Middle-Up Cracking Potential in Flexible Pavements with Stabilized Foundations

2021 ◽  
pp. 036119812199069
Author(s):  
Mostafa Nakhaei ◽  
David H. Timm
Keyword(s):  
Tensile Strain ◽  
Elevated Temperatures ◽  
Compressive Strain ◽  
Flexible Pavements ◽  
Fatigue Cracking ◽  
Full Scale ◽  
Computational Simulations ◽  
Cracking Potential ◽  
Maximum Tensile Strain ◽  
New Perspective

This investigation presents a new perspective on the structural behavior of stabilized foundation pavements through full-scale testing and simulation where the historical premise of bottom-up fatigue cracking has been challenged. Two full-scale pavement sections were constructed at the National Center for Asphalt Technology Test Track in 2018. One section featured a stabilized foundation under the asphalt layers while the other was a thick-lift asphalt section on conventional base and subgrade materials. Both sections were embedded with pavement response instrumentation and their behavior was observed over time under accelerated truck trafficking. In addition, computational simulations were executed to explain the observed behavior. The strain measurement at the bottom of the asphalt concrete (AC) for the thick-lift section showed a familiar trend in which the tensile strain at the bottom of the AC increased exponentially with temperature. In contrast, the strain at the bottom of the AC in the stabilized foundation pavement was predominantly in compression at elevated temperatures. Further analysis revealed that compressive strain at the bottom of the AC increased exponentially with temperature similar to conventional flexible pavements but with a reversed sign. The results were confirmed by falling weight deflectometer testing that was conducted directly above the embedded pavement sensors. Computational simulations confirmed the behavior and suggested that the maximum tensile strain could occur at shallower depths, possibly mid-depth of the AC, in stabilized foundation pavements. This indicates stabilized foundation pavements could be prone to middle-up cracking and subsequent precautions should be taken to avoid middle-up fatigue cracking.

The Strain Change Rules of Full-Scale High Strength Concrete Frame Columns with High Axial Compression Rations

2014 ◽  
Vol 919-921 ◽  
pp. 288-291
Author(s):  
Guo Jun Zhang ◽  
Yong Bin Jia ◽  
Xi Lin Lu
Keyword(s):  
Axial Compression ◽  
High Strength Concrete ◽  
Tensile Strain ◽  
High Strength ◽  
Full Scale ◽  
Longitudinal Reinforcement ◽  
Strength Concrete ◽  
Concrete Frame ◽  
Strain Change ◽  
Maximum Tensile Strain

Based on experimental study of 9 full-scale high-strength concrete(HSC) rectangular frame columns with high axial compression ratios, high-strength longitudinal reinforcements and transverse reinforcements and rectangular interlocking ties, their strain change rules of longitudinal reinforcement, stirrups and concrete were discussed and analyzed. The main results indicate as follows. The maximum tensile strain of longitudinal reinforcement decrease and the tensile strain of concrete increase quickly as the axial compression ratios and the strength grades of concrete are higher; the strains of outer stirrups are all the time greater than those of inner stirrups; the single brace stirrups have the same action with the closed stirrups.

scholarly journals Enhanced Flexible Pavement Performance Using Treated Compared to Untreated Aggregate Bases: A Comparative Case Study in the Southern United States

2021 ◽  
Vol 6 (8) ◽  
pp. 110
Author(s):  
Mena I. Souliman ◽  
Hemant GC ◽  
Zabi Mohammed
Keyword(s):  
Surface Roughness ◽  
Tensile Strain ◽  
Compressive Strain ◽  
Base Material ◽  
Fatigue Cracking ◽  
Base Layer ◽  
Pavement Performance ◽  
Comparative Case Study ◽  
Stabilizing Agents ◽  
The Impact

One of the important aspects of highway design is aggregates. Aggregates strength and consistency has an effect on pavement structure’s overall performance. The consistency of the base material near the site of the construction doesn’t always match the requirements of pavement construction and carrying quality aggregate raises the cost of construction. Stabilizing agents such as asphalt cement, lime, fly ash were used to improve the strength of these materials in order to make greater use of locally available materials. Layer materials present in the pavements and the structure of them influence pavement performance. The compressive strain and the tensile strain in the layer of subgrade and asphalt layer respectively are influenced by the stiffness of the base layer. The important aspects causing rutting and fatigue cracking are compressive strain in the top region of the subgrade layer and tensile strain at the bottom of the asphalt layer, respectively. In this research study, field performance (cracking, rutting, and surface roughness) of pavement sections with untreated and treated bases were collated to assess the impact of the stabilizing agents. The treated sections performed well significantly compared to the untreated sections in terms of pavement surface roughness and fatigue cracking. The treated sections performed higher than the untreated sections in terms of the cumulative average values of all 3 distresses with fatigue cracking averaging 5 times lower than the untreated sections. The combined IRI and rutting of treated sections averaged about 1.5 times and 0.11 inches smaller, respectively than those of untreated sections.

