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Buckling and post-buckling of delaminated Reissner-Mindlin panels subjected to hygro-thermal-mechanical multi-field loading

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THIN-WALLED STRUCTURES 2021年 162卷 107583-107583页

作者： Xia, Fei Xue, Jianghong He, Zanhang Yao, Sishi Jin, Fusong Yuan, Hong Jinan Univ Sch Mech & Construct Engn MOE Key Lab Disaster Forecast & Control Engn Guangzhou 510632 Peoples R China

This paper proposed a theoretical study on buckling and post-buckling responses for delaminated Reissner- Mindlin composite panels under hygrothermal environment based on the first order shear deformation theory. Constitutive equations of the laminated panel which takes into consideration of the transverse shear and the hydrothermal effects were conducted. Using the von-Kaman nonlinear displacement-strain relationship governing equations in terms of displacements and the slope functions were derived in which the nonlinear contact effect at the interface of delamination was included. Asymptotic solutions of the delaminated composite panel were obtained using perturbation approach and the post-buckling equilibrium paths of the panel characterized by the in-plane load vs deflection amplitude curves were determined via Galerkin approach. By developing Matlab programs, theoretical solutions were computed and parametric studies were carried out to examine the effect of the temperature, the hygroscopic concentration and the delamination conditions on the buckling and post-buckling behaviors of the delaminated panel. It is found that increasing the environmental temperature and hygroscopic concentration will significantly reduce the load carrying capacity of the delaminated composite panels in buckling and post-bucking stage. Solutions from the analysis were validated against finite element results from ABAQUS analysis and were found in good agreement with the latter.

关键词： Hygrothermal effect Transverse shear deformation Buckling and post-buckling analysis Contact effect Delamination

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A Multi-State Strategy for Structural Damage Detection Using Sensitivity of Weighted Transmissibility Function

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INTERNATIONAL JOURNAL OF STRUCTURAL STABILITY AND DYNAMICS 2021年第10期21卷

作者： Luo, Ziwei Liu, Huanlin Yu, Ling Jinan Univ Sch Mech & Construct Engn MOE Key Lab Disaster Forecast & Control Engn Guangzhou 510632 Peoples R China

In practice, a model-based structural damage detection (SDD) method is helpful for locating and quantifying damages with the aid of reasonable finite element (FE) model. However, only limited information in single or two structural states is often used for model updating in existing studies, which is not reasonable enough to represent real structures. Meanwhile, as an output-only damage indicator, transmissibility function (TF) is proven to be effective for SDD, but it is not sensitive enough to change in structural parameters. Therefore, a multi-state strategy based on weighted TF (WTF) is proposed to improve sensitivity of TF to change in parameters and in order to further obtain a more reasonable FE model for SDD in this study. First, WTF is defined by TF weighted with element stiffness matrix, and relationships between WTFs and change in structural parameters are established based on sensitivity analysis. Then, a multi-state strategy is proposed to obtain multiple structural states, which is used to reasonably update the FE model and detect structural damages. Meanwhile, due to fabrication errors, a two-stage scheme is adopted to reduce the global and local discrepancy between the real structure and the FE model. Further, the l(1)-norm and the l(1/2)-norm regularization techniques are, respectively, introduced for both model updating and SDD problems by considering the characteristics of problems. Finally, the effectiveness of the proposed method is verified by a simply supported beam in numerical simulations and a six-storey frame in laboratory. From the simulation results, it can be seen that the sensitivity to structural damages can be improved by the definition of WTF. For the experimental studies, compared with the FE model updated from the single structural state, the FE model obtained by the multi-state strategy has an ability to more reasonably describe the change of states in the frame. Moreover, for the given structural damages, the proposed method can

关键词： Structural damage detection (SDD) model updating transmissibility function (TF) multi-state strategy regularization techniques

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Ultra-high performance concrete reinforced with macro fibres recycled from waste GFRP composites

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CASE STUDIES IN CONSTRUCTION MATERIALS 2023年 18卷

作者： You, X. M. Lin, L. B. Fu, Bing Xiang, Yu Jinan Univ Sch Mech & Construct Engn Guangzhou 510632 Peoples R China Jinan Univ MOE Key Lab Disaster Forecast & Control Engn Guangzhou 510632 Peoples R China Hong Kong Polytech Univ Dept Civil & Environm Engn Hong Kong Peoples R China

