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Stress-strain behaviour of carbon fibre reinforced polymer-confined concrete containing macro fibres recycled from waste glass fibre reinforced polymer

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ADVANCES IN STRUCTURAL engineering 2024年第7期27卷 1189-1208页

作者： Zou, Qi-Qi Fu, Bing Chen, Jian-Fei Teng, Jin-Guang Harbin Inst Technol Sch Astronaut Harbin Peoples R China Southern Univ Sci & Technol Dept Ocean Sci & Engn Shenzhen Peoples R China Jinan Univ Sch Mech & Construct Engn Guangzhou Peoples R China Jinan Univ MOE Key Lab Disaster Forecast & Control Engn Guangzhou Peoples R China Hong Kong Polytech Univ Dept Civil & Environm Engn Hong Kong Peoples R China Jinan Univ Sch Mech & Construct Engn 601 Whampoa Ave West Guangzhou 510632 Peoples R China Southern Univ Sci & Technol Dept Ocean Sci & Engn 1088 Xuanyuan Ave Shenzhen 518055 Peoples R China

Glass fibre-reinforced polymer (GFRP) wastes may be mechanically processed into small strips called "macro fibres," which were used as short reinforcement fibres to produce macro fibre reinforced concrete (MFRC). The addition of such macro fibres into concrete has proven to be effective in enhancing the flexural strength and toughness of concrete, but it also slightly reduces the compressive strength of concrete. This paper presents a study on the behaviour of CFRP-confined MFRC. A total of 84 CFRP-confined MFRC cylinders were prepared and tested in axial compression. The test parameters included the CFRP confinement stiffness, macro fibre content, and fibre length. The test results show that the compressive strength and ultimate axial strain can be significantly enhanced through the use of CFRP confinement. The ultimate axial strain of CFRP-confined concrete with macro fibres is slightly higher than that without macro fibres. The test results were compared with two well-known stress-strain models for FRP-confined concrete, including Teng et al.'s design-oriented model and Jiang and Teng's analysis-oriented model. A comparative analysis showed that both models slightly underestimate the compressive strength and slightly overestimate the ultimate axial strain for CFRP-confined MFRC.

关键词： macro fibres mechanical recycling glass fibre-reinforced polymer waste confinement carbon fibre reinforced polymer concrete

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Vibration Characteristic Measurement Method of MEMS Gyroscopes in Vacuum, High and Low Temperature Environment and Verification of Excitation Method

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IEEE ACCESS 2021年 9卷 129582-129593页

作者： Luo, Wenhao Su, Wei Nie, Zhenhua Huang, Qinwen Li, Shiyuan Dong, Xianshan MOE Key Lab Disaster Forecast & Control Engn Guangzhou 510632 Peoples R China China Elect Prod Reliabil & Environm Testing Res Sci & Technol Reliabil Phys & Applicat Technol El Guangzhou 510610 Peoples R China Jinan Univ Sch Mech & Construct Engn Guangzhou 510632 Peoples R China

A method for measuring vibration characteristics of MEMS (Micro Electro Mechanical System) is presented. This method aims to simulate a real environment where MEMS operates. At first, the method of applying high and low temperature in a vacuum environment is studied. And the excitation method applying to movable microstructures of MEMS in this environment is found. Based on the above environmental conditions, the vibration characteristics of MEMS movable microstructure are measured by micro-laser vibration measurement. The base excitation method is used to measure the vibration characteristics of MEMS movable microstructures outside the plane. ANSYS 14.0 was used for finite element simulation to verify this method. The electrostatic excitation method is used to measure the inside of the plane. The stroboscopic method is used to verify the electrostatic excitation by fitting the displacement signal of the movable microstructure and the excitation output signal. The results show that the out-of-plane first-order frequency is 11.926 kHz, and the error is 0.30% compared with the experimental results. The amplitude is 44.218 nm, and the error is 0.59%. The in-plane first-order frequency is 5715.7Hz, which achieves the requirement of design precision. Both the numerical simulation and the stroboscopic method verify the excitation method well. The effect of temperature on the natural frequency of the structure is negatively correlated. And as the temperature drops, the motion of the structure becomes increasingly violent. The findings of this study provide important guidance for maintenance, reliable operation and optimal design of MEMS.