scholarly journals Influence of Modulus of Base Layer on The Strain Distribution for Asphalt Pavement

2021 ◽  
Vol 16 (4) ◽  
pp. 126-152
Author(s):  
Kang Yao ◽  
Xin Jiang ◽  
Jin Jiang ◽  
Zhonghao Yang ◽  
Yanjun Qiu
Keyword(s):  
Strain Distribution ◽  
Tensile Strain ◽  
Asphalt Pavement ◽  
Compressive Strain ◽  
Three Dimensional ◽  
Vertical Direction ◽  
Element Model ◽  
Neutral Axis ◽  
Base Layer ◽  
Maximum Tensile Strain

In order to investigate the influence of modulus of the base layer on the strain distribution for asphalt pavement, the modulus ratio of the base layer and the AC layer (Rm) is introduced as a controlled variable when keeping modulus of the AC layer as a constant in this paper. Then, a three-layered pavement structure is selected as an analytical model, which consists of an AC layer with the constant modulus and a base layer with the variable modulus covering the subgrade. A three dimensional (3D) finite element model was established to estimate the strains along the horizontal and vertical direction in the AC layer under different Rm. The results show that Rm will change the distribution of the horizontal strains along the depth in the AC layer; the increase of Rm could reduce the maximum tensile strain in the AC layer, but its effect is limited; the maximum tensile strain in the AC layer does not necessarily occur at the bottom, but gradually rises to the middle with the increase of Rm. Rm could significantly decline the bottom strain in the AC layer, and there is a certain difference between the bottom and the maximum strain when Rm is greater than or equal to one, which will enlarge with increasing Rm. Rm could change the depth of the neutral axis in the AC layer, and the second neutral axis will appear at the bottom of the AC layer under a sufficiently large Rm. The average vertical compressive strain in the AC layer will significantly enlarge with the increase of Rm.

scholarly journals Numerical Method of Flexible Pavement considering Moisture and Stress Sensitivity of Subgrade Soils

2019 ◽  
Vol 2019 ◽  
pp. 1-10 ◽  
Author(s):  
Jue Li ◽  
Jianlong Zheng ◽  
Yongsheng Yao ◽  
Junhui Zhang ◽  
Junhui Peng
Keyword(s):  
Tensile Stress ◽  
Compressive Strain ◽  
Flexible Pavements ◽  
Fatigue Cracking ◽  
Flexible Pavement ◽  
Stress Sensitivity ◽  
Fem Model ◽  
Moisture Condition ◽  
Subgrade Soils ◽  
Moisture Variation

Weaknesses of the subgrade structure induce the asphalt surface diseases and shorten the service life of flexible pavement. However, the resilient modulus (Mr) of subgrade soils is difficult to be evaluated directly since the subgrade is hidden and covered by the granular or asphalt layer. This study aimed to establish a numerical approach to predict the dynamic behavior of flexible pavements considering the stress sensitivity and moisture variation of subgrade soils. Firstly, 2D FEM simulations of flexible pavements were performed with half-sine loadings. A constitutive model of subgrade soils was proposed to incorporate soil suction and octahedral shear stress. It was validated using the laboratory triaxial test data of 3 selected soils. Then, the developed model was programmed by the user-defined material subroutine (UMAT) in the software ABAQUS. Subsequently, the validity of FEM model was verified by the laboratory tank model. Finally, the effect of moisture contents on the dynamic response of pavement structures was studied by tensile stress and vertical compressive strain. Results show that the surface deflection of the FEM model is similar to that of the actual pavement structure with the R2 of 98.44%. The developed UMAT program is reliable since the distribution of Mr in the FEM model is influenced by the stress and moisture condition of subgrade soils. When the moisture content is increased by 63%, the average Mr of subgrade soils is decreased by 18.7%. Meanwhile, the stiffness softening of subgrade soils increases vertical compressive strain at the top of the subgrade and the tensile stress at the bottom of the surface layer. It is interesting that the developed model can be applied to analyze the fatigue cracking of both subgrade and surface layers in the future.

A new perspective on hanzi: Based upon 
the multi-dialectical analysis of the Four 
Ways of Writing

2021 ◽  
Vol 5 (1) ◽  
pp. 15-30
Author(s):  
Guk-jo Jeon
Keyword(s):  
Analytical Framework ◽  
Full Scale ◽  
Scale Analysis ◽  
Human Beings ◽  
Academic Identities ◽  
Dialectical Relationship ◽  
New Perspective ◽  
Dialectical Analysis

