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Energy Absorption Investigation of SFRFC-Filled Double Circular Tubes Under Quasi-Static Compression and Low Velocity Impact Loading

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SSRN 2023年

作者： Wang, Langke Zhong, Xingu Zhao, Chao Zhang, Tianyu Hunan Provincial Key Laboratory of Structures for Wind Resistance and Vibration Control School of Civil Engineering Hunan University of Science and Technology Taoyuan Road Yuhu District Xiangtan China

The filled thin-walled tube (FTT) is a common energy absorption device, which consists of two important parts: filled materials and thin-walled tubes. According to existing researches, the filled materials significantly influence the mechanical properties of FTTs, especially the energy absorption capacity. In this study, a novel design of FTTs is proposed, which adopts the double aluminum (Al) pipe and is filled with the steel fiber reinforced foamed concrete (SFRFC), and the energy absorption properties under quasi-static compression and low velocity impact loading are investigated experimentally and numerically. Firstly, the double tube filled with five kinds of steel fiber contents SFRFC are prepared and tested under quasi-static compression, and the influence of dynamic velocity are considered;then, numerical modeling is used to study the influence of structural parameters on the energy absorption properties of composite structures under quasi-static compression. Results show that an appropriate amount of steel fiber can prolong the stress platform under quasi-static compression and stabilize the fluctuation during dynamic plastic buckling. The thickness、diameter、aspect ratio of SFRFC-FTTS have a significant effect on the SEA and CFE, especially the thickness of the inner tubes. © 2023, The Authors. All rights reserved.

关键词： Thin walled structures

Predicting roof-surface wind pressure induced by conical vortex using a BP neural network combined with POD

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Building Simulation 2022年第8期15卷 1475-1490页

作者： Fubin Chen Wen Kang Zhenru Shu Qiusheng Li Yi Li YFrank Chen Kang Zhou School of Civil Engineering Changsha University of Science and TechnologyChangsha410082China School of Civil Engineering Central South UniversityChangsha410083China Department of Architecture and Civil Engineering City University of Hong KongKowloonHong KongChina Hunan Provincial Key Laboratory of Structures for Wind Resistance and Vibration Control&School of Civil Engineering Hunan University of Science and TechnologyXiangtan411201China Department of Civil Engineering The Pennsylvania State UniversityMiddletownPA 17057USA

This study aims to examine the feasibility of predicting surface wind pressure induced by conical vortex using a backpropagation neural network(BPNN)combined with proper orthogonal decomposition(POD),in which a 1:150 scaled model with a large-span retractable roof was tested in wind tunnel under both laminar and turbulent flow *** distributions of mean and fluctuating wind pressure coefficients were first described,and the effects of inflow turbulence,wind direction,roof opening were examined *** the prediction of wind pressure,the POD-BPNN model was trained using measurement data from adjacent *** prediction results are overall *** root-mean-square-error(RMSE)between test and predicted data lies mostly within 10%.In particular,the prediction of mean wind pressure is found to be better than that of fluctuating wind *** outcomes in this study highlight that the proposed POD-BPNN model can be well used as a useful tool to predict surface wind pressure.

关键词： wind tunnel test-roof-surface wind pressure conical vortex proper orthogonal decomposition(POD) backpropagation neural network(BPNN)

Time Delay Dynamics and Low-Codimension Bifurcations in Excitatory and Inhibitory Coupled Neurons

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SSRN 2023年

作者： Peng, Jian Chen, Xiaowen Sun, Hongxin Hu, Xia Hunan Provincial Key Laboratory of Structures for Wind Resistance and Vibration Control Hunan University of Science and Technology Hunan Xiangtan411201 China Department of Engineering Mechanics Hunan University of Science and Technology Hunan Xiangtan411201 China

In this study, the dynamic behaviors of the excitatory and inhibitory coupled neurons are investigated. The characteristic equation of the linear system is obtained to discuss the possible low-codimension bifurcations. It is shown that the connection topology of the network plays a fundamental role in classifying the rich dynamics and bifurcation phenomena. Applying the normal form theory and center manifold reduction, the codimension one and codimension two bifurcations are investigated as well as the stability and direction of these bifurcations. Moreover, the spatiotemporal patterns of periodic oscillations are examined. Numerical simulation are applied to support the obtained results. © 2023, The Authors. All rights reserved.