关键词： Temperature measurement Vibrations Micromechanical devices Microstructure Resistance heating Vibration measurement Heat transfer MEMS reliability vibration measurement with laser vacuum large temperature range

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Fault structure, seismicity, and magmatism of the Littoral Fault zone, northern South China sea: Insights from high-resolution seismic reflection data

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MARINE AND PETROLEUM GEOLOGY 2024年 160卷

作者： Zhang, Yanxin Ye, Xiuwei Wan, Kuiyuan Lv, Zuoyong Wen, Genggeng Xu, Shunshan Guangdong Earthquake Agcy CEA Key Lab Earthquake Monitoring & Disaster Mitig Guangzhou 510070 Peoples R China Guangdong Sci & Technol Collaborat Innovat Ctr Ear Guangzhou 510070 Peoples R China Urban Earthquake Safety Lab MOE Key Lab Disaster Forecast & Control Engn Guangzhou 510070 Peoples R China Chinese Acad Sci South China Sea Inst Oceanol CAS Key Lab Ocean & Marginal Sea Geol Guangzhou 510301 Peoples R China Southern Marine Sci & Engn Guangdong Lab Guangzhou Guangzhou 511458 Peoples R China Univ Nacl Autonoma Mexico Ctr Geociencias Queretaro 76230 Mexico

Four destructive M7+ earthquakes and 18 M6+ earthquakes demonstrate that the Littoral Fault Zone (LFZ) is one of the most seismically active regions in the offshore area of South China. However, the location, geometry, and structural characteristics of the LFZ, which spans over 1000 km, have not been properly examined. In this study, we investigate the precise position of the LFZ offshore East Guangdong (EGD) and map the fault structure using recently acquired high-resolution multi-channel seismic (MCS) reflection data. The LFZ consists of an array of normal faults that collectively form a terraced sidewall fault zone linked to the continental rifting of the South China Sea (SCS). This fault zone is approximately 35-75 km wide and runs parallel to the shoreline. The primary faults of the LFZ EGD segment correlate to a high-gravity gradient zone and serve as the northern boundary of the Zhu-I Depression. During the syn-rift phase, the LFZ experienced significant intra-plate deformation, resulting in fault throws of up to 1000 m. This deformation was locally influenced by pre-existing structures, giving rise to a listric geometry at depth. In the post-rift period, the LFZ exhibited inherited activity along its rift-related faults. The presence of growth fault structures suggests that the LFZ remained active throughout the Cenozoic, with numerous active faults extending practically to the seafloor. The negative flower structure confirms the strikeslip character of the LFZ, which is influenced by the modern tectonic stress field. Intense multi-phase Cenozoic magmatism, including igneous intrusion, volcanism, and lava flows, has been detected in the offshore area of Nan'ao Island. The frequent earthquakes in the study area are primarily attributed to far-field stress release resulting from the subduction of the Philippine Sea Plate beneath the Eurasian Plate. Additionally, the intense magmatism weakens crustal structures, further facilitating stress release and the frequ

关键词： Littoral Fault zone Active fault Magmatism Multi-channel seismic profile Northern South China sea

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Structural damage identification based on pattern matching using the flexibility change rate

EARTHQUAKE ENGINEERING AND RESILIENCE

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EARTHQUAKE engineering AND RESILIENCE 2023年第1期2卷 29-51页

作者： Nie, Zhenhua Chen, Tao Xia, Guanghao Li, Zuanfeng Gao, Ruofan Ma, Hongwei Jinan Univ Sch Mech & Construct Engn Guangzhou Guangdong Peoples R China Key Lab Disaster Forecast & Control Engn Guangzhou Guangdong Peoples R China Dongguan Univ Technol Sch Environm & Civil Engn Dongguan Peoples R China

