• Title/Summary/Keyword: composites column

Search Result 45, Processing Time 0.027 seconds

Stability Evaluation & Determination of Critical Buckling Load for Non-Linear Elastic Composite Column (비선형 탄성 복합재료 기둥의 임계 좌굴하중 계산 및 안정성 평가)

  • 주기호;정재호;강태진
    • Proceedings of the Korean Society For Composite Materials Conference
    • /
    • 2003.04a
    • /
    • pp.215-219
    • /
    • 2003
  • Buckling and post-buckling Analysis of Ludwick type and modified Ludwick type elastic materials was carried out. Because the constitutive equation, or stress-strain relationship is different from that of linear elastic one, a new governing equation was derived and solved by $4^{th}$ order Runge-Kutta method. Considered as a special case of combined loading, the buckling under both point and distributed load was selected and researched. The final solution takes distinguished behavior whether the constitutive relation is chosen to be modified or non-modified Ludwick type as well as linear or non-linear. We also derived strain energy function for non-linear elastic constitutive relationship. By doing so, we calculated the criterion function which estimates the stability of the equilibrium solutions and determines critical buckling load for non-linear cases. We applied this theory to the constitutive relationship of fabric, which also is the non-linear equation between the applied moment and curvature. This results has both technical and mathematical significance.

  • PDF

Development of Antibiotic-intercalated Smectite Composites and Its Drug Delivery Potential in Gastric System (항생제-스멕타이트 복합물 유도 및 소화기계 약물전달체로의 가능성)

  • Song, Yungoo;Chung, Donghoon;Song, Young Goo;Choi, Woohyun
    • Economic and Environmental Geology
    • /
    • v.48 no.3
    • /
    • pp.199-204
    • /
    • 2015
  • In this study, we aimed to make antibiotic-intercalated smectite composites using amoxicillin and clarithromycin as hygroscopic antibiotics, and gentamicin, tobramycin and netilmicin as non-hygroscopic aminoglucosides, and to check their drug delivery potential in gastric system using preliminary in-situ column release test for clarithromycinsmectite composite. All antibiotics were successfully intercalated into the interlayer of smectite by cation-exchange reaction in the batch experiment. Equilibrium batch test showed that clarithromycin-intercalation followed Langmuir isotherm and the possible maximum amount was calculated as 1.811 mmole/g. Clarithromycin was continuously released by the solutions of pH=2, 3, and 4 and the amount was decreased with pH increase.

Parametric Study on Design of Composite-Foam Sandwich Structures for Micro EDM Machine tool structures (미세 방전가공 기계 구조를 위한 복합재료-포움 샌드위치 구조 설계에 관한 파라메트릭 연구)

  • Kim Dae-Il;Chang Seung-Hwan
    • Composites Research
    • /
    • v.19 no.2
    • /
    • pp.13-19
    • /
    • 2006
  • In this paper, parametric study was carried out to design sandwich structures for EDM machines controlling stacking sequence, stacking thickness of composites and rib configuration. Sandwich structures which are dealt with in this paper are composed of fibre reinforced composite for skin material and foam or resin concrete for core materials. The sandwich column has cruciform rib to enhance bending stiffness of the structure and the bed has several vertical ribs to resist the normal forces and vibration. The design parameters such as rib thickness and stacking sequence were controlled to enhance the system robustness. Finite element analysis was also carried out to verify the variation of static and dynamic stiffness of the structures according to the variation of the parameters. Vibration tests were performed to verify the natural frequencies and damping ratios of the manufactured composite structures. The appropriate shape and configuration conditions for micro-EDM machine structures are proposed.

Seismic Performance of Precast Infill Walls with Strain-Hardening Cementitious Composites (변형경화형 시멘트 복합체를 사용한 프리캐스트 끼움벽의 내진성능)

