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Empirical models and design codes in prediction of modulus of elasticity of concrete

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Frontiers of Structural and Civil Engineering 2019年第1期13卷 38-48页

作者： Behnam VAKHSHOURI Shami NEJADI Centre for Built Infrastructure Research University of Technology SydneySydneyAustralia

modulus of Elasticity (MOE)is a key parameter in reinforced concrete design.It represents the stressstrain relationship in the elastic range and is used in the prediction of concrete structures.Out of range estimation of MOE in the existing codes of practice strongly affect the design and performance of the concrete structures.This study includes: (a)evaluation and comparison of the existing analytical models to estimating the MOE in normal strength concrete,and (b)proposing and verifying a new model.In addition,a wide range of experimental databases and empirical models to estimate the MOE from compressive strength and density of concrete are evaluated to verification of the proposed model. The results show underestimation of MOE of conventional concrete in majority of the existing models.Also,considering the consistency between density and mechanical properties of concrete,the predicted MOE in the models including density effect,are more compatible with the experimental results.

关键词： modulus of elasticity normal strength normal weight concrete empirical models design codes compressive strength density

Predicting resilient modulus of recycled concrete and clay masonry blends for pavement applications using soft computing techniques

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Frontiers of Structural and Civil Engineering 2019年第6期13卷 1379-1392页

作者： Mosbeh R.KALOOP Alaa R.GABR Sherif M.EL-BADAWY Ali ARISHA Sayed SHWALLY Jong Wan HU Department of Civil and Environmental Engineering Incheon National UniversityIncheon 22012South Korea Incheon Disaster Prevention Research Center Incheon National UniversityIncheon 22012South Korea Department of Public Works and Civil Engineering Mansoura UniversityMansoura 35516Egypt

To date,very few researchers employed the Least Square Support Vector Machine(LSSVM)in predicting the resilient modulus(Mr)of Unbound Granular Materials(UGMs).This paper focused on the development of a LSSVM model to predict the MT of recycled materials for pavement applications and comparison with other different models such as Regression,and Artificial Neural Network(ANN).Blends of Recycled Concrete Aggregate(RCA)with Recycled Clay Masonry(RCM)with proportions of 100/0,90/10,80/20,70/30,55/45,40/60,20/80,and 0/100 by the total aggregate mass were evaluated for use as UGMs.RCA/RCM materials were collected from dumps on the sides of roads around Mansoura city,Egypt.The investigated blends were evaluated experimentally by routine and advanced tests and the Mr values were detennined by Repeated Load Triaxial Test(RLTT).Regression,ANN,and LSSVM models were utilized and compared in predicting the Mr of the investigated blends optimizing the best design model.Results showed that the Mx values of the investigated RCA/RCM blends were generally increased with the decrease in RCM proportion.Statistical analyses were utilized for evaluating the performance of the developed models and the inputs sensitivity parameters.Eventually,the results approved that the LSSVM model can be used as a novel tool to estimate the Mx of the investigated RCA/RCM blends.

关键词： Least Square Support Vector Machine Artificial Neural Network resilient modulus Recycled Concrete Aggregate Recycled Clay Masonry

Cluster-formula-embedded machine learning for design of multicomponent β-Ti alloys with low Young’s modulus

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npj Computational Materials 2020年第1期6卷 824-834页

作者： Fei Yang Zhen Li Qing Wang Beibei Jiang Biaojie Yan Pengcheng Zhang Wei Xu Chuang Dong Peter K.Liaw Key Laboratory of Materials Modification by Laser Ion and Electron Beams(Ministry of Education)School of Materials Science and EngineeringDalian University of TechnologyDalian116024 LiaoningChina School of Mechanical Engineering Dalian University of TechnologyDalian116024 LiaoningChina Analysis and Test Center Guangdong University of TechnologyGuangzhou510006 GuangdongChina Institute of Materials China Academy of Engineering PhysicsJiangyou621908 SichuanChina State Key Laboratory of Rolling and Automation Northeastern UniversityShenyang110819 LiaoningChina Department of Materials Science and Engineering The University of TennesseeKnoxville37996 TNUSA

The present work formulated a materials design approach,a cluster-formula-embedded machine learning(ML)model,to search for body-centered-cubic(BCC)β-Ti alloys with low Young’s modulus(E)in the Ti–Mo–Nb–Zr–Sn–Ta system.The characteristic parameters,including the Mo equivalence and the cluster-formula approach,are implemented into the ML to ensure the accuracy of prediction,in which the former parameter represents the BCC-βstructural stability,and the latter reflects the interactions among elements expressed with a composition formula.Both auxiliary gradient-boosting regression tree and genetic algorithm methods were adopted to deal with the optimization problem in the ML model.

