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Molecular mechanics mechanisms for ultralow bending stiffness of monolayer silicene

MATERIALS TODAY COMMUNICATIONS 2022年 33卷

作者： Yang, Mengyu Kuang, Youdi Jinan Univ Sch Mech & Construct Engn MOE Key Lab Disaster Forecast & Control Engn Guangzhou Peoples R China Wuyi Univ Sch Civil Engn & Architecture Jiangmen Peoples R China

Monolayer silicene, as one-atom thick membrane, has a bending stiffness of about 0.31 eV, even much lower than that of monolayer graphene for which only weak out-of-plane p-bonding interactions contribute to the elastic constant. To clarify the underlying mechanisms, we explore the origin of bending stiffness for silicene from the viewpoint of molecular mechanics. An approach to achieve high precision atomic interaction potential parameters are developed by combining independent deformation modes of lattices with quantum mechanical calculations. For comparison, the corresponding studies are also conducted for graphane and graphene. It is found that, different with the out-of-plane p-bonding interactions for graphene, the bending stiffness of silicene and graphane origins from the covalent angle interactions, the covalent bond interactions contribute little to their bending stiffness. The reasons for the significant discrepancy of bending stiffness value between these monolayers are clarified by means of the quantitative comparison of atomic interaction strength. Present work has a general implication in understanding nanomechanics of one atom thick monolayers.

关键词： Ultrathin monolayer Quantum mechanics calculations Lattice dynamics calculations Molecular mechanics mechanism Origin of bending stiffness

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Interfacial properties of CFRP sheets and concrete subjected to variable amplitude fatigue loading

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STRUCTURAL CONCRETE 2021年第4期22卷 1927-1945页

作者： Yuan, Hong Luo, Guangyun Liu, Chang Zeng, Lan Jinan Univ Sch Mech & Construct Engn MOE Key Lab Disaster Forecast & Control Engn Guangzhou 510632 Peoples R China

In order to better understand the interfacial fatigue behavior of concrete and fiber-reinforced polymer (FRP), bending fatigue tests were conducted on plain concrete beams strengthened with carbon FRP (CFRP) sheets under variable amplitude cyclic loading which deteriorates structural performance in actual projects more dramatically than constant amplitude loading. The test parameters were four types of loading modes including static loading, constant amplitude cyclic loading, alternating amplitude cyclic loading and incremental amplitude cyclic loading. Miner damage rule, modified Miner damage rule and Corten-Dolan cumulative damage rule were used to predict the fatigue life of specimens. The relationship between loads and deflections, the relationship between strains and cycle times and the crack propagation were analyzed. The results have shown that the fatigue life of specimens under variable amplitude cyclic loading, especially alternating one, is shorter than that of specimens under constant one, and the modified Miner damage rule is more suitable to predict fatigue life. The crack lengths on the lateral faces of beams recorded by digital image correlation (DIC) method developed more slowly than those at the bottom sides recorded by strain gauges. A proposed damage model describing the relationship between the crack lengths and fatigue life for specimens under alternating amplitude fatigue loading is consistent with the experimental results well.

关键词： carbon fiber reinforced polymer (CFRP) concrete reinforcement crack length interfacial properties variable amplitude fatigue loading

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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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Parallel system reliability analysis with a CECBO algorithm

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STRUCTURAL AND MULTIDISCIPLINARY OPTIMIZATION 2021年第1期64卷 71-88页

作者： Cheng, Jiaming Zhao, Wei Jinan Univ Sch Mech & Construct Engn MOE Key Lab Disaster Forecast & Control Engn Guangzhou 510632 Peoples R China

The existing engineering structural system is featured by complicated limit state functions of high nonlinearity, resulting in the conventional reliability analysis approach that is unable to evaluate these problems accurately or even unavailable. Various analytical methods have been presented by researchers over the past decades. However, these methods have difficulties in striking a balance between accuracy and computational efficiency. This paper proposes a relatively efficient and accurate procedure to estimate the failure probability of the parallel system based on the FORM and a new metaheuristic algorithm, chaotic enhanced colliding bodies optimization algorithm (CECBO). The CECBO has shown robustness, high accuracy, and implementation simplicity for solving optimization problems from previous work. Thus, the CECBO is employed to search the point of maximum likelihood (PML), a point that yields the highest value of the probability density function in the failure domain, through solving an optimization model and then approximates the failure domain of the parallel system to estimate the failure probability accurately. The results of the test examples indicate that the proposed procedure is promising for the estimation of the failure probability of a parallel system in terms of accuracy and efficiency.

