Incremental Formulation of Concrete Creep under Stress History

2017 ◽  
Vol 865 ◽  
pp. 313-319
Author(s):  
Si Hyung Park ◽  
Yeong Seong Park ◽  
Ta Lee ◽  
Yong Hak Lee
Keyword(s):  
Elastic Modulus ◽  
Constitutive Equation ◽  
Drying Shrinkage ◽  
Concrete Specimen ◽  
Creep Model ◽  
Beam Specimen ◽  
First Order ◽  
Age Dependent ◽  
Incremental Formulation ◽  
Basic Equations

An incremental format of the age-dependent constitutive equation was derived by expanding the total form of the constitutive equation by using the first-order Taylor series to describe the persistent change in the creep-causing stress state as well as drying shrinkage and the development of the elastic modulus. The resulting incremental constitutive equation was defined by three basic equations for basic creep, drying shrinkage, and the development of the elastic modulus. Three types of laboratory experiments were carried out to validate the performance of the presented age-dependent constitutive equation; these included cylindrical concrete specimen tests with and without axial reinforcements and reinforced beam specimen tests. The performance of the creep model was compared with those calculated by the other age-dependent constitutive equations.

scholarly journals The analysis of rheological damage of anchorage body based on visco-elasto-plastic model

2021 ◽  
Vol 303 ◽  
pp. 01060
Author(s):  
Qing-duo Wang ◽  
Feng-hai Yu ◽  
Aleksei Renev ◽  
Sergei Tsibaev ◽  
Xue-rui Yang
Keyword(s):  
Elastic Modulus ◽  
Constitutive Equation ◽  
Creep Curve ◽  
Damage Model ◽  
Rheological Characteristics ◽  
Plastic Model ◽  
Experimental Creep ◽  
Calculation Results

In order to study the rheological damage of anchorage body, rheological damage model of anchorage body is established in this paper, and it is based on visco-elasto plastic model that is often used to simulate rock rheological characteristics. The expressions of creep constitutive equation and elastic modulus of anchorage body are obtained through the analysis of rheological damage model of anchorage body, and by the fitting calculation results, finding that the theoretical creep curve is matched with the experimental creep curve under certain conditions. The research conclusions have critical significance to the bolting support and design.

scholarly journals WATER ABSORPTION AND DRYING SHRINKAGE OF RECYCLED FOAMED AGGREGATE CONCRETE

2018 ◽  
Vol 30 (3) ◽  
Author(s):  
Chai Teck Jung ◽  
Tang Hing Kwong ◽  
Koh Heng Boon
Keyword(s):  
Water Absorption ◽  
Absorption Rate ◽  
Drying Shrinkage ◽  
Casting Process ◽  
Concrete Specimen ◽  
Sieve Analysis ◽  
Cement Ratio ◽  
Water Cement Ratio ◽  
Water Absorption Rate ◽  
Foamed Concrete

Abstract: This paper presents some experimental results and discusses the used of recycled foamed aggregates as natural coarse aggregates replacement in producing concrete. The physical properties of recycled foamed aggregates concrete were investigated. The properties studied are water absorption and drying shrinkage from the concrete early ages until the periods of 56 days. The 100 mm x 100 mm cube specimen was used to study the water absorption at the age of 7, 28 and 56 days. Meanwhile, the 100 mm x 100 mm x 300 mm length prism had been casted and used for drying shrinkage test for recycled foamed aggregates concrete. The foamed aggregates was produced from crushing recycled foamed concrete blocks. It were coated with cement paste to reduce its water absorption ability during casting process. Superplasticizer was used to maintain the workability of fresh concrete with a slump vary between 50 mm to 100 mm. The physical tests were conducted on recycled foamed aggregates to determine their initial properties such as loose bulk density, sieve analysis and water absorption rate. Recycled foamed aggregate concretes were produced with varied water cement ratio. The results obtained indicated that the linear elastic relationship between water cement ratio and water absorption rate. The higher the water cement ratio of concrete specimen will obtained higher water absorption rate. Vice versa, the density is low for drying shrinkage. The water absorption decreased while drying shrinkage becomes more stabilized over curing period.

Numerical Simulation of 3-D Failure Process of Reinforced Concrete Specimen under Uniaxial Tension

2007 ◽  
Vol 353-358 ◽  
pp. 949-952 ◽  
Author(s):  
Juan Xia Zhang ◽  
Chun An Tang ◽  
Xiu Yan Zhou ◽  
Xing Jie Hui ◽  
Zheng Zhao Liang ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Elastic Modulus ◽  
Reinforced Concrete ◽  
Uniaxial Tension ◽  
Process Analysis ◽  
Failure Process ◽  
Plain Concrete ◽  
Concrete Specimen ◽  
Numerical Code ◽  
Concrete Prism