关键词： alloys modulus formula

Simultaneous prediction of rock matrix modulus and critical porosity

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Applied Geophysics 2019年第1期16卷 14-24页

作者： Li Nuo Chen Hao Zhang Xiu-Mei Han Jian-Qiang Wang Jian Wang Xiu-Ming State Key Laboratory of Acoustics Institute of AcousticsChinese Academy of SciencesBeijing 100190China University of Chinese Academy of Sciences Beijing 100049China Beijing Engineering Research Center of sea deep drilling and exploration Beijing 100190China

The matrix modulus and critical porosity in rocks are two critical parameters to seismic rock physics models;however, the critical porosity is diffi cult to obtain. Based on the linear relation between the effective bulk modulus and porosity, we propose a fast method for calculating the matrix modulus and critical porosity by least square fi tting of effective bulk modulus and porosity data measured in laboratory or fi eld. The proposed method is well suited for samples with wide porosity range. The calculation results accurately refl ect the differences in clay content, pressure, and saturation state. Samples with high clay content have low matrix modulus and critical porosity. The matrix modulus is independent of pressure, whereas the critical porosity increases with increasing pressure. The calculated matrix modulus for watersaturated samples is higher than that for dry rock samples.

关键词： modulus porosity clay content pressure saturation

Origin of modulus Improvement for Epoxide-terminated Hyperbranched Poly(ether sulphone)/DGEBA/TETA Systems

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Chinese Journal of Polymer Science 2018年第8期36卷 991-998页

作者： Xue-Pei Miao Dao-Jian Cheng Ya-Dong Dai Yan Meng Xiao-Yu Li Key Laboratory of Carbon Fiber and Functional Polymers Ministry of Education College of Materials Science and Engineering Beijing University of Chemical Technology Beijing 100029 China State Key Laboratory of Organic-Inorganic Composites Beijing University of Chemical Technology Beijing 100029 China Neo Trident Technology Ltd (Beijing) Beijing 100190 China

It has been experimentally shown that epoxide-terminated hyperbranched polyether sulphone （EHBPES） can significantly improve the mechanical properties of traditional diglycidyl ether of bisphenol A/triethylenetetramine （DGEBA/TETA） systems, but the origin of the improvement is still unclear. In this work, we used molecular dynamics （MD） simulations to gain a thorough understanding of the origin of modulus improvement for EHBPES/DGEBA/TETA systems. It is found that the modulus of EHBPES/DGEBA/TETA systems increases with the increase of EHBPES loading. In addition, the crosslinking density, cohesive energy density （CED）, and free volume can be used to understand the modulus for EHBPES/DGEBA/TETA systems. It is shown that the highest modulus is achieved at 7 wt% EHBPES loading due to the highest crosslinking density and CED. When EHBPES loading is below 7 wt%, the higher CED and crosslinking density are responsible for the higher modulus. At higher loadings （〉 7 wt%）, the decreased modulus is closely related to the decreased crosslinking density and increased fractional free volume. It is expected that our results could be of great implications for designing high-performance epoxy materials.

关键词： modulus Molecular simulation Epoxy resin

Random field characterization of uniaxial compressive strength and elastic modulus for intact rocks

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Geoscience Frontiers 2018年第6期9卷 1609-1618页

作者： Huaxin Liu Xiaohui Qi School of Civil and Environmental Engineering Nanyang Technological University

Rock properties exhibit spatial variabilities due to complex geological processes such as sedimentation,metamorphism, weathering, and tectogenesis. Although recognized as an important factor controlling the safety of geotechnical structures in rock engineering, the spatial variability of rock properties is rarely quantified. Hence, this study characterizes the autocorrelation structures and scales of fluctuation of two important parameters of intact rocks, i.e. uniaxial compressive strength(UCS) and elastic modulus(EM).UCS and EM data for sedimentary and igneous rocks are collected. The autocorrelation structures are selected using a Bayesian model class selection approach and the scales of fluctuation for these two parameters are estimated using a Bayesian updating method. The results show that the autocorrelation structures for UCS and EM could be best described by a single exponential autocorrelation function. The scales of fluctuation for UCS and EM respectively range from 0.3 m to 8.0 m and from 0.3 m to 8.4 m.These results serve as guidelines for selecting proper autocorrelation functions and autocorrelation distances for rock properties in reliability analyses and could also be used as prior information for quantifying the spatial variability of rock properties in a Bayesian framework.

