scholarly journals Modeling of Surface Drainage during the Service Life of Asphalt Pavements Showing Long-Term Rutting: A Modular Hydromechanical Approach

2020 ◽  
Vol 2020 ◽  
pp. 1-15 ◽  
Author(s):  
Stefan Alber ◽  
Barbara Schuck ◽  
Wolfram Ressel ◽  
Ronny Behnke ◽  
Gustavo Canon Falla ◽  
...  
Keyword(s):  
Water Film ◽  
Material Behavior ◽  
Asphalt Pavements ◽  
Computationally Efficient ◽  
Surface Drainage ◽  
Pavement Surface ◽  
Road Geometry ◽  
Longitudinal Slope ◽  
Steady State Rolling

This paper presents a modular hydromechanical approach to assess the short- and long-term surface drainage behavior of arbitrarily deformable asphalt pavements. The modular approach consists of three steps. In the first step, the experimental characterization of the thermomechanical asphalt material behavior is performed. In the second step, information about the long-term material behavior of the asphalt mixtures is integrated on the structural scale via a finite element (FE) tire-pavement model for steady-state rolling conditions and time homogenization in order to achieve a computationally efficient long-term prediction of inelastic deformations of the pavement surface (rut formation). In the third step, information regarding the current pavement geometry (deformed pavement surface) is used to carry out a surface drainage analysis to predict, e.g., the thickness of the water film or the water depth in the pavement ruts as a function of several influencing quantities. For chosen numerical examples, the influence of road geometry (cross and longitudinal slope), road surface (mean texture depth and state of rut deformation), and rainfall properties (rain intensity and duration) on the pavement surface drainage capacity is assessed. These parameters are strongly interrelated, and general statements are not easy to find. Certain trends, however, have been identified and are discussed.

scholarly journals Surface Texture And Layer Permeability Of Aquaplaning Resistant Asphalt Pavements

2021 ◽  
Vol 1202 (1) ◽  
pp. 012026
Author(s):  
Audrius Vaitkus ◽  
Dovydas Skrodenis ◽  
Ovidijus Šernas ◽  
Viktoras Vorobjovas
Keyword(s):  
Traffic Safety ◽  
Surface Texture ◽  
Large Scale ◽  
Water Film ◽  
Limestone Powder ◽  
Asphalt Pavements ◽  
Porous Asphalt ◽  
Permeability Characteristics ◽  
Pavement Surface ◽  
Noise Absorption

Abstract Tire/pavement noise is one of the biggest environmental problems caused by the contact between the car tire and the pavement surface. It is known that porous asphalt (PA) pavements has good properties in noise absorption, however these mixtures could also solve another important problem which appear on roads – aquaplaning. This phenomenon reduces traffic safety and driving comfort. Aquaplaning appears when tires become separated from the pavement surface by thin water film and the ability to increase braking force or control the vehicle motion is almost entirely lost. Although, PA pavements have relatively low durability properties. This research aims analyse surface texture and permeability characteristics of aquaplaning resistant asphalt pavements. Four different mixtures with different largest particle size (AT 5, AT 8, AT 11 and AT 16) were tested. Large-scale laboratory testing was performed to evaluate their surface texture and permeability properties The research revealed, that mixtures with 8 % activated mineral limestone powder (AMLP) showed better mechanical and physical properties than comparing to other mixtures with 4 % AMLP and 4 % granite screenings or just 4 % AMLP.