In this paper, a rapid identification method for postearthquake structural damage is proposed based on pattern matching using the flexibility change rate. In the first stage, a small number of dynamic signals are collected for extracting the modal information, which is used as a reference for model updating. Using the updated finite element model of the structure to be monitored, the characteristic vector of the flexibility change rate is calculated by modal analysis from the first two orders of modal information of various damage scenarios to establish a pattern database. For the real structure, the measured responses are used to identify the modal parameters to calculate the flexibility change rate characteristic vector, which is treated as the observed pattern. Then, the similarity between the observed pattern and the pattern in the pattern database is calculated using the Euclidean distance (ED). The damage location and severity of the measured structure are treated to be the same as the pattern corresponding to the minimum value of ED, so that the damage is identified. Numerical simulations and experiments of two types of concentrated mass structures, four floors, and six floors confirm that the proposed method can identify the damage well. In addition, the matching results based on different sensor combinations demonstrate that the method can quickly identify the damage location and severity of a structure even using a limited number of sensors. The proposed method can provide support for the government in rapid postearthquake emergency decision-making. imageThis paper proposes a rapid damage identification method for postearthquake structure based on pattern matching using the flexibility change rate. Since the flexibility change rate is analytically related to the natural frequency and mode shape of the structure, it is not affected by external excitation. The first two orders of modal information are obtained from the target finite element method, and the f

关键词： flexibility change rate model updating pattern matching rapid damage identification

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Machine learning-based design and optimization of double curved beams for multi-stable honeycomb structures

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EXTREME MECHANICS LETTERS 2023年 65卷

作者： Yu, Jizhou Shi, Xinlai Feng, Yuxuan Chang, Jinke Liu, Junbang Xi, Huifeng Huang, Shiqing Zhang, Wenhua Jinan Univ MOE Key Lab Disaster Forecast & Control Engn Guangzhou 510632 Peoples R China Jinan Univ Sch Mech & Construct Engn Guangzhou 510632 Peoples R China UCL Div Surg & Intervent Sci London NW3 2PF England

Curved beams with bistable and negative stiffness properties can be used to design multi-stable metamaterials or honeycomb structures. Consequently, the deformation patterns and mechanical properties of curved beams under load have attracted many attentions. However, due to the nonlinear characteristics of variable thickness double curved beams, it is impossible to exhaust all possible structural forms through experimental and theoretical approaches. This paper presents a machine learning (ML) method for designing and optimizing double curved beam structures. The ML model is used to establish the underlying mapping relationship between thickness parameters and mechanical properties. After optimizing the double curved beam in different directions, the optimal thickness distributions of the backward snapping force and energy absorption are obtained. Double curved beams with optimal thickness distributions are used to construct multi-stable honeycomb structures, demonstrating the optimization process from single cell structure to periodic structure. Under the same mass, compared to the constant thickness honeycomb structure, the optimized variable thickness honeycomb structures exhibit a 140% increase in backward snapping force and a 57% increase in energy absorption. The objective of this study is to utilize machine learning technique to obtain a general approach for optimizing model of 'multiparameter input' to 'single-parameter output', which is valuable for guiding the optimization and design of metamaterial structures in the future. This paper is a good case study of the mechanical structure performance optimization, whose implementation path is given detailly in appendix. Other disciplines with similar optimization goals can also use this method to carry out researches.

