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Flexural performance of layered macro fiber reinforced concrete beams

CONSTRUCTION AND BUILDING MATERIALS 2022年 357卷

作者： Yuan, Hong Fu, X. H. Fan, Y. C. Fu, Bing Zouc, Q. Q. 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 Southern Univ Sci & Technol Dept Ocean Sci & Engn Shenzhen 518055 Peoples R China

Fiber-reinforced polymer (FRP) composites have been increasingly used in various sectors, which inevitably results in an increasing amount of FRP waste to be dealt with. A recent study conducted by the authors' group explored a novel mechanical recycling method to process glass fiber-reinforced polymer (GFRP) waste into small slender elements (referred to as "macro fibers") for reinforcing concrete, leading to so called "macro fibre reinforced concrete" (i.e., MFRC). The macro fibres recycled from waste FRP composites shows to effectively enhance the tensile performance of the resulting concrete (e.g., tensile strength, tensile toughness), while have a negligible effect on the compressive properties of MFRC. The concept of the layered beams has been therefore adopted with the bottom layer fabricated with MFRC and the top layer with plain concrete (PC) to improve the utilization and added values of the macro fibers from the structural level. A series of tests were conducted to justify the proposed technique. Test results indicate that an increase of 4.6%, 27.6%, and 44.3% in splitting tensile strength was observed for concrete with a macro fiber content of 1%, 1.5%, and 2%, respectively. Some of other mechanical properties of the resulting concrete (e.g., the compressive toughness, flexural strength and flexural toughness) were apparently enhanced as well by the incorporation of macro fibers. In addition, the flexural performance of concrete beams shows to be superior if the macro fibers mainly concentrated in the bottom layer (i.e., a layered beam), demonstrating a higher utilization and added values of macro fibers achieved by the application of layered beams.

关键词： GFRP wastes Mechanical recycling Macro fiber Fiber reinforced concrete Layered beam

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Nonlinear Flutter Analysis for a Long-Span Suspension Bridge

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SHOCK AND VIBRATION 2021年第1期2021卷

作者： Liu, Jieshan Wang, Fan Yang, Yang Liu, Renhuai 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

The wind-induced flutter of the long-span suspension bridge structure is extremely harmful to the bridge. Therefore, it is necessary to study the nonlinear problem of wind-induced flutter. Here, the nonlinear flutter problem of a long-span suspension bridge with cubic torsional stiffness is analyzed by the equivalent linearization method. The system has Hopf bifurcation and limit cycle oscillations (LCOs) under critical wind speed. Replacing the nonlinear stiffness term of the original nonlinear equation with the equivalent linear stiffness, we can obtain the equivalent linearized equation of the nonlinear flutter system and the solution, critical wind speed, and flutter frequency of the suspension bridge flutter system. At the same time, the system has a limit cycle vibration, and the Hopf bifurcation point is obtained. Compared with the numerical method, the calculation results are consistent. The influence of the damping ratio on the flutter system is analyzed. Increasing the system damping ratio can increase the flutter critical wind speed and reduce the amplitude of LCOs. The influence of cubic torsional stiffness on the flutter system is analyzed. The increase of the cubic stiffness coefficient does not change the critical state of flutter, but reduces the amplitude of LCOs.

关键词： Nonlinear equations

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Experimental analysis and prediction of mechanical properties of soft palate using machine learning 10

Experimental analysis and prediction of mechanical propertie...

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10th Australasian Congress on Applied Mechanics, ACAM 2021

作者： Chen, Liujie He, Chaobo Yao, Haodong Ng, Ching Tai Xiao, Tan Zhang, Xiangming 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 Center for Mechanical Teaching and Testing Guangdong University of Petrochemical Technology Guangdong Maoming China The sixth Affiliated Hospital of Sun Yat-sen University Guangdong Guangzhou China

ISBN: (纸本)9781925627596

The mechanical properties of the soft palate are nonlinear and anisotropic, which are important for explaining the occurrence of Obstructive Sleep Apnea Hypopnea Syndrome (OSAHS). The thick and hypertrophic soft palate in the upper airway cavity can easily lead to OSAHS. Therefore, understanding the mechanical properties of the soft palate is essential for further analysis of the mechanical mechanism of OSAHS. Previous studies on the mechanical properties of soft tissue established the constitutive relation between material deformation and internal force by constructing explicit function to fit experimental data for obtaining the related mechanical parameters. However, this process inevitably introduces errors and uncertainties, and some of the information in the data is lost. In this study, we used a pig soft palate as an example and carried out uniaxial tension and stress relaxation experiments for understanding the nonlinear and viscoelastic mechanical characteristics of the soft palate. Furthermore, the experimental data was used to construct the Multi-Layer Perceptron (MLP) model for studying the stress-strain relationship. To verify the proposed method, the predicted elastic modulus of the fitted data using the MLP model were compared with that calculated by the experimental data. The results show that the elastic modulus of soft palate predicted by MLP model is very close to that obtained by the experimental results. Therefore, the machine learning model based on MLP can provide a better prediction on the elastic modulus of the soft palate. In particular, there are three key findings: (i) the stress-strain curves of the soft palate with different sections have small variation and different sections have similar tensile properties;(ii) the soft palate has obvious stress relaxation phenomenon, and smaller magnitude of the initial stress has faster rate of decrease and larger reduction in stress over time;(iii) the initial stress of the soft palate is linearly c