The periodically distributed fracture spacing phenomenon exists in the failure process of the reinforced concrete prism under uniaxial tension. In this paper, A numerical code RFPA3D (3D Realistic Failure Process Analysis) is used to simulate the three-dimensional failure process of plain concrete prism specimen and reinforced concrete prism specimen under uniaxial tension. The reinforced concrete is represented by a set of elements with same size and different mechanical properties. They are uniform cubic elements and their mechanical properties, including elastic modulus and peak strength, are distributed through the specimens according to a certain statistical distribution. The elastic modulus and other mechanical properties are weakened gradually when the stresses in the elements meet the specific failure criterion. The displacement-controlled loading scheme is used to simulate the complete failure process of reinforced concrete. The analyses focus on the failure mechanisms of the concrete and reinforcement. The complete process of the fracture for the plain concrete prism and the fracture initiation, infilling and saturation of the reinforced concrete prism is reproduced. It agrees well with the theoretical analysis. Through 3D numerical tests for the specimen, it can be investigated the interaction between the reinforcement and concrete mechanical properties in meso-level and the numerical code is proved to be an effective way to help thoroughly understand the rule of the reinforcement and concrete and also help the design of the structural concrete components and systems.

Probabilistic Analysis on the Uncertainty in Natural Frequency of Functionally Graded Material Beams

2019 ◽  
Vol 889 ◽  
pp. 484-488
Author(s):  
Van Thuan Nguyen ◽  
Duy Liem Nguyen
Keyword(s):  
Elastic Modulus ◽  
Natural Frequency ◽  
Functionally Graded Material ◽  
Functionally Graded ◽  
Order Perturbation ◽  
First Order ◽  
Graded Material ◽  
Natural Frequency Analysis ◽  
Mcs Method ◽  
First Order Perturbation

This paper applies the stochastic finite element method (SFEM) to perform the natural frequency analysis of functionally graded material (FGM). It is assumed that the elastic modulus and width of the FGM beam vary along the thickness and width directions following exponential functions. The stochastic eigenvalue problem is solved independently by first-order perturbation and Monte Carlo simulation (MCS) method through changing elastic modulus as spatial randomness. The results show that the first-order perturbation method based SFEM produces a very close value to MCS method.

Influence of coarse coal gangue aggregates on elastic modulus and drying shrinkage behaviour of concrete

2020 ◽  
Vol 32 ◽  
pp. 101748
Author(s):  
Qinghe Wang ◽  
Zhe Li ◽  
Yuzhuo Zhang ◽  
Huan Zhang ◽  
Mei Zhou ◽  
...  
Keyword(s):  
Elastic Modulus ◽  
Drying Shrinkage ◽  
Coal Gangue ◽  
Shrinkage Behaviour

Research of Steel Fiber Self-Compacting Concrete Frost Resistance

2012 ◽  
Vol 174-177 ◽  
pp. 721-725 ◽  
Author(s):  
Ming Bao Gao ◽  
Yan Ru Zhao ◽  
Xiao Yan He
Keyword(s):  
Elastic Modulus ◽  
Frost Resistance ◽  
Steel Fiber ◽  
Concrete Specimen ◽  
Test Method ◽  
Dynamic Elastic Modulus ◽  
Self Compacting Concrete ◽  
Freeze Thaw ◽  
Thaw Cycle ◽  
Freeze Thaw Cycle

With the fast freeze-thaw test method, the c50 steel fiber self-compacting concrete was carried out 300 tests of freeze-thaw cycle. In the process of freeze-thaw cycles, it determined by the quality of the concrete specimen, dynamic elastic modulus and strength, and analyzed the steel fibers and their different contents on frost resistance of self-compacting concrete impact. The results showed that: steel fiber self-compacting concrete in freeze-thaw cycle can play constrained role in the quality loss, dynamic elastic modulus and intensity, and can significantly improve the self-compacting concrete frost resistance. Within a certain range, the more steel fiber, the stronger of frost resistance.

NANOINDENTATION AND ASH CONTENT STUDY OF AGE DEPENDENT CHANGES IN PORCINE CORTICAL BONE

2015 ◽  
Vol 15 (05) ◽  
pp. 1550074 ◽  
Author(s):  
MICHAEL CHITTENDEN ◽  
AHMAD RAEISI NAJAFI ◽  
JUN LI ◽  
IWONA JASIUK
Keyword(s):  
Mechanical Properties ◽  
Elastic Modulus ◽  
Cortical Bone ◽  
Age Groups ◽  
Structure Property ◽  
Micro Computed Tomography ◽  
Mineral Contents ◽  
Age Related ◽  
Age Dependent ◽  
Composition Structure

Composition-structure-property relations of bone provide fundamental understanding of bone quality. The objective of this paper was to investigate age dependent changes in the composition, structure and mechanical properties of porcine femoral cortical bone at mid-diaphysis region from six age groups (1, 3.5, 6, 12, 30, 48 months). This study was motivated by the fact that limited data is available in the literature on young porcine cortical bone. Nanoindentation technique with Berkovich fluid cell tip was employed to measure the elastic modulus and hardness. Individual lamellae were indented in the longitudinal direction of bone in different microstructural components (osteonal, interstitial and plexiform bone). A grid of indentations was also made on one bone sample to obtain spatial variations in the elastic modulus and hardness. Ash and water content tests were performed to measure water, organic and mineral contents of bone as a function of age. Finally, high resolution micro-computed tomography was used to measure porosity and visualize three-dimensional void structures. We found that the elastic modulus and hardness of bone increased with age but at different rates in each microstructural component. The mineral content increased correspondingly with age while the porosity decreased. The obtained structure, composition, and mechanical properties data give new insights on the age related changes in young cortical bone and can serve as inputs for and validation of multiscale models of bone.

