Prediction of Potential Cracking Failure Modes in Three-Dimensional Airfield Rigid Pavements with Existing Cracks and Flaws

2012 ◽  
Vol 2266 (1) ◽  
pp. 11-19 ◽  
Author(s):  
Francisco Evangelista ◽  
Jeffery R. Roesler ◽  
C. Armando Duarte
Keyword(s):  
Failure Modes ◽  
Concrete Slab ◽  
Three Dimensional ◽  
Fatigue Cracking ◽  
Crack Size ◽  
Concrete Slabs ◽  
Shear Mode ◽  
Generalized Finite Element Method ◽  
Top Down ◽  
Bottom Up

This paper predicts the potential for crack propagation in concrete pavements under aircraft loading given a starter fatigue crack at the bottom of the concrete slab or a surface-initiated shrinkage crack on top of the slab. The generalized finite element method was used to evaluate the stress intensity factors for quarter elliptical cracks placed at the critical top and bottom tensile stress locations. The pavement was loaded with a single triple-dualtandem (TDT) gear and two TDTs accounting for the entire belly gears. When the pavement was loaded with the two TDT gear configuration, the analyses showed significantly higher KI (shear mode) values for surface-initiated cracks than for bottom-initiated cracks for the same crack size. Therefore, concrete slabs with preexisting surface cracks are more likely to exhibit top-down crack growth despite being designed for bottom-up fatigue cracking under certain loading conditions. The theoretical framework allows for improved assessment of the fracture susceptibility of concrete slabs under aircraft loading, specifically the potential for top-down over bottom-up cracking.

THE EFFECT OF IMPACT LOADS ON PRESTRESSED CONCRETE SLABS

2018 ◽  
Vol 5 (1) ◽  
Author(s):  
Youmn Al Rawi ◽  
Yehya Temsah ◽  
Hassan Ghanem ◽  
Ali Jahami ◽  
Mohamad Elani
Keyword(s):  
Reinforced Concrete ◽  
Prestressed Concrete ◽  
Impact Loading ◽  
Concrete Slab ◽  
Concrete Slabs ◽  
Shear Mode ◽  
Reinforced Concrete Slab ◽  
Finite Element Program ◽  
Reinforced Concrete Slabs ◽  
The Impact

Many research studies have been conducted on the effect of impact loading on structures, and design procedures were proposed for reinforced concrete (RC) slabs; however the availability of these studies and procedures are limited for prestressed slabs. The proposed research will examine, using numerical analysis, the impact of rock fall on prestressed concrete slabs with equivalent moment capacity reinforced concrete slabs. It is expected that prestressed concrete slabs will have different behavior to resist impact loading compared with traditional reinforced concrete slabs. The thickness of the prestressed concrete slab will be 25cm whereas that of the reinforced concrete slab will be 30cm. The impact loading consists of 500Kg drop weight. The drop height will be 10m, 15m and 20m.The structural analysis is performed using a Finite Element program "ABAQUS". A comparison will be done between both slab types in terms of failure mode, damage, and deflection. It has been found that both slabs failed in punching. However, the RC slab performed better than the prestressed concrete slab with respect to the value of the deflection at mid-span, while both showed punching shear mode of failure.

Manufacturing of two and three-dimensional micro/nanostructures by integrating optical tweezers with chemical assembly

Robotica ◽  
2005 ◽  
Vol 23 (4) ◽  
pp. 435-439 ◽  
Author(s):  
Kenneth Castelino ◽  
Srinath Satyanarayana ◽  
Metin Sitti
Keyword(s):  
Optical Tweezers ◽  
Manufacturing System ◽  
Three Dimensional ◽  
Inorganic Materials ◽  
Top Down ◽  
Bottom Up ◽  
Complementary Dna ◽  
Nanoscale Manufacturing ◽  
2D And 3D

Optical tweezers have been used as versatile tools for non-contact manipulation of micrometer-sized entities. This paper proposes a hybrid micro/nanoscale manufacturing system using optical tweezers and chemical linkages for fabricating 2D and 3D micro/nanostructures. A holographic multiple trap optical tweezers system is first used to trap particles in a desired pattern. The particles are then connected to form rigid units using suitable chemistry. Connection schemes based on gold seeding, complementary-DNA linkage and streptavidin-biotin chemistry are presented and possible applications of this technique are explored. This method combines the advantages of top-down and bottom-up approaches and is compatible with organic and inorganic materials.