Improving the Long-Term Performance of Elastomeric Seals by Material Behavior Design

2009 ◽  
Vol 131 (4) ◽  
Author(s):  
Ryan B. Sefkow ◽  
Nicholas J. Maciejewski ◽  
Barney E. Klamecki
Keyword(s):  
Energy Density ◽  
Contact Pressure ◽  
Strain Energy ◽  
Applied Pressure ◽  
Material Behavior ◽  
Time Dependent ◽  
Ring Section ◽  
Stiff Material ◽  
Elastomeric Seals

Previously it was shown that including smaller inset regions of less stiff material in the larger O-ring section at locations of high stress results in lower strain energy density in the section. This lower energy content is expected to lead to improved long-term seal performance due to less permanent material deformation and so less loss of seal-housing contact pressure. The shape of the inset region, the time-dependent change in material properties, and hence change in seal behavior over time in use were not considered. In this research experimental and numerical simulation studies were conducted to characterize the time-dependent performance of O-ring section designs with small inset regions of different mechanical behaviors than the larger surrounding section. Seal performance in terms of the rate of loss of contact pressure of modified designs and a baseline elastic, one-material design was calculated in finite element models using experimentally measured time-dependent material behavior. The elastic strain energy fields in O-ring sections were calculated under applied pressure and applied displacement loadings. The highest stress, strain, and strain energy regions in O-rings are near seal-gland surface contacts with significantly lower stress in regions of applied pressure. If the size of the modified region of the seal is comparable to the size of the highest energy density region, the shape of the inset is not a major factor in determining overall seal section behavior. The rate of loss of seal-housing contact pressure over time was less for the modified design O-ring sections compared with the baseline seal design. The time-dependent performance of elastomeric seals can be improved by designing seals based on variation of mechanical behavior of the seal over the seal section. Improvement in retention of sealing contact pressure is expected for seal designs with less stiff material in regions of high strain energy density.

Prediction of Stress Relaxation in Power Plant Components Based on a Constitutive Model

2017 ◽  
Author(s):  
Y. Kostenko ◽  
K. Naumenko
Keyword(s):  
Power Plant ◽  
Stress Relaxation ◽  
Constitutive Model ◽  
Evolution Equations ◽  
Material Behavior ◽  
Assessment Procedure ◽  
Reliable Prediction ◽  
Inelastic Material ◽  
Plant Components

Many power plant components and joint connections are subjected to complex thermo-mechanical loading paths under severe temperature environments over a long period. An important part in the lifetime assessment is the reliable prediction of stress relaxation using improved creep modeling to avoid possible integrity or functionality issues and malfunction in such components. The aim of this work is to analyze the proposed constitutive model for advanced high chromium steels with the goal of predicting stress relaxation over the long term. The evolution equations of the constitutive model for inelastic material behavior are introduced to account for hardening and softening phenomena. The material properties were identified for 9–12%CrMoV steels in the creep range. The model is applied to the stress relaxation analysis of power plant components. The results for long-term assessment, which are encouragingly close to reality, will be presented and discussed. An outlook on further developments of the model and assessment procedure is also provided.

scholarly journals Mysteriously high Δ<sup>14</sup>C of the glacial atmosphere: Influence of <sup>14</sup>C production and carbon cycle changes

2020 ◽  
Author(s):  
Ashley Dinauer ◽  
Florian Adolphi ◽  
Fortunat Joos
Keyword(s):  
Carbon Cycle ◽  
Production Rate ◽  
Polar Regions ◽  
Computationally Efficient ◽  
Drastic Reduction ◽  
Qualitative And Quantitative ◽  
Time Period ◽  
Climate Simulations ◽  
The Last Glacial