关键词： Stress-strain curves

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The Change in the Distribution of the ‘Three Zones’ of Spontaneous Combustion of Coal in a Coal Mine Goaf with a Retained Roadway by Roof Cutting

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Solid Fuel Chemistry 2025年第1期59卷 60-75页

作者： Li, Lin Zhang, Shufan Chen, Xiangjun Li, Zhiqiang Wang, Lin Yuan, Junwei College of Safety Science and Engineering Henan Polytechnic University Jiaozuo China MOE Engineering Center of Mine Disaster Prevention and Rescue Henan Polytechnic University Jiaozuo China Collaborative Innovation Center of Coal Work Safety and Clean High Efficiency Utilization Henan Polytechnic University Jiaozuo China Henan Provincial Key Lab of Gas Geology and Control-Cultivation Base of Provincial and Ministry Joint State Key Henan Polytechnic University Jiaozuo China

The roof-cutting and pressure-release (RCPR) mining mode can eliminate coal pillar between the adjacent mining faces by automatically forming roadways, which shows the better mining efficiency and economy than the traditional longwall mining mode. However, this mining mode causes changes in the collapse characteristics of the overlying rock and air leakage in a coal mine goaf, which may influence spontaneous combustion of coal in a coal mine goaf. To study the distribution of the spontaneous coal combustion zone in the coal mine goaf under the RCPR mining mode, the distributions of oxygen concentration and temperature in a coal mine goaf are simulated and analyzed after the simulation verification to reveal the new characteristics of the spontaneous coal combustion zone. The research results show that (1) the spontaneous coal oxidation zone is in the type of letter C, different from the one under the traditional longwall mining mode; (2) the air leakage pathway in the type of letter S causes the unique spontaneous coal oxidation zone, which is different from the air leakage pathway in the type of right parenthesis under the traditional longwall mining mode; (3) a temperature index to divide the spontaneous coal combustion zone is determined by the comparison between the temperature distribution and oxygen concentration distribution.

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Valorization of macro fibers recycled from decommissioned turbine blades as discrete reinforcement in concrete

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JOURNAL OF CLEANER PRODUCTION 2022年第Part2期379卷

作者： Xu, Guang-Ti Liu, Ming-Jie Xiang, Yu Fu, Bing Jinan Univ Sch Mech & Construct Engn Guangzhou 510632 Peoples R China Hong Kong Polytech Univ Dept Civil & Environm Engn Hong Kong Peoples R China Jinan Univ MOE Key Lab Disaster Forecast & Control Engn Guangzhou 510632 Peoples R China

The extensive use of glass fiber-reinforced polymer (GFRP) composites has inevitably resulted in a large amount of FRP waste, posing a significant environmental threat. A recent study performed by the authors' group of the present study pioneered a new mechanical method of recycling GFRP wind turbine blades into macro fibers, in which the macro fibers characterized by a fixed-length have been produced using a manual process of low efficiency and high cost, making it impossible for use in a practical application. In the present study, a shredding machine has been therefore used to efficiently process waste GFRP wind turbine blades into macro fibers of hybrid lengths lesser than 100 mm for being incorporated into concrete. A series of tests were carried out to investigate the properties of the resulting concrete, and the test results of beam specimens were then analyzed using a twice inverse analysis approach. The results of compression tests and four-point bending tests showed that the incorporation of recycled macro fibers led to a slump loss of 54%, a compressive strength reduction of 14.07%, a flexural strength improvement of 37.85% and a significant flexural toughness enhancement of 36.8 times at a fiber volume ratio of 2.5%, as compared to those of plain concrete. The direct-tensile strength and the corresponding tensile strain obtained by a twice inverse analysis approach were about 2.26 MPa and 134 mu epsilon, respectively, as predicted by the inverse analysis based on flexural load-deflection curves. The macro fibers processed using a shredding machine are feasible for enhancing the performance of the resulting concrete, and can be economic-efficiently used for industrial scale applications.

