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

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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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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A general continuum damage model for soft composites

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JOURNAL OF THE MECHANICS AND PHYSICS OF SOLIDS 2023年第1期175卷

作者： Zhan, Lin Wang, Siyu Qu, Shaoxing Steinmann, Paul Xiao, Rui Zhejiang Univ Dept Engn Mech State Key Lab Fluid Power & Mechatron Syst Key Lab Soft Machines & Smart Devices Zhejiang Pro Hangzhou 310027 Peoples R China Jinan Univ Coll Mech & Construct Engn MOE Key Lab Disaster Forecast & Control Engn Guangzhou 510632 Peoples R China Friedrich Alexander Univ Erlangen Nuremberg Inst Appl Mech Egerland Str 5 D-91058 Erlangen Germany

Soft composites, including filled rubbers, nanocomposite gels, double network hydrogels, and multiple network elastomers, all exhibit stress-softening behavior in loading-unloading cycles, also denoted as the Mullins effect. Though qualitatively this damage behavior shows similar features, the details still vary with material types. In this work, we provide a general approach towards modeling the Mullins effect for soft composites based on continuum damage mechanics. We start with formulating a one-dimensional damage model. A logarithmic damage variable is employed, while a damage potential function is adopted to obtain the evolution law for the damage variable. We then extend the one-dimensional damage model to three-dimensions. The eight-chain type micro-macro transition is used to formulate an isotropic damage model. An anisotropic damage model is constructed based on the full network model, while a new micro-macro mapping is used to determine the micro stretch from the macro deformation. With this new mapping, the full network model appears in a consistent format in that the free energy, dissipation, and stress are respectively given by the average of their directional micro counterparts. In the current approach, two constitutive functions need to be determined: the elastic free energy density and the stored energy limit. Simple forms of these two constitutive functions are provided with only a small set of model parameters. The resulting models are then successfully applied to describe the stress response in loading-unloading cycles and the anisotropic response of predeformed materials for different kinds of soft composites.

关键词： Mullins effect Continuum damage mechanics Micro-macro mapping Anisotropic damage model Soft composites

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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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Weighted Transmissibility Assurance Criterion for Structural Damage Detection

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JOURNAL OF AEROSPACE engineering 2021年第3期34卷 04021016-04021016页

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

Transmissibility function (TF) is a useful damage indicator for effective structural damage detection (SDD) under unknown external excitations. However, TF is not sensitive enough to structural damage under measurement noise. To improve the sensitivity of this indicator, a common model reduction technique, that is, the system equivalent reduction expansion process (SEREP) was first adopted to obtain reduced element stiffness matrices in the initial analytical finite-element model of a structure;this was used to weight the TFs in this study. Then, inspired by the cosine similarity measure, a novel damage indicator, called the weighted transmissibility assurance criterion (WTAC), was proposed for evaluating structural states. The effectiveness of the proposed damage indicator, WTAC, was first studied by a six-story frame in numerical simulations. The results showed that the TF weighted by the reduced element stiffness matrices improved the signal-to-noise ratio of the TF, and the proposed WTAC detected changes in structural states under noise. Moreover, further experimental studies on an aluminum alloy frame were conducted in order to assess the proposed WTAC. The results indicated that the proposed WTAC may provide a potential tool for effective SDD with strong robustness and stability for long-term monitoring on site.

关键词： Structural damage detection (SDD) Transmissibility function (TF) Damage indicator Output-only method Cosine similarity measure

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Probabilistic Prediction of Post-Earthquake Rubble Risk Distribution Range for Bottom Frame Structures

SSRN

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SSRN 2024年

作者： He, Yuhan Zhai, Changhai Wen, Weiping Key Lab of Structures Dynamic Behavior and Control The Ministry of Education Harbin Institute of Technology Harbin150090 China Key Lab of Smart Prevention and Mitigation of Civil Engineering Disaster The Ministry of Industry and Information Technology Harbin Institute of Technology Harbin150090 China

The rubble generated by the massive collapse of street-front buildings after an earthquake can seriously block roads, affecting the connectivity of the road network in a city and causing serious damage. In order to achieve the needs of urban planning, buildings facing the street are mainly bottom frame structures that cater for both commercial and residential use. However, once an earthquake occurs, the poor seismic performance of the bottom frame structures is quite prone to collapse, which produces a large amount of rubble and brings a great burden to the post-earthquake traffic system. In this paper, based on finite element models for various cases, considering the uncertainty of seismic intensity and height of the bottom frame structure, and combining with the fragility of structural collapse, we propose a method to predict the risk range of the bottom frame structure rubble to quantify the capacity of the transportation system after the earthquake, which can better assess the seismic resilience of the transportation system in the urban area. © 2024, The Authors. All rights reserved.

