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摘要 :
The thermomechanical coupling constitutive model of concrete is a critical subject for the theoretical investigation and numerical simulation of the mechanical behaviors of concrete members and structures at high temperature. This paper presents a thermomechanical coupling constitutive model for the description of the mechanical behaviors of concrete at different temperatures. The expression of the elastic strain increment is derived with the free energy function including the temperature variable. The expression of the plastic strain increment is derived from the yield function based on the Drucker-Prager strength criterion. The elastoplastic damage effect is included in this constitutive model. The damage variable is included in the yield function to consider the effect of the damage on the elastoplastic mechanical behaviors of concrete. The proposed constitutive model is validated by the comparison of the simulation results of the uniaxial compression tests of concrete at different temperatures with the corresponding test results. The simulation results accord well with the test results at different temperatures. This indicates that the proposed constitutive model can characterize the mechanical behaviors of concrete at different temperatures with considerable accuracy. The proposed constitutive model was applied to simulate an axially compressive concrete column. The simulation results are consistent with the essential mechanical response behaviors of concrete members at different temperatures.
关键词 :
concrete concrete constitutive model constitutive model elastoplastic damage elastoplastic damage thermodynamics thermodynamics thermomechanical coupling thermomechanical coupling
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GB/T 7714 | Li, Liang , Wang, Hongwei , Wu, Jun et al. A Thermomechanical Coupling Constitutive Model of Concrete Including Elastoplastic Damage [J]. | APPLIED SCIENCES-BASEL , 2021 , 11 (2) . |
MLA | Li, Liang et al. "A Thermomechanical Coupling Constitutive Model of Concrete Including Elastoplastic Damage" . | APPLIED SCIENCES-BASEL 11 . 2 (2021) . |
APA | Li, Liang , Wang, Hongwei , Wu, Jun , Jiang, Wenhua . A Thermomechanical Coupling Constitutive Model of Concrete Including Elastoplastic Damage . | APPLIED SCIENCES-BASEL , 2021 , 11 (2) . |
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摘要 :
The permeability of saturated soils has great influence on the velocities and attenuation characteristics of fast compressional wave P1, low compressional wave P2, and shear wave S in saturated soils, respectively. In three different cases, namely zero, finite, and infinite permeability, the wave equations and theoretical velocities of P1, P2, and S wave in saturated soils are given based on the u-w-p equation, respectively. According to the solutions of the wave equations, the real velocities and attenuation coefficients of three waves are redefined, respectively. In different saturated soils, the influences of the permeability and the loading frequency on the wave velocities and attenuation are discussed, respectively. Moreover, the suitable application scope of the u-p equation is discussed based on different permeabilities and loading frequencies.
关键词 :
attenuation attenuation frequency dispersion frequency dispersion permeability permeability saturated porous media saturated porous media wave velocity wave velocity
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GB/T 7714 | Song, Jia , Xu, Chengshun , Li, Liang . The Influence of Permeability on the Propagation Characteristics of the Waves in Different Saturated Soils [J]. | APPLIED SCIENCES-BASEL , 2021 , 11 (17) . |
MLA | Song, Jia et al. "The Influence of Permeability on the Propagation Characteristics of the Waves in Different Saturated Soils" . | APPLIED SCIENCES-BASEL 11 . 17 (2021) . |
APA | Song, Jia , Xu, Chengshun , Li, Liang . The Influence of Permeability on the Propagation Characteristics of the Waves in Different Saturated Soils . | APPLIED SCIENCES-BASEL , 2021 , 11 (17) . |
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摘要 :
The explicit numerical algorithm for the near-field wave motion of fluid-saturated porous media in time domain is investigated based on u-p dynamic formulation. The wave motion equations are decoupled, and dynamic coupling is eliminated by the diagonalization of the mass matrix and pore fluid compression matrix. Based on the decoupled wave motion equations, the central difference method and Newmark constant average acceleration method are adopted for the solution of solid-phase displacement and velocity, respectively. The formulation of pore fluid pressure is derived based on the backward difference method. Then the explicit staggered calculating formulas for the dynamic response of fluid-saturated porous media are derived, and a new full explicit numerical algorithm for the near-field wave motion of fluid-saturated porous media in time domain is developed. The rationality of matrix diagonalization in the algorithm is validated. The numerical results gained by the proposed algorithm accord well with the corresponding analytical results. This indicates the accuracy of the proposed algorithm. Combining the time domain numerical calculation method proposed with the transmission artificial boundary method, it is applied to the near field wave motion problem of fluid-saturated porous media, and the seismic response of saturated soil site is calculated and studied. The numerical results of the seismic response of saturated soil field accord with the elastic wave motion theory. This indicates the applicability of the developed algorithm to the near-field wave motion problem of fluid-saturated porous media. The stability characteristic of the developed algorithm is investigated based on the transfer matrix of the iterative calculating formulas of the algorithm. In the developed algorithm, all the variables of dynamic response are calculated in an iterative pattern. Thusly, this algorithm has the basic characteristic of the full explicit numerical algorithm in time domain. In the developed algorithm, all the components of the dynamic response are solved by recursive and iterative modes, which avoids solving the coupled dynamic equations. This developed algorithm has high computational efficiency and is an effective algorithm for solving near-field wave motion problems in fluid-saturated porous media in time domain. © 2020, Engineering Mechanics Press. All right reserved.