关键词： Fiber -reinforced concrete (FRC) Fiber -reinforced polymer (FRP) Recycled Macro fibers Concrete

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Enhancing the Tribological Properties of Ta1 Titanium Alloy Via Surface Mechanical Composite Strengthening

SSRN

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SSRN 2022年

作者： Dai, Yan Li, Mao Kun Liu, Gang Ou, Gui Mei Yang, Feng Liu, Jing School of Materials and Architectural Engineering Guizhou Normal University Guiyang550025 China School of Materials and Metallurgy Guizhou University Guiyang550025 China Institute of Advanced Wear & Corrosion Resistance and Functional Materials MOE Key Lab of Disaster Forecast and Control in Engineering Jinan University Guangzhou510632 China

The main factor hindering the application of TA1 titanium alloy is its poor wear resistance. In this study, surface mechanical composite strengthening technology was proposed to prepare a gradient structure composite layer on the surface of TA1 titanium alloy to enhance the friction and wear properties. Experimental results show that the gradient structure composite layer can be effectively prepared using the surface mechanical composite strengthening technology on the surface of TA1 titanium alloy. Moreover, the microstructure and properties of the composite-strengthening layer were characterised using scanning electron microscopy, X-ray diffraction, electron backscatter diffraction, metallography microscopy, micro-scratch and friction wear tester . The composite-strengthening layer comprised an ~60-μm-thick mechanical deformation layer and a 20-μm-thick WC ( Tungsten Carbide , WC) particle-reinforced coating that formed a mechanical bond with the matrix. The mechanical deformation layer comprised the surface fine-grain zone and subsurface deformation twinning. The nano-hardness of the coating area is 21.771 GPa, ~8.3 times the TA1 matrix nano -hardness. Under the same conditions, the wear rate of the composite-strengthening layer is 4.03 × 10−4 (mm3·N−1·m−1), which is only 24.8% of the matrix wear rate. The wear mechanisms of the composite-strengthening layer are mainly abrasion wear and oxidation wear. The formation of the composite-strengthening layer improves the friction and wear properties of the TA1 titanium alloy. © 2022, The Authors. All rights reserved.

关键词： Wear resistance

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Shear transferring mechanism of the FPR-to-concrete bonded joint with end U-jacketing: A theoretical study

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STRUCTURES 2023年 56卷

作者： Lu, Tianhao Li, Peilong Cui, Chuying Wu, Jiayu Fu, Bing Jinan Univ Sch Mech & Construct Engn Guangzhou 510632 Peoples R China Southern Univ Sci & Technol Dept Ocean Sci & Engn Shenzhen 518000 Peoples R China Hong Kong Polytech Univ Dept Civil & Environm Engn Hong Kong Peoples R China Jinan Univ MOE Key Lab Disaster Forecast & Control Engn Guangzhou 510632 Peoples R China

Installation of fiber reinforced polymer (FRP) U-jackets is an effective method for improving the low utilization rate of the expensive FRP material in the application of flexural strengthening of the reinforced concrete (RC) beam. The stress transfer mechanism of the FPR-to-concrete bonded joint with end U-jacket still remains poorly understood. This study proposed a new analytical model to predict the interfacial debonding process and the load carrying capacity of the joint with end U-jacket. The failure process of the FRP-to-concrete joint with an inclined U-jacket features five stages including elastic, elastic-softening, elastic-softening-debonding, softening-debonding and completely debonding stages. Expressions for the interfacial shear stress distribution and load-displacement relation are derived for these five stages. The load-displacement curve predicted by the analytical model, indicating that the bearing capacity of the joint with end U-jacket has increased by 200%, is in good agreement with the experimental and FE analysis results. Finally, the results from analytical solutions are presented to clarify the effects of the bond length, the FRP plate stiffness and the elasticity coefficient of end U-jacket on the load-displacement relations, the ultimate load and the effective bond length.

关键词： FRP Reinforced concrete beams Flexural strengthening Debonding Anchorages

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Monitoring abnormal vibration and structural health conditions of an in-service structure from its SHM data

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JOURNAL OF SOUND AND VIBRATION 2022年 537卷

作者： Li, X. Y. Guan, Y. H. Law, S. S. Zhao, W. Jinan Univ Sch Mech & Construct Engn MOE Key Lab Disaster Forecast & Control Engn Guangzhou 510632 Peoples R China Jinan Univ Sch Mech & Construct Engn Guangzhou 510632 Peoples R China Chongqing Univ Sch Civil Engn Chongqing 400044 Peoples R China