关键词： Enhanced colliding bodies optimization (ECBO) Point of maximum likelihood (PML) Chaos System reliability

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Effect of incorporating recycled macro fibres on the properties of ultra-high-performance seawater sea-sand concrete

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JOURNAL OF BUILDING engineering 2024年 83卷

作者： Fu, Bing Lin, L. B. Zhou, X. You, X. M. Deng, D. Y. 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 Southeast Univ Sch Civil Engn Nanjing 210096 Peoples R China China Construct Steel Engn Co Ltd Shenzhen 518057 Peoples R China

Ultra-high-performance concrete (UHPC) is an ideal material for constructing marine infrastructures, but faces obstacles such as limited local raw materials (i.e., freshwater and riversand) and corrosion of steel reinforcement. Non-metallic reinforcement is preferable for reinforcing marine UHPC, especially when seawater and sea-sand are used to develop ultra-highperformance seawater sea-sand concrete (USSC). Recently, the authors' group proposed a costefficient UHPC reinforced with discrete macro fibres mechanically processed from waste glass fibre-reinforced polymer (GFRP) composites. This present study aimed to explore the potential application of incorporating macro fibres in USSC. A series of tests were conducted to investigate the fundamental properties of macro fibre reinforced USSC with the examined variables including the content (0 %, 2 %, 4 %, and 6 %) and lengths (30 mm and 60 mm) of macro fibres. Comparisons were made between USSC and UHPC with river-sand and freshwater (UTRC), which were both reinforced with macro fibres. The results revealed that incorporating macro fibres in USSC improved the compressive toughness index (CTI) and flexural toughness by up to 84.00 % and 40.15 times respectively, but decreased the workability and compressive strength by up to 42.22 % and 21.45 % respectively. The effect of incorporating macro fibres on the properties of USSC was more prominent than that of its counterpart of UTRC. A theoretical model was then developed for predicting the flexural toughness of various concrete with macro fibres based on the regression analysis on the available test results.

关键词： Ultra-high-performance concrete Ultra-high-performance seawater sea-sand concrete Recycling Glass fibre-reinforced polymer (GFRP) waste Macro fibres

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A-stable linear two-step time integration methods with consistent starting and their equivalent single-step methods in structural dynamics analysis

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INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN engineering 2021年第9期122卷 2312-2359页

作者： Zhang, Jie Jinan Univ MOE Key Lab Disaster Forecast & Control Engn Sch Mech & Construct Engn Guangzhou 510632 Peoples R China

A spectral consistent starting procedure is proposed for the first-order-type A-stable linear two-step (LTS) time integration methods in structural dynamics analysis. The accuracy analysis for the LTS methods in structural dynamics is presented based on the first-order model, which enables the algorithms in first-order transient systems to be extended to structural dynamics under the umbrella of a consistent framework. It is indicated that the approximation of the loads plays an essential role in the equivalence between the LTS methods and some single-step methods. An algorithmic equivalence feature, which is stricter than the spectral equivalence, is revealed between the two-leg generalized-alpha methods in first-order systems and the A-stable LTS methods. The measures of the error constant in the LTS methods and the ultimate spectral radius are extended to optimize a class of single-step methods of a given convergence order. The spectral consistent starting procedure for the A-stable LTS methods is developed by utilizing the algorithmic equivalence of the single-step methods, which results in an optimal A-stable LTS (OALTS) method possessing a consistent spectral radius with controllable numerical dissipation in the starting step and the steps thereafter. Comparing with the equivalent single-step methods, the present OALTS method does not need the auxiliary variables, and its displacement, velocity and acceleration can achieve second-order accuracy simultaneously. The performance of the present OALTS method is verified by numerical examples including physical damping, external loads, and/or nonlinearity.