关键词： Earthquakes

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Bond behavior between recycled macro fibers and ultra-high-performance concrete matrix: Tests and property characterization

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JOURNAL OF BUILDING engineering 2024年 95卷

作者： You, X. M. Xu, Y. B. Fan, Y. C. Zou, Q. Q. Fu, Bing Jinan Univ Sch Mech & Construct Engn Guangzhou 510632 Peoples R China Harbin Inst Technol Sch Astronaut Harbin 150001 Peoples R China Southern Univ Sci & Technol Dept Ocean Sci & Engn Shenzhen 518055 Peoples R China Jinan Univ MOE Key Lab Disaster Forecast & Control Engn Guangzhou 510632 Peoples R China

A green and cost-efficient ultra-high-performance concrete (UHPC) has been proposed using discrete macro fibers recycled from waste glass fiber reinforced polymer (GFRP). The tensile properties of such composites are significantly affected by the macro fiber/UHPC bond properties. However, there is very little work characterizing the bond properties of the macro fiber/UHPC interface. Furthermore. lack of study focused on the methods for macro fiber surface treatment and their effects on macro fiber/UHPC interfacial bonding. Therefore, the present study first carried out pullout tests in two series consisting of 128 pullout specimens. Series 1 aimed to characterize the bond behavior of the macro fiber/UHPC interface, while Series 2 aimed to investigate the effect of surface-modifying agents on macro fiber/UHPC interfacial bonding. The results demonstrated that the bond strength increased from 19.3 to 20.9 MPa when the embedded length of the 8 mm-wide fiber increased from 5 to 10 mm. The modification of neutral Nano SiO2 (NNS) enhanced the bond strength by up to 20.5 %, while alkaline Nano SiO2 (ANS) and silane coupling agent (SCA) showed a negative effect on bond strength. Then, the shear-lag theory was utilized for predicting the pull force-slip curves of the fibers embedded in UHPC, and then the bond parameters of the interfaces were obtained through an inverse analysis. A good agreement is exhibited with integral absolute error (IAE) from 4.5 % to 10.5 % between predicted results and test results.

关键词： Glass fiber reinforced polymer composites Ultra -high -performance concrete Recycling Macro fibers Interfacial bond

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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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Flexural Performance of Layered Macro Fiber Reinforced Concrete Short Beams

SSRN

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SSRN 2022年

作者： Yuan, Hong Fu, Xiao-Hui Fan, Ya-Chen Fu, Bing Zou, Qi-Qi School of Mechanics and Construction Engineering Jinan University Guangzhou510632 China MOE Key Lab of Disaster Forecast and Control in Engineering Jinan University Guangzhou510632 China Department of Ocean Science and Engineering Southern University of Science and Technology Shenzhen518055 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 author’s group explored a novel mechanical recycling method to process 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 bridge the cracks in concrete and mitigate their development, thus enhancing the flexural strength and toughness of MFRC flexural members. However, the macro fibres have a negligible effect on the compressive properties of MFRC, which implies that the macro fibres in the compressive zone cannot be efficiently utilized. As motivated by the concept of the layered structure, this paper presents an experimental investigation on the flexural performance of the layered beams with the MFRC bottom layer and PC (plain concrete) top layer, expecting to improve the utilization of the incorporated macro fibres. The investigated test parameters include the height of the bottom layer as well as the macro fiber content in the bottom layer. The test results show that the application of layer structure effectively enhances the utilization of macro fibers and hence promotes the future technological application of the proposed mechanical recycling method. © 2022, The Authors. All rights reserved.

关键词： Fibers

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Low-coordinated surface sites make truncated Pd tetrahedrons as robust ORR electrocatalysts outperforming Pt for DMFC devices

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Nano Research 2022年第9期15卷 7951-7958页

作者： Xiaoling Wang Jingwei Li Xiaotong Yang Fengling Zhao Yongfei Li Daliang Zhang Li-Yong Gan Ke Xin Yao Qiang Yuan State-Local Joint Laboratory for Comprehensive Utilization of Biomass Center for R&D of Fine ChemicalsCollege of Chemistry and Chemical EngineeringGuizhou UniversityGuiyang 550025China State Key Laboratory of Coal Mine Disaster Dynamics and Control Chongqing UniversityChongqing 400044China Key Lab of Organic Optoelectronics&Molecular Engineering Tsinghua UniversityBeijing 100084China Multi-scale Porous Materials Center Institute of Advanced Interdisciplinary Studies&School of Chemistry and Chemical EngineeringChongqing UniversityChongqing 400044China College of Physics and Center of Quantum Materials and Devices Chongqing UniversityChongqing 401331China

Developing highly stable and active non-Pt oxygen reduction reaction(ORR)electrocatalysts for power generation device raises great concerns and remains a ***,we report novel truncated Pd tetrahedrons(T-Pd-Ths)enclosed by{111}facets with excellent uniformity,which have both low-coordinated surface sites and distinct lattice distortions that would induce“local strain”.In alkaline electrolyte,the T-Pd-Ths/C achieves remarkable ORR specific/mass activity(SA/MA)of 2.46 mA·cm^(−2)/1.69 A·mgPd^(−1),which is 12.3/16.9 and 10.7/14.1 times higher than commercial Pd/C and Pt/C,*** T-Pd-Ths/C also exhibits high in-situ carbon monoxide(CO)tolerance and 50,000 cycles durability with an activity loss of 7.69%and morphological *** rotating ring-disk electrode(RRDE)measurements show that a 4-electron process occurs on T-PdThs/*** calculations demonstrate that the low-coordinated surface sites contribute largely to the enhancement of ORR *** actual direct methanol fuel cell(DMFC)device,the T-Pd-Ths/C delivers superior open-circuit voltage(OCV)and peak power density(PPD)to commercial Pt/C from 25 to 80℃,and the maximum PPD can reach up to 163.7 mW·cm−*** study demonstrates that the T-Pd-Ths/C holds promise as alternatives to Pt for ORR in DMFC device.

关键词： Pd tetrahedrons low-coordinated sites lattice distortion oxygen reduction reaction direct methanol fuel cells

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