Ultra-high-performance concrete (UHPC) is a promising cementitious composite to produce lightweight and high-performance structures. Steel fibres are an essential constituting material of UHPC to prevent the brittle failure of UHPC, but the high cost steel fibres impedes the wider application of UHPC to some extent. This paper proposes a concept to produce UHPC reinforced with macro fibres processed from waste glass-fibre-reinforced polymer (GFRP) composites, therefore addressing two issues of the high cost of UHPC as well as the difficulty in disposal of waste GFRP simultaneously. A series of tests have been carried out to investigate the effect of adding macro fibres on the properties of UHPC. The test results show that the incorporation of macro fibres leads to a loss of the workability and a reduction of up to 21.8 % in the compressive strength, but improves the flexural strength and flexural toughness greatly by up to 27.9 % and 46.9 times, respectively. The tensile constitutive relationship has been converted from the results of the bending tests through inverse analyses. The proposed concept of producing UHPC with recycled macro fibres contributes to lowering the price of UHPC, whose properties are compa-rable to that of UHPC with steel fibres, and establishing an effective routine to valorise the waste GFRP.

关键词： Ultra -high-performance concrete (UHPC) GFRP waste Mechanical recycling Fibre -reinforced concrete Macro fibres

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A semi-convex function for both constant and time-varying moving force identification

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MECHANICAL SYSTEMS AND SIGNAL PROCESSING 2021年 146卷 107062-107062页

作者： Liu, Huanlin Luo, Ziwei Yu, Ling Jinan Univ Sch Mech & Construct Engn MOE Key Lab Disaster Forecast & Control Engn Guangzhou 510632 Peoples R China

In recent years, many moving force identification (MFI) methods have been proposed to monitor moving forces indirectly from structural responses. However, the prior knowledge about moving forces has not been reasonably considered in the existing methods, so the identified moving forces are not accurate enough. To improve the accuracy of MFI results, a novel MFI method is proposed based on a semi-convex function in this study. Firstly, a model of a simply-supported beam subjected to moving forces is taken as an example to establish the relationship between moving forces and structural responses. Then, the prior knowledge that time-varying force component of a moving force usually fluctuates around its static weight in the time domain is adopted. Thus, the moving force is decomposed into constant and time-varying force components. The constant force component is unchanged over time and the time-varying force component is changed over time. Based on this prior knowledge, a semi-convex function is defined for MFI, which is inspired by an alternating iterative method (AIM) and regularization techniques. As a result, the semi-convex function is solved by the AIM, so the constant and time-varying force components can be respectively obtained through iterations, and the moving forces are identified from structural responses. Finally, to evaluate the effectiveness of the proposed method, both numerical simulations and experimental verifications are carried out. The identified results show that the proposed method can further improve the MFI results by comparing with the L-2 regularization and the moving average Tikhonov regularization. The characteristics of the identified moving forces are consistent with that described in the given prior knowledge. Moreover, the proposed method can provide a good ability to estimate the total weight of the model car. (C) 2020 Elsevier Ltd. All rights reserved.

关键词： Moving force identification (MFI) Alternating iterative method (AIM) Semi-convex function Regularization technique

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A size-dependent model for shear deformable laminated micro-nano plates based on couple stress theory

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COMPOSITE STRUCTURES 2021年 259卷 113457-113457页

作者： He, Zanhang Xue, Jianghong Yao, Sishi Wu, Yongfu Xia, Fei Jinan Univ Sch Mech & Construct Engn MOE Key Lab Disaster Forecast & Control Engn Guangzhou 510632 Peoples R China

In this paper, a modified first order shear deformation theory is proposed for laminated micro-nano plates. Couple stress components are involved in the differential equations of equilibrium for shear deformable micro-nano plates, which are established by considering the deformation mechanism of an element cut from the micro-nano plate. Based on the mechanics of composite materials and Koiter's theory, the constitutive equations for laminated micro-nano plates are established to characterize the relationships between Cauchy stress tensor and the strain tensor, the couple-stress tensor and the curvature tensor. Governing equations with size-dependent effect are derived and are expressed in terms of the displacements and the rotation functions. The proposed theory is applied to investigate the eigenvalue buckling and free vibration of laminated micronano plates simply supported at the four sides. Matlab program based on the analytical solutions is developed and is testified by comparing the solutions for isotropic micro-nano plates from the proposed theory against those from an available model and from ABAQUS analysis. Various examples are studied to investigate the influence of scale ratio, aspect ratio, length-to-thickness ratio, material properties and stacking sequence on the buckling and free vibration response of the laminated micro-nano plates. The size-dependent effect is captured for all examples, particularly for micro-nano isotropic laminated plate with geometry size similar to its material length scale parameter, where the buckling load may be nearly up to 10 times larger than that given by the FSDT theory. A good agreement among solutions from the Matlab program, the existing literature and ABAQUS analysis demonstrates the efficiency and accuracy of the proposed theory.

