
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    • pp.321-327
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    • 2020
  • Purpose: The purpose of this study was to measure and compare the strain value exerted on the cervical area using different screw tightening protocols in implant-supported, screw-retained 3-unit prostheses. Materials and methods: Strain gauges were attached to four implants: two external and two internal. Thereafter, two study model were designed each type using acrylic resin. CAD-CAM was used to design hex and nonhex abutments for each group (EH, ENH, IH, and INH group) and Screw-cement-retained prostheses were also designed using a nonprecious base metal. Abutment was fixed with 10 Ncm torque, and the prosthesis was cemented. Screws were fixed with 30 Ncm torque using different three protocols. After 5 min, the strain gauge level was measured, and group analysis was performed (α=.05). Results: External group showed significantly lower strain values than internal group and the EH group showed significantly lower strain values than the ENH group (P<.05). There was no difference in strain value based on the types of screw tightening protocols in same group (P>.05). The IH group exhibited significantly higher strain values than the INH group and the IH group showed a significant difference in strain values based on the types of screw tightening protocols used (P<.05). Conclusion: There was no significant effect on the external type in the implant-supported, screw-retained prostheses. However, strain values were high in the internal type, and the types of screw tightening protocol significantly affected these implants.

Geometric Hermite Curves Based on Curvature Variation Minimization

  • Chi, Jing;Zhang, Caiming;Wu, Xiaoming
    • International Journal of CAD/CAM
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    • v.6 no.1
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    • pp.65-71
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    • 2006
  • Based on the smoothness criterion of minimum curvature variation of the curve, tangent angle constraints guaranteeing an optimized geometric Hermite (OGH) curve both mathematically and geometrically smooth is given, and new methods for constructing composite optimized geometric Hermite (COH) curves are presented in this paper. The comparison of the new methods with Yong and Cheng's methods based on strain energy minimization is included.

High Strain Rate Tensile Test of Composite Material for Automotive Front End Module Carrier (자동차 프론트엔드모률 캐리어용 경량 복합소재의 고속인장 시험)

  • Kang, Woo-Jong;Kim, Sung-Tae
    • Composites Research
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    • v.24 no.3
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    • pp.12-16
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    • 2011
  • High strain rate tensile tests were performed to measure the strain rate sensitivity of fiber reinforced composite material. The composite material was developed for the light weight design of an automotive FEM(front end module) carrier. Standard specimens for quasi-static tests of fiber reinforced composites can be found in ASTM D3039. However, in case of high strain rate tests, it was hard to find standard specimen shapes. In this study, three kinds of tensile specimens designed based on ASTM D638 were investigated to determined the adequate gauge width of tensile specimen for fiber reinforced composite. A drop tower type of high speed tensile apparatus was developed for strain rates of about 15/s and 100/s. Gauge width of 6mm, 8mm and 10mm were investigated. Test results showed the specimen of 8mm width was adequate for the high strain rate tensile tests of fiber reinforced composite. It was found the strength of the composite material increased as the strain rate increased.

Lightweight Design of Shell Structures Using Adaptive Inner-Front Level Set Based Topology Optimization (AIFLS-TOP) (적응적 내부 경계 레벨셋 기반 위상최적화를 이용한 쉘 구조물의 경량화 설계)

  • Park, Kang-Soo;Youn, Sung-Kie
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.31 no.12
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    • pp.1180-1187
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    • 2007
  • In the present work, topology optimization method using adaptive inner-front level set method is presented. In the conventional level set based topology optimization method, there exists an incapability for inner-front creation during optimization process. In this regard, as a new attempt to avoid and to overcome the limitation, an inner-front creation algorithm is proposed. In the inner-front creation algorithm, the strain energy density of a structure along with volume constraint is considered. Especially, to facilitate the inner-front creation process during the optimization process, the inner-front creation map which corresponds to the discrete valued function of strain energy density is constructed. In the evolution of the level set function during the optimization process, the least-squares finite element method (LSFEM) is employed. As an application to shell structures, the lightweight design of doubly curved shell and segmented mirror is carried out.

Facilitation of the Diverse Processing of High Ductile ECC (Engineered Cementitious Composite) Based on Micromechanics and Rheological Control (마이크로 역학과 레올로지 제어에 의한 고인성 섬유복합재료 ECC(Engineered Cementitious Composite)의 다양한 타설 공정 구현)