关键词 :
Computational efficiency Computational efficiency Computation theory Computation theory Dynamic response Dynamic response Elastic waves Elastic waves Equations of motion Equations of motion Iterative methods Iterative methods Numerical methods Numerical methods Porous materials Porous materials Seismic response Seismic response Time domain analysis Time domain analysis Transfer matrix method Transfer matrix method
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GB/T 7714 | Li, Liang , Li, Guo , Du, Xiu-Li et al. A full explicit numerical algorithm for near-field wave motion of fluid-saturated porous media in time domain [J]. | Engineering Mechanics , 2020 , 37 (8) : 20-31 . |
MLA | Li, Liang et al. "A full explicit numerical algorithm for near-field wave motion of fluid-saturated porous media in time domain" . | Engineering Mechanics 37 . 8 (2020) : 20-31 . |
APA | Li, Liang , Li, Guo , Du, Xiu-Li , Song, Jia . A full explicit numerical algorithm for near-field wave motion of fluid-saturated porous media in time domain . | Engineering Mechanics , 2020 , 37 (8) , 20-31 . |
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摘要 :
An engineered cementitious composite (ECC) was reinforced with a steel grid and fibers to improve its tensile strength and ductility. A series of tensile tests have been carried out to investigate the quasi-static tensile capacity of the reinforced ECC. The quasi-static tensile capacities of reinforced ECCs with different numbers of steel-grid layers, types of fibers (Polyvinyl alcohol (PVA) fiber, KEVLAR fiber, and polyethylene (PE) fiber), and volume fractions of fibers have been tested and compared. It is indicated by the test results that: (1) On the whole, the steel grid-PVA fiber and steel grid-KEVLAR fiber reinforced ECCs have high tensile strength and considerable energy dissipation performance, while the steel grid-PE fiber reinforced ECC exhibits excellent ductility. (2) The ultimate tensile strength of the reinforced ECC can be improved by the addition of steel grids. The maximal peak tensile stress increase is about 50-95% or 140-190% by adding one layer or two layers of steel grid, respectively. (3) The ultimate tensile strength of the reinforced ECC can be enhanced with the increase of fiber volume fraction. For a certain kind of fiber, a volume fraction between 1.5% and 2% grants the reinforced ECC the best tensile strength. Near the ultimate loading point, the reinforced ECC exhibits strain hardening behavior, and its peak tensile stress increases considerably. The energy dissipation performance of the reinforced ECC can also be remarkably enhanced by such an increase in fiber volume fraction. (4) The ductility of the steel grid-PVA fiber reinforced ECC can be improved by the addition of steel grids and the increase of fiber volume fraction. The ductility of the steel grid-KEVLAR fiber reinforced ECC can be improved by the addition of steel grids alone. The ductility and energy dissipation performance of the steel grid-PE fiber reinforced ECC can be improved with the increase of fiber volume fraction alone. A mechanical model for the quasi-static initial and ultimate tensile strength of the steel grid-fiber reinforced ECC is proposed. The model is validated by the test data from the quasi-static tension experiments on the steel grid-PE fiber reinforced ECC.
