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Annual concentrating solar resource map of the United States in 2009 (http://www.nrel.gov/gis/solar.html, as in May 2010).
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![FIGURE 18 Prediction of the EELTG using Equation [10] for the 100-mm...](profile/Feng-Mu/publication/270209874/figure/fig2/AS:667784870629380@1536223728271/Prediction-of-the-EELTG-using-Equation-10-for-the-100-mm-4-in-utrathin-whitetopping_Q320.jpg)
The effective linear temperature gradient is a significant input needed to characterize the effects of environmental loadings when available pavement design procedures are used for bonded concrete overlays on asphalt (BCOA), also known as thin or ultrathin whitetopping. Establishing such an input is challenging and therefore has not been well guide...
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This paper presenting an experimental investigation has conducted on shear behavior of M-sand based geopolymer concrete, in this study low calcium flyash is used to make geopolymer concrete along with sodium hydroxide, sodium silicate solutions. The experimental study included a total of 5 beams and 12 cube specimens are casted, beam of size 100 x...
Citations
... Damage accrued when vehicle loads are applied while the pavement is curled upward is the most critical. Therefore, damage accumulated during times when negative gradients are present has been historically correlated to predicted faulting (DeSantis et al., 2016;Yu et al., 1998;Mu and Vandenbossche, 2010;Mu and Vandenbossche, 2012). For this reason, the effect of temperature gradients must be considered in the design process so as to ensure accurate damage prediction. ...
... While EELTG has been used to effectively quantify the effects of temperature in the design process, it is known that EELTG varies with geographic location, pavement structure, and the type of damage under consideration (Mu and Vandenbossche, 2012). Therefore, each pavement design requires an independent determination of EELTG, and climate data is Prediction of EELTG for BCOAs needed to calculate EELTG from the hourly ELTGs. ...
... To eliminate the need for separate calculations but still evaluate EELTG based on climate and pavement structure, recent pavement design frameworks incorporated prediction models that rapidly determine EELTG given climatic and pavement features. This approach has been adopted in the BCOA-ME for fatigue damage (Mu and Vandenbossche, 2012). In that study, a database of EELTGs was developed for a range of pavement structures and used to train an EELTG prediction model for fatigue damage in BCOAs. ...
Purpose
The time-varying equivalent linear temperature gradient (ELTG) significantly affects the development of faulting and must therefore be accounted for in pavement design. The same is true for faulting of bonded concrete overlays of asphalt (BCOA) with slabs larger than 3 x 3 m. However, the evaluation of ELTG in Mechanistic-Empirical (ME) BCOA design is highly time-consuming. The use of an effective ELTG (EELTG) is an efficient alternative to calculating ELTG. In this study, a model to quickly evaluate EELTG was developed for faulting in BCOA for panels 3 m or longer in size, whose faulting is sensitive to ELTG.
Design/methodology/approach
A database of EELTG responses was generated for 144 BCOAs at 169 locations throughout the continental United States, which was used to develop a series of prediction models. Three methods were evaluated: multiple linear regression (MLR), artificial neural networks (ANNs), and multi-gene genetic programming (MGGP). The performance of each method was compared, considering both accuracy and model complexity.
Findings
It was shown that ANNs display the highest accuracy, with an R ² of 0.90 on the validation dataset. MLR and MGGP models achieved R ² of 0.73 and 0.71, respectively. However, these models consisted of far fewer free parameters as compared to the ANNs. The model comparison performed in this study highlights the need for researchers to consider the complexity of models so that their direct implementation is feasible.
Originality/value
This research produced a rapid EELTG prediction model for BCOAs that can be incorporated into the existing faulting model framework.
... The two design procedures also consider environmental conditions differently. The BCOA-ME procedure uses the concept of strain based effective equivalent linear temperature gradient (EELTG) and effective elastic modulus of the asphalt layer (Ehma) to account for environmental effects on the slab curvature and the stiffness of the asphalt respectively (16,17). This concept involves determining a single value for EELTG and monthly values of Ehma, which produces equivalent damage to an hourly analysis. ...
... This analysis does not consider the effect of additional stresses due to the nonlinearity of the temperature gradient. However, these stresses were found to be negligible for BCOA structures (17). ...
Bonded concrete overlays of asphalt pavements (BCOA) consist of a concrete overlay placed on an existing asphalt or composite pavement. This technique is intended as a cost-effective rehabilitation solution for marginally distressed in-service asphalt or composite pavements. BCOA with panel sizes between 4.5 ft and 8.5 ft have become popular as they reduce curling stresses while keeping the longitudinal joints out of the wheelpath. The BCOA-ME (mechanistic empirical) design procedure and Pavement ME short jointed plain concrete pavement (SJPCP) module can both be used to design BCOA with mid-size panels. However, these design procedures differ in the assumptions used to develop the mechanistic computational model, fatigue models used to predict failure, treatment of environmental conditions, estimate of asphalt stiffness, consideration of structural fibers, the application of traffic loading, and the calibration process. This results in the procedures producing different overlay thicknesses and predicted distresses. The strengths and limitations of each procedure are evaluated and comparisons are made between the design thicknesses obtained from them.
... On the contrary, the viscosity of asphalt decreases sharply at high temperatures, which leads to the decrease of cohesive force between aggregates. As a result, the elastic modulus of AC increases with decrease in temperature and decreases with increase in temperature [31]. ...
