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Buckling of composite laminates with multiple delaminations: Part I Theoretical and numerical analysis

COMPOSITE STRUCTURES 2020年 250卷 112491-112491页

作者： Jin, Fusong Xu, Peng Xia, Fei Liang, Haofeng Yao, Sishi Xue, Jianghong Jinan Univ Sch Mech & Construct Engn MOE Key Lab Disaster Forecast & Control Engn Guangzhou 510632 Peoples R China

Buckling of composite laminates containing multiple delaminations are analyzed theoretically based on the proposed equivalent model. From the exact analysis in which the nonlinear contact effect between the two portions above and beneath the delamination is included, it is found that (1) the two portions above and below the delamination undergoes exactly identical global deflection;(1) the composite laminate is subjected to Mode II delamination propagation due to in-plane slipping. According to such observations, an equivalent model which is perfect, delamination free is proposed to replace the delaminated portion of the laminate. The substitute model has the same geometric size and is stacked in the same sequence as that of the delaminated portion. The exact solution of the global deflection mode also suggests that the stiffness of the substitute model is taken as the sum of the stiffness of the two portions above and beneath the delamination. Buckling of composite laminates simply supported at the four sides with a single delamination is examined for different delamination length and depth using equivalent model, exact model and the finite element model. A good agreement between them demonstrates the efficiency and accuracy of the presented equivalent model. Using the established equivalent model, buckling of composite laminates with multiple delaminations along thickness and horizontal directions are investigated. Parametric studies are executed analytically and numerically to inspect the influence of delamination conditions, such as the number of delamination as well as the depth, the position and the length of each delamination, on the buckling performance of the composite laminates.

关键词： Multiple delaminations Equivalent model Contact effect Laminated composites Buckling analysis

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Weakening Influence of Spring Soil Moisture over the Indo-China Peninsula on the Following Summer Mei-Yu Front and Precipitation Extremes over the Yangtze River Basin

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JOURNAL OF CLIMATE 2020年第23期33卷 10055-10072页

作者： Gao, Chujie Li, Gen Xu, Bei Hohai Univ Minist Educ Coastal Disaster & Protect Key Lab Marine Hazards Forecasting Minist Nat ResourcesKey LabColl Oceanog Nanjing Peoples R China Nanjing Univ Informat Sci & Technol Minist Educ Key Lab Meteorol Disaster Nanjing Peoples R China Nanjing Univ Informat Sci & Technol Collaborat Innovat Ctr Forecast & Evaluat Meteoro Nanjing Peoples R China Southern Marine Sci & Engn Guangdong Lab Zhuhai Zhuhai Peoples R China Jingling Inst Technol Coll Intelligent Sci & Control Engn Nanjing Peoples R China

The seasonal prediction of precipitation extremes over the Yangtze River basin (YRB) has always been a great challenge. This study investigated the effects of spring soil moisture over the Indo-China Peninsula (ICP) on the following summer mei-yu front and YRB precipitation extremes during 1961-2010. The results indicated that the frequency of summer YRB precipitation extremes was closely associated with the mei-yu front intensity, which exhibited a strong negative correlation with the preceding spring ICP soil moisture. However, the lingering climate influence of the ICP soil moisture was unstable, with an obvious weakening since the early 1990s. Due to its strong memory, an abnormally lower spring soil moisture over the ICP would increase local temperature until the summer by inducing less evapotranspiration. Before the early 1990s, the geopotential height elevation associated with the ICP heating affected the western Pacific subtropical high (WPSH), strengthening the southwesterly summer monsoon. Consequently, the mei-yu front was intensified as more warm, wet air was transported to the YRB, and local precipitation extremes also occurred more frequently associated with abnormal ascending motion mainly maintained by the warm temperature advection. In the early 1990s, the Asian summer monsoon underwent an abrupt shift, with the changing climatological states of the large-scale circulations. Therefore, the similar ICP heating induced by the anomalous soil moisture had different effects on the monsoonal circulation, resulting in weakened responses of the mei-yu front and YRB precipitation extremes since the early 1990s.