  • Kim, Sun-Woo;Yun, Hyun-Do;Jang, Gwang-Soo;Yun, Yeo-Jin
    • Journal of the Korea Concrete Institute
    • /
    • v.21 no.3
    • /
    • pp.327-335
    • /
    • 2009
  • In the seismic region, non-ductile structures often form soft story and exhibit brittle collapse. However, structure demolition and new structure construction strategies have serious problems, as construction waste, environmental pollution and popular complain. And these methods can be uneconomical. Therefore, to satisfy seismic performance, so many seismic retrofit methods have been investigated. There are some retrofit methods as infill walls, steel brace, continuous walls, buttress, wing walls, jacketing of column or beam. Among them, the infilled frames exhibit complex behavior as follows: flexible frames experiment large deflection and rotations at the joints, and infilled shear walls fail mainly in shear at relatively small displacements. Therefore, the combined action of the composite system differs significantly from that of the frame or wall alone. Purpose of research is evaluation on the seismic performance of infill walls, and improvement concept of this paper is use of SHCCs (strain-hardening cementitious composites) to absorb damage energy effectively. The experimental investigation consisted of cyclic loading tests on 1/3-scale models of infill walls. The experimental results, as expected, show that the multiple crack pattern, strength, and energy dissipation capacity are superior for SHCC infill wall due to bridging of fibers and stress redistribution in cement matrix.

Seismic performance of RC frame structures strengthened by HPFRCC walls

  • Yun, Hyun-Do;Hwang, Jin-Ha;Kim, Mee-Yeon;Choi, Seung-Ho;Park, Wan-Shin;Kim, Kang Su
    • Structural Engineering and Mechanics
    • /
    • v.75 no.3
    • /
    • pp.389-399
    • /
    • 2020
  • An infill wall made of high-performance fiber-reinforced cementitious composites (HPFRCC) was utilized in this study to strengthen the reinforced concrete (RC) frame structures that had not been designed for seismic loads. The seismic performance of the RC frame structures strengthened by the HPFRCC infill walls was investigated through the experimental tests, and the test results showed that they have improved strength and deformation capabilities compared to that strengthened by the RC infill wall. A simple numerical modeling method, called the modified longitudinal and diagonal line element model (LDLEM), was introduced to consider the seismic strengthening effect of the infill walls, in which a section aggregator approach was also utilized to reflect the effect of shear in the column members of the RC frames. The proposed model showed accurate estimations on the strength, stiffness, and failure modes of the test specimens strengthened by the infill walls with and without fibers.

Relative static and dynamic performances of composite conoidal shell roofs

  • Bakshi, Kaustav;Chakravorty, Dipankar
    • Steel and Composite Structures
    • /
    • v.15 no.4
    • /
    • pp.379-397
    • /
    • 2013
  • Conoidal shells are doubly curved stiff surfaces which are easy to cast and fabricate due to their singly ruled property. Application of laminated composites in fabrication of conoidal shells reduces gravity forces and mass induced forces compared to the isotropic constructions due to the high strength to weight ratio of the material. These light weight shells are preferred in the industry to cover large column free open spaces. To ensure design reliability under service conditions, detailed knowledge about different behavioral aspects of conoidal shell is necessary. Hence, in this paper, static bending, free and forced vibration responses of composite conoidal shells are studied. Lagrange's equation of motion is used in conjunction with Hamilton's principle to derive governing equations of the shell. A finite element code using eight noded curved quadratic isoparametric elements is developed to get the solutions. Uniformly distributed load for static bending analysis and three different load time histories for solution of forced vibration problems are considered. Eight different stacking sequences of graphite-epoxy composite and two different boundary conditions are taken up in the present study. The study shows that relative performances of different shell combinations in terms of static behaviour cannot provide an idea about how they will relatively behave under dynamic loads and also the fact that the points of occurrence of maximum static and dynamic displacement may not be same on a shell surface.

Study on Analysis of Vulcanized Rubber by Pyrolysis-Gas Chromatography(I) (Vulcanizates of NR BR and SBR) (Pyrolysis-Gas Chromatography를 이용한 가황 고무의 열분석에 관한연구(I) (NR, BR 및 SBR의 가황체))

  • Huh, D.S.;Kim, J.S.;Kim, K.J.;Ahn, B.K.;Suh, S.K.;Han, O.K.
    • Elastomers and Composites
    • /
    • v.22 no.1
    • /
    • pp.11-19
    • /
    • 1987
  • A coil pyrolyzer and processor-controlled gas chromatograph were used for analysis of rubber for compounding ratio of the single and blend rubber vlucanizates. Variables such as sample size, pyrolysis temperature, time allowed for pyrolysis, the column packing material, its length and programmable temperature for gas chromatography were examined to obtain optimum condition for application to NR, BR and SBR blends. By application fixed conditions, three kinds of standard curves were finally obtained from thirty samples of blend vulcanizates which were prepared in the pilot plant, NIRI. It is possible to determine rubber composition and their ratio in NR, BR and SBR products by pyrolysis.