Visional Attentional Allocation of Top-down and Bottom-up Cues in Three-Dimensional Space

2011 ◽  
Vol 179-180 ◽  
pp. 1322-1326
Author(s):  
Ru Ting Xia
Keyword(s):  
Visual Attention ◽  
Dimensional Space ◽  
Three Dimensional ◽  
Depth Information ◽  
Top Down ◽  
Bottom Up ◽  
Attentional Allocation ◽  
3D Space ◽  
Target Locations ◽  
Three Dimensional Space

The aim of the present experiment was to investigate visual attentional allocation of top-down and bottom-up cues in three-dimensional (3D) space. Near and far stimuli were used by a 3D attention measurement apparatus. Two experiments were conducted in order to examine top-down and bottom-up controls of visual attention. In the experiment 1, the cue about the location of a target by means of location information. In the experiment 2, color cue by brief change of color at target locations was presented. Observers were required to judge whether the target presented nearer than fixation point or further than it. The results in experiment 1 and experiment 2 show that both location and color cue have the effect on reaction time, and that shift of attention were faster from far to near than the reverse. These findings suggest that (1) attention in 3D space might be operated with both location and color controls included the depth information, (2) the shift of visual attention in 3D space has an asymmetric characteristic in depth.

A New Process to Fabricate Three Dimensional Ordered Nano Dot Array Structures by Nano Plastic Forming and Dewetting

2012 ◽  
Vol 523-524 ◽  
pp. 627-632
Author(s):  
Zhen Xing Li ◽  
Akinori Yamanaka ◽  
Masahiko Yoshino
Keyword(s):  
Metal Layer ◽  
Low Cost ◽  
Three Dimensional ◽  
Process Conditions ◽  
Top Down ◽  
Bottom Up ◽  
Spacer Layer ◽  
New Process ◽  
Plastic Forming ◽  
Array Structures

Three dimensional (3D) nano/quantum dot array structures have attracted more and more attention due to their broad applications. A new fabrication method of multilayer ordered nano dot array with low cost and high throughput is developed in this paper. This process is combination of Top-down and Bottom-up approaches: Nano Plastic Forming (NPF) patterning of metal layer coated on the substrate as Top-down approach and self-organization by dewetting as Bottom-up approach. Effects of process conditions on 3D nano-dot array formation are studied experimentally. Regularity and uniformity of first layer nano-dot array is transferred to the second layer nano-dots by optimizing thickness of the spacer layer and Au coating layer. Multilayer ordered nano dot array structures with good alignment are obtained by repeating coating and annealing processes.

Mechanical Behavior of Ultrathin Whitetopping Structure Under Stationary and Moving Loads

2003 ◽  
Vol 1823 (1) ◽  
pp. 102-110 ◽  
Author(s):  
Tatsuo Nishizawa ◽  
Yoshiki Murata ◽  
Katsuro Kokubun
Keyword(s):  
Load Transfer ◽  
Concrete Slab ◽  
Three Dimensional ◽  
Element Model ◽  
Interface Condition ◽  
Interface Element ◽  
Concrete Slabs ◽  
Moving Loads ◽  
Mechanical Interaction ◽  
Loading Test

The structural design of ultrathin whitetopping (UTW) requires precise predictions of the loading stresses in the concrete slabs. A plate finite element model (FEM) is not used for structures with UTW because the model is not able to account for the asphalt subbase behaviors and the mechanical interaction between the concrete slab and asphalt subbase. A three-dimensional FEM (3DFEM) was used for the stress calculation of UTW. To take into account the mechanical interaction at the interface between the concrete slab and asphalt subbase as well as the load transfer across the joint, a general interface element was developed and incorporated into 3DFEM. Also, the viscosities of asphalt materials were considered by the viscoelastic formulation in the 3DFEM. A loading test was conducted on a test pavement. Stationary and moving loads were applied to the concrete slabs, and the strains in the slabs and the asphalt subbase were measured. By comparing the strains computed by 3DFEM with the measured strains, it was found that the viscosity of the asphalt subbase and the interface condition significantly affect the stresses in the concrete slab.

Three-Dimensional Trait System: Binding Together the Main Sources of Diversity in Personality Traits

2019 ◽  
Author(s):  
Sergei Shchebetenko
Keyword(s):  
Personality Traits ◽  
Big Five ◽  
Personality Trait ◽  
Three Dimensional ◽  
Lifespan Development ◽  
Top Down ◽  
Bottom Up ◽  
The Third ◽  
History Of

Why are there various personality traits and why are those traits revealed in widely-acclaimed models such as the Big Five? The Three-Dimensional Trait System (3D-TRASY) states that any personality trait can be defined in terms of three basic sources. The first source represents traits’ variability with regard to the brain’s functioning in terms of bottom-up and top-down processes. The second source connects to positive (rewards) and negative (punishments) social reinforcements of the trait. The third source reflects a multitude of situations in which a trait may unfold. Thus, Extraversion can be defined as a proximate bottom-up positive while Conscientiousness is a distal top-down positive. 3D-TRASY provides a framework for formal, non-tautological definitions of traits; it provides explanations for various phenomena in trait research including the super-traits of Stability and Plasticity and the maturity principle of lifespan development. 3D-TRASY presumes that some traits can occasionally closely correlate and thus establish an amalgam, which exemplifies itself in Eysenckian Psychoticism and the Big-Five’s Agreeableness. In the history of trait research, this amalgamation may explain controversies that would have facilitated emergence of novel models such as the Big Five or HEXACO. The paper contains empirical demonstrations on how 3D-TRASY can explain apparently empirical artifacts.