关键词： Dynamics

Experimental Study on the Mix Proportion of Self-Heating Grouting Materials in Alpine Regions

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SSRN 2022年

作者： Shu, Xiaojuan Zhao, Yang Li, Haohao Zhao, Chao Hunan Provincial Key Laboratory of Structures for Wind Resistance and Vibration Control School of Civil Engineering Hunan University of Science and Technology Taoyuan Road Yuhu District Xiangtan China

The frost heave disease of cement-based grouting materials occurred in the pre-stressed pipeline in alpine regions. This paper proposes a self-heating grouting material and verifies its feasibility by a series of mechanical properties and working properties experiments. Firstly, the water-cement ratio and the dosage of admixture are determined by an orthogonal test at room temperature at 5°C, and relevant experiments determine the dosage of silica fume to improve its fluidity. Secondly, experiments carried out at -5°C are used to analyze the influence of calcium oxide and nano-silica on the temperature of the grouting material system. Thirdly, through adiabatic temperature rise test, the exothermic contribution of calcium oxide and nano-silica heating materials in cement-based grouting material is tested, respectively, and the working performance and mechanical properties of grouting material are tested under different negative curing temperatures. Finally, the feasibility of the self-heating grouting material proposed is verified by the confirmatory test of wrapped concrete. The test results show that the self-heating grouting material under the hostile temperature can be stabilized above five degrees, and its expansion stress does not exceed the specification requirements, which can meet the construction requirements in the hostile temperature environment in the Qinghai Tibet Plateau and other Alpine regions. © 2022, The Authors. All rights reserved.

关键词： Silica fume

Revisited dynamic modeling and eigenvalue analysis of the cable-stayed beam

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Acta Mechanica Sinica 2020年第4期36卷 950-963页

作者： Lianhua Wang Xiaoyu Zhang Kai He Jian Peng College of Civil Engineering Hunan UniversityChangsha 410082China Key Laboratory for Wind and Bridge Engineering of Hunan Province Hunan UniversityChangsha 410082China Guangxi Communications Design Group Co. LtdNanning 530022China Hunan Provincial Key Laboratory of Structures for Wind Resistance and Vibration Control Hunan University of Science and TechnologyXiangtan 411201China

In this study,the Hamilton’s principle is applied to revisit the dynamic modeling of the cable-stayed beam,and the motion equations governing the nonlinear response of the cable-stayed beam are *** corresponding boundary terms are transformed to the dynamic equilibrium conditions through the continuity of the displacement at the anchoring *** the standard condensation procedure,the condensed model of the cable-stayed beam is *** eigenvalue analysis is performed to determine the closed-form eigenvalue solution of the linear problems,and two types of eigenvalue solution are *** is shown that the frequency spectrum of the cable-stayed beam exhibits the curve veering and crossover *** to these phenomena,the mode shapes of the cable-stayed beam may exhibit the coupling ***,the discrete model of the cable-stayed beam is determined,and the possible nonlinear interactions are discussed.

关键词： Cable-stayed beam Dynamic modeling Natural frequencies Mode shapes Curve veering

Time-Delay Feedback control of a Suspended Cable Driven by Subharmonic and Superharmonic Resonance

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SSRN 2024年

作者： Peng, Jian Li, Yanan Li, Luxin Lenci, Stefano School of Civil Engineering Hunan University of Science and Technology Hunan Xiangtan411201 China Hunan Provincial Key Laboratory of Structures for Wind Resistance and Vibration Control Hunan University of Science and Technology Hunan Xiangtan411201 China School of Civil Engineering and Communication North China University of Water Resources and Electric Power Zhengzhou450045 China Department of Civil and Building Engineering and Architecture Polytechnic University of Marche Ancona60131 Italy

The longitudinal time-delay feedback control strategy is adopted to suppress the subharmonic and superharmonic responses of the suspended cable. Based on the Hamilton variational principle and the longitudinal time-delay feedback strategy, the in-plane nonlinear differential equations for a suspended cable are formulated, and Galerkin method is utilized to transform the equations into delayed differential equations. By using the method of multiple scales, approximate solutions for the 1/2-subharmonic and second-order superharmonic resonance responses of the controlled suspended cable were derived. The effects of the time delay and control gain are obtained through numerical examples. The research results demonstrate that by adjusting the control gain and time delay, resonance regions can be avoided, effectively suppressing the large-amplitude vibrations of the suspended cable and achieving favorable control performance. © 2024, The Authors. All rights reserved.