关键词： Couple stress theory Scale effect Laminated micro-nano plates Shear deformation theory Buckling Free vibration

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Experimental study of magnetic bistable nonlinear energy sink for structural seismic control

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SOIL DYNAMICS AND EARTHQUAKE engineering 2023年 164卷

作者： Chen, Yangyang Su, Weite Tesfamariam, Solomon Qian, Zhichao Zhao, Wei Yang, Zhenyu Zhou, Fulin Guangzhou Univ Earthquake Engn Res & Test Ctr MOE Key Lab Earthquake Resistance Earthquake Miti Guangzhou 510006 Peoples R China Guangzhou Univ Guangdong Prov Key Lab Earthquake Engn & Appl Tec Guangzhou Peoples R China Univ British Columbia Sch Engn Okanagan Campus Kelowna BC Canada Jinan Univ Sch Mech & Construct Engn MOE Key Lab Disaster Forecast & Control Engn Guangzhou 510632 Peoples R China

In previous work, magnetic bistable nonlinear energy sink (MBNES) had been numerically demonstrated as an efficient absorber for seismic mitigation of shear-frame structures. The present paper, for the first time, exper-imentally investigates the MBNES device, as well as its control performance using both cyclic-load and shake -table tests. Both spatial magnetic force and sliding friction were included in the proposed MBNES model and the device was designed, manufactured, and assembled in the lab. The cyclic-load tests were conducted to validate and calibrate the theoretical model of the MBNES. Subsequently, a series of shake-table tests of a one-story shear frame equipped with the present MBNES device was performed. By a proposed algorithm, the nu-merical model of the control system was successfully identified based on the response data. A comparison of the experimental and numerical results revealed the accuracy of the identified numerical model. By using the present device, significant suppressions of the seismic responses were observed. The transient internal resonance cap-tures of the MBNES control system can also be observed during the seismic responses. The study experimentally demonstrates the potential of the MBNES device as an efficient absorber for seismic mitigation of structures.

关键词： Nonlinear energy sink Shake table test Cyclic-loading test Magnetic charge model Seismic mitigation

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Application of MobilenetV3-Large model improved by transfer learning and CBAM Module in crack recognition and classification 10

Application of MobilenetV3-Large model improved by transfer ...

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10th Australasian Congress on Applied Mechanics, ACAM 2021

作者： Chen, Liujie Yao, Haodong Ng, Ching Tai Fu, Jiyang School of Civil Engineering Guangzhou University Guangdong Guangzhou China MOE Key Lab of Disaster Forecast and Control in Engineering Guangdong Guangzhou China School of Civil Environmental & Mining Engineering The University of Adelaide SA Australia Research Center for Wind Engineering and Engineering vibration Guangzhou University Guangdong Guangzhou China

ISBN: (纸本)9781925627596

Crack is an important indication for assessing the condition and safety of concrete structures. Quick and accurate crack feature extraction and classification performance of deep learning model are important in crack classification. Therefore, this study proposed a crack classification method based on the modified lightweight neural network. The proposed method uses MobileNetV3-Large pre-trained using an ImageNet dataset as backbone and then adopts the Convolution Block Attention Module (CBAM), which contains two modules, Channel Attention Module and Spatial Attention Module. Without increasing the number of model parameters, CBAM can strengthen the ability of the neural network in crack feature extraction. The image dataset of concrete structures for verifying the proposed method contains four different types of cracks: transverse cracks, vertical cracks, diagonal cracks, and irregular cracks. Other deep learning models, such as MobileNetV3-Large, VGG16, EfficentNetB0, GoogLeNet, Efficentnetv2-S, are also used for the crack classification in this study and the results are compared with those obtained by the proposed method. The results demonstrate that the proposed method has the best performance with the minimum training time at 100 images/s and prediction time at 47.6 images/s, Accuracy of 95.93%, Precision of 95.95%, Recall of 95.95%, and Macro-F1 of 96.20%. The results indicate that the proposed method can effectively improve the accuracy of crack recognition and classification. It can also strengthen the ability of the network in extracting the complex crack image features. The proposed method can be applied practically for automatic crack detection. © ACAM 2021. All rights reserved.

关键词： Concrete buildings

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The Effects of RF Power and Cavity Structure on the Plasma Discharge Characteristics of RPS

The Effects of RF Power and Cavity Structure on the Plasma D...