关键词 :
energy dissipation energy dissipation engineered cementitious composites engineered cementitious composites fiber fiber steel grid steel grid tensile capacity tensile capacity
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GB/T 7714 | Li, Liang , Liu, Wenli , Wu, Jun et al. Experimental Investigation on the Quasi-Static Tensile Capacity of Engineered Cementitious Composites Reinforced with Steel Grid and Fibers [J]. | MATERIALS , 2019 , 12 (17) . |
MLA | Li, Liang et al. "Experimental Investigation on the Quasi-Static Tensile Capacity of Engineered Cementitious Composites Reinforced with Steel Grid and Fibers" . | MATERIALS 12 . 17 (2019) . |
APA | Li, Liang , Liu, Wenli , Wu, Jun , Wu, Wenjie , Wu, Meng . Experimental Investigation on the Quasi-Static Tensile Capacity of Engineered Cementitious Composites Reinforced with Steel Grid and Fibers . | MATERIALS , 2019 , 12 (17) . |
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摘要 :
We present a time-domain, explicit, finite-element method (FEM) for dynamic analysis of transversely isotropic fluid-saturated porous media (TIFSPM). Wave propagation equations in TIFSPM are derived based on continuum mechanics. An explicit FE procedure for solving wave propagation equations is developed by applying the decoupling technique in the spatial domain and central difference method and the Newmark constant average acceleration method in the time domain. The explicit FEM is applied to simulate dynamic response of TIFSPM, and simulation results are compared with dynamic response of isotropic fluid-saturated porous media (IFSPM). Parametric studies are performed on the anisotropy coefficient to investigate the effect of material anisotropy on TIFSPM dynamic response. We find that dynamic response of TIFSPM is significantly different from that of IFSPM, and anisotropy impacts largely on TIFSPM dynamic response.
关键词 :
anisotropy coefficient anisotropy coefficient explicit finite-element method explicit finite-element method fluid-saturated porous medium fluid-saturated porous medium transverse isotropy transverse isotropy wave propagation wave propagation
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GB/T 7714 | Li Liang , Du Xiuli , Shi Peixin et al. TIME-DOMAIN EXPLICIT FINITE-ELEMENT METHOD FOR DYNAMIC ANALYSIS OF TRANSVERSELY ISOTROPIC FLUID-SATURATED POROUS MEDIA [J]. | JOURNAL OF POROUS MEDIA , 2018 , 21 (9) : 793-811 . |
MLA | Li Liang et al. "TIME-DOMAIN EXPLICIT FINITE-ELEMENT METHOD FOR DYNAMIC ANALYSIS OF TRANSVERSELY ISOTROPIC FLUID-SATURATED POROUS MEDIA" . | JOURNAL OF POROUS MEDIA 21 . 9 (2018) : 793-811 . |
APA | Li Liang , Du Xiuli , Shi Peixin , Zhai Wei . TIME-DOMAIN EXPLICIT FINITE-ELEMENT METHOD FOR DYNAMIC ANALYSIS OF TRANSVERSELY ISOTROPIC FLUID-SATURATED POROUS MEDIA . | JOURNAL OF POROUS MEDIA , 2018 , 21 (9) , 793-811 . |
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摘要 :
A precise time-integration method for the time-domain solution of the dynamic consolidation problem of fluid-saturated porous media is proposed on the basis of u-p dynamic formulation. The solid-phase displacement u is computed by the precise time-integration algorithm, and the pore fluid pressure p is computed by the backward difference algorithm. The proposed method is verified by a standard numerical example. The characteristic of the proposed method is also investigated. The computational accuracy is compared when several numerical integral methods are employed to calculate the special solution term of u-p dynamic formulation. The computational accuracy of Gauss integral method is also compared when different numbers of integral points are employed. It is shown that (1) the proposed precise time-integration method has fine computational accuracy. (2) Gauss integral method, Simpson integral method and Coates integral method all have fine computational accuracy, while trapezoidal integral method has poor computational accuracy when used to compute the special solution term. (3) the effect of the number of Gauss integral points on computational accuracy is insignificant. © 2017, Editorial Office of Chinese Journal of Computational Mechanics. All right reserved.