Abstract. Despite intense focus on the ~ 190 permil drop in atmospheric Δ14C across the deglacial “mystery interval”, the specific mechanisms responsible for the apparent Δ14C excess in the glacial atmosphere have received considerably less attention. The computationally efficient Bern3D earth system model of intermediate complexity, designed for long-term climate simulations, allows us to address a very fundamental but still elusive question concerning the atmospheric Δ14C record: How can we explain the persistence of relatively high Δ14C values during the millennia after the Laschamp event? Large uncertainties in the pre-Holocene 14C production rate, as well as in the older portion of the Δ14C record, complicate our qualitative and quantitative interpretation of the glacial Δ14C elevation. Here we begin with sensitivity experiments that investigate the controls on atmospheric Δ14C in more idealized settings. We show that the long-term process of sedimentation may be much more important to the simulation of Δ14C than had been previously thought. In order to provide a bounded estimate of glacial Δ14C change, the Bern3D model was integrated with five available estimates of the 14C production rate as well as reconstructed and hypothesized paleoclimate forcing. Model results demonstrate that none of the available reconstructions of past changes in 14C production can reproduce the elevated Δ14C levels during the last glacial. In order to increase atmospheric Δ14C to glacial levels, a drastic reduction of air-sea exchange efficiency in the polar regions must be assumed, though discrepancies remain for the portion of the record younger than ~ 33 kyr BP. We end with an illustration of how the 14C production rate would have had to evolve to be consistent with the Δ14C record, by combining an atmospheric radiocarbon budget with the Bern3D model. The overall conclusion is that the remaining discrepancies with respect to glacial Δ14C may be linked to an underestimation of 14C production and/or a biased-high reconstruction of Δ14C over the time period of interest. Alternatively, we appear to still be missing an important carbon cycle process for atmospheric Δ14C.

The Utilization of Rice Husks Powder as an Antioxidant in Asphalt Binder

2014 ◽  
Vol 567 ◽  
pp. 539-544 ◽  
Author(s):  
Mohammed Hadi Nahi ◽  
Ibrahim B. Kamaruddin ◽  
Napiah Madzlan
Keyword(s):  
Thermal Stresses ◽  
Asphalt Binder ◽  
Fine Powder ◽  
Age Hardening ◽  
Asphalt Pavements ◽  
Rice Husks ◽  
Antioxidant Additive ◽  
Oxidative Aging ◽  
Point Test

Aging is one of the main contributors for asphalt failure. Oxidation aging is the main cause of long-term deterioration in asphalt pavements as a pavement ages, oxidation stiffens a pavement, making it more susceptible to failure from load and thermal stresses. Slowing a pavement’s oxidative aging would maintain its elastic properties and delay aging problems. There is no performance enhancer in widespread use, acting as an antioxidant that slows the oxidative aging of asphalt binder. The main objective of this research is to investigate the feasibility of using biomass powder derived from rice husks as an antioxidant additive to control the asphalt age hardening. The waste of rice husks was dried at 40°C for 9–11 days. The dried materials was grounded, and sieved to get fine powder. To evaluate the performance of the antioxidant, samples have to be aged according to SUPERPAVE standards (RTFOT and PAV) and physical, chemical, and rheological properties have to be analyzed. The preliminary results of penetration test softening point test shows that adding 4% of rice husks’ powder to 80/100 binder didn’t change the grade of the binder.

Observed evidence of subgrade moisture influence on pavement longitudinal profile

2008 ◽  
Vol 35 (10) ◽  
pp. 1050-1063 ◽  
Author(s):  
Abraham Bae ◽  
Shelley M. Stoffels ◽  
Charles E. Antle ◽  
Seung Woo Lee
Keyword(s):  
Monitoring Program ◽  
Surface Profile ◽  
Asphalt Pavements ◽  
Moisture Index ◽  
Power Spectral ◽  
Moisture Variation ◽  
Moisture Influence ◽  
Pavement Thickness ◽  
The Relationship

The relationship between subgrade moisture parameters and pavement profile was explored for 34 asphalt pavements of the seasonal monitoring program (SMP) in the long-term pavement performance (LTPP) program. Volumetric moisture content was quantified in terms of the moisture index (MI), representing moisture as reasonably related to subgrade performance. Using power spectral density (PSD), roughness was evaluated in 21 individual wavebands. From statistical analysis, it was concluded that subgrade moisture significantly affects roughness in the wavebands of 14.9 to 31.2 m and 24.0 to 31.2 m for nonfreezing sites, and in the waveband of 14.9 to 24.0 m for freezing sites. At nonfreezing sites, as the magnitude and variation of moisture increase, pavement surface profile deteriorates quickly. At freezing sites, it was found that moisture variation by freezing contributes to roughness deterioration. Moreover, it was found that pavement thickness and the percent passing the top 0.002 mm of subgrade are significant factors accelerating roughness progression at nonfreezing and freezing sites, respectively.