Vortex-induced vibration occurred recently in several important engineering structures in China. Very large mono-frequency periodic vibration was noted. This study reports on the analysis of recorded data from the structural health monitoring (SHM) system of a suspension bridge with the aim to develop some indicators that may be useful to evaluate if there is any abnormal vibration or change of health conditions of a structure in future. The power spectrum of measured acceleration responses is plotted in three-dimensions of time, frequency and power. Acceleration responses from 16 sensors on the target bridge deck in 233 days are analyzed. The evolution of different dynamic parameters in the period encompassing the occurrences of large vortex-induced vibration are reported. The changes in these parameters are identified to be closely associated with some temporary installations on the deck and temporary measures for vibration suppression. The changes in vibration power at different natural frequencies of the structure can be used to demonstrate the evolution of the unexpected event. The trend and abrupt changes of natural frequencies and modal components show the flow of vibration energy between different vibration modes. In addition to the intuitive three-dimension power spectral plot, two state vectors are also developed from the power spectrum. The identification of abnormal vibration and structural state can then be carried out automatically with the novelty detection method and a threshold. The analysis of the SHM acceleration responses of the bridge deck demonstrates the implementation procedure and the effectiveness of the proposed method.

关键词： Abnormal vibration Long-term monitoring Vibration power Power spectral density Novelty detection

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Experimental testing and system identification of the sliding bistable nonlinear energy sink implemented to a four-story structure model subjected to earthquake excitation

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JOURNAL OF BUILDING engineering 2022年 61卷

作者： Chen, Yang-Yang Su, Wei-Te Tesfamariam, Solomon Qian, Zhi-Chao Zhao, Wei Shen, Chao-Yong Zhou, Fu-lin Guangzhou Univ Earthquake Engn Res & Test Ctr Key Lab Earthquake Resistance Earthquake Mitigat & Struct SafetyMOE Guangzhou 510006 Peoples R China Univ British Columbia Sch Engn Okanagan Campus Kelowna BC Canada Jinan Univ Sch Mech & Construction Engn Key Lab Disaster Forecast & Control Engn MOE Guangzhou 510632 Peoples R China

Bistable nonlinear energy sink system has been explored as an efficient vibration absorber in many areas. This paper aims to experimentally validate the seismic mitigation performance of sliding bistable nonlinear energy sink (SBNES) for multi-story building structures. An SBNES device was designed and placed on top of a four-story building structure model. Earthquake ground motions were applied through a shake table as the base excitation input into the structure model. By matching the time history envelope curves between the experiment and numerical simulation, the structural parameters of the primary structure, as well as the constitutive model of the SBNES, were experimentally determined. The comparisons between mitigated and unmitigated structural responses, including inter-story drift, acceleration, base-shear force and baseoverturning moment of the primary structure, show that substantial reduction of structural seismic responses can be achieved by the SBNES device. The 1:1 transient internal resonance is verified as the dominant scheme for highly efficient targeted energy transfer. With respect to variation of peak ground acceleration, a relatively optimal interval distributed near the borderline of intra-well and inter-well regime is proposed for robust SBNES design. The test validates the potential of the SBNES strategy for both acceleration and displacement control of multi-story building structures.

关键词： Sliding bistable nonlinear energy sink Seismic response mitigation Shake table test Parametric identification Targeted energy transfer

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Investigation of nonlinear torsional guided wave mixing in pipes buried in soil

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engineering STRUCTURES 2022年 273卷 1页

作者： Ng, Ching Tai Yeung, Carman Yin, Tingyuan He, Yuncheng Chen, Liujie Univ Adelaide Sch Civil Environm & Min Engn Adelaide SA 5005 Australia Guangzhou Univ Res Ctr Wind Engn & Engn Vibrat Guangzhou 510006 Guangdong Peoples R China Guangzhou Univ Key Lab Disaster Forecast & Control Engn 3MOE Guangzhou Guangdong Peoples R China

Pipes have been widely applied in different engineering areas, such as drainage and the conveyance of chemical products and they are usually installed underground. This makes the structural integrity inspection becomes challenging. Numerous studies investigated the phenomenon of guided wave propagation in buried pipes and the wave interaction with different types of damage, e.g. corrosion and thermal damage. However, very limited studies focused on studying guided wave mixing in embedded pipes, which has recently attracted significant research interest for damage detection. This study develops a three-dimensional (3D) finite element (FE) model incorporating strain energy function to analyse wave mixing phenomena in pipes embedded in the soil. To characterise nonlinear features, such as combinational harmonic generation, due to guided wave mixing, the 3D FE model is used to simulate two torsional guided waves interacting with each other. The numerical results are then verified by experimentally measured data and the results show that the amplitude in the frequency-domain exhibits a sharp drop due to the energy leakage in the existence of soil medium at fundamental frequencies, second and combinational harmonics.

关键词： Guided wave mixing Combinational harmonic Second harmonic Material nonlinearity Finite element Buried pipes

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