  • PDF

Investigation of interface response of reinforced concrete columns retrofitted with composites

  • Achillopoulou, Dimitra V.;Kiziridou, Alexandra N.;Papachatzakis, Georgios A.;Karabinis, Athanasios I.
    • Steel and Composite Structures
    • /
    • v.22 no.6
    • /
    • pp.1337-1358
    • /
    • 2016
  • The current study focuses on the assessment and interface response of reinforced concrete elements with composite materials (carbon fiber reinforced polymers-CFRPs, glass fiber reinforced polymers-GFRPs, textile reinforced mortars-TRM's, near surface mounted bars-NSMs). A description of the transfer mechanisms from concrete elements to the strengthening materials is conducted through analytical models based on failure modes: plate end interfacial debonding and intermediate flexural crack induced interfacial debonding. A database of 55 in total reinforced concrete columns (scale 1:1) is assembled containing elements rehabilitated with various techniques (29 wrapped with CFRP's, 5 wrapped with GFRP's, 4 containing NSM and 4 strengthened with TRM). The failure modes are discussed together with the performance level of each technique as well as the efficiency level in terms of ductility and bearing/ bending capacity. The analytical models' results are in acceptable agreement with the experimental data and can predict the failure modes. Despite the heterogeneity of the elements contained in the aforementioned database the results are of high interest and point out the need to incorporate the analytical expressions in design codes in order to predict the failure mechanisms and the limit states of bearing capacities of each technique.

Compressive behavior of steel stirrups-confined square Engineered Cementitious Composite (ECC) columns

  • Zheng, Pan-deng;Guo, Zi-xiong;Hou, Wei;Lin, Guan
    • Advances in concrete construction
    • /
    • v.11 no.3
    • /
    • pp.193-206
    • /
    • 2021
  • Extensive research has been conducted on the basic mechanical property and structural applications of engineered cementitious composites (ECC). Despite the high tensile ductility and high toughness of ECC, transverse steel reinforcement is still necessary to confine ECC for high performance. However, limited research has examined performance of ECC confined with practical amount of transverse reinforcement. This paper presents the results of axial compression tests on 14 square ECC columns and 4 conventional concrete columns (used as control specimens) with transverse reinforcement. The test variables were spacing, configuration (square ties or square and diamond shape ties), and yield strength of stirrups. The test showed that ECC columns confined with steel stirrup had good compressive ductility, and the stirrup spacing had the greatest effect on the compressive performance. The self-confinement effect of ECC results in a more uniform but slower expansion of the whole column compared with CC ones. The test results are then compared against the predictions from a number of existing models for conventional confined concrete. It is indicated that these models fail to predict the axial strains at peak axial stress and the trend of the stress-strain curve of steel stirrups-confined ECC with sufficient accuracy. Several new equations are then proposed for the compressive properties of steel-confined ECC based on test results and potential approaches for future studies are proposed.

The Effect of Vertical Strut in Circular Arch Lattice Structure by Selective Laser Sintering for Lightweight Structure

  • Sangwon Lee;Jae-An Jeon;Sang-Eui Lee
    • Composites Research
    • /
    • v.36 no.3
    • /
    • pp.173-179
    • /
    • 2023
  • The sandwich structure, consisting of a core and a face sheet, is used for lightweight structural application. Generally, cellular structures like honeycomb, foam, and lattice structures are utilized for the core. Among these, lattice structures have several advantages over other types of structures. In other studies, curved lattice structures were reported to have higher mechanical properties than straight structures by converting shear stresses acting on the structure into compressive stresses. Moreover, the addition of vertical struts can have a positive effect on the mechanical properties of the lattice structure. For the purpose, two lattice structures with Circle Arch (CC) and Circular Arch with a vertical column (CC_C) were studied, which were fabricated by using selective laser sintering was conducted. The result showed that CC_C has dramatic performance improvements in specific strength, modulus, and strain energy density compared to CC, confirming that vertical struts played a significant role in the lattice core. Finite element analysis was employed to determine the cause of the stress behavior of CC and CC_C. This study is expected to help design structurally superior lattice cores and sandwich structures.