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Actuated bending of a long cantilevered glassy nematic bilayer strip: Failure of the beam model

engineering Research Express 2021年第2期3卷

作者： Lin, Y.L. He, L.H. MOE Key Lab of Disaster and Control in Engineering Jinan University Guangzhou510632 China State Key Laboratory of Fire Science University of Science and Technology of China Hefei230026 China

Cantilevered long glassy nematic bilayer strips bend in response to light, and thus are attractive for actuation applications. The objective of this work is to examine whether the deformation can be predicted by the one-dimensional beam model as in usual practice. To do so, we consider a bilayer with orthogonal director orientations in the upper and lower layers and analyze its bending in the framework of the classical plate *** that the deflection is much larger than that given by the beam model, because the spontaneous bending in the width direction increases the curvature along the long axis. Therefore, the one-dimensional beam model fails to describe the bending behavior of the cantilevered bilayer strips. © 2021 IOP Publishing Ltd. © International Journal of Extreme Manufacturing.

关键词： Glass

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Bistable Nonlinear Energy Sink Using Magnets and Linear Springs: Application to Structural Seismic control

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SHOCK AND VIBRATION 2021年第1期2021卷

作者： Chen, Y. Y. Zhao, W. Shen, C. Y. Qian, Z. C. Guangzhou Univ MOE Key Lab Earthquake Resistance Earthquake Miti Earthquake Engn Res & Test Ctr Guangzhou 510405 Peoples R China Guangzhou Univ Guangdong Prov Key Lab Earthquake Engn & Appl Tec Guangzhou 510405 Peoples R China Jinan Univ MOE Key Lab Disaster Forecast & Control Engn Sch Mech & Construct Engn Guangzhou 510632 Peoples R China

Nonlinear energy sink (NES) has proven to be very effective in reducing the vibration response of structures. In this paper, a magnetic bistable nonlinear energy sink (BNES) that composed of a guided moving mass attached with linear springs and permanent magnets is proposed. To assess the seismic control performance of the proposed BNES, a shear frame model equipped with the proposed BNES is compared with the same shear frame model equipped with an optimized cubic NES and with a linear tuned mass damper (TMD) system. The results show that, in the idealized situation, where the mass and stiffness is clearly defined (no uncertainty), the BNES can achieve similar performance as a thoroughly in-tuned TMD system. Moreover, in the detuned condition, due to broadband high internal resonance capability, the proposed BNES can outperform the linear TMD and the cubic NES. The study demonstrates that the proposed BNES can be used as an efficient passive vibration absorber for structural seismic control.

关键词： Seismology

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An accurate and explicit approach to modeling realistic hardening-to-softening transition effects of metals

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ZAMM-ZEITSCHRIFT FUR ANGEWANDTE MATHEMATIK UND MECHANIK 2021年第2期101卷

作者： Xu, Zi-Han Zhan, Lin Wang, Si-Yu Xi, Hui-Feng Xiao, Heng Jinan Univ Sch Mech & Construct Engn West Huangpu Ave 601 Guangzhou 510632 Peoples R China Jinan Univ MOE Key Lab Disaster Forecast & Control Engn West Huangpu Ave 601 Guangzhou 510632 Peoples R China

A finite strainJ(2)-flow model of von Mises type for elastoplastic behaviors of metals is proposed with a new characterization of the evolving yield strength. It is intended for providing solutions to a few unresolved issues concerning a simultaneous simulation of realistic hardening and softening effects for metals up to failure. Such issues are concerned with three respects, namely, how to ensure that the simulation is accurate in the sense that sufficient uniaxial experimental data for both hardening and softening effects can be matched with no errors, how to ensure that the simulation is explicit in the sense that any implicit trial-and-error iterative procedures in identifying numerous parameters can be bypassed, and how to ensure that the simulation is of broad applicability in the sense that any given uniaxial data for metals can be automatically matched. With the new model proposed, solutions to such issues are obtained by presenting an accurate and explicit form of the yield strength function that automatically matches any given test data. Numerical examples with realistic hardening-to-softening transition effects are presented for the first time for the finite strain responses of both uniaxial stretching and simple shearing up to the eventual failure.