关键词： accuracy analysis numerical dissipation stability structural dynamics time integration

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Structural Damage Identification Based on Quadratic Optimization of Objective Functions with Modal Residual Force and Weighting Strategy

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JOURNAL OF AEROSPACE engineering 2024年第1期37卷 04023089-04023089页

作者： Li, Jiawei Yu, Ling Qi, Tengrun Chen, Yuhan Jinan Univ Sch Mech & Construct Engn Key Lab Disaster Forecast & Control Engn Minist Educ MOE Guangzhou 510632 Peoples R China

Structural damage identification (SDI), an important issue in the field of structural health monitoring (SHM), is usually converted into a constrained optimization problem. However, the conventional objective functions defined by natural frequencies and mode shapes are insensitive enough to structural damage. To tackle this problem, this study proposed a new SDI method based on quadratic optimization of objective functions with both modal residual force and weighting strategy. First, a new structural damage index was constructed by Taylor expansion and sensitive matrix analysis about the modal residual force with respect to damage factor, and then the new index was introduced into a new objective function together with the frequency and mode shape. Then, to balance the magnitude effects of each term in objective functions, a weighting strategy was introduced to define the second new objective function for higher SDI accuracy and robustness to noise. The two proposed objective functions were further solved for SDI with a novel metaheuristic optimization technique, the whale optimization algorithm (WOA). To evaluate the effectiveness of the proposed SDI method, numerical simulations on a simply supported beam and a truss structure, as well as various experimental verifications on a simply supported beam in the laboratory, were carried out. The results show that the proposed SDI method outperforms the traditional method with a higher SDI accuracy and robustness to noise, and the second objective function is more suitable for multiple damage identification in complex structures.

关键词： Structural damage identification (SDI) Modal residual force Weighting strategy Objective function optimization Structural health monitoring (SHM) Whale optimization algorithm (WOA)

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A Broyden-Fletcher-Goldfarb-Shanno algorithm for reliability-based design optimization

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APPLIED MATHEMATICAL MODELLING 2021年 92卷 447-465页

作者： Zhao, Wei Jinan Univ Sch Mech & Construct Engn MOE Key Lab Disaster Forecast & Control Engn Guangzhou 510632 Peoples R China

Classic mean value methods of performance measure approach in reliability-based design optimization may become computationally challenging due to their instability and inefficiency as the degree of nonlinearity grows in problems. In this paper, sequential quadratic programming method associated with the Broyden-Fletcher-Goldfarb-Shanno algorithm is introduced to take information about the curvature of the performance function into account and determine the search direction of the minimum performance target point within the performance measure approach. A new mean value method of performance measure approach is developed in accordance with the search direction defined by a technique akin to the non-monotone line search of globalization strategy in the unconstrained optimization problem. The minimum performance target point, on the one hand, is rapidly located in the local domain along the search direction by the steepest descend method, and on the other hand, globally explored along a direction from the origin with exponentially decreasing step sizes. The behavior of the proposed method is illustrated and compared with some other existing algorithms through two reliability examples with highly-nonlinear performance functions and two representative reliability-based design optimization problems in engineering practice. The results show that the proposed method is robust, accurate and efficient with relatively less iterations in contrast with the other representative algorithms of performance measure approach in the literature. (c) 2020 Elsevier Inc. All rights reserved.

关键词： Broyden-Fletcher-Goldfarb-Shanno algorithm Reliability-based design optimization Performance measure approach The minimum performance target point Mean value method

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Intrinsic bending stiffness of narrow graphene nanoribbons from quantum mechanics lattice dynamics calculations

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MOLECULAR SIMULATION 2021年第7期47卷 560-564页

作者： Lin, Z. Kuang, Y. Hu, N. Jinan Univ Sch Mech & Construct Engn MOE Key Lab Disaster Forecast & Control Engn Guangzhou Peoples R China

The bending stiffness is a key quantity to determine mechanical bending behaviours, thermodynamical stability and even electronic transports of Graphene nanoribbons (GNRs). Using quantum mechanics lattice dynamics calculations, we characterise chirality and width dependent bending stiffness of GNRs. The results show that, in the width range (<1.6 nm) considered, out-of-plane bending stiffness of zigzag graphene nanoribbon is 17.5% larger than that of armchair graphene nanoribbon with the same width whereas their in-plane bending stiffness is very close and tend to coincide with an increase of width. These trends are attributed to differences in microscopic deformation mechanisms. We also find that, for the narrowest graphene nanoribbon, that is, polyethylene and polyacetylene, the latter has much higher out-of-plane and in-plane bending stiffness than the former.

关键词： Intrinsic bending stiffness graphene nanoribbons quantum mechanics lattice dynamics calculations

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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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