Influences of Steel Fiber Content on Size Effect of the Fracture Energy of High-Strength Concrete

Ping Xu,Jinyi Ma,Yahong Ding,Minxia Zhang 대한토목학회 2021 KSCE JOURNAL OF CIVIL ENGINEERING Vol.25 No.3

Quasi-brittleness is an important factor affecting the size effect of concrete, and the addition of steel fiber can effectively change this effect in concrete. The size effect on the fracture energy of steel fiber reinforced high-strength concrete was investigated in this paper. A total of 156 concrete single-edge notched beams (SENB) of various span-to-depth ratios, crack-to-depth ratios and steel fiber contents were tested to study the size effect of fracture energy of the high-strength concrete added steel fibers. The parameters of fracture in the boundary effect model (BEM) and size effect law (SEL) were deeply analyzed. The results show that the addition of steel fiber will generate significant influence on the parameter values obtained from both BEM and SEL. Based on the BEM, the relationship among Gf (experimental test fracture energy), gf(local fracture energy), and GF (fracture energy unaffected by specimen boundary) could be obtained. Thus, a method for analyzing the influence of steel fiber on GF was proposed using small-size SENB specimens at laboratory. In addition, based on the SEL, the impact of size effect on the fracture energy was effectively mitigated by the addition of steel fibers in high-strength concrete to a certain extent.

Effect of activator types on cement mortar with polymeric aluminum chloride waste residue

Ping Xu,Yuhao Cui,Dong Han,Minxia Zhang,Yahong Ding Techno-Press 2023 Advances in concrete construction Vol.15 No.3

Water glass (WG) and sodium sulfate (SS) were used to prepare polymeric aluminum chloride residue cement mortar (PACRM) by single and compound blending with polymeric aluminum chloride waste residue, respectively. The structural strength and textural characteristics examinations showed that PACRM consistency increased by incorporating WG, but decreased by incorporating SS. When WG and SS were compounded, the mortar consistency initially rose before falling. The compressive strength of PACRM increased and then decreased as WG was increased. The mechanical properties of PACRM were better enhanced by SS than WG, showing no strength deterioration. The main reason for the improved mechanical properties of polymeric aluminum chloride waste residue in the presence of activators is the increased precipitation of reactive substances, such as C-S-H gels, calcium silica, and Ca(OH)₂. The density of the specimens with PACRM and the degree of aggregation of hydration products were significantly enhanced by generating more hydration products in the mortar. Further, the cracks and pores were significantly reduced, and the matrix structure was continuous and dense at 5% SS doping and 3% compound doping.

Design and Analysis of Lorentz Force-type Magnetic Bearing Based on High Precision and Low Power Consumption

Guofeng Xu,Yuanwen Cai,Yuan Ren,Chaojun Xin,Yahong Fan,Dengliang Hu 한국자기학회 2017 Journal of Magnetics Vol.22 No.2

Magnetically suspended control & sensitive gyroscope (MSCSG) is a novel type of gyroscope with the integration of attitude control and attitude angular measurement. To improve the precision and reduce the power consumption of Lorentz Force-type Magnetic Bearing (LFMB), the air gap flux density distribution of LFMB has been studied. The uniformity of air gap flux density is defined to qualify the uniform degree of the air gap flux density distribution. Considering the consumption, the average value of flux density is defined as well. Some optimal designs and analyses of LFMB are carried out by finite element simulation. The strength of the permanent magnet is taken into consideration during the machining process. To verify the design and simulation, a high-precision instrument is employed to measure the 3-dimensional magnetic flux density of LFMB. After measurement and calculation, the uniform degree of magnetic flux density distribution reaches 0.978 and the average value of the flux density is 0.482T. Experimental results show that the optimal design is effective and some useful advice can be obtained for further research.