关键词： accurate simulation elastoplasticity finite deformation hardening metals softening

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An effective first order reliability method based on Barzilai-Borwein step

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APPLIED MATHEMATICAL MODELLING 2020年第Part2期77卷 1545-1563页

作者： Zhao, Wei Chen, YangYang Liu, Jike Jinan Univ Sch Mech & Construct Engn MOE Key Lab Disaster Forecast & Control Engn Guangzhou 510632 Guangdong Peoples R China Guangzhou Univ Earthquake Engn Res & Test Ctr Guangzhou 510405 Guangdong Peoples R China Sun Yat Sen Univ Dept Mech Guangzhou 510275 Guangdong Peoples R China

In nonlinear problems, the Hasofer-Lind-Rackwitz-Fiessler algorithm of the first order reliability method sometimes is puzzled by its non-convergence. A new Hasofer-Lind-Rackwitz-Fiessler algorithm incorporating Barzilai-Borwein step is investigated in this paper to speed up the rate of convergence and performs in a stable manner. The algorithm is essentially established on the basis of the global Barzilai-Borwein gradient method, which is dealt with two stages. The first stage, implemented by the traditional steepest descent method with specific decayed step sizes, prepares a good initial point for the global Barzilai-Borwein gradient algorithm in the second stage, which takes the merit function as the objective to locate the most probable failure point. The efficiency and convergence of the proposed method and some other reliability analysis methods are presented and discussed in details by several numerical examples. It is found that the proposed method is stable and very efficient in the nonlinear problems except those super nonlinear ones, even more accurate than the descent direction method with step sizes following the fixed exponential decay strategy. (C) 2019 Elsevier Inc. All rights reserved.

关键词： Hasofer-Lind-Rackwitz-Fiessler algorithm Barzilai-Borwein step size The most probable failure point Reliability index

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Performance enhancement of recycled coarse aggregate concrete by incorporating with macro fibers processed from waste GFRP

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CONSTRUCTION AND BUILDING MATERIALS 2024年 411卷

作者： Fu, Bing Xu, Guang-Ti Peng, Wei-Sen Huang, Ji-Zhi Zou, Qi-Qi Kuang, You-Di 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 South China Agr Univ Coll Water Conservancy & Civil Engn Guangzhou 510642 Peoples R China Harbin Inst Technol Sch Astronaut Harbin 150001 Peoples R China Southern Univ Sci & Technol Dept Ocean Sci & Engn Shenzhen 518000 Peoples R China Wuyi Univ Sch Civil Engn & Architecture Jiangmen 529020 Peoples R China

Reprocessing into coarse aggregates of concrete is a sustainable solution for the disposal of construction and demolition (C&D) waste. The use of recycled coarse aggregates however leads to a degradation in the mechanical properties of the resulting concrete, which then limits the use of recycled aggregates concrete (RAC) in structural elements. The incorporation of discrete fibers shows to be effective in eliminating the mechanical degradation problem of RAC, and this paper has therefore proposed to use macro fibers recycled from waste glass fiber reinforced polymer (GFRP) to reinforce RAC, thus improving the robustness of using RAC in structural elements. The effect of incorporating macro fibers on the mechanical properties of RAC has been first examined through a series of compression and bending tests. The tensile constitutive law of concrete was then derived based on the load-deflection response of the beam specimens using an inverse analysis. The results revealed that the mechanical properties (e.g., compressive toughness, flexural strength, flexural toughness) of RAC can be significantly enhanced by adding macro fibers. For concrete with 50% recycled aggregate (RA), the increase of macro fibers (from 0% to 0.5%, 1%, and 1.5%) leads to the enhancement of flexural strength from 3.13 MPa to 3.54, 4.69, and 5.97 MPa, and the toughness (T150) from 1.4 J to 35.5, 59.2 and 77.6 J, respectively. Such enhancements in the mechanical properties of RAC demonstrate the feasibility of the proposed method.

