Experimental and Numerical Studies on the Mechanical Performance of a Wall-beam-strut Joint with Mechanical Couplers for Prefabricated Underground Construction

Tingjin Liu,Jiandong Lu,Hongyuan Liu 한국콘크리트학회 2020 International Journal of Concrete Structures and M Vol.14 No.5

This paper investigates the nonlinear behavior of wall-beam-strut joints with mechanical couplers, which are proposed for prefabricated underground constructions, under monotonic and cyclic loading conditions using full-scale experimental tests and three-dimensional finite element modelings. The nonlinear behavior of the joint is discussed in terms of the load–displacement curves, concrete cracking distributions, and strains in the reinforcements obtained from both the experimental tests and the numerical modeling. The comparison indicates that the trends of both load–displacement curves are similar, although the cracking, yield and ultimate loads of the joints determined by the numerical modeling are 2.5% lower, 2.6% higher and 3.8% higher, respectively, than those determined by the experimental tests. The numerical simulation can capture the concrete cracking process in the joint in the early loading stage but cannot accurately model the crack distribution in later stages. Moreover, the reinforcement strains and the skeleton curve from the numerical modeling show the same tendency as those from the experimental test, but it is difficult to compare their exact values, especially after yielding. The differences are believed due to the fact that the numerical modeling idealizes the materials and fails to model the slippage between the reinforcements and concrete after the concrete cracking. On the basis of the experimental and numerical investigations, it is concluded that the proposed wall-beam-strut joint has not only an ultimate bearing capacity that is at least 3 times higher than the design load but also a good ductility. Therefore, the design of the wall-beam-strut joint satisfies the requirements for the prefabricated underground construction.

Experimental Investigation of the Mechanical Behaviour of Wall-Beam-Strut Joints for Prefabricated Underground Construction

Tingjin Liu,Jiandong Lu,Di Wang,Hongyuan Liu 한국콘크리트학회 2021 International Journal of Concrete Structures and M Vol.15 No.1

Prefabricated construction is becoming increasingly prevalent, however, it is rarely applied in underground constructions, except for tunnel linings, due to the difficulties that arise in jointing various prefabricated components in underground conditions. To solve the vertical location problem of embedded mechanical couplers during the construction of wall–beam–strut joints for a prefabricated metro station, a new connection using welded steel plates is proposed. In this paper, four full-scale specimens of wall–beam–strut joints connected using welded steel plates and mechanical couplers were experimentally tested under monotonic and low-reversed cyclic loading conditions. The testing results were analysed in terms of the ultimate bearing capacity, failure mode, hysteresis, skeleton curve, stiffness degradation, energy dissipation and strain of the reinforcement bars. Notably, the two kinds of joints had similar ultimate bearing capacities and failure modes, but the crack distributions on the tops of the waler beams were different. For the specimens with the welded steel plate connection, tensile horizontal cracks first appeared on the top surface of the beam, where the welded steel plate was located, and then coalesced gradually; however, this cracking pattern was not observed during the experimental test of the specimens connected with the mechanical couplers. Furthermore, it was determined that the energy dissipation and ductility of the welded steel plate connection were better than those of the mechanical coupler connected joint, because the steel plate could redistribute the internal force in the joint and increase the stiffness. It was concluded that the proposed welded steel plate connection could be more favourable than the mechanical coupler connection in the construction of a prefabricated metro station in Guangzhou. Moreover, the results obtained from these experiments could provide guidelines for the corresponding connections employed in underground-prefabricated structures.

Tunnel Lining Segment Deformation and Cracking Mechanisms during Tunneling in Complex Mixed Grounds with the Combined Mining and Shield Tunneling Method

Tingjin Liu,Shuyi Zhang,Kepeng Yu,Hongyuan Liu 대한토목학회 2023 KSCE Journal of Civil Engineering Vol.27 No.1

The combined mining and shield tunneling method solves the challenge that shield machine is slow to excavate hard rock formations during tunneling in complex mixed grounds such as soft soils mixed with hard rocks, which, however, causes the deformation and cracking of tunnel segments. Both in-situ field measurements and three-dimensional numerical simulations are conducted in this study to analyze the segment deformation and cracking mechanism of a tunnel excavated in complex mix grounds with the combined mining and shield tunneling method. It is concluded that the segment deformation and cracking are caused by insufficient pea-gravel fillings and uneven grouting pressures. To ensure the tunnel ovality satisfying standards and minimize the segment deformation and cracking, the angle range of the tunnel wrapped in the pea gravel should be greater than 180° and the resistance coefficient provided by the filling layer after grouting should be greater than 20 MPa/m. Moreover, it is found that the difference between the grouting pressures at the top and bottom of the tunnel has a significant impact on the overall deformation and opening amount of the joints between the segments.

Parameter Optimization Based on Evolutionary Algorithms for Green Cognitive Radio

Hongyuan Gao,Dandan Liu,Yanan Du 한국산학기술학회 2015 SmartCR Vol.5 No.5

In this paper, we study parameter adjustments that maximize the energy efficiency of green cognitive radio. Because the problem of parameter adjustments for green cognitive radio can be looked at as a complex discrete optimization problem, evolutionary algorithms can be applied to solve it. Parameter optimization methods based on quantum genetic algorithm (QGA), particle swarm optimization (PSO), and chaotic quantum particle swarm optimization (CQPSO) are designed. In particular, CQPSO integrates the characteristics of chaos with quantum particle swarm optimization (QPSO), which gives it strong global search abilities. Chaotic mutation is introduced into the proposed CQPSO to avoid premature convergence and keep diversity in populations. Quantum computing has excellent features used to increase optimization speed and enhance the search abilities of the algorithm. The proposed CQPSO method provides good performance in terms of convergence rate and convergence accuracy, and can search for an optimal solution to parameter adjustments in green cognitive radio networks. Through simulations comparing it to QGA and PSO, we conclude that the proposed CQPSO can improve energy efficiency and meet users’ quality of service needs.

