Nonlinear finite element analysis of circular concrete-filled steel tube structures

Tengfei Xu,Tianyu Xiang,Renda Zhao,Yulin Zhan 국제구조공학회 2010 Structural Engineering and Mechanics, An Int'l Jou Vol.35 No.3

The structural behaviors of circular concrete filled steel tube (CFT) structures are investigated by nonlinear finite element method. An efficient three-dimensional (3D) degenerated beam element is adopted. Based on those previous studies, a modified stress-strain relationship for confined concrete which introduces the influence of eccentricity on confining stress is presented. Updated Lagrange formulation is used to consider the geometrical nonlinearity induced by large deformation effect. The nonlinear behaviors of CFT structures are investigated, and the accuracy of the proposed constitutive model for confined concrete is mainly concerned. The results demonstrate that the confining effect in CFT elements subjected to combining action of axial force and bending moment is far sophisticated than that in axial loaded columns, and an appropriate evaluation about this effect may be important for nonlinear numerical simulation of CFT structures.

Nonlinear finite element analysis of circular concrete-filled steel tube structures

Xu, Tengfei,Xiang, Tianyu,Zhao, Renda,Zhan, Yulin Techno-Press 2010 Structural Engineering and Mechanics, An Int'l Jou Vol.35 No.3

The structural behaviors of circular concrete filled steel tube (CFT) structures are investigated by nonlinear finite element method. An efficient three-dimensional (3D) degenerated beam element is adopted. Based on those previous studies, a modified stress-strain relationship for confined concrete which introduces the influence of eccentricity on confining stress is presented. Updated Lagrange formulation is used to consider the geometrical nonlinearity induced by large deformation effect. The nonlinear behaviors of CFT structures are investigated, and the accuracy of the proposed constitutive model for confined concrete is mainly concerned. The results demonstrate that the confining effect in CFT elements subjected to combining action of axial force and bending moment is far sophisticated than that in axial loaded columns, and an appropriate evaluation about this effect may be important for nonlinear numerical simulation of CFT structures.

Reversible MoS₂ Origami with Spatially Resolved and Reconfigurable Photosensitivity

Xu, Weinan,Li, Tengfei,Qin, Zhao,Huang, Qi,Gao, Hui,Kang, Kibum,Park, Jiwoong,Buehler, Markus J.,Khurgin, Jacob B.,Gracias, David H. American Chemical Society 2019 Nano letters Vol.19 No.11

<P>Two-dimensional layered materials (2DLMs) have been extensively studied in a variety of planar optoelectronic devices. Three-dimensional (3D) optoelectronic structures offer unique advantages including omnidirectional responses, multipolar detection, and enhanced light-matter interactions. However, there has been limited success in transforming monolayer 2DLMs into reconfigurable 3D optoelectronic devices due to challenges in microfabrication and integration of these materials in truly 3D geometries. Here, we report an origami-inspired self-folding approach to reversibly transform monolayer molybdenum disulfide (MoS<SUB>2</SUB>) into functional 3D optoelectronic devices. We pattern and integrate monolayer MoS<SUB>2</SUB> and gold (Au) onto differentially photo-cross-linked thin polymer (SU8) films. The devices reversibly self-fold due to swelling gradients in the SU8 films upon solvent exchange. We fabricate a wide variety of optically active 3D MoS<SUB>2</SUB> microstructures including pyramids, cubes, flowers, dodecahedra, and Miura-oris, and we simulate the self-folding mechanism using a coarse-grained mechanics model. Using finite-difference time-domain (FDTD) simulation and optoelectronic characterization, we demonstrate that the 3D self-folded MoS<SUB>2</SUB> structures show enhanced light interaction and are capable of angle-resolved photodetection. Importantly, the structures are also reversibly reconfigurable upon solvent exchange with high tunability in the optical detection area. Our approach provides a versatile strategy to reversibly configure 2D materials in 3D optoelectronic devices of broad relevance to flexible and wearable electronics, biosensing, and robotics.</P> [FIG OMISSION]</BR>

Dynamic analysis of thin-walled open section beam under moving vehicle by transfer matrix method