This work is, most of all, designed to wrestle with taken-for-granted explanations as to how hanzi is composed and in what ways the composition the Four Ways of Writing (四書) can be analysed. Beginning with posing a self-reflective question on the academic identities of us, the hanzi civilisation researchers, and looking for a possible answer to it within the context of an Eagletonian conceptualisation of human animality or creatureliness, the work then methodologises the multi-dialectical analysis by virtue of méta-linguistique, transduction, and abstraction concreté. The full-scale analysis of the Four Ways of Writing comes next, taking four steps: first, synthesising the existing definitions, explanations and interpretations of them; second, abstracting the synthesis up to the multi-dialectical analysis; third, introducing a topology of the Four Ways of Writing; and fourth, analysing characters related to and expanding from two radical characters of 門 and 刀 with the aid of a dynamics of trialectics between the form, sound and meaning. Resting upon all the analyses performed, the work suggests the following conclusion. Amongst hanzi’s main characteristics is morphographicality (表形性), still the most distinctive within the analytical framework of the Four Ways of Writing. It is the very form of hanzi, as a matter of fact, that also turns out to be multi-dialectical: first, that which constitutes writing as the character trialectically related with both the sound and meaning; second, that which characterises writing as écriture of the dialectical relationship between human beings and nature; and last, that which dialectically elucidates who we are and what we are capable of.

Consideration of the Cross-Anisotropy of Different Materials of the Asphalt Surface Layer and Temperature to Determine Pavement Responses

2021 ◽  
Vol 13 (1) ◽  
pp. 140-151
Author(s):  
Minrui Guo ◽  
Xinglin Zhou
Keyword(s):  
Surface Layer ◽  
High Temperatures ◽  
Low Temperatures ◽  
Compressive Strain ◽  
Fatigue Cracking ◽  
Element Model ◽  
Rate Of Change ◽  
Temperature Relationship ◽  
The Cross ◽  
Cross Anisotropy

The effects of the cross-anisotropy of different materials of the asphalt surface layer and the depth-temperature relationship on pavement responses and damage are investigated. A three-dimensional Finite-Element Model (FEM) of the pavement, which considers the depth-temperature relationship of the surface layer under moving tire load, is developed. Pavement damage models are established to evaluate the damage ratio for primary rutting and fatigue cracking. The results show that the compressive strain at the bottom of the surface layer increases as the temperature increases, and the cross-anisotropy (n-value) decreases, indicating that a decrease in the horizontal modulus of different materials of the surface layer increases the damage ratio for primary rutting at high temperatures. The tensile strain at the bottom of the surface layer declines as the n-value increases to 1. For the same change in the n-value, the rate of change of the damage ratio for fatigue cracking is greater at low temperatures than at high temperatures, demonstrating that the number of allowable load repetitions is more sensitive at low temperatures. In addition, the effect of cross-anisotropy and temperature on the vertical stress are larger on the top of the base than in the subbase and subgrade.

Required Linepipe Properties for High Strain Applications and Possible Resolution by Pipe Manufacturing Technology

2008 ◽  
Author(s):  
Hitoshi Asahi ◽  
Eiji Tsuru
Keyword(s):  
Tensile Strain ◽  
Compressive Strain ◽  
Bending Moment ◽  
Uniaxial Tensile ◽  
Buckling Behavior ◽  
Strain Limit ◽  
Bent Pipe ◽  
Uniaxial Tensile Stress ◽  
The Relationship ◽  
Pipe Manufacturing

Application of strain based design to pipelines in arctic or seismic areas has recently been recognized as important. So far, there has been much study performed on tensile strain limit and compressive strain limit. However, the relationship between bending buckling (compressive strain limit) and tensile strain limit has not been discussed. A model using actual stress strain curves suggests that the tensile strain limit increases as Y/T rises under uniaxial tensile stress because a pipe manufacturer usually raises TS instead of lowering YS to achieve low Y/T. Under bending of a pipe with a high D/t, an increase in compressive strain on intrados of a bent pipe at the maximum bending moment (ε-cp*) improves the tensile strain limit because the tensile strain limit is controlled by the onset of buckling or ε-cp* which is increased by lowering Y/T. On the other hand, under bending of a pipe with a low D/t, the tensile strain limit may not be influenced by improvement of buckling behavior because tensile strain on the extrados is already larger than the tensile limit at ε-cp*. Finally, we argue that the balance of major linepipe properties is important. Efforts other than the strict demands for pipe properties are also very important and inevitable to improve the strain capacity of a pipeline.

Validation of Inelastic Analysis by Full-Scale Component Testing

1987 ◽  
Vol 109 (1) ◽  
pp. 42-49 ◽  
Author(s):  
D. S. Griffin ◽  
A. K. Dhalla ◽  
W. S. Woodward
Keyword(s):  
Life Prediction ◽  
Elevated Temperatures ◽  
Full Scale ◽  
Prediction Methods ◽  
Material Models ◽  
Component Testing ◽  
Inelastic Analysis ◽  
Creep Buckling ◽  
Design Requirements ◽  
Thermal Striping

This paper compares theoretical and experimental results for full-scale, prototypical components tested at elevated-temperatures to provide validation for inelastic analysis methods, material models, and design limits. Results are discussed for piping elbow plastic and creep buckling, creep ratcheting, and creep relaxation; nozzle creep ratcheting and weld cracking; and thermal striping fatigue. Comparisons between theory and test confirm the adequacy of components to meet design requirements, but identify specific areas where life prediction methods could be made more precise.

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