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Electronics and Devices, Computational Science (ICEDCS), International Conference on

作者： Hai Lin Wei Su Ming Chen Renhuai Liu School of Mechanics and Construction Engineering Jinan University Guangzhou China Science and Technology on Reliability Physics and Application Technology of Electronic Component Laboratory China Electronic Product Reliability and Environmental Testing Research Institute Guangzhou China MOE Key Lab of Disaster Forecast and Control in Engineering Guangzhou China

In this paper, a two-dimensional model of plasma diffusion in remote plasma source discharge chamber is established by COMSOL plasma module. The electron density and electron temperature distributions inside the discharge cavity were obtained by adjusting the thickness of alumina coating and the magnitude of RF power parameters. Based on the results, the authors discuss the effects of different alumina coating thickness and RF power on the electron density and electron temperature inside the discharge cavity, which provide theoretical guidance for the subsequent optimization of the internal structure of the discharge cavity and the discharge parameters.

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The mechanism of inward and outward expansion of multiscale dynamic permeability of coalbed methane at different temperatures

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Deep Underground Science and engineering 2023年第1期2卷 88-101页

作者： Zhiqiang Li Xiaoqiang Hao Yanwei Liu Lin Li MOE Engineering Center of Mine Disaster Prevention and Rescue Henan Polytechnic UniversityJiaozuoChina Collaborative Innovation Center of Coal Work Safety and Clean High Efficiency Utilization Henan Polytechnic UniversityJiaozuoChina Collaborative Innovation Center of Coalbed Methane and Shale Gas for Central Plains Economic Region(Henan Province) Henan Polytechnic UniversityJiaozuoChina Henan Provincial Key Lab of Gas Geology and Control‐Cultivation Base of Provincial and Ministry Joint State Key Henan Polytechnic UniversityJiaozuoChina

The multiscale micro-nano pores in coal can result in the ultra-low permeability of coal,which restricts the efficiency of gas *** is difficult for the conventional seepage-enhancement measures to affect the nanoscale pores within the coal *** stimulation can reach deep into the micro-nano pores within coal matrix to improve the ***,it is important to study the diffusivity and permeability of the multiscale micro-nano pores at different *** this study,the experiments of diffusion-seepage measured by the methods of GRI(Gas Research Institution)and steady-state were conducted using a cylindrical coal at different temperatures and *** experimental results show that the apparent diffusion coefficient of cylindrical coal is not constant but variable dynamically;and the classical diffusion model fails to describe the full-time process of gas flow *** this basis,a model of multiscale dynamic apparent diffusion-seepage that can accurately describe the full-time flow process was *** is observed,the apparent permeability attenuates dynamically with time without stress loading,and the initial apparent permeability and the attenuation coefficient increase monotonically with the rise of *** the stress constraint,the steady-state permeability increases after a decrease as the temperature rises,displaying a“U-shaped”*** stress constraint,the increasing temperature causes the exterior multiscale pores to expand outward by different degrees so as to increase permeability,while the interior micro-nano pores show three inward and outward expansion *** stress constraint,at low temperature and high effective stress,the increasing temperature causes pores to expand inward and the permeability decreases *** temperature continues to increase,coal expands outward because the effective stress is counteracted by the thermal stress,leading to an increase in permea

关键词： diffusion dynamic gas permeability seepage temperature

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A first order reliability method based on hybrid conjugate approach with adaptive Barzilai-Borwein steps

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COMPUTER METHODS IN APPLIED MECHANICS AND engineering 2022年第PartB期401卷 1页

作者： Wang, Xiaoping Zhao, Wei Chen, Yangyang Li, Xueyan Jinan Univ Sch Mech & Construct Engn MOE Key Lab Disaster Forecast & Control Engn Guangzhou 510632 Peoples R China Guangzhou Univ Earthquake Engn Res & Test Ctr Guangzhou 510405 Peoples R China

In the first order reliability method (FORM), the Hasofer-Lind and Rackwitz-Flessler (HL-RF) algorithm sometimes encounters numerical instability problems due to the highly nonlinear limit state function (LSF). In this paper, an improved HL-RF algorithm introducing the hybrid conjugate gradient method with adaptive Barzilai-Borwein step sizes is developed to enhance the robustness and efficiency of the original HL-RF method. The proposed algorithm is composed of two stages, the steepest descent method is performed in the first stage to move to the vicinity of the most probable failure point (MPFP) and provide a good initial location for the second stage. Along with the hybrid conjugate search direction defined by the descent direction of the non-differential merit function, the second stage quantizes the adaptive Barzilai-Borwein step sizes to accelerate the process of locating the final MPFP under the nonmonotone line search rule. Eight illustrative examples with nonlinear LSFs are analyzed in detail to validate the performance of the proposed algorithm compared with other first order reliability methods. The results indicate that the proposed algorithm is not only computationally efficient but also robust in terms of convergence, especially for those problems with super nonlinear LSFs and with nonlinear LSFs involving high-frequency noise terms. (c) 2022 Elsevier B.V. All rights reserved.

关键词： First order reliability method Most probable failure point Reliability index Conjugate gradient method Barzilai-Borwein step size

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