关键词 :
Backward difference algorithm; Dynamic consolidation; Fluid-saturated porous media; Precise time-integration method; U-p dynamic formulation Backward difference algorithm; Dynamic consolidation; Fluid-saturated porous media; Precise time-integration method; U-p dynamic formulation
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GB/T 7714 | Li, L. , Gao, C. , Wu, L.-H. . Precise time-integration method for the time-domain solution of the dynamic consolidation problem of fluid-saturated porous media [J]. | Chinese Journal of Computational Mechanics , 2017 , 34 (1) : 27-34 . |
MLA | Li, L. et al. "Precise time-integration method for the time-domain solution of the dynamic consolidation problem of fluid-saturated porous media" . | Chinese Journal of Computational Mechanics 34 . 1 (2017) : 27-34 . |
APA | Li, L. , Gao, C. , Wu, L.-H. . Precise time-integration method for the time-domain solution of the dynamic consolidation problem of fluid-saturated porous media . | Chinese Journal of Computational Mechanics , 2017 , 34 (1) , 27-34 . |
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摘要 :
The behaviour of an asphalt concrete structure subjected to severe loading, such as blast and impact loadings, is becoming critical for safety and anti-terrorist reasons. With the development of high-speed computational capabilities, it is possible to carry out the numerical simulation of an asphalt concrete structure subjected to blast or impact loading. In the simulation, the constitutive model plays a key role as the model defines the essential physical mechanisms of the material under different stress and loading conditions. In this paper, the key features of the Karagozian and Case concrete model (KCC) adopted in LSDYNA are evaluated and discussed. The formulations of the strength surfaces and the damage factor in the KCC model are verified. Both static and dynamic tests are used to determine the parameters of asphalt concrete in the KCC model. The modified damage factor is proposed to represent the higher failure strain that can improve the simulation of the behaviour of AC material. Furthermore, a series test of the asphalt concrete structure subjected to blast and impact loadings is conducted and simulated by using the KCC model. The simulation results are then compared with those from both field and laboratory tests. The results show that the use of the KCC model to simulate asphalt concrete structures can reproduce similar results as the field and laboratory test.
关键词 :
asphalt concrete asphalt concrete blast loading blast loading constitutive model constitutive model impact loading impact loading numerical simulation numerical simulation
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GB/T 7714 | Wu, Jun , Li, Liang , Du, Xiuli et al. Numerical Study on the Asphalt Concrete Structure for Blast and Impact Load Using the Karagozian and Case Concrete Model [J]. | APPLIED SCIENCES-BASEL , 2017 , 7 (2) . |
MLA | Wu, Jun et al. "Numerical Study on the Asphalt Concrete Structure for Blast and Impact Load Using the Karagozian and Case Concrete Model" . | APPLIED SCIENCES-BASEL 7 . 2 (2017) . |
APA | Wu, Jun , Li, Liang , Du, Xiuli , Liu, Xuemei . Numerical Study on the Asphalt Concrete Structure for Blast and Impact Load Using the Karagozian and Case Concrete Model . | APPLIED SCIENCES-BASEL , 2017 , 7 (2) . |
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摘要 :
This paper presents an experimental study on the damage and failure model of a new type multi-layer pavement system under drop weight impact. Such a composite pavement consists of three layers including asphalt concrete at the top, high strength concrete in the middle, and engineered cementitious composites at the bottom. The aim is to quantify the extent to which the multi-layer composite improves the resistance of protective pavements against impact load. The large scale drop weight tests were conducted on multi-layer composite pavement samples to study their response and performance under impact loading. Conventional rigid concrete pavement and flexible asphalt pavement were also tested to identify the advantages of the multi-layer composite pavement system. The impact resistance of three different pavements is evaluated in terms of the extent of damage, failure mode, deformation, and accelerations against double impacts. The test results show that the multi-layer composite pavement system exhibits less damage, significantly improved impact resistance against double impacts and improved ductility and energy absorption capacity compared with both conventional concrete and asphalt pavements. © 2017, Editorial Board of Journal of Tianjin University(Science and Technology). All right reserved.
关键词 :
Asphalt Asphalt Asphalt mixtures Asphalt mixtures Asphalt pavements Asphalt pavements Concrete testing Concrete testing Drops Drops Engineered cementitious composite Engineered cementitious composite High performance concrete High performance concrete Scales (weighing instruments) Scales (weighing instruments)
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GB/T 7714 | Wu, Jun , Li, Liang , Du, Xiuli et al. Experiment on Dynamic Properties of Multi-Layer Pavement System Under Impact Load [J]. | Journal of Tianjin University Science and Technology , 2017 , 50 (12) : 1321-1328 . |
MLA | Wu, Jun et al. "Experiment on Dynamic Properties of Multi-Layer Pavement System Under Impact Load" . | Journal of Tianjin University Science and Technology 50 . 12 (2017) : 1321-1328 . |
APA | Wu, Jun , Li, Liang , Du, Xiuli , Liu, Zhongxian . Experiment on Dynamic Properties of Multi-Layer Pavement System Under Impact Load . | Journal of Tianjin University Science and Technology , 2017 , 50 (12) , 1321-1328 . |
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摘要 :
This paper discusses numerical simulation of seismic response of underground structures in saturated soil deposits. A fully fluid solid coupling model is developed to simulate the dynamic behavior of saturated soils during an earthquake and is implemented into the commercial software ABAQUS with a user-defined element. The model is then applied to simulate seismic response of a structure buried in a saturated soil deposit. The effect of burial depth on the dynamic response of the underground structure is explored. The numerical simulations show that the user-defined element developed in this paper is capable of simulating the dynamic response of the underground structure in a saturated soil deposit. With the increase of burial depth, stress in the underground structure is transferred from the exterior walls, top slab, and bottom slab of the structure to its interior columns. The stress in the deeply buried underground structure varies more significantly than that in the shallowly buried structure during earthquake excitation.