  • Kim, Yun-Yong;Kim, Jeong-Su
    • Journal of The Korean Society of Agricultural Engineers
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    • v.47 no.5
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    • pp.27-39
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    • 2005
  • In the recent design of high ductile fiber-reinforced ECC (engineered cementitious composite), optimizing both processing and mechanical properties for specific applications is critical. This study presents an innovative method to develop new class ECCs, which possess the different fluid properties to facilitate diverse types of processing (i.e., self-consolidating or shotcrete processing) while maintaining ductile hardened properties. In the material design concept, we employ a parallel control of fresh and hardened properties by using micromechanics and cement rheology. Control of colloidal interaction between the particles is regarded as a key factor to allow the performance of the specific processing. To determine how to control the particle interactions and the viscosity of cement suspension, we first introduce two chemical admixtures including a highly charged polyelectrolyte and a non-ionic polymer. Optimized mixing steps and dosages we, then, obtained within the solid concentration predetermined based on micromechanical principle. Test results indicate that the rheological properties altered by this approach were revealed to be highly effective in obtaining the desired function of the fresh ECC, allowing us to readily achieve hardened properties, represented by pseudo strain-hardening behavior in uniaxial tension.

Modification of Local Ice Load Prediction Formula Based on IBRV ARAON's Arctic Field Data (쇄빙연구선 ARAON호의 북극해 실측 데이터에 기초한 국부 빙하중 추정식의 수정)

  • Cho, Sungrok;Choi, Kyungsik
    • Journal of Ocean Engineering and Technology
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    • v.33 no.2
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    • pp.161-167
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    • 2019
  • This paper focuses on a newly designed ice load formula based on the ARAON's 2016 Arctic field data in order to improve a structural design against ice loads. The strain gage signals from ARAON's hull plating were converted to the local ice pressure upon the hull plating using the influence coefficient matrix and finite element analysis. First, a traditional pressure-area relationship is derived by applying probabilistic approaches to handle the strains measured onboard the ARAON. Then, the local ice load prediction formula is re-analyzed after reviewing the ARAON's additional field data to consider information about the ship speed and thickness of the sea ice. It is shown that the newly developed pressure-area relationship well reflects the influence of other design parameters such as the ship speed and ice thickness in the prediction of local ice loads on Arctic vessels.

Determination of the elastic properties in CFRP composites: comparison of different approaches based on tensile tests and ultrasonic characterization

  • Munoz, Victor;Perrin, Marianne;Pastor, Marie-Laetitia;Welemane, Helene;Cantarel, Arthur;Karama, Moussa
    • Advances in aircraft and spacecraft science
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    • v.2 no.3
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    • pp.249-261
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    • 2015
  • The mechanical characterization of composite materials is nowadays a major interest due to their increasing use in the aeronautic industry. The design of most of these materials is based on their stiffness, which is mainly obtained by means of tensile tests with strain gauge measurement. For thin laminated composites, this classical method requires adequate samples with specific orientation and does not provide all the independent elastic constants. Regarding ultrasonic characterization, especially immersion technique, only one specimen is needed and the entire determination of the stiffness tensor is possible. This paper presents a study of different methods to determine the mechanical properties of transversely isotropic carbon fibre composite materials (gauge and correlation strain measurement during tensile tests, ultrasonic immersion technique). Results are compared to ISO standards and manufacturer data to evaluate the accuracy of these techniques.

The Shear Strength and Deformability of R/C Coupling Beams using Strut-and-Tie Models (스트럿-타이 모델을 이용한 철근 콘크리트 연결보의 전단강도와 변형능력)

  • Jang, Sang-Ki;Hong, Sung-Gul
    • Proceedings of the Korea Concrete Institute Conference
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    • 2004.11a
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    • pp.349-352
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    • 2004
  • In this study, a strut-and-tie models for the coupling beam based on deformations are presented. To design shear-dominated R/C coupling beams, it is important to consider shear strength deterioration with required deformations. This study proposes the method of estimating shear strength of the reinforced concrete coupling beams. The proposed method determines the strain states from target displacements based on the nonlinear truss analysis. The estimated horizontal strain of beam is then used in calculating the strength of the diagonal strut with compatibility conditions. The deterioration of shear strength of the coupling beam depends on the strength degradation of struts due to plastic deformations.

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Torsional strength model of reinforced concrete members subjected to combined loads

  • Ju, Hyunjin;Lee, Deuckhang;Zhang, Wei;Wang, Lei
    • Computers and Concrete
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    • v.29 no.5
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    • pp.285-301
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    • 2022
  • This study aims at developing a torsional strength model based on a nonlinear analysis method presented in the previous studies. To this end, flexural neutral axis depth of a reinforced concrete section and effective thickness of an idealized thin-walled tube were formulated based on reasonable approximations. In addition, various sectional force components, such as shear, flexure, axial compression, and torsional moment, were considered in estimating torsional strength by addressing a simple and linear strain profile. Existing test results were collected from literature for verifications by comparing with those estimated from the proposed model. On this basis, it can be confirmed that the proposed model can evaluate the torsional strength of RC members subjected to combined loads with a good level of accuracy, and it also well captured inter-related mechanisms between shear, bending moment, axial compression, and torsion.