关键词： Time delay

Exothermic Hydration Model of Cement Slurry with Different Reaction Rates of Multi-Component Active Substances

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SSRN 2022年

作者： Shu, Xiaojuan Jiang, Yuxiang Zhao, Yang Xu, Zhenghui Shen, Mingyan Zhong, Xingu Hunan Provincial Key Laboratory of Structures for Wind Resistance and Vibration Control School of Civil Engineering Hunan University of Science and Technology Taoyuan Road Yuhu District Xiangtan China China National Building Materials Group Corp Beijing China

Cement components usually contain two or more hydration active substances with different hydration reaction rates, and the existing hydration exothermic model of cement-based materials never consider the difference in reaction rates of active substances. This paper proposes a new exothermic hydration model of cement-based materials, considering different reaction rates of multi-component active substances. Firstly, the hydration heat release and the representative temperature of cement slurry, the water-cement ratio of 0.3, is tested through adiabatic and dissolution heat methods. Secondly, the hydration reaction is considered a superimposed process of multi-component active substances, and a multiparameter exponential function linear superimposed model is used to fit the exothermic hydration of cement slurry based on Arrhenius chemical expression. The experimental results show that the double exponential function superimposed model better fits the experimental data than the single exponential function superimposed model. The former's advantages are significant at the early age before the initial setting time. In conclusion, the proposed multiparameter exponential function model can illustrate the impact of the different impacts of the hydration reaction process, which cause the different reaction rates of different active substances. © 2022, The Authors. All rights reserved.

关键词： Reaction rates

A Study on the Mix Proportion of Fiber-Polymer Composite Reinforced Cement-Based Grouting Material

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SSRN 2021年

作者： Shu, Xiaojuan Zhao, Yang Liu, Zhu Zhao, Chao Hunan Provincial Key Laboratory of Structures for Wind Resistance and Vibration Control School of Civil Engineering Hunan University of Science and Technology Taoyuan Road Yuhu District Xiangtan China

Cement-based grouting materials are widely used to repair slab hollows under cement concrete pavement slabs. However, the existing cement-based grouting materials fail to meet the needs of rapid penetration reinforcement. In this paper, a cement-based grouting material, which is reinforced by fiber-polymer composite, is proposed to repair slab hollows between the cement concrete slab and cement stabilized base, which has excellent characteristics of high permeability and micro expansion. Firstly, take the fluidity, compressive strength and flexural strength as the evaluation indexes and determine the reasonable mixing amount of each component by single mixing tests. Secondly, take the water-cement ratio, early strength agent content, modified fiber content and VAE polymer content as object factors and optimize the mix proportion of the grouting material by orthogonal tests. The effectiveness of the proposed grouting materials is identified by indoor model tests, and the results show that the mechanical properties of the proposed materials (including compressive strength and flexural strength) are improved significantly compared with ordinary grouting materials. © 2021, The Authors. All rights reserved.

关键词： Mortar

Concrete Early Shrinkage Performance Based on Machine Learning Algorithms for Multi-Objective Optimization

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SSRN 2023年

作者： Wang, Jianqun Liu, Heng Sun, Junbo Huang, Bo Wang, Yufei Zhao, Hongyu Saafi, Mohamed Wang, Xiangyu Hunan Provincial Key Laboratory of Structures for Wind Resistance and Vibration Control Hunan University of Science and Technology Xiangtan411201 China School of Civil Engineering and Architecture East China Jiao Tong University Nanchang330013 China Institute for Smart City of Chongqing University in Liyang Chongqing University Jiangsu213300 China School of Design and Built Environment Curtin University PerthWA6102 Australia School of Civil Engineering Chongqing University Chongqing400045 China Department of Engineering Lancaster University LancasterLA1 4YR United Kingdom

Cracking-based afflictions impacting tunnel side wall structures (TSWS) have becomeincreasingly prevalent, bringing the longevity of TSWS into disrepute due to waterleakage, reinforcement corrosion, and wall collapse. Especially, the hydration reactionresulting in early age-shrinkage constitutes the majority and has a significant bearingon the structural stability and longevity. The expansion agent (EA) and fiber in concreteis a promising method to inhibit early age shrinkage (EAS) cracking due to its loweconomic and time cost. However, due to the lack of research into the influencingfactors, the implementation of it is hindered. Therefore, this study investigates theeffects of EA content, CaO-MgO ratio and fiber on the flexural strength (FS),compressive strength (CS), and EAS. Results showed that EA and CaO content hadnegative effects on the mechanical properties, but had positive effect on ***, Random Forest (RF) was constructed as one of the machine learning(ML) models, and its hyperparameters were optimized through the firefly algorithm (FA)based on the experimental data. The validity of the built RF-FA models was verified bysubstantial correlation coefficients and low root-mean-square errors. Subsequently, acoFA-based firefly algorithm (MOFA) was proposed to optimise tri-objectives ofmechanical properties, EAS, and cost simultaneously. The Pareto fronts were obtainedeffectively for the optimal mixture designs, leading to the practical utilization of theTSWS concrete. © 2023, The Authors. All rights reserved.

关键词： Mean square error