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Performances of Concrete Columns with Modular UHPC Permanent Formworks Under Axial Load
Yibo Yang,Baixi Chen,Yong Chen,Huanyang Zhou,Fucai Liu,Xiangming Xie,Junsheng Chen,Wenying Guo,Hengchang Wang 한국콘크리트학회 2023 International Journal of Concrete Structures and M Vol.17 No.5
This research proposed the modular prefabricated permanent formwork system made of ultra-high-performance concrete (UHPC). Two kinds of modular formwork shapes were designed: the flat formwork and the ribbed. The experimental investigation on the axial compression performance of the composite columns that consist of the normal strength concrete (NSC) core and the modular UHPC permanent formwork was demonstrated. Compared with the flat formwork, the ribbed formwork exhibited better bonding with the NSC core. As observed from the test results, the composite column with the ribbed formwork presented a similar axial behavior as the NSC column with a slight improvement in ultimate loads. Therefore, the modular UHPC ribbed permanent formwork could be regarded as the additional cover to the conventional NSC column. In addition, the finite element analysis (FEA) model was also developed to simulate the composite columns numerically. The predicted capacities agreed with the experimental results, which validated the numerical models. The crack pattern estimated by the FEA model revealed that the interaction between the permanent formwork and the inner concrete introduced many tiny cracks to the concrete core. However, as protected by the UHPC permanent formwork, the overall durability of the composite columns can still be enhanced.
Behaviour insights on damage-control composite beam-to-beam connections with replaceable elements
Xiuzhang He,Michael C. H. Yam,Ke Ke,Xu-Hong Zhou,Huanyang Zhang,Zi Gu 국제구조공학회 2023 Steel and Composite Structures, An International J Vol.46 No.6
Connections with damage concentrated to pre-selected components can enhance seismic resilience for moment resisting frames. These pre-selected components always yield early to dissipate energy, and their energy dissipation mechanisms vary from one to another, depending on their position in the connection, geometry configuration details, and mechanical characteristics. This paper presents behaviour insights on two types of beam-to-beam connections that the angles were designed as energy dissipation components, through the results of experimental study and finite element analysis. Firstly, an experimental programme was reviewed, and key responses concerning the working mechanism of the connections were presented, including strain distribution at the critical section, section force responses of essential components, and initial stiffness of test specimens. Subsequently, finite element models of three specimens were established to further interpret their behaviour and response that were not observable in the tests. The moment and shear force transfer paths of the composite connections were clarified through the test results and finite element analysis. It was observed that the bending moment is mainly resisted by axial forces from the components, and the dominant axial force is from the bottom angles; the shear force at the critical section is primarily taken by the slab and the components near the top flange. Lastly, based on the insights on the load transfer path of the composite connections, preliminary design recommendations are proposed. In particular, a resistance requirement, quantified by a moment capacity ratio, was placed on the connections. Design models and equations were also developed for predicting the yield moment resistance and the shear resistance of the connections. A flexible beam model was proposed to quantify the shear resistance of essential components.
Simultaneous regulation of photoabsorption and ferromagnetism of NaTaO3 by Fe doping
Huan Yang,Liguo Zhang,Lifang Yu,Fang Wang,Zhenzhen Ma,Jie Zhou,Xiaohong Xu 한국물리학회 2018 Current Applied Physics Vol.18 No.11
NaTa1-xFexO3 (0≤x≤0.40) nanocubes were synthesized by a relatively low temperature hydrothermal method, using Ta2O5, FeCl3 and NaOH as the precursors. The UV–vis diffuse reflectance spectra showed that NaTa1-xFexO3 had significant visible-light-absorbing capability, and the absorption edge of NaTaO3 shifted to longer wavelength with the increase of Fe dopants. Moreover, NaTa1-xFexO3 exhibited room-temperature ferromagnetism when Fe3+ occupied Ta5+ sites in NaTaO3 crystal lattice. The ferromagnetism is mainly attributed to the superexchange interactions between doped Fe3+, rather than the contribution of oxygen vacancies caused by Fe doping. Therefore, Fe doping can simultaneously regulate the optical and magnetic properties of NaTaO3 semiconductor, which will enable its potential applications in multifunctional optical-electronics and opticalspintronics devices.