Effectiveness of Meso-Scale Approach in Modeling of Plain Concrete Beam

2018 ◽  
Vol 24 (8) ◽  
pp. 71
Author(s):  
Alaa H. Al-Zuhairi ◽  
Ali I. Taj
Keyword(s):  
Finite Element ◽  
Concrete Beam ◽  
Coarse Aggregate ◽  
Beam Theory ◽  
Plain Concrete ◽  
Experimental Models ◽  
Scale Model ◽  
Element Analysis ◽  
Flexural Testing ◽  
Meso Scale

The main aim of this research paper is investigating the effectiveness and validity of Meso-Scale Approach (MSA) as a modern technique for the modeling of plain concrete beams. Simply supported plain concrete beam was subjected to two-point loading to detect the response in flexural. Experimentally, a concrete mix was designed and prepared to produce three similar standard concrete prisms for flexural testing. The coarse aggregate used in this mix was crushed aggregate. Numerical Finite Element Analysis (FEA) was conducted on the same concrete beam using the meso-scale modeling. The numerical model was constructed to be a bi-phasic material consisting of cement mortar and coarse aggregate. The interface between the two consisting materials was assumed fully bonded interface. In the ABAQUS program, the Extended Finite Element Method (XFEM) was employed for the treatment of the discontinuity problems, which is accompanied by cracking during the fracture process of plain concrete. The behavior and response of the beam in both meso-scale numerical analysis and experimental test were found in a good agreement. Another check was added by comparing the results using thin-beam theory assuming the concrete as a homogenous linear-elastic material. The result of this comparison showed that the meso-scale model analysis lies between theoretical and experimental models.  

scholarly journals Finite Element Analysis of Concrete Beam under Flexural Stresses Using Meso-Scale Model

2018 ◽  
Vol 4 (6) ◽  
pp. 1288
Author(s):  
Alaa H. Al-Zuhairi ◽  
Ali Ihsan Taj
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Concrete Beam ◽  
Plain Concrete ◽  
Point Load ◽  
Scale Model ◽  
Interfacial Zone ◽  
Element Analysis ◽  
Meso Scale ◽  
Aggregate Particles

Two dimensional meso-scale concrete modeling was used in finite element analysis of plain concrete beam subjected to bending. The plane stress 4-noded quadrilateral elements were utilized to model coarse aggregate, cement mortar. The effect of aggregate fraction distribution, and pores percent of the total area – resulting from air voids entrapped in concrete during placement on the behavior of plain concrete beam in flexural was detected. Aggregate size fractions were randomly distributed across the profile area of the beam. Extended Finite Element Method (XFEM) was employed to treat the discontinuities problems result from double phases of concrete and cracking that faced during the finite element analysis of concrete beam. Cracking was initiated at a small notch located at the middle of the bottom face of the concrete beam. The response of plain concrete beam subjected to pure bending via two point load application was detected using (XFEM) analysis of meso-scale concrete model. Assuming full bond between aggregate particles, and mortar at interfacial zone, the flexural strength of plain concrete beam is increased when aggregate particles size is increased, so that bending and shear stress were affected by void percentage and aggregate particles distribution. The maximum deflection at midspan was increased when the aggregate particles size decreases.

scholarly journals Extended Finite Element Analysis of Reinforced Concrete Beams Using Meso-Scale Modeling

2020 ◽  
Vol 27 (1) ◽  
pp. 19-29
Author(s):  
Eman Abbas ◽  
Alaa H. Al-zuhairi
Keyword(s):  
Finite Element ◽  
Reinforced Concrete ◽  
Coarse Aggregate ◽  
Mesoscale Model ◽  
Maximum Size ◽  
Reinforced Concrete Beams ◽  
Rc Beams ◽  
Extended Finite Element ◽  
Element Analysis ◽  
Meso Scale

Four simply supported reinforced concrete (RC) beams were test experimentaly and analyzed using the extended finite element method (XFEM). This method is used to treat the discontinuities resulting from the fracture process and crack propagation in that occur in concrete. The Meso-Scale Approach (MSA) used to model concrete as a heterogenous material consists of a three-phasic material (coarse aggregate, mortar, and air voids in the cement paste). The coarse aggregate that was used in the casting of these beams rounded and crashed aggregate shape with maximum size of 20 mm. The compressive strength used in these beams is equal to 17 MPa and 34 MPa, respectively. These RC beams are designed to fail due to flexure when subjected to load as a two-point loading. To model the coarse aggregate realistically, the aggregate must distributed randomly according to the gradient and amount actually used in the mix design. This property is not found in the ABAQUS program that resulted in the use of an alternate program to represent the aggregate randomly. Next, the random representation of the aggregate were transfered to the ABAQUS program by using commands and instructions that the program can understand, to draw as a sketch. The comparison between experimental and numerical results showed that the XFEM is a good method used to simulate the non-smooth behavior in RC beams such as discontinuitiy and singularity. While a mesoscale model can be simulated the non-homogeneity in the concrete.

scholarly journals MESO-Scale Modeling of CFRP-Confined Concrete: Microplane-Based Approach

Fibers ◽  
2020 ◽  
Vol 8 (6) ◽  
pp. 38
Author(s):  
Serena Gambarelli ◽  
Joško Ožbolt
Keyword(s):  
Finite Element ◽  
Size Distribution ◽  
Coarse Aggregate ◽  
Three Dimensional ◽  
Aggregate Size ◽  
Confined Concrete ◽  
Scale Model ◽  
Brittle Behavior ◽  
Aggregate Size Distribution ◽  
Meso Scale