The Research on Automatic Recognition of Assembly Feature and Converse Parametric Design Method Based on UG

2012 ◽  
Vol 580 ◽  
pp. 87-90
Author(s):  
Bin Fang ◽  
Liang Tian
Keyword(s):  
Parametric Design ◽  
Design Method ◽  
Three Dimensional ◽  
Automatic Recognition ◽  
One Dimension ◽  
Top Down ◽  
Bottom Up ◽  
Assembly Features ◽  
Assembly Feature ◽  
One To One

No matter the bottom-up design mode is adopted or the top-down design is chosen, one-to-one dimension relation can be realized alone among assembly-components in three-dimensional CAD systems.In the paper, a method of automatic recognition is put forward based on assembly features in UG and various definitions as well as expressional methods of assembly features are analyzed. The interrelated dimension relation is established on account of the fit dimension chain. The converse parametric design is realized besides an independent module in UG is developed to achieve the function.

scholarly journals Classification of Surface Pavement Cracks as Top-down, Bottom-up, and Cement-Treated Reflective Cracking Based on Deep Learning Methods

2021 ◽  
Author(s):  
Nirmal Dhakal ◽  
Mostafa A. Elseifi ◽  
Zia U. Zihan ◽  
Zhongjie Zhang ◽  
Christophe N. Fillastre ◽  
...  
Keyword(s):  
Neural Network ◽  
Deep Learning ◽  
Asphalt Concrete ◽  
Fatigue Cracking ◽  
Ann Model ◽  
Reflective Cracking ◽  
Top Down ◽  
Bottom Up ◽  
Concrete Layer ◽  
Artificial Neural Network Ann

The treatment and repair strategies of reflective and fatigue cracking that initiate at the pavement surface (i.e. top-down cracking) and at the bottom of the asphalt concrete layer (i.e. bottom-up cracking) are noticeably different. However, pavement engineers are facing difficulties in identifying these cracks in the field as they usually appear in visually identical patterns. The objective of this study was to develop Artificial Neural Network (ANN) and Convolutional Neural Network (CNN) applications to differentiate and classify top-down, bottom-up, and cement-treated reflective cracking in in-service pavements using deep-learning models. The developed CNN model achieved an accuracy of 93.8% in the testing and 91% in the validation phases and the ANN model showed an overall accuracy of 92%. The ANN classification tool was developed based on variables related to pavement and crack characteristics including age, Average Daily Traffic , thickness of Asphalt Concrete layer, type of base, crack orientation and location.

scholarly journals Numerical Evaluation of the Opening Effects on the Reinforced Concrete Slab Structural Performance

2021 ◽  
Vol 2021 ◽  
pp. 1-16
Author(s):  
Meysam Aminitabar ◽  
Omar Kanaani ◽  
Amir Reza Eskenati
Keyword(s):  
Reinforced Concrete ◽  
Concrete Slab ◽  
Three Dimensional ◽  
Great Influence ◽  
Concrete Slabs ◽  
Shear Stresses ◽  
Three Dimensional Model ◽  
Reinforced Concrete Slab ◽  
Tensile Stresses ◽  
Nonlinear Properties

A finite element method was used in this study to investigate the effects of openings on the resistive behavior of concrete slabs. The presented modeling procedure is used to conduct numerical analyses on the response of reinforced concrete slab subjected to in-plane monotonic loads in X (perpendicular to the beam) and Z (parallel to the beam) directions. Initially, the developed numerical model was calibrated and compared with laboratory results. In building this three-dimensional model, it is attempted to accurately model all nonlinear properties of steel and concrete materials as well as the interactions between them. Then, the behavior of bilaterally concrete slabs under different loads was investigated and used as a reference. Finally, the effect of openings under different loads on the strength of concrete slabs was studied. The results confirm that openings have a great influence on the change of hardness, ductility, initiation and cracking path, and stress distribution under shear and gravitational loading. Moreover, by adding an opening inside the diaphragm, not only did beam and block flooring show more fragile behavior, but also its strength and resistance decreased against lateral load. Given the results of the parametric study of the effect of layout, generally, its place became critical at the state that opening disturbed transmission of shear stresses to the collector beams. By adding the area of the opening and loading in X direction, the concentration of the tensile stresses (equivalent to main maximum stresses) was at the tensile edge as well as at the middle of the flooring around the opening. It is worth noting that an increase in the opening’s area caused the number of tensile stresses to be increased at the middle of the flooring. Meanwhile, the concentration of maximum compressive stresses which is equivalent to the main minimum stresses was at the compressive edge, started at the area of the collectors, and stretched to the edge of the opening. Among different layouts, X-1 and Z-3 states were more critical than other states. Considering openings with different layouts, X-1 and Z-3 have the most stiffness deteriorating and strength in such a way that stiffness deteriorating and strength were 39.93% and 37.89%, respectively, for Z-3 model and 38.68% and 43.33%, respectively, for Z-3 model.

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