scholarly journals THEORETICAL JUSTIFICATION OF INCREASING THE EFFICIENCY OF REINFORCEMENT OF FLEXIBLE CELLULAR CONCRETE STRUCTURES

2021 ◽  
Vol 6 (6) ◽  
pp. 27-35
Author(s):  
Polina Kladieva ◽  
V. Mozgovoy ◽  
M. Moiseev
Keyword(s):  
Concrete Beam ◽  
Numerical Study ◽  
Concrete Structures ◽  
Cross Sectional ◽  
Load Bearing ◽  
Masonry Material ◽  
Steel Consumption ◽  
Efficient Construction ◽  
Aerated Concrete ◽  
Cellular Concrete

Aerated concrete is actively used in energy efficient construction, mainly as a masonry material for vertical load-bearing structures. At the same time, the creation of a closed thermal contour of the building, which is the basis of modern energy saving requirements, is rational by the use of aerated concrete in load-bearing horizontal structures that require reinforcement. Traditionally bar reinforcement is ineffective in aerated concrete due to low specific adhesion at the contact of the reinforcement with concrete and significantly less than that of heavy concrete, the distribution capacity of concrete around a rod, which evenly transforms concrete stress to bar extension, the consequence of which is the significant bar understress while pulling it in concrete. The authors’ research in the field of rationalization of reinforcing elements that are effective in cellular concrete, aimed at increasing the contact surface of the reinforcing element with concrete while maintaining the original steel consumption, makes it possible to recommend tape reinforcement for use in reinforced aerated concrete structures. Punched steel tapes equal to the bar reinforcement of the cross-sectional area, but having developed lateral surface, provide an increase in the adhesion strength of the reinforcement and preventing its pulling. The article presents the results of a numerical study of stress-strain state in reinforced aerated concrete beam with rectangular section, reinforced with the proposed tape reinforcement in comparison with traditional bar reinforcement

scholarly journals Numerical study on beam-column connection of cantilever precast concrete beam with asymmetric shape under static load

2018 ◽  
Vol 195 ◽  
pp. 02009
Author(s):  
Hakas Prayuda ◽  
Robbi’al Rollyas Syandy ◽  
Bagus Soebandono ◽  
Taufiq Ilham Maulana ◽  
Martyana Dwi Cahyati
Keyword(s):  
Concrete Beam ◽  
Static Load ◽  
Numerical Study ◽  
Precast Concrete ◽  
Concrete Structures ◽  
Damage Mechanism ◽  
Cantilever Beams ◽  
Three Samples ◽  
Section Shape ◽  
Asymmetric Shape

Cantilever beams are generally used in all infrastructures, including precast concrete structures. In that type of structure, the asymmetric-section shape usage will be optimum and effective. However, in precast concrete structures, it might be susceptible especially in beamto- connection parts due to its strength. In this research, the damage mechanism of connections between cantilever beams and columns in precast concrete will be analyzed. The asymmetric shape will be applied in cantilever beams. Three samples were made with a length of 1500 mm equipped with six 10 mm-diameter deformed rebar and stirrup with 6 mmdiameter plain rebar. The results show that each of the three speciments has its own effectiveness based on stress, strain, displacement, load, and other related parameters.

Load-Bearing Capacity of Direct Inlay-Retained Fibre-reinforced Composite Fixed Partial Dentures with Different Cross-Sectional Pontic Design

2017 ◽  
Vol 68 (1) ◽  
pp. 94-100
Author(s):  
Oana Tanculescu ◽  
Adrian Doloca ◽  
Raluca Maria Vieriu ◽  
Florentina Mocanu ◽  
Gabriela Ifteni ◽  
...  
Keyword(s):  
Bearing Capacity ◽  
Fracture Pattern ◽  
Load Bearing Capacity ◽  
Cross Sectional ◽  
Load Bearing ◽  
Reinforced Composite ◽  
Polyethylene Fibre

The load-bearing capacity and fracture pattern of direct inlay-retained FRC FDPs with two different cross-sectional designs of the ponticwere tested. The aim of the study was to evaluate a new fibre disposition. Two types of composites, Filtek Bulk Fill Posterior Restorative and Filtek Z250 (3M/ESPE, St. Paul, MN, USA), and one braided polyethylene fibre, Construct (Kerr, USA) were used. The results of the study suggested that the new tested disposition of the fibres prevented in some extend the delamination of the composite on buccal and facial sides of the pontic and increased the load-bearing capacity of the bridges.

scholarly journals A Numerical Study of Sub-Millisecond Integrated Mix-and-Inject Microfluidic Devices for Sample Delivery at Synchrotron and XFELs