关键词： Atmosphere-land interaction Atmospheric circulation Extreme events Monsoons Evapotranspiration Decadal variability

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Metal failure effects predicted accurately with a unified and explicit criterion

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ZAMM-ZEITSCHRIFT FUR ANGEWANDTE MATHEMATIK UND MECHANIK 2021年第11期101卷

作者： Wang, Si-Yu Zhan, Lin Bruhns, Otto Timme Xiao, Heng Jinan Univ MOE Key Lab Disaster Forecast & Control Engn Sch Mech & Construct Engn West Huangpu Ave 601 Guangzhou 510632 Guangdong Peoples R China Ruhr Univ Bochum Inst Mech D-44780 Bochum Germany

A new criterion for predicting metal failure effects under cyclic loading conditions is derived from an innovative elastoplasticity model established most recently. As compared with usual approaches, novel results with this new criterion are presented in four respects: (i) both low and high cycle fatigue effects can be simultaneously simulated in a unified and direct manner;(ii) cumbersome trial-and-error procedures in identifying numerous unknown parameters can be bypassed;(iii) time-consuming numerical procedures are not involved in treating responses in cyclic loading processes;and, for the first time, (iv) data sets for fatigue failure can be simultaneously matched for various cases of the cyclic stress ratio. Numerical examples show that model predictions are in accurate agreement with test data.

关键词： elastoplasticity model fatigue failure effects metals unified criterion

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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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Buckling of composite laminates with multiple delaminations: Part II experiments

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COMPOSITE STRUCTURES 2020年 247卷 112498-112498页

作者： Zhu, Zhipeng Yang, Peng Xia, Fei Jin, Fusong Liang, Haofeng He, Zanhang Xue, Jianghong Jinan Univ Sch Mech & Construct Engn MOE Key Lab Disaster Forecast & Control Engn Guangzhou 510632 Peoples R China

This paper focus on the experimental study of the buckling of composite laminates with multiple delamina- tions, as a succession to the theoretical and numerical studies in Part I. Test specimens containing delamina- tions of different length and different depth were fabricated by embedding Te flon plastic film using hot pressing machine. Compressive tests were carried out to investigate the in fluence of the delamination condi- tions on the buckling and post -buckling performances of the composite laminates. It was found that a surface delamination deteriorates the stiffness of the laminate less than a deep -buried delamination does, while iso- thickness-spaced multiple delaminations damage the stiffness severely compared with non -equal -thickness - spaced delamination for the same number of delamination. In general the larger the length and the number of delamination, the smaller the buckling load. Nevertheless, when the total length and the number of the delamination are fixed, the laminates containing multiple delaminations of equal length have a higher buckling load. Furthermore, it was observed that regardless of the number of delamination, all laminates are suffered to a global buckling. Local buckling does not occur until global buckling occurs. The experimental results justify the theoretical prediction;thereby con firm the correctness and validity of the theoretical approach proposed in Part I.

关键词： Experimental study Composite laminates Multiple delaminations Equivalent model Buckling and post-buckling

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Influence of Al₂O₃ particles on the tribological properties of CoCrAlYTa coating produced by laser-induction hybrid cladding

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CERAMICS INTERNATIONAL 2021年第14期47卷 19434-19442页

作者： Yi Yanliang Long Shaolei Zhang Rui Wu Changyi Zhou Shengfeng Jinan Univ Inst Adv Wear & Corros Resistant & Funct Mat Guangzhou 510632 Guangdong Peoples R China Guizhou Inst Technol Sch Mech Engn Guiyang 550003 Peoples R China Tianjin Univ Technol Sch Phys Sci & Technol Laser Technol Inst Tianjin 300387 Peoples R China Hunan First Normal Univ Dept Educ Sci Changsha 410205 Hunan Peoples R China Jinan Univ MOE Key Lab Disaster Forecast & Control Engn Guangzhou 510632 Peoples R China

The influence of Al2O3 addition on the microstructure, mechanical and tribological properties of CoCrAlYTa coating produced by laser-induction hybrid cladding was systematically investigated. The results show that the coatings exhibit high metallurgy quality with no obvious defects, and mainly consist of gamma, beta and TaC phases. In the cladding process, a part of O element exists in the TaC and increases with the increased Al2O3 content, while the other exists in the form of Y2O3 due to low Gibbs free energy. As the Al2O3 content increases, the volume fraction of beta phase (V beta) changes from 23.82 vol% to 67.72 vol%, and leading to the microhardness of coating increased from 515.15 HV to 610.17 HV. Meanwhile, the wear rate of coating increases with the V beta in a relationship of y = -5.97x+110.65, due to a fact that the wear mechanism changes from adhesive wear to microcutting.