关键词： Recycled aggregate concrete GFRP Waste Mechanical recycling Fiber reinforced concrete

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A nonparametric seismic reliability analysis method based on Bayesian compressive sensing-Stochastic harmonic function method and probability density evolution method

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MECHANICAL SYSTEMS AND SIGNAL PROCESSING 2023年第1期196卷

作者： He, Jingran Gao, Ruofan Zhou, Hao Guangdong Univ Technol Guangzhou Univ Mega Ctr Sch Civil & Transportat Engn Guangzhou Peoples R China Jinan Univ Sch Mech & Construct Engn 601 West Huangpu Ave Guangzhou 510632 Guangdong Peoples R China South China Univ Technol Sch Civil & Transportat Engn 381 Wushan Rd Guangzhou 510641 Guangdong Peoples R China Jinan Univ MOE Key Lab Disaster Forecast & Control Engn 601 West Huangpu Ave Guangzhou Peoples R China

In engineering practice, the evaluation of seismic reliability of high-rise reinforced concrete structure relies on the probabilistic modelling of material properties. However, the measured data of material parameters in engineering practice is usually inadequate to determine the probability model accurately, especially for the problems involving spatial variability. Traditional parametric reliability analysis methods can be biased for this kind of problem. Therefore, a nonparametric seismic reliability analysis method is proposed based on the Bayesian compressive sensing - stochastic harmonic function method and the probability density evolution method. In this method, the conditional random fields are generated and applied to represent material properties of concrete. As a result, the seismic reliability of a high-rise reinforced concrete shear wall model structure is analyzed using the probability density evolution method.

关键词： Seismic reliability Conditional random field Probability density evolution method Stochastic finite element method

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Inorganic adhesive based near-surface-mounted fibre reinforced polymer for strengthening of concrete structures: An overview

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STRUCTURES 2021年 33卷 2099-2120页

作者： Yu, Jin-Guang Cheng, Liang Liu, Shu Fu, Bing Li, Bo Xian Univ Architecture & Technol Sch Civil Engn Xian 710055 Peoples R China Univ Nottingham Ningbo China Ningbo Nottingham New Mat Inst Ningbo 315100 Peoples R China Univ Min & Technol State Key Lab GeoMech & Deep Underground Engn Xuzhou 100083 Jiangsu Peoples R China 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 Univ Nottingham Ningbo China Dept Civil Engn Ningbo 315100 Peoples R China

Organic adhesives (e.g. epoxy resin) have been widely used in the near-surface-mounted (NSM) fibre reinforced polymer (FRP) strengthening system for reinforced concrete (RC) structures. However, the drawbacks of the organic adhesives in terms of high-temperature resistance and compatibility with concrete urge the development of inorganic adhesives (e.g. cement-based and alkali-activated materials). Moreover, a premature debonding of NSM FRPs from concrete substrate adversely affects the performance of strengthened RC structures, as well as the efficiency of NSM FRPs. Various anchorage strategies have been consequently proposed to improve the bond between the NSM FRPs and the concrete. This paper presents an overview on the bond behaviour between inorganic adhesive based NSM FRPs and concrete. Flexural strengthening of RC beams with inorganic adhesive based NSM FRPs, and the anchorage strategies for NSM FRPs are also summarized. Different from epoxy-based adhesives, the bond strength of inorganic adhesive based NSM FRPs decreases as the groove dimension increases. The RC beams strengthened by inorganic adhesive based NSM FRPs tend to fail due to an intermediate crack debonding of FRPs, which is probably caused by the low deformation capacity of inorganic adhesives. Anchorage strategies, such as adding external wrapping FRP fabrics or internal additional ribs, could significantly enhance the strengthening efficiency and the constructability of NSM FRPs. In the end, recommendations for future studies on the use of inorganic adhesive based NSM FRPs for structural strengthening are outlined.

关键词： NSM FRPs Inorganic adhesive Bonding behaviour Flexural behaviour RC beams Anchorage strategy

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Sensitivity of sequence seismic effects of double-layer reticulated domes

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Zhendong yu Chongji/Journal of Vibration and Shock 2020年第5期39卷 150-156页

作者： Zhang, Yingnan Zhi, Xudong Fan, Feng MOE Key Lab of Structural Engineering Disaster Control Harbin Institute of Technology Harbin150090 China MOII Key Lab of Civil Engineering Intelligent Disaster Prevention and Mitigation Control Harbin Institute of Technology Harbin150090 China