An Efficient Provable Data Possession based on Elliptic Curves in Cloud Storage

Hongyuan Wang,Liehuang Zhu,Feng Wang,Yijia Lilong,Yu Chen,Chang Liu 보안공학연구지원센터 2014 International Journal of Security and Its Applicat Vol.8 No.5

Human Activities Recognition Based on Skeleton Information via Sparse Representation

Liu, Suolan,Kong, Lizhi,Wang, Hongyuan Korean Institute of Information Scientists and Eng 2018 Journal of Computing Science and Engineering Vol.12 No.1

Human activities recognition is a challenging task due to its complexity of human movements and the variety performed by different subjects for the same action. This paper presents a recognition algorithm by using skeleton information generated from depth maps. Concatenating motion features and temporal constraint feature produces feature vector. Reducing dictionary scale proposes an improved fast classifier based on sparse representation. The developed method is shown to be effective by recognizing different activities on the UTD-MHAD dataset. Comparison results indicate superior performance of our method over some existing methods.

Simultaneous Quantification of Multiple Alkaloids in Sophora Flavescens Ait and Human Urine by HPLC

Junyu Liu,Hongyuan Yan,Kyung Ho Row 한국생물공학회 2009 Biotechnology and Bioprocess Engineering Vol.14 No.5

This study developed a simple and sensitive liquid chromatography method to quantify the multiple active alkaloids (matrine, sophocarpine, and sophoridine) from sophora flavescens ait in urine samples simultaneously. The results showed that liquid- liquid extraction using water as the solvent could effectively isolate all the analyses with the lowest matrix effects. A low concentration of diethylamine (0.07%, v/v) in the mobile phase improved dramatically the resolution of all the alkaloids with less interference from the matrix. Good linearity ranging from 0.025 to 1250.0 μg/mL for all analytes was obtained, and the accuracy and precision varied from 73.25 to 87.86% and 1.4 to 2.2%, respectively. Finally, the suitability of the proposed method was demonstrated in the urinary drug excretion of 4 volunteers receiving an oral dose of a sophora flavescens ait extract. The intra and inter RSD were ≤ 1.9% This study developed a simple and sensitive liquid chromatography method to quantify the multiple active alkaloids (matrine, sophocarpine, and sophoridine) from sophora flavescens ait in urine samples simultaneously. The results showed that liquid- liquid extraction using water as the solvent could effectively isolate all the analyses with the lowest matrix effects. A low concentration of diethylamine (0.07%, v/v) in the mobile phase improved dramatically the resolution of all the alkaloids with less interference from the matrix. Good linearity ranging from 0.025 to 1250.0 μg/mL for all analytes was obtained, and the accuracy and precision varied from 73.25 to 87.86% and 1.4 to 2.2%, respectively. Finally, the suitability of the proposed method was demonstrated in the urinary drug excretion of 4 volunteers receiving an oral dose of a sophora flavescens ait extract. The intra and inter RSD were ≤ 1.9%

Human Activities Recognition Based on Skeleton Information via Sparse Representation

Suolan Liu,Lizhi Kong,Hongyuan Wang 한국정보과학회 2018 Journal of Computing Science and Engineering Vol.12 No.1

Human activities recognition is a challenging task due to its complexity of human movements and the variety performed by different subjects for the same action. This paper presents a recognition algorithm by using skeleton information generated from depth maps. Concatenating motion features and temporal constraint feature produces feature vector. Reducing dictionary scale proposes an improved fast classifier based on sparse representation. The developed method is shown to be effective by recognizing different activities on the UTD-MHAD dataset. Comparison results indicate superior performance of our method over some existing methods.

Mediastinal Emphysema, Giant Bulla, and Pneumothorax Developed during the Course of COVID-19 Pneumonia

Ruihong Sun,Hongyuan Liu,Xiang Wang 대한영상의학회 2020 Korean Journal of Radiology Vol.21 No.5

The coronavirus disease 2019 (COVID-19) pneumonia is a recent outbreak in mainland China and has rapidly spread to multiple countries worldwide. Pulmonary parenchymal opacities are often observed during chest radiography. Currently, few cases have reported the complications of severe COVID-19 pneumonia. We report a case where serial follow-up chest computed tomography revealed progression of pulmonary lesions into confluent bilateral consolidation with lower lung predominance, thereby confirming COVID-19 pneumonia. Furthermore, complications such as mediastinal emphysema, giant bulla, and pneumothorax were also observed during the course of the disease.

An overview on advances in computational fracture mechanics of rock

Mohammadnejad Mojtaba,Liu Hongyuan,Chan Andrew,Dehkhoda Sevda,Fukuda Daisuke 한국자원공학회 2021 Geosystem engineering Vol.24 No.4

Due to its complexities, rock fracturing process still poses many pressing challenges despite intense research efforts. With the rapid development of computational mechanics, numerical techniques have gradually become robust tools for the investigation of rock fracture. Nevertheless, not all of the devised methods are capable of adequately modelling the rock fracture process. For an accurate simulation of the process, a numerical method needs to be capable of modelling crack initiation, propagation, bifurcation, coalescence and separation. This paper provided a review of recent advances in computational analysis of the rock fracture process, which is built upon a number of literature on numerical modelling of mechanics of failure in rock and other brittle materials. After briefly discussing the fundamentals of rock fracture mechanisms, the basic structure of the existing and recently developed numerical techniques such as finite element method, boundary element method, distinct element method, combined methods and multi-scale coupled method are illustrated. Finally, the strengths and weaknesses of these numerical techniques are discussed and the most promising methods are highlighted.