Probabilistic Liquefaction Assessment Based on An In-situ State Parameter Considering Soil Spatial Variability and Various Uncertainties

Huajian Yang,Zhikui Liu,Yongxiong Xie 대한토목학회 2023 KSCE Journal of Civil Engineering Vol.27 No.10

The state parameter (ψ) is based on a framework of critical state soil mechanics, which reflects the influences of soil compactness and stress level and has significant advantages for liquefaction analysis. In engineering practice, a simplified procedure based on the cone penetration test (CPT) to assess the liquefaction potential in the field involves model and parameter uncertainties. Furthermore, the use of limited CPT measurements involves project-specific test uncertainties, and the spatial variability of soil properties has a remarkable effect on soil liquefaction. To tackle these challenges, this study develops a ψ-based liquefaction probability framework to integrate the prior information of project-specific CPT, and uses limited tests to characterize the 2D spatial distribution of liquefaction potential with proper consideration of various uncertainties and soil spatial variability. The framework is developed based on simulation of Gaussian stationary random fields and Markov Chain Monte Carlo simulation. The proposed method is demonstrated using real CPT data from the 2011 Tohoku-Oki earthquake in Japan. The results indicate that the ψ-based evaluation performs well and can reasonably assess the liquefaction phenomenon of heterogeneous soils. This study incorporating the spatial variability of ψ into the liquefaction probability framework provides valuable information for geotechnical engineering design.

DRIVER-IN-THE-LOOP HANDLING STABILITY CONTROL OF 4WID-EV

Yu Song,Jun Liu,Huajian Weng,Yaozhong Hu,He Huang 한국자동차공학회 2022 International journal of automotive technology Vol.23 No.2

An eight-degree-of-freedom vehicle dynamic model with electromechanical coupling was established for a four-wheel-independent-drive electric vehicle (4WID-EV). Based on the single-point preview optimal curvature theory, an adaptive fuzzy PID driver model with lateral acceleration feedback was designed, and the control of vehicle trajectory tracking was achieved in the driver-vehicle-road closed-loop coupling model. With the sideslip angle and yaw rate as control variables, the upper layer of a fuzzy sliding mode controller and the lower layer of an optimal distribution controller of the yaw moment were designed. The optimal longitudinal forces of four driving wheels were determined to achieve vehiclehandling stability. J-turn, fishhook, and snake-shaped pile simulations were carried out in MATLAB/Simulink. The results showed that the fuzzy sliding mode controller significantly improved the driving stability of the system, and it had a better anti-chattering ability than the sliding mode control strategy. The established lateral acceleration feedback adaptive fuzzy PID driver model had good trajectory tracking ability. Integration of the two controllers can better achieve both trajectory tracking and driving stability of a 4WID-EV.

Synergistic Effects of Polypropylene and Glass Fiber on Mechanical Properties and Durability of Recycled Aggregate Concrete

Bin Lei,Wengui Li,Huajian Liu,Zhuo Tang,Vivian W. Y. Tam 한국콘크리트학회 2020 International Journal of Concrete Structures and M Vol.14 No.5

To better understand the synergistic effects of combined fibers on mechanical properties and durability of recycled aggregate concrete (RAC), different types of fibers with various lengths and mass ratios were adopted in this study. Experimental investigations were conducted to study the 28-day compressive strength and strength loss after exposed to salt-solution freeze–thaw cycles and the coupled action of mechanical loading and salt-solution freeze–thaw cycles. The microstructure was also characterized to evaluate the mechanism of this synergistic effect. To determine the effectiveness of the combined fibers on improving the mechanical properties and durability of RAC, the synergistic coefficient was proposed and applied for various combinations of fibers. The results indicate that the incorporation of fibers slightly decreased the 28-day compressive strength of RAC, but combining different sizes and types of fibers can mitigate this negative effect. Moreover, the incorporation of fibers greatly improves the freeze–thaw resistance of RAC. The combining different fibers exhibited a synergistic effect on the enhancement in properties of RAC, which could not be predicted with only one simplistic rule of fibre mixtures. In addition, microstructural characterization shows that the bonding strength of the interfacial transition zone (ITZ) between the fiber and cement matrix is mainly determined by the chemical bonding force which is due to the hydration reaction between fiber surface and cement matrix.