Methods for Reducing a Large Number of Current Profiles to a Small Subset for Riser VIV Analysis

2005 ◽  
Author(s):  
Kostas F. Lambrakos ◽  
Djoni E. Sidarta ◽  
Hugh M. Thompson ◽  
Atle Steen ◽  
Roger W. Burke
Keyword(s):  
Fatigue Damage ◽  
Average Power ◽  
Small Subset ◽  
Large Set ◽  
Computationally Efficient ◽  
Excitation Mode ◽  
Average Value ◽  
Vortex Induced Vibrations ◽  
Simplified Procedure

The paper presents two different approaches to construct subsets of current profiles from a large set of long term current profiles for the purpose of performing calculations for riser fatigue damage from vortex induced vibrations (VIV). The subsets are intended to reproduce the fatigue damage from the full set of current profiles. In the first approach, the full set of profiles is first sorted into bins based on current magnitude, direction and shear in the profile. The profiles within each bin are then reduced to a single constructed profile through one of many possible current averaging schemes. The present study includes two types of constructed profiles; one profile is generated by the average value of the currents for each bin and the other by the average value plus one standard deviation. The second approach is based on first performing a simplified and computationally efficient VIV analysis of the full set of profiles. The profiles are then sorted into bins by the dominant excitation mode, and then a single profile is chosen to represent all the profiles that excite the mode of interest. The chosen profile for the mode of interest has VIV power-in which is close to the average power-in for all the profiles that excite the mode. The number of profiles in the subset is equal to the number of modes that are excited by the full set of profiles. The VIV power-in in this paper is estimated through a simplified procedure that is consistent with the SHEAR7 methodology. Other available codes can also be used for the simplified VIV calculations.

scholarly journals Chemical and Rheological Evaluation of Aged Lignin-Modified Bitumen

Materials ◽  
2019 ◽  
Vol 12 (24) ◽  
pp. 4176 ◽  
Author(s):  
Yi Zhang ◽  
Xueyan Liu ◽  
Panos Apostolidis ◽  
Wolfgang Gard ◽  
Martin van de Ven ◽  
...  
Keyword(s):  
Environmental Benefits ◽  
Asphalt Pavements ◽  
Environmental Scanning ◽  
Physical Interaction ◽  
Test Results ◽  
Modified Bitumen ◽  
Oxidative Aging ◽  
Anti Oxidant ◽  
Rheological Effect

As bitumen oxidizes, material stiffening and embrittlement occur, and bitumen eventually cracks. The use of anti-oxidants, such as lignin, could be used to delay oxidative aging and to extend the lifetime of asphalt pavements. In this study, the chemical and rheological effect of lignin on bitumen was evaluated by using a single dosage organsolv lignin (10 wt.% dosage). A pressure aging vessel (PAV) was used to simulate the long-term aging process after performing the standard short-term aging procedure, and the lignin-modified bituminous binders were characterized by an environmental scanning electron microscope (ESEM), Fourier-transform infrared (FTIR) spectroscopy, and a dynamic shear rheometer (DSR). From the ESEM results, the uniform microstructure was observed, indicating that the addition of lignin did not affect the worm structure of bitumen. Based on the FTIR test results, lignin-modified bitumen showed that a lower number of carbonyl and sulfoxide compounds were generated after aging than for neat bitumen. Based on the linear amplitude sweep (LAS) results, the addition of lignin slightly reduced the fatigue life of bitumen. From the frequency sweep results, it showed that lignin in bitumen acts as a modifier since the physical interaction between lignin and bitumen predominantly affects the material rheology. Overall, lignin could be a promising anti-oxidant due to its economic and environmental benefits.

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