The present paper shows the results of three-dimensional (3D) meso-scale numerical simulations that were performed on unconfined and Carbon Fibre Reinforced Polymer (CFRP)-confined concrete specimens under uniaxial compression. The numerical results are compared with available experimental data. The meso-scale structure of concrete is composed by two phases, namely: the coarse aggregate and the mortar matrix. The presence of Interfacial Transition Zone (ITZ) is neglected. A simple generation procedure is used to randomly place the coarse aggregate inside the concrete specimens. The finite element code MASA is used to perform the three-dimensional (3D) Finite Element meso-scale simulations. The constitutive laws for mortar and epoxy resin are based on the microplane model, while an elastic-brittle behavior is assumed for the fibers. Aggregate in concrete is considered to be linear elastic. The adopted meso-scale model for concrete can realistically reproduce the mechanical behavior of both unconfined and CFRP-confined specimens. However, in the case of small corner radius, the effect of confinement predicted by the model is overestimated with respect to the experimental results. This is partially related to the simplifications introduced in the model in terms of aggregate volumetric fraction (10%) and aggregate size distribution. It is shown that a more detailed meso-scale model, which is characterized by 30% of the coarse aggregate and realistic aggregate size distribution, can better capture the interaction between the concrete heterogeneity and the confining effect provided by CFRP.

scholarly journals Stator Non-Uniform Radial Ventilation Design Methodology for a 15 MW Turbo-Synchronous Generator Based on Single Ventilation Duct Subsystem

Energies ◽  
2021 ◽  
Vol 14 (10) ◽  
pp. 2760
Author(s):  
Ruiye Li ◽  
Peng Cheng ◽  
Hai Lan ◽  
Weili Li ◽  
David Gerada ◽  
...  
Keyword(s):  
Finite Element ◽  
Temperature Distribution ◽  
Design Methodology ◽  
Large Scale ◽  
Synchronous Generator ◽  
Axial Direction ◽  
Scale Model ◽  
Element Analysis ◽  
Axial Temperature ◽  
Ventilation Duct

Within large turboalternators, the excessive local temperatures and spatially distributed temperature differences can accelerate the deterioration of electrical insulation as well as lead to deformation of components, which may cause major machine malfunctions. In order to homogenise the stator axial temperature distribution whilst reducing the maximum stator temperature, this paper presents a novel non-uniform radial ventilation ducts design methodology. To reduce the huge computational costs resulting from the large-scale model, the stator is decomposed into several single ventilation duct subsystems (SVDSs) along the axial direction, with each SVDS connected in series with the medium of the air gap flow rate. The calculation of electromagnetic and thermal performances within SVDS are completed by finite element method (FEM) and computational fluid dynamics (CFD), respectively. To improve the optimization efficiency, the radial basis function neural network (RBFNN) model is employed to approximate the finite element analysis, while the novel isometric sampling method (ISM) is designed to trade off the cost and accuracy of the process. It is found that the proposed methodology can provide optimal design schemes of SVDS with uniform axial temperature distribution, and the needed computation cost is markedly reduced. Finally, results based on a 15 MW turboalternator show that the peak temperature can be reduced by 7.3 ∘C (6.4%). The proposed methodology can be applied for the design and optimisation of electromagnetic-thermal coupling of other electrical machines with long axial dimensions.

Natural frequency analysis of a functionally graded rotor-bearing system with a slant crack subjected to thermal gradients

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Arnab Bose ◽  
Prabhakar Sathujoda ◽  
Giacomo Canale
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Power Law ◽  
Beam Theory ◽  
Functionally Graded ◽  
Thermal Gradients ◽  
Element Analysis ◽  
Rotor Bearing ◽  
Natural Frequency Analysis ◽  
Bearing System

Abstract The present work aims to analyze the natural and whirl frequencies of a slant-cracked functionally graded rotor-bearing system using finite element analysis for the flexural vibrations. The functionally graded shaft is modelled using two nodded beam elements formulated using the Timoshenko beam theory. The flexibility matrix of a slant-cracked functionally graded shaft element has been derived using fracture mechanics concepts, which is further used to develop the stiffness matrix of a cracked element. Material properties are temperature and position-dependent and graded in a radial direction following power-law gradation. A Python code has been developed to carry out the complete finite element analysis to determine the Eigenvalues and Eigenvectors of a slant-cracked rotor subjected to different thermal gradients. The analysis investigates and further reveals significant effect of the power-law index and thermal gradients on the local flexibility coefficients of slant-cracked element and whirl natural frequencies of the cracked functionally graded rotor system.

Burst Pressure of Pressurized Cylinders With Hillside Nozzle

2009 ◽  
Vol 131 (4) ◽  
Author(s):  
H. F. Wang ◽  
Z. F. Sang ◽  
L. P. Xue ◽  
G. E. O. Widera
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Experimental Models ◽  
Burst Pressure ◽  
Element Analysis ◽  
Test Models ◽  
Scale Test ◽  
Failure Location ◽  
Dimensional Instability ◽  
Good Agreement

The burst pressure of cylinders with hillside nozzle is determined using both experimental and finite element analysis (FEA) approaches. Three full-scale test models with different angles of the hillside nozzle were designed and fabricated specifically for a hydrostatic test in which the cylinders were pressurized with water. 3D static nonlinear finite element simulations of the experimental models were performed to obtain the burst pressures. The burst pressure is defined as the internal pressure for which the structure approaches dimensional instability, i.e., unbounded strain for a small increment in pressure. Good agreement between the predicted and measured burst pressures shows that elastic-plastic finite element analysis is a viable option to estimate the burst pressure of the cylinders with hillside nozzles. The preliminary results also suggest that the failure location is near the longitudinal plane of the cylinder-nozzle intersection and that the burst pressure increases slightly with an increment in the angle of the hillside nozzle.

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