To study whether or not structural responses of double-layer reticulated domes was sensitive to sequence earthquake to avoid structure collapse under aftershocks, a structure's finite element model was established based on the finite element software ABAQUS. Data of main shock and aftershock responses to sequence earthquake in database of the pacific earthquake engineering research center (PEER) were selected to collect 342 groups of main shock and aftershock acceleration response time histories data. The dynamic time history analysis method in full load domain was adopted to obtain variation laws of structural characteristic responses with changes of acceleration amplitude under various sequence earthquakes. 4 effect levels on reticulated shell structures' multiple seismic responses were classified and defined. Then, statistic analysis was done for a lot of example results to obtain the relation between reticulated shells' characteristic responses of maximum nodal displacement, proportion of yield members and structural damage factor when main shock was over and structures' anti-aftershock ability. Finally, the proportion of yield members was taken as the index to measure double-layer reticulated domes' anti-aftershock ability, and sensitive limit values of proportion of yield members for double-layer reticulated domes with different spans were given. The study results provided a reference for aseismic design and aseismic performance evaluation of reticulated shell structures. © 2020, Editorial Office of Journal of Vibration and Shock. All right reserved.

关键词： Earthquakes

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Structural damage detection via combining weighted strategy with trace Lasso

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ADVANCES IN STRUCTURAL engineering 2019年第3期22卷 597-612页

作者： Chen, Chengbin Pan, Chudong Chen, Zepeng Yu, Ling Jinan Univ Sch Mech & Construct Engn Guangzhou 510632 Guangdong Peoples R China Jinan Univ MOE Key Lab Disaster Forecast & Control Engn Guangzhou Guangdong Peoples R China

With the rapid development of computation technologies, swarm intelligence-based algorithms become an innovative technique used for addressing structural damage detection issues, but traditional swarm intelligence-based structural damage detection methods often face with insufficient detection accuracy and lower robustness to noise. As an exploring attempt, a novel structural damage detection method is proposed to tackle the above deficiency via combining weighted strategy with trace least absolute shrinkage and selection operator (Lasso). First, an objective function is defined for the structural damage detection optimization problem by using structural modal parameters;a weighted strategy and the trace Lasso are also involved into the objection function. A novel antlion optimizer algorithm is then employed as a solution solver to the structural damage detection optimization problem. To assess the capability of the proposed structural damage detection method, two numerical simulations and a series of laboratory experiments are performed, and a comparative study on effects of different parameters, such as weighted coefficients, regularization parameters and damage patterns, on the proposed structural damage detection methods are also carried out. Illustrated results show that the proposed structural damage detection method via combining weighted strategy with trace Lasso is able to accurately locate structural damages and quantify damage severities of structures.

关键词： antlion optimizer algorithm sparse regularization structural damage detection trace Lasso weighted strategy

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A computing method for bending problem of thin plate on Pasternak foundation

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ADVANCES IN MECHANICAL engineering 2020年第7期12卷

作者： Gan, Jiarong Yuan, Hong Li, Shanqing Peng, Qifeng Zhang, Huanliang Jinan Univ MOE Key Lab Disaster Forecast & Control Engn Sch Mech & Construct Engn Guangzhou 510632 Peoples R China

The governing equation of the bending problem of simply supported thin plate on Pasternak foundation is degraded into two coupled lower order differential equations using the intermediate variable, which are a Helmholtz equation and a Laplace equation. A new solution of two-dimensional Helmholtz operator is proposed as shown in Appendix 1. The R-function and basic solutions of two-dimensional Helmholtz operator and Laplace operator are used to construct the corresponding quasi-Green function. The quasi-Green's functions satisfy the homogeneous boundary conditions of the problem. The Helmholtz equation and Laplace equation are transformed into integral equations applying corresponding Green's formula, the fundamental solution of the operator, and the boundary condition. A new boundary normalization equation is constructed to ensure the continuity of the integral kernels. The integral equations are discretized into the nonhomogeneous linear algebraic equations to proceed with numerical computing. Some numerical examples are given to verify the validity of the proposed method in calculating the problem with simple boundary conditions and polygonal boundary conditions. The required results are obtained through MATlab programming. The convergence of the method is discussed. The comparison with the analytic solution shows a good agreement, and it demonstrates the feasibility and efficiency of the method in this article.

关键词： Plate bending problem Pasternak foundation Helmholtz equation Laplace equation R-function Green's function

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