Radiation shielding optimization design research based on bare-bones particle swarm optimization algorithm

Jichong Lei,Chao Yang,Huajian Zhang,Chengwei Liu,Dapeng Yan,Guanfei Xiao,Zhen He,Zhenping Chen,Tao Yu Korean Nuclear Society 2023 Nuclear Engineering and Technology Vol.55 No.6

In order to further meet the requirements of weight, volume, and dose minimization for new nuclear energy devices, the bare-bones multi-objective particle swarm optimization algorithm is used to automatically and iteratively optimize the design parameters of radiation shielding system material, thickness, and structure. The radiation shielding optimization program based on the bare-bones particle swarm optimization algorithm is developed and coupled into the reactor radiation shielding multi-objective intelligent optimization platform, and the code is verified by using the Savannah benchmark model. The material type and thickness of Savannah model were optimized by using the BBMOPSO algorithm to call the dose calculation code, the integrated optimized data showed that the weight decreased by 78.77%, the volume decreased by 23.10% and the dose rate decreased by 72.41% compared with the initial solution. The results show that the method can get the best radiation shielding solution that meets a lot of different goals. This shows that the method is both effective and feasible, and it makes up for the lack of manual optimization.

Concrete Crack of Ballastless Track Structure and its Repair

Xie Yongjiang,Li Huajian,Feng Zhongwei,Lee Ilwha 한국철도학회 2009 International Journal of Railway Vol.2 No.1

Crack and its damage of structure concrete in both FBS and TBS ballastless track are presented. The cause of concrete crack is analyzed. According to corresponding quantitative equation, effective technical measures to depression crack of concrete are put forward, at the same time the rationality of elastic ratio for HGT has been proved. At last, by the analysis of the characteristic of high-speed train, which are serving in the open air, bearing fatigue load, the short time for maintenance window and high speed of service, technical requirement for concrete repair material, repair technology and repair tools of ballastless track structure are presented.

<i>Ruga</i> mechanics of creasing: from instantaneous to setback creases

Diab, Mazen,Zhang, Teng,Zhao, Ruike,Gao, Huajian,Kim, Kyung-Suk Royal Society 2013 Proceedings, Mathematical, physical, and engineeri Vol.469 No.2157

<P>We present mechanics of surface creasing caused by lateral compression of a nonlinear neo-Hookean solid surface, with its elastic stiffness decaying exponentially with depth. Nonlinear bifurcation stability analysis reveals that neo-Hookean solid surfaces can develop instantaneous surface creasing under compressive strains greater than 0.272 but less than 0.456. It is found that instantaneous creasing is set off when the compressive strain is large enough, and the longest-admissible perturbation wavelength relative to the decay length of the elastic modulus is shorter than a critical value. A compressive strain smaller than 0.272 can only trigger bifurcation of a stable wrinkle that can prompt a setback crease upon further compression. The minimum compressive strain required to develop setback creasing is found to be 0.174. If the relative longest-admissible perturbation wavelength is long enough, then the wrinkle can fold before it creases, and the specimen can be compressed further beyond the Biot critical strain limit of 0.456. Various bifurcation branches on a plane of normalized longest-admissible wavelength versus compressive strain delineate different phases of corrugated surface configurations to form a <I>ruga</I> phase diagram. The phase diagram will be useful for understating surface crease, as well as for controlling <I>ruga</I> structures for various applications, such as designing stretchable electronics.</P>

Is Stress Concentration Relevant for Nanocrystalline Metals?