Tianyu Xiang,Tengfei Xu,Xinpeng Yuan,Renda Zhao,Yuqiang Tong 국제구조공학회 2008 Structural Engineering and Mechanics, An Int'l Jou Vol.30 No.5

Three dimensional coupled bending-torsion dynamic vibrations of thin-walled open section beam subjected to moving vehicle are investigated by transfer matrix method. Through adopting the idea of Newmark-β method, the partial differential equations of structural vibration can be transformed to the differential equations. Then, those differential equations are solved by transfer matrix method. An iterative scheme is proposed to deal with the coupled bending-torsion terms in the governing vibration equations. The accuracy of the presented method is verified through two numerical examples. Finally, with different eccentricities of vehicle, the torsional vibration of thin-walled open section beam and vertical and rolling vibration of truck body are investigated. It can be concluded from the numerical results that the torsional vibration of beam and rolling vibration of vehicle increase with the eccentricity of vehicle. Moreover, it can be observed that the torsional vibration of thin-walled open section beam may have a significant nonlinear influence on vertical vibration of truck body.

Dynamic analysis of thin-walled open section beam under moving vehicle by transfer matrix method

Xiang, Tianyu,Xu, Tengfei,Yuan, Xinpeng,Zhao, Renda,Tong, Yuqiang Techno-Press 2008 Structural Engineering and Mechanics, An Int'l Jou Vol.30 No.5

Three dimensional coupled bending-torsion dynamic vibrations of thin-walled open section beam subjected to moving vehicle are investigated by transfer matrix method. Through adopting the idea of Newmark-${\beta}$ method, the partial differential equations of structural vibration can be transformed to the differential equations. Then, those differential equations are solved by transfer matrix method. An iterative scheme is proposed to deal with the coupled bending-torsion terms in the governing vibration equations. The accuracy of the presented method is verified through two numerical examples. Finally, with different eccentricities of vehicle, the torsional vibration of thin-walled open section beam and vertical and rolling vibration of truck body are investigated. It can be concluded from the numerical results that the torsional vibration of beam and rolling vibration of vehicle increase with the eccentricity of vehicle. Moreover, it can be observed that the torsional vibration of thin-walled open section beam may have a significant nonlinear influence on vertical vibration of truck body.

Multifunctional nanozyme‑reinforced copper‑coordination polymer nanoparticles for drug‑resistance bacteria extinction and diabetic wound healing

Jiahui Zhao,Tengfei Xu,Jichao Sun,Haitao Yuan,Mengyun Hou,Zhijie Li,Jigang Wang,Zhen Liang 한국생체재료학회 2023 생체재료학회지 Vol.27 No.00

Background Drug-resistant bacterial infections in chronic wounds are a persistent issue, as they are resistant to antibiotics and can cause excessive inflammation due to generation of reactive oxygen species (ROS). An effective solution would be to not only combat bacterial infections but also scavenge ROS to relieve inflammation at the wound site. Scaffolds with antioxidant properties are attractive for their ability to scavenge ROS, and there is medical demand in developing antioxidant enzyme-mimicking nanomaterials for wound healing. Methods In this study, we fabricated copper-coordination polymer nanoparticles (Cu-CPNs) through a self-assembly process. Furthermore, ε-polylysine (EPL), an antibacterial and cationic polymer, was integrated into the Cu-CPNs structure through a simple one-pot self-assembly process without sacrificing the glutathione peroxidase (GPx) and superoxide dismutase (SOD)-mimicking activity of Cu-CPNs. Results The resulting Cu-CPNs exhibit excellent antioxidant propertiesin mimicking the activity of glutathione peroxidase and superoxide dismutase and allowing them to effectively scavenge harmful ROS produced in wound sites. The in vitro experiments showed that the resulting Cu-CPNs@EPL complex have superior antioxidant properties and antibacterial effects. Bacterial metabolic analysis revealed that the complex mainly affects the cell membrane integrity and nucleic acid synthesis that leads to bacterial death. Conclusions The Cu-CPNs@EPL complex has impressive antioxidant properties and antibacterial effects, making it a promising solution for treating drug-resistant bacterial infections in chronic wounds. The complex’s ability to neutralize multiple ROS and reduce ROS-induced inflammation can help relieve inflammation at the wound site.