The Early-Age Drying Shrinkage of Cement-Based Materials with the same Workability after Temperature Compensation

2013 ◽  
Vol 405-408 ◽  
pp. 2604-2609
Author(s):  
Li Feng Zhang ◽  
Jun Ying Lai ◽  
Xiao Qian Qian ◽  
Chong Shen
Keyword(s):  
Temperature Compensation ◽  
Setting Time ◽  
Drying Shrinkage ◽  
Concrete Specimen ◽  
Temperature Deformation ◽  
Control Group ◽  
Early Age ◽  
Peak Time ◽  
Initial Setting Time ◽  
Cement Based Materials

The early age drying shrinkage of cement-based materials with same the same workability staring from the initial setting time was studied. Superplasticizers (SP) were used to get the same workability. The drying shrinkage of paste was measured by clock gauge, and CABR-NES deformation instrument was used to measure the shrinkage of concrete. Temperature probes were buried into both paste and concrete specimen cores to measure the temperature curve, and temperature deformation was considered into the early shrinkage. Results show the addition of SP increases much more shrinkage than the control group, and polycarboxylate SP increases more shrinkage than naphthalene SP. The different temperature peak time of different mixtures show that the addition of SP changes the hydration process of cement, and the shrinkage of cement-based materials after temperature compensation is bigger than the measured value in the first 6 hours, but the gap is not big.

scholarly journals Concrete with Reused Concrete Sand

2019 ◽  
Vol 8 (6) ◽  
pp. 4868-4873
Keyword(s):  
Elastic Modulus ◽  
Compression Strength ◽  
Drying Shrinkage ◽  
Shrinkage Strain ◽  
Ordinary Concrete ◽  
Mixed Concrete

This paper examines the impacts of substitution of reused concrete sand (RCS) with sands, on the new and hardened physiognomies of concrete. the property of RCS blended concrete was examined and likened with ordinary concrete of 40 MPa compression strength. the physiognomies of RCS concrete vary from ordinary concrete arranged with characteristic sand, as an outcome of the quality of connected mortar, old cement glue, and more fines. the outcomes demonstrate that the RCS concrete demonstrations tantamount workability in contrast with ordinary concrete. the mechanical physiognomies (compressive, flexure, split tensile and elastic modulus) of concrete developed with RCS was lower in compression to ordinary concrete however worthy up to 60percentage RCS in the blend. The drying shrinkage strain of 100percentage RCC mixed concrete at twenty-eight days was watched twice in compression to controlled concrete and it demonstrated more abrasion value in that comparison and furthermore concrete developed with 100 percent RCS indicated 41percentage and 11.3percentage lower in sorption value at ahead of schedule and later age organize individually in that examination.

scholarly journals A Constitutive Equation of Turbulence

Fluids ◽  
2021 ◽  
Vol 6 (11) ◽  
pp. 414
Author(s):  
Peter W. Egolf ◽  
Kolumban Hutter
Keyword(s):  
Constitutive Equation ◽  
Turbulence Model ◽  
Turbulence Models ◽  
Turbulent Shear ◽  
Fractional Dynamics ◽  
Physics First ◽  
First Order ◽  
Flow Problems ◽  
Closure Scheme ◽  
Theoretical Considerations

Even though applications of direct numerical simulations are on the rise, today the most usual method to solve turbulence problems is still to apply a closure scheme of a defined order. It is not the case that a rising order of a turbulence model is always related to a quality improvement. Even more, a conceptual advantage of applying a lowest order turbulence model is that it represents the analogous method to the procedure of introducing a constitutive equation which has brought success to many other areas of physics. First order turbulence models were developed in the 1920s and today seem to be outdated by newer and more sophisticated mathematical-physical closure schemes. However, with the new knowledge of fractal geometry and fractional dynamics, it is worthwhile to step back and reinvestigate these lowest order models. As a result of this and simultaneously introducing generalizations by multiscale analysis, the first order, nonlinear, nonlocal, and fractional Difference-Quotient Turbulence Model (DQTM) was developed. In this partial review article of work performed by the authors, by theoretical considerations and its applications to turbulent flow problems, evidence is given that the DQTM is the missing (apparent) constitutive equation of turbulent shear flows.

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