Kumar, Sandeep,Li, Xiaoyan,Haque, Aman,Gao, Huajian American Chemical Society 2011 Nano letters Vol.11 No.6

<P>Classical fracture mechanics as well as modern strain gradient plasticity theories assert the existence of stress concentration (or strain gradient) ahead of a notch tip, albeit somewhat relaxed in ductile materials. In this study, we present experimental evidence of extreme stress homogenization in nanocrystalline metals that result in immeasurable amount of stress concentration at a notch tip. We performed in situ uniaxial tension tests of 80 nm thick (50 nm average grain size) freestanding, single edge notched aluminum specimens inside a transmission electron microscope. The theoretical stress concentration for the given notch geometry was as high as 8, yet electron diffraction patterns unambiguously showed absence of any measurable stress concentration at the notch tip. To identify possible mechanisms behind such an anomaly, we performed molecular dynamics simulations on scaled down samples. Extensive grain rotation driven by grain boundary diffusion, exemplified by an Ashby–Verrall type of grain switching process, was observed at the notch tip to relieve stress concentration. We conclude that in the absence of dislocations, grain realignment or rotation may have played a critical role in accommodating externally applied strain and neutralizes any stress concentration during the process.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/nalefd/2011/nalefd.2011.11.issue-6/nl201083t/production/images/medium/nl-2011-01083t_0006.gif'></P>

Experimental Study on Cracking Behaviour of Intermittent Double S-shaped Fissures under Uniaxial Compression

Qianqian Dong,Chengwang Xiong,Chunlei Ma,Huajian Wei 대한토목학회 2019 KSCE JOURNAL OF CIVIL ENGINEERING Vol.23 No.6

Extensive efforts have been made in the understanding of the failure characteristics of straight fissure, but the failure patterns of rock mass with intermittent non-straight fissures have not been examined comprehensively. To address this problem, the present study investigated the cracking behaviors of natural marble specimens containing double S-shaped fissures under compression. Seven types of coalescence patterns for S-shaped fissures are classified, two of which are firstly reported and featured by the occurrence of the self-coalescence phenomenon. It is found that the decrease of strength is accompanied by the internal crack at the stage of crack growth and propagation, following the occurrence of the external crack, at relatively large flaw and ligament angle. The numerical simulations with the corresponding parameters were carried out for comparison. This research provides helpful information for understanding the failure modes induced by crack propagation of intermittent double S-shaped fissures.

Protein from Hylocereus polyrhizus protects MRC-5 cells against hydrogen peroxide (H2O2)-induced damage

Haomiao Ding,Yuzhe Zhang,Yue Zha,Sijia Zhou,Chaoqing Cao,Huajian Zhu,Feng Xu,Xiuqiang Zhang,Caisheng Wang 한국식품과학회 2022 Food Science and Biotechnology Vol.31 No.13

The cytoprotective and potential molecular mechanisms of Hylocereus polyrhizus protein (RFPP) were investigated on the hydrogen peroxide (H2O2)-triggered damage in normal human embryonic lung (MRC-5) cells. An MTT assay was conducted to assess the MRC-5 cell viability after exposure to H2O2 or RFPP. Cell cycle distribution and apoptosis were explored via flow cytometry. The contents of related proteins were assessed via western blot. MRC-5 cells exhibited markedly decreased cellular viability after treatment with H2O2; however, treatment with RFPP suppressed this decrease. Additionally, RFPP interference dampened H2O2-triggered intracellular apoptosis levels and increased H2O2-triggered intracellular S phase. In these processes, the contents of phosphorylated (p)-AKT along with p-mTOR proteins were downregulated in 120 µM H2O2-treated cells compared with vehicle-treated cells. Nevertheless, in MRC-5 cells inoculated with RFPP, the levels expression of these proteins were reversed. To conclude, RFPP protected MRC-5 cells from H2O2-triggered damage via activation of the PI3K/AKT/mTOR cascade.

Hardening and toughening mechanisms in nanotwinned ceramics

Li, Xiaoyan,Yin, Sheng,Oh, Sang Ho,Gao, Huajian Elsevier 2017 Scripta materialia Vol.133 No.-

<P><B>Abstract</B></P> <P>Recent experiments have reported that nanotwinned ceramics with covalent or ionic bonds exhibit unprecedented hardness, enhanced fracture toughness and improved thermal stability. In this viewpoint paper, we highlight some preliminary studies on mechanical properties of nanotwinned ceramics either synthesized in the laboratory or extracted from biological materials, with an emphasis on their hardening and toughening mechanisms from the point of view of defects and bonding structures. Some discussions are also made on possible future research directions, such as exploring underlying deformation mechanisms via in situ TEM testing and large-scale atomistic simulations, and investigating the twin size and orientation effects.</P>