关键词： Laser-induction hybrid cladding MCrAlY coating Friction and wear Tribological property

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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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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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Dynamic Responses and Cumulative Damage of Coastal Bridges Subjected to Extreme Sequential Earthquake-Tsunamis

SSRN

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SSRN 2024年

作者： Zhu, Deming Dong, You Feng, Ruiwei Li, Yaohan Zhai, Changhai Department of Civil and Environmental Engineering The Hong Kong Polytechnic University Hong Kong Research Institute for Sustainable Urban Development The Hong Kong Polytechnic University Hong Kong Department of Construction and Quality Management Hong Kong Metropolitan University Hong Kong Key Lab of Structures Dynamic Behavior and Control of 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

Coastal bridges, as vital components of transportation networks, are vulnerable to damage from successive earthquake-tsunami (EQ-TS) events in rapidly developing coastal hazard-prone cities. Understanding how these bridges perform under the combined effects of earthquakes and tsunamis is crucial. Though studies have investigated coastal buildings facing these hazards, there is limited research on bridges experiencing extreme EQ-TS events, especially on the generation of load sequences, dynamic structural responses, and cumulative damage assessment. To overcome these limitations, this study aims to thoroughly examine the dynamic behavior of reinforced concrete coastal bridges subjected to successive EQ-TS hazards. To generate practical sequential EQ-TS loads, records of the 2011 Tohoku earthquake and resulting tsunami heights, which are calculated based on the earthquake magnitude and epicentral distance, are utilized for analyses. The tsunami wave load time series for each earthquake record is created using a high-fidelity computational fluid dynamics model. Nonlinear time-history analyses are then performed for the bridge model in OpenSees under the synthetic EQ-TS sequences, quantifying structural responses and cumulative damage. Moreover, the comparative results of structural performance under single and successive hazard scenarios are presented and discussed. Results indicate that successive EQ-TS hazards not only induce much larger structural responses as compared to a single EQ hazard, but also produce considerable residual displacements for both bearings and decks. The wave height is more appropriate than the peak ground acceleration as an individual intensity measure for predicting the cumulative damage of bridges under cascading EQ-TS hazards. Relying solely on peak responses for assessing the dynamic performance of piers under successive EQ-TS sequences may underestimate the actual damage. © 2024, The Authors. All rights reserved.

关键词： Earthquakes

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Spatial differences in impacts of CO2 effect on China's meteorological droughts: Analysis from surface resistance perspective

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JOURNAL OF HYDROLOGY 2023年 621卷

作者： Sun, Shanlei Zhang, Yifang Chai, Rongfan Liu, Yi Mu, Mengyuan Zhou, Botao Zhou, Yang Li, Jinjian Chen, Haishan Nanjing Univ Informat Sci & Technol Collaborat Innovat Ctr Forecast & Evaluat Meteorol Key Lab Meteorol Disaster Int Joint Res Lab Climate & Environm ChangeMinist Nanjing Peoples R China China Elect Power Res Inst Renewable Energy Ctr Beijing Peoples R China State Key Lab Operat & Control Renewable Energy & Beijing Peoples R China Univ New South Wales Sch Civil & Environm Engn Sydney Australia Univ New South Wales ARC Ctr Excellence Climate Extremes Sydney Australia Univ New South Wales Climate Change Res Ctr Sydney Australia Chengdu Univ Informat Technol Sch Atmospher Sci Plateau Atmosphere & Environm Key Lab Sichuan Prov Chengdu Peoples R China

Studying impacts of the CO2 effect on potential evapotranspiration (PET) and offline drought indices from surface resistance perspective is significant for understanding and accessing droughts. This study comprehensively investigated impacts of the CO2 effect on PET and Standardized Precipitation-Evapotranspiration Index (SPEI) over China during 1971-2010 based on two simulations with and without CO2 effect, respectively. We found that the CO2 effect led to decreased PET and increased SPEI, and decreased drought, which showed strong spatial variations with the greatest impact over northern China (excluding westernmost part for PET). Such spatial variations had functional relationships not only with CO2 concentration but also climatological conditions, i.e., climatological wind speed (U) and slope of vapour pressure curve (s) for PET, but climatological U, s and pre-cipitation (P) for SPEI. Further analyses implied that climatological U (climatological U and P) determined the spatial variations in the CO2 effect-induced PET (SPEI) changes over China during 1971-2010.

关键词： Drought CO 2 effect Surface resistance Standardized Precipitation -Evapotranspiration Index China

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