关键词： Uniaxial compressive strength Elastic modulus Scale of fluctuation Autocorrelation function Spatial variability Bayesian approach

Impedance and modulus studies of Na_(0.9)Ba_(0.1)Nb_(0.9)(Sn_(0.5)Ti_(0.5))_(0.1)O_(3) ceramic

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Journal of Advanced Dielectrics 2021年第2期11卷 34-41页

作者： A.Oueslati A.Aydi Laboratory of Spectroscopic Characterization and Optical Materials Faculty of Sciences University of Sfax B.P.11713000 SfaxTunisia Laboratory of Multifunctional Materials and Applications(LaMMA)LR16ES18 Faculty of Sciences of SfaxUniversity of Sfax BP 11713000 SfaxTunisia

Polycrystalline Na_(0.9)Ba_(0.1)Nb_(0.9)(Sn_(0.5)Ti_(0.5))_(0.1)O_(3) is prepared by the solid-state reaction technique.The formation of single-phase material was confirmed by an X-ray diffraction study and it was found to be a tetragonal phase at room temperature.Nyquist plots(Z″versus Z′)show that the conductivity behavior is accurately represented by an equivalent circuit model which consists of a parallel combination of bulk resistance and constant phase elements(CPE).The frequency dependence of the conductivity is interpreted in terms of Jonscher’s law.The conductivity s_(dc) follows the Arrhenius relation.The modulus plots can be characterized by the empirical Kohlrausch-Williams-Watts(KWW),j(t)=exp(−(t/t)^(β))function and the value of the stretched exponent(b)is found to be almost independent of temperature.The near value of activation energies obtained from the analyses of modulus and conductivity data confirms that the transport is through an ion hopping mechanism dominated by the motion of the(O^(2−))ions in the structure of the investigated material.

关键词： Ceramics impedance spectroscopy equivalent circuit modulus electrical conductivity

Modification of Longitudinal modulus of 3D Full Five Directional Braided Composite Materials Base on Energy Theory

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Journal of Beijing Institute of Technology 2019年第3期28卷 651-658页

作者： Apeng Dong Shu Li Wenguo Zhu Jing Pu School of Aeronautic Science and Engineering Beihang UniversityBeijing 100191China Faculty of Engineering University of NottinghamNottingham NG7 2RDUnited Kingdom

The aim of this paper is to investigate the longitudinal modulus of three dimensional full five directional (3Df5d) braided composite. First, the analytical model of the internal unit cell is established based on its topological structure. Then, according to the intrinsic relation of different cells, the axial moduli of internal, surface and corner cells are systematically deduced, and the influence of corner-cell periodic discontinuity on the moduli is also analyzed. Finally, considering the actual shape of axial yarns after consolidation, the longitudinal moduli of the different cells are modified based on energy theory. The technology factor λ is also proposed in this modification. The results show that the axial mechanical properties of this material can be strongly designable. The straightness of the axial yarns greatly affects the longitudinal modulus. Technology factor λ is between 1 to 2, corresponding to the minimum and the maximum modulus, respectively.

关键词： braided composites braiding parameters elastic modulus strain energy technology factor

DSC modelling for predicting resilient modulus of crushed rock base as a road base material for Western Australia roads

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交通运输工程学报 2013年第2期13卷 10-16页

作者： KHOBKLANG Pakdee VIMONSATIT Vanissorn JITSANGIAM Peerapong NIKRAZ Hamid Department of Civil Engineering Curtin UniversityGPO Box U1987 Perth 6845Western AustraliaAustralia

In order to increase the applied efficiency of crushed rock base(CRB) in pavement structure design for Western Australia roads,the material modelling based on the experimental results was investigated,and the disturbed state concept(DSC) was used to predict the resilient modulus of CRB because of its simplicity and strong ability in capturing the elastic and inelastic responses of materials to loads.The actual deformation of DSC,at any loading state,was determined from its assumed relative intact(RI) state.The DSC equation of CRB was constructed by using a set of experimental results of resilient modulus tests,and an idealized material model,namely the linear elastic model,of relative intact(RI) part was considered.Analysis results reveal that the resilient modulus-applied stress relationships back-predicted by using the DSC modelling are consistent with the experimental results,so,the DSC equation is suited for predicting the resilient modulus of CRB specimen.However,the model and the equation coming from the test results are conducted in accordance with the Austroads standard,so further investigation and validation with respect to the field behaviours of pavement structure should be performed.

关键词： pavement engineering CRB resilient modulus DSC RI triaxial test