Flexural Behavior of RC Beams with NSM Prestressed Helical Rib Steel Wire

Meixiang Zhang,Xiaolin Yang,Yahong Ding,Ping Xu,Bo Sun,Xiaoyi Zhang,Xianggang Zhang 대한토목학회 2023 KSCE Journal of Civil Engineering Vol.27 No.9

The reinforcement technique of near-surface mounted?NSM?prestressed helical rib steel wire (PHRSW) with wide raw material sources, lower in price and high application value can significantly enhance the flexural behavior of reinforced-concrete (RC) structures. Based on 8 flexural RC beams reinforced with NSM PHRSW, performance of test beams under different groove widths (10 mm, 15 mm and 20 mm) and concrete strengths (C30 and C40) was analyzed, including load-deflection, ductility, flexural capacity, strain of longitudinal steel bar and HRSW, failure mode and crack propagation. The results show that the overall flexural behavior RC beams reinforced with NSM PHRSW was significantly improved. There is a good entirety bearing capacity between the longitudinal reinforcement and PHRSW of reinforced beam with suitable groove size. The comprehensive performance of reinforced beams increases first then decreases, with the increase of groove size. The higher the strength of concrete, the more significant the influence of groove size. There is an optimal match between groove width and concrete strength for RC beams reinforced with NSM PHRSW. Considering comprehensive property of reinforced beams, groove width with 15mmwas best in this research. The results can make the research of RC beams reinforced with NSM PHRSW more comprehensive and in-depth, and provide design basis for its engineering application.

Analysis, Modeling and Compensation of Dynamic Imbalance Error for a Magnetically Suspended Sensitive Gyroscope

Xin Chaojun,Cai Yuanwen,Ren Yuan,Fan Yahong,Xu Guofeng,Lei Xu 한국자기학회 2016 Journal of Magnetics Vol.21 No.4

Magnetically suspended sensitive gyroscopes (MSSGs) provide an interesting alternative for achieving precious attitude angular measurement. To effectively reduce the measurement error caused by dynamic imbalance, this paper proposes a novel compensation method based on analysis and modeling of the error for a MSSG. Firstly, the angular velocity measurement principle of the MSSG is described. Then the analytical model of dynamic imbalance error has been established by solving the complex coefficient differential dynamic equations of the rotor. The generation mechanism and changing regularity of the dynamic imbalance error have been revealed. Next, a compensation method is designed to compensate the dynamic imbalance error and improve the measurement accuracy of the MSSG. The common issues caused by dynamic imbalance can be effectively resolved by the proposed method in gyroscopes with a levitating rotor. Comparative simulation results before and after compensation have verified the effectiveness and superiority of the proposed compensation method.

Numerical analysis on tensile properties of composite hybrid bonded/bolted joints with flanging

Xiaoquan Cheng,Jie Zhang,Jikui Zhang,Peng Liu,Yujia Cheng,Yahong Xu 국제구조공학회 2018 Steel and Composite Structures, An International J Vol.26 No.3

A detailed study was carried out on the tensile properties of the single-lap joint of a steel panel bolted/bonded to a composite laminate with a flanging. Finite element model (FEM) was established to predict the strength and to analyze the damage propagation of the hybrid joints by ABAQUS/Standard, which especially adopted cohesive elements to simulate the interface between the laminate and adhesive. The strength and failure mode predicted by FEM were in good agreement with the experimental results. In addition, three influence factors including adhesive thickness, bolt preload and bolt-hole clearance were studied. The results show that the three parameters have effect on the first drop load of the load-displacement curve, but the effect of bolt-hole clearance is the largest. The bolt-hole clearance should be avoided for hybrid joints.

Buckling and post-buckling behaviors of 1/3 composite cylindrical shell with an opening

Yihao Ma,Xiaoquan Cheng,Zhaodi Wang,Xin Guo,Jie Zhang,Yahong Xu 국제구조공학회 2018 Steel and Composite Structures, An International J Vol.27 No.5

A 1/3 composite cylindrical shell with a central rectangular opening was axially compressed experimentally, and its critical buckling load and displacement, and strains were measured. A finite element model (FEM) of the shell with Hashin failure criteria was established to analyze its buckling and post-buckling behaviors by nonlinear Newton-Raphson method. The geometric imperfection sensitivity and the effect of side supported conditions of the shell were investigated. It was found that the Newton-Raphson method can be used to analyze the buckling and post-buckling behaviors of the shell. The shell is not sensitive to initial geometric imperfection. And the support design of the shell by side stiffeners is a good way to obtain the critical buckling load and simplify the experimental fixture.