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- 저자 : Juntao Zhu (검색결과 4 건)
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Local Bond Stress-Slip Model of High-Strength Stainless Steel Wire Ropes in ECC
Ke Li,Dapeng Zhao,Jiajun Fan,Juntao Zhu 대한토목학회 2022 KSCE Journal of Civil Engineering Vol.26 No.5
Engineered cementitious composites (ECC) reinforced with high-strength stainless steel wire ropes (HSSSWR) is a new composite that has attracted much attention. Comprehensive understanding of the local bond stress-slip relationship of HSSSWR in ECC is a significant aspect to popularize the application of this new composite. In this research, the local bond stress-slip relationship between HSSSWR and ECC was investigated experimentally and theoretically, considering the influences of bond lengths, nominal diameters of HSSSWR and compressive strength of ECC. In order to accurately predict the bond stress and slip at different positions along the embedded length, a local bond stress-slip model was proposed for HSSSWR-ECC interface, and the model parameters were determined based on the pull-out test results and microsegment analysis of HSSSWR in ECC by using a nested iteration procedure. Furthermore, the three-dimension (3D) nonlinear finite element (FE) modeling method by using the proposed model was used to predict the bond-slip performance of HSSSWR in ECC. Finally, the global load-slip relationships calculated by using the iterative procedure and the 3D FE modeling method were compared with test results, which validated the acceptability of the developed local bond stress-slip model and the FE modeling method.
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Lang He,Sheng Li,Chengzhi Xu,Benmei Wei,Juntao Zhang,Yuling Xu,Beirong Zhu,Yang Cao,Xilin Wu,Zhijin Xiong,Rongrui Huang,Jian Yang,Haibo Wang 한국고분자학회 2020 Macromolecular Research Vol.28 No.9
Pure collagen materials are expensive with poor mechanical properties, which need modifications in most cases. As the degradation product of collagen, gelatin is cheap, degradable and biocompatible, but few literatures have reported the research about gelatin-collagen composite materials. This is because gelatin and collagen have different soluble temperatures—gelatin is soluble in hot water (≥30 oC) and swells in cold water. However, a low temperature (2-10 oC) is required to prepare and store collagen solution, and neutral collagen solution denatures quickly above the room temperature. In this study, gelatin was ground into powders and swelled in neutral bovine tendon pepsin-soluble collagen solution (BPSC) to form a homogeneous gelatin-collagen mixture, in light of the swelling characteristics of gelatin in cold water. The assembly properties and gel properties of this composite material were further studied. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) test results showed that the bovine tendon collagen had typical type-I collagen structural characterizations with two α chains of about 100 kDa and one β chain of about 200 kDa; while the SDS-PAGE pattern of gelatin displayed bands continuously distributed from 30 to 200 kDa. Amino acid composition analysis test indicated that the content of polar amino acids and the sum of acidic and base amino acids for gelatin were higher than that of BPSC. Studies on gel properties demonstrated that gelatin-collagen mixed solution had collagenlike assembly characteristics and assembly kinetics. The moduli of the assembled gel at 35 oC were equivalent to that of pure bovine tendon collagen system; moreover, the system moduli didn’t change with time with elastic moduli (G') of about 40 Pa. However, at 25 oC, the moduli of gelatin-collagen composite hydrogel increased with the extension of time, its G' increased about 18 times within 8 h, and the ratio of elastic modulus to viscous modulus (G'') increased 4.6 times, showing a significant aging effect of structural strength. Meanwhile, the mechanical strength of the composite hydrogel was also regulated by temperature—the gel was highly elastic (G'≈3,000 Pa, G'>>G'') at a low temperature (5 oC); as the temperature rose, the system moduli gradually decreased and the elastic gel transformed into waterlike fluid at 50 oC little by little. What’s more, gelatin-collagen composite hydrogel also had reversible sol-gel performances and self-healing capability similar to the gelatin hydrogel. This novel preparation method for preparing composite materials and the resultant composite hydrogel are expected to be used in the fields of natural food gels, injectable hydrogels, cell scaffolds, drug sustained-release materials and so on, and improve and promote the processing performances, price and large-scale production of collagen-based materials.
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Tensile Behavior of High-Strength Stainless Steel Wire Rope (HSSSWR)-Reinforced ECC
Xinling Wang,Guanghua Yang,Wenwen Qian,Ke Li,Juntao Zhu 한국콘크리트학회 2021 International Journal of Concrete Structures and M Vol.15 No.6
Engineered cementitious composites (ECC) show the distinguished characteristics of high post-cracking resistance and ductility. High-strength stainless steel wire rope (HSSSWR) has been successfully used for restoring or strengthening of existing structures. By combining the advantages of these two materials, a new composite system formed by embedding HSSSWR into ECC was proposed and expected to be a promising engineering material for repair or strengthening of structures. To investigate the tensile failure mechanism and mechanical properties of HSSSWR-reinforced ECC, an experimental study on 27 HSSSWR-reinforced ECC plates was conducted considering the effects of the reinforcement ratio of longitudinal HSSSWRs, formula of ECC and width of the plate. Test results revealed that HSSSWR-reinforced ECC exhibit superior post-cracking resistance, deformation capacity and crack-width control capacity. Increasing the reinforcement ratio of longitudinal HSSSWRs can effectively enhance the tensile strength, crack-width control capacity, deformation capacity and tensile toughness of HSSSWR-reinforced ECC. Adding thickener in ECC can significantly improve the crack-width control capacity and deformation capacity of HSSSWR-reinforced ECC due to enhancing uniform distribution of polyvinyl alcohol fibers, but would slightly reduce the cracking stress and maximum tensile stress by bringing small bubbles in the matrix. The tensile properties of HSSSWR-reinforced ECC plates are almost not affected by varying the plate width. Besides, a tensile constitutive model was developed for charactering the stress-strain relationship of HSSSWR-reinforced ECC in tension. Based on mechanical theories and failure characteristics of HSSSWR-reinforced ECC, the model parameters were determined, and calculation equations of cracking stress and tensile strength were proposed. The accuracy of the developed model and calculation equations was verified by test results.
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