关键词 :
ABAQUS ABAQUS earthquake earthquake fluid solid coupling fluid solid coupling saturated soil deposit saturated soil deposit Soil structure interaction Soil structure interaction user-defined element user-defined element
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GB/T 7714 | Li, Liang , Shi, Peixin , Du, Xiuli et al. Using Numerical Simulation to Determine the Seismic Response of Coastal Underground Structures in Saturated Soil Deposits [J]. | JOURNAL OF COASTAL RESEARCH , 2017 , 33 (3) : 583-595 . |
MLA | Li, Liang et al. "Using Numerical Simulation to Determine the Seismic Response of Coastal Underground Structures in Saturated Soil Deposits" . | JOURNAL OF COASTAL RESEARCH 33 . 3 (2017) : 583-595 . |
APA | Li, Liang , Shi, Peixin , Du, Xiuli , Jiao, Hongyun . Using Numerical Simulation to Determine the Seismic Response of Coastal Underground Structures in Saturated Soil Deposits . | JOURNAL OF COASTAL RESEARCH , 2017 , 33 (3) , 583-595 . |
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摘要 :
To explore the dynamic properties of asphalt concrete under severe dynamic loading, the apparatus of servo hydraulic machine and split Hopkinson pressure bar (SHPB) were employed to conduct the dynamic compression test for asphalt concrete material. The dynamic increase factor (DIF) and dynamic stress-strain curve were then obtained for asphalt concrete under middle to high strain rates. At same time, the advanced elasto-plastic damaged model strain rate effect was used to simulate the dynamic behavior of asphalt concrete in SHPB test. The key parameters for the selected material models, i.e. parameters of strength surfaces and the damage factor, were calibrated and quantified through laboratory tests. The results obtained are stated as follows: the apparatus of hydraulic servo machine and SHPB can be effectively used to obtain the DIF curve for asphalt concrete under middle to high strain rates. The compressive strength of asphalt concrete increased with the enhancement of strain rates. Laboratory tests can be used to quickly determine the key parameters of advanced elasto-plastic damaged model in order to represent the dynamic stress strain behavior of asphalt concrete. It was also found that the compressive DIFs of asphalt concrete obtained from SHPB test should consider contribution from two factors, one was the moisture effect at lower stain rates which was related to the first branch of DIFs curve obtained from SHPB test, and another was the lateral inertial confinement effect at higher stain rates which was related to the second branch of DIFs curve obtained from SHPB test. However, for the numerical model of asphalt concrete under dynamic loading, adopting the DIFs curve obtained from SHPB test would duplicate the inertial effects. Hence, when the numerical simulation of asphalt concrete under high strain rate loading was conducted, the second phase of compressive DIF obtained from SHPB test should not be considered, that is, the compressive DIFs obtained from SHPB test should be modified. © 2017, Editorial Board of Journal of Tianjin University(Science and Technology). All right reserved.
关键词 :
Asphalt concrete Asphalt concrete Compression testing Compression testing Compressive strength Compressive strength Concretes Concretes Concrete testing Concrete testing Dynamic loads Dynamic loads Elastoplasticity Elastoplasticity Numerical models Numerical models Strain rate Strain rate Stress-strain curves Stress-strain curves
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GB/T 7714 | Wu, Jun , Du, Xiuli , Li, Liang . Dynamic Increase Factor of Asphalt Concrete Under Middle to High Strain Rates [J]. | Journal of Tianjin University Science and Technology , 2017 , 50 (9) : 921-930 . |
MLA | Wu, Jun et al. "Dynamic Increase Factor of Asphalt Concrete Under Middle to High Strain Rates" . | Journal of Tianjin University Science and Technology 50 . 9 (2017) : 921-930 . |
APA | Wu, Jun , Du, Xiuli , Li, Liang . Dynamic Increase Factor of Asphalt Concrete Under Middle to High Strain Rates . | Journal of Tianjin University Science and Technology , 2017 , 50 (9) , 921-930 . |
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