2021 ◽  
Vol 11 (8) ◽  
pp. 3404
Author(s):  
Majid Hejazian ◽  
Eugeniu Balaur ◽  
Brian Abbey
Keyword(s):  
Molecular Dynamics ◽  
Flow Rate ◽  
Numerical Study ◽  
Three Dimensional ◽  
Microfluidic Devices ◽  
Liquid Jets ◽  
Mixing Efficiency ◽  
X Ray Diffraction ◽  
Cross Sectional ◽  
Time Required

Microfluidic devices which integrate both rapid mixing and liquid jetting for sample delivery are an emerging solution for studying molecular dynamics via X-ray diffraction. Here we use finite element modelling to investigate the efficiency and time-resolution achievable using microfluidic mixers within the parameter range required for producing stable liquid jets. Three-dimensional simulations, validated by experimental data, are used to determine the velocity and concentration distribution within these devices. The results show that by adopting a serpentine geometry, it is possible to induce chaotic mixing, which effectively reduces the time required to achieve a homogeneous mixture for sample delivery. Further, we investigate the effect of flow rate and the mixer microchannel size on the mixing efficiency and minimum time required for complete mixing of the two solutions whilst maintaining a stable jet. In general, we find that the smaller the cross-sectional area of the mixer microchannel, the shorter the time needed to achieve homogeneous mixing for a given flow rate. The results of these simulations will form the basis for optimised designs enabling the study of molecular dynamics occurring on millisecond timescales using integrated mix-and-inject microfluidic devices.

Study of Correctly Expanded Sonic Jet with Air Tabs

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Arun Prasad R ◽  
Thanigaiarasu S ◽  
Sembaruthi M ◽  
Rathakrishnan E
Keyword(s):  
Numerical Study ◽  
Cross Sectional ◽  
Potential Core ◽  
Convergent Nozzle ◽  
Jet Mixing ◽  
Pressure Profiles ◽  
Constant Diameter ◽  
Sonic Jet ◽  
Sectional Shape ◽  
Length Reduction

AbstractThe present numerical study is to understand the effect of air tabs located at the exit of a convergent nozzle on the spreading and mixing characteristics of correctly expanded sonic primary jet. Air tabs used in this study are two secondary jets issuing from constant diameter tubes located diametrically opposite at the periphery of the primary nozzle exit, normal to the primary jet. Two air tabs of Mach numbers 1.0 to 1.4, in steps of 0.1 are considered in this study. The mixing modification caused by air tabs are analysed by considering the mixing of uncontrolled (free) primary jet as a reference. Substantial enhancement in jet mixing is achieved with Mach 1.4 air tabs, which results in 80 % potential core length reduction. The total pressure profiles taken on the plane (YZ) normal to the primary jet axis, at various locations along the primary jet centreline revealed the modification of the jet cross sectional shape by air tabs. The stream-wise vortices and bifurcation of the primary jet caused by air tabs are found to be the mechanism behind the enhanced jet mixing.

scholarly journals Estimating Deterioration in the Concrete Tie-Ballast Interface Based on Vertical Tie Deflection Profile: A Numerical Study

2016 ◽  
Author(s):  
Hailing Yu
Keyword(s):  
Direct Detection ◽  
Numerical Study ◽  
Interface Condition ◽  
Vertical Deflection ◽  
Cohesive Elements ◽  
Material Loss ◽  
Element Analysis ◽  
Cross Sectional ◽  
Technical Requirements ◽  
Support Conditions

In ballasted concrete tie track, the tie-ballast interface can deteriorate resulting in concrete tie bottom abrasion, ballast pulverization and/or voids in tie-ballast interfaces. Tie-ballast voids toward tie ends can lead to unfavorable center binding support conditions that can result in premature concrete tie failure and possible train derailment. Direct detection of these conditions is difficult. There is a strong interest in assessing the concrete tie-ballast interface conditions indirectly using measured vertical deflections. This paper seeks to establish a link between the vertical deflection profile of a concrete tie top surface and the tie-ballast interface condition using the finite element analysis (FEA) method. The concrete tie is modeled as a concrete matrix embedded with prestressing steel strands or wires. The configurations of two commonly used concrete ties, one with 8 prestressing strands and the other with 20 prestressing wires, are employed in this study. All models are three-dimensional and symmetric about the tie center. A damaged plasticity model that can predict onset and propagation of tensile cracks is applied to the concrete material. The steel-concrete interface is homogenized and represented with a thin layer of cohesive elements sandwiched between steel and concrete elements. Strand- or wire-specific elasto-plastic bond models developed at the Volpe Center are applied to the cohesive elements to account for the interface bonding mechanisms. FE models are developed for both original and worn concrete ties, with the latter assuming hypothetical patterns of reduced cross sections resulting from abrasive interactions with the ballast. Static analyses of pretension release in these concrete ties are conducted, and vertical deflection gradients along tie lengths are calculated and shown to correspond well with the worn cross sectional patterns for a given reinforcement type. The ballast is further modeled with Extended Drucker-Prager plasticity, and hypothetical voids are applied toward the tie ends along the concrete tie-ballast interface to simulate center binding support conditions. The distance range over which the concrete tie is supported in the center is variable and yields different center binding severity. Static simulations are completed with vertical rail seat loads applied on the concrete tie-ballast assembly. The influences of various factors on the vertical deflection profile, including tie type, vertical load magnitude, center binding severity, cross sectional material loss and prestress loss, are examined based on the FEA results. The work presented in this paper demonstrates the potential of using the vertical deflection profile of concrete tie top surfaces to assess deteriorations in the tie-ballast interface. The simulation results further help to clarify minimum technical requirements on inspection technologies that measure concrete tie vertical deflection profiles.