关键词： Double curved beam Multi-stable structures Backward snapping force Energy absorption Structural optimization Machine learning

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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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Dynamics of a Gaussian and Non-Gaussian Vibration Excited Discrete Product Packaging System with Hyperbolic Tangent Nonlinearity

SSRN

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SSRN 2023年

作者： Yang, Song-Ping Deng, Pei-Chang Wang, Zhi-Wei Packaging Engineering Institute College of Packaging Engineering Jinan University Zhuhai519070 China MOE Key Laboratory of Disaster Forecast and Control in Engineering School of Mechanics and Construction Engineering Jinan University Guangzhou510632 China Key Laboratory of Product Packaging and Logistics of Guangdong Higher Education Institutes Jinan University Zhuhai519070 China

This paper reveals the dynamical properties of a Gaussian and non-Gaussian vibration excited multi-degree-of-freedom (MDOF) discrete product packaging system (DPPS) with hyperbolic tangent nonlinearity base on a more systematic acceleration response analysis. Firstly, the product package considering multiple critical components is modeled as a general model of MDOF DPPS, centered around the opposite designed purpose with the similar multiple tuned mass damper (MTMD) model, in which the hyperbolic tangent nonlinearity is rarely considered, then approximate solution theory is established to effectively predicate the acceleration response spectrum of the hyperbolic tangent MDOF DPPS under Gaussian random vibration. Secondly, Hermite polynomial is adopted to simulate non-Gaussian vibration excitation, and verified by the actual road excitation signal. On this basis, the non-Gaussian random vibration analysis method is introduced to analyze the acceleration non-Gaussian stochastic response of the system, the sensitivity of the response to the external excitation and system parameters is discussed. Finally, the reliability analysis via the first-passage distribution of the acceleration stochastic response is given. Approximate solution theory can effectively predict acceleration response spectrum of the system under Gaussian random vibration. The proposed non-Gaussian vibration analysis approach can conveniently reproduce actual non-Gaussian vibration excitation and analyze the dynamic properties, the investigation provides a guidance for packaging vibration absorption design. © 2023, The Authors. All rights reserved.

关键词： Reliability analysis

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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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Fusion of structural damage identification results from different test scenarios and evaluation indices in structural health monitoring

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STRUCTURAL HEALTH MONITORING-AN INTERNATIONAL JOURNAL 2021年第5期20卷 2540-2565页

作者： Li, X. Y. Lin, S. J. Law, S. S. Lin, Y. Z. Lin, J. F. Jinan Univ Sch Mech & Bldg Engn MOE Key Lab Disaster Forecast & Control Engn Guangzhou Peoples R China Jinan Univ Sch Mech & Bldg Engn Guangzhou Peoples R China Chongqing Univ Sch Civil Engn Chongqing Peoples R China Shenzhen Acad Disaster Prevent & Reduct China Earthquake Adm Ctr Safety Monitoring Engn Struct Shenzhen 518003 Peoples R China

There are many existing algorithms and damage indices that can effectively meet the engineering need in damage diagnosis. However, all of them (except those with an exact formulation) are based on certain assumptions with approximations, and their performances depend on the combination of test parameters, for example, type, number, and location of excitations and sensors;identification algorithm adopted;and environmental noise effect. Results obtained from different combinations of these test parameters are different and they may be mathematically biased or contradicting. Existing practice adopts the general indication of result for further maintenance decisions or by subjective screening the results with engineering sense. This article demonstrates the possibility to have a better design of the structural health monitoring system where the benefits of different damage indices and evaluation methodologies can be reaped via the fusion of the identified results. The scenario for discussion is the vibration-based damage localization problem. The change in mode shape in the modal domain and change in the covariance of impulse response function change in the time domain are selected as damage indices for the illustration. An exact form of the covariance of impulse response function is also proposed for this purpose. The demonstration is conducted via a simulated truss structure, an experimental beam, and 280 days valid recorded data from an in-service suspension bridge deck. Different measurements are analyzed to produce large number of identified results for reducing traffic excitation effect, the temperature effect, and so on, and to enhance the structural damage information in the final set of results. Experiences in handling the structural health monitoring data for monitoring the movement of a structural joint before and after a typhoon are also presented. The proposed strategy does not need a mathematical model of the structure, but this leads to heavy sensor requi

关键词： Damage identification acceleration Bayesian fusion covariance mode shape structural health monitoring damage localization

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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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