Asphalt concrete (AC) overlays placed over old asphalt pavement have become an alternative to repairing and reinforcing pavements. The strength contributed by the AC overlay is strongly influenced by the anisotropic properties of the pavement material. This study was conducted to analyze the influence of anisotropy, modulus gradient properties, and the condition of the AC overlay and old pavement contact plane on the mechanical behaviors of AC overlays, as well as to quantify the influence of the degree of anisotropy on the mechanical behaviors of AC overlay by a sensitivity analysis (SA). The mechanical behaviors of the AC overlay were numerically obtained using the three-dimensional finite element method with the aid of ABAQUS, a commercial program. Variations in the AC overlay’s modulus as a function of temperature as well as the contact state between the AC overlay and AC layer were considered. The SA is based on standardized regression coefficients method. Comparing the mechanical behavior in terms of surface deflection, stress, and strain of the anisotropy model against those corresponding to the isotropic model under static loads show that the anisotropic properties had greater effects on the mechanical behavior of the AC overlay. In addition, the maximum shear stress in the AC overlay was the most significant output parameter affected by the degree of anisotropy. Therefore, future research concerning the reinforcement and repair of pavements should consider the anisotropic properties of the pavement materials.
... This equivalent linear gradient provides the same deformation in the slab as that of the nonlinear temperature distribution. It should be noted that an equivalent strain approach produces comparable equivalent linear gradients, while the equivalent stress does not produce equivalent results (Mu and Vandenbossche 2012). The effective EETG was obtained by further matching the equivalent fatigue concept. ...
... The effective EETG was obtained by further matching the equivalent fatigue concept. For detail, please refer to the paper (Mu and Vandenbossche 2012). ...
... The EELTG represents a single equivalent linear gradient that can be applied to all load applications and produce equivalent damage to a prediction utilising the hourly variation in the temperature distribution. The PCA and CDOT procedures provide little guidance for recommended values to be for defining this input (Mu and Vandenbossche 2012). The BCOA-ME design procedure has established appropriate values for this input in the approach described below. ...
Development of design procedures for bonded whitetopping overlays has been based on the assumption that failure mechanisms are a function of overlay thickness; namely, thin whitetopping results in longitudinal cracking and ultrathin whitetopping results in corner cracking. However, field data from whitetopping sections indicate that failure modes are dictated by slab size rather than overlay thickness. The revised procedure presented here for thin whitetopping and ultrathin whitetopping offers four primary enhancements to the Portland Cement Association and Colorado Department of Transportation procedures that traditionally have been used: (a) the failure mode is dictated by the joint spacing and not the overlay thickness, (b) the stress adjustments factors have been calibrated with an extensive data set, (c) the equivalent gradients to be used as the design input are defined according to the pavement structure and geographical location of the project and, (d) the effect of temperature change on hot-mix asphalt stiffness is considered. Comparisons of the predicted performance for the revised procedure with the actual performance for four separate projects showed that the predicted thicknesses are reasonable. It was also found that the predicted thickness obtained with the revised procedure was sensitive to the thickness of hot-mix asphalt, the level of traffic, and the modulus of rupture of the portland cement concrete, as expected.
The purpose of the Guide to Concrete Overlays of Asphalt Parking Lots is to provide information for decision makers and practitioners about selecting, designing, and constructing successful concrete overlays on existing asphalt parking lot pavements that serve multifamily residential, public, or commercial buildings. It focuses on parking areas that carry and store light vehicles (primarily automobiles and pickup trucks), but it also addresses adjacent access roads and truck lanes that regularly carry heavy trucks for the delivery and pickup of goods and materials, including solid waste containers. It offers expert guidance to supplement practitioners’ own professional experience and judgment. With this information, parking lot owners can confidently include concrete overlays in their toolbox of asphalt parking lot solutions and make informed decisions about overlay design and construction based on existing asphalt conditions.
This guide is a companion document to the Guide to Concrete Overlays: Sustainable Solutions for Resurfacing and Rehabilitating Existing Pavements, Second Edition, and the Guide to the Design of Concrete Overlays Using Existing Methodologies.
Bonded concrete overlays of asphalt pavements (BCOAs) are becoming a common rehabilitation technique used for distressed hot mix asphalt (HMA) roadways. The original design procedures were based primarily on data from instrumented pavements and finite element modelling. They were governed by the assumption that the failure mechanism was a function of the overlay thickness. However, field observations have indicated that the actual failure modes are dictated by slab size. The newly developed Bonded Concrete Overlay of Asphalt Mechanistic-Empirical design procedure (BCOA-ME) presented here is valid for overlays that are between 2.5 and 6.5 in (64–154 mm), and includes five primary enhancements to the Portland Cement Association and Colorado Department of Transportation procedures that have been traditionally used: 1.) the failure mode is dictated by the joint spacing; 2.) a new structural model for longitudinal cracking for 6-ft × 6-ft (1.8 m × 1.8 m) concrete overlays has been developed to better predict the critical stresses; 3.) the stress adjustment factors have been calibrated with performance data; 4.) the equivalent temperature gradients used as design input are defined based on the pavement structure and geographical location of the project; and 5.) the effect of temperature change on underlying HMA stiffness is considered. Finally, validation studies were completed on the new procedure and comparisons made between the revised procedure and actual performance data for five separate projects showed reasonable results. A sensitivity analysis also revealed that the predicted thickness obtained using the revised procedure was sensitive to HMA thickness, the modulus of rupture of the Portland cement concrete, and the level of traffic, as would be expected.