Numerical Study of the Effect of Inlet Constriction on Bubble Growth During Flow Boiling in Microchannels

2005 ◽  
Author(s):  
Abhijit Mukherjee ◽  
Satish G. Kandlikar
Keyword(s):  
Stokes Equations ◽  
Numerical Study ◽  
Flow Boiling ◽  
Navier Stokes ◽  
Channel Cross Section ◽  
Vapor Bubbles ◽  
Reversed Flow ◽  
Cross Sectional ◽  
Parallel Microchannels ◽  
Energy Equations

Flow boiling through microchannels is characterized by nucleation of vapor bubbles on the channel walls and their rapid growth as they fill the entire channel cross-section. In parallel microchannels connected through a common header, formation of vapor bubbles often results in flow maldistribution that leads to reversed flow in certain channels. The reversed flow is detrimental to the heat transfer and leads to early CHF condition. One way of eliminating the reversed flow is to incorporate flow restrictions at the channel inlet. In the present numerical study, a nucleating vapor bubble placed near the restricted end of a microchannel is numerically simulated. The complete Navier-Stokes equations along with continuity and energy equations are solved using the SIMPLER method. The liquid-vapor interface is captured using the level set technique. The results show that with no restriction the bubble moves towards the nearest channel outlet, whereas in the presence of a restriction, the bubble moves towards the distant but unrestricted end. It is proposed that channels with increasing cross-sectional area may be used to promote unidirectional growth of the vapor plugs and prevent reversed flow.

On the crack characterization of reinforced concrete structures: Experimental and data-driven numerical study

Structures ◽  
2021 ◽  
Vol 30 ◽  
pp. 134-145
Author(s):  
Sandeep Das ◽  
Subhrajit Dutta ◽  
Dibyendu Adak ◽  
Shubhankar Majumdar
Keyword(s):  
Reinforced Concrete ◽  
Numerical Study ◽  
Concrete Structures ◽  
Data Driven ◽  
Reinforced Concrete Structures

A comparative numerical study of the combustion performance of the syngas-fueled HCCI engine using a toroidal piston, square bowl piston, and flat piston shape at different loads

2021 ◽  
pp. 1-27
Author(s):  
Kabbir Ali ◽  
Changup Kim ◽  
Yonggyu Lee ◽  
Seungmook Oh ◽  
Ki-Seong Kim
Keyword(s):  
Numerical Study ◽  
Pressure Rise ◽  
Fuel Mixture ◽  
Combustion Efficiency ◽  
Maximum Pressure ◽  
Cross Sectional ◽  
Combustion Performance ◽  
Hcci Engine ◽  
Heat Loss Rate ◽  
Piston Bowl

Abstract This study analyzes the combustion performance of a syngas-fueled homogenous charge compression ignition (HCCI) engine using a toroidal piston, square bowl, and flat piston shape, at low, medium, and high loads, with a constant compression ratio of 17.1. In this study, the square bowl shape is optimized by reducing the piston bowl depth and squish area ratio (squish area/cylinder cross-sectional area) from (34 to 20, 10, and 2.5) %, and compared with the flat piston shape and toroidal piston shape. This HCCI engine operates under an overly lean air–fuel mixture condition for power plant usage. ANSYS Forte CFD with GRI Mech3.0 chemical kinetics is used for combustion analysis, and the calculated results are validated by the experimental results. All simulations are accomplished at maximum brake torque (MBT) by altering the air–fuel mixture temperature at IVC with a constant equivalence ratio of 0.27. This study reveals that the main factors that affect the start of combustion , maximum pressure rise rate (MPRR), combustion efficiency, and thermal efficiency by changing the piston shape are the squish flow and reverse squish flow effects. Therefore, the square bowl piston D is the optimized piston shape that offers low MPRR and high combustion performance for the syngas-fueled HCCI engine, due to the weak squish flow and low heat loss rate through the combustion chamber wall, respectively, compared to the other piston shapes of square bowl piston A, B, and C, flat piston, and toroidal (baseline) piston shape.

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