Interpretation of pavement deflection measurement data using an elastodynamic stochastic approach

1998 ◽  
Vol 25 (1) ◽  
pp. 151-160 ◽  
Author(s):  
Mehdi Parvini ◽  
Dieter FE Stolle
Keyword(s):  
Finite Element ◽  
Measurement Data ◽  
Stochastic Approach ◽  
Falling Weight Deflectometer ◽  
Stochastic Finite Element ◽  
Element Approach ◽  
Subgrade Modulus ◽  
Low Sensitivity ◽  
Falling Weight ◽  
Surface Deflections

Pavement deflection measurements, together with backcalculation procedures, are widely used to estimate the layer moduli of pavement-subgrade systems. Sensitivity analysis of a sample problem indicates that conclusions drawn from static analyses with regards to deflection sensitivity to variation in layer moduli may apply when characterizing uncertainty associated with the interpretation of the falling weight deflectometer (FWD) data. The uncertainty associated with the values of the backcalculated parameters from deflection data is investigated in this paper using an elastodynamic, stochastic finite element approach. The results of the simulations indicate that, in order to properly estimate surface layer moduli, loading frequencies higher than that of excitation by typical FWD loading are required. The low sensitivity of deflection uncertainty to random variations in surface modulus, when compared with that associated with subgrade modulus, is demonstrated to contribute to high variations in backcalculated surface modulus from measured surface deflections. Although focus is placed on uncertainties in elastic modulus and deflection, the methodology presented in the paper can be used to quantify uncertainties associated with other layer properties and pavement responses.Key words: stochastic, finite element, pavement deflection, elastodynamic, backcalculation, layer moduli, falling weight deflectometer test.

Application of Stochastic Finite-Element Method to Deflection Analysis of Pavement Structures

1996 ◽  
Vol 1540 (1) ◽  
pp. 65-71
Author(s):  
Mehdi Parvini ◽  
Dieter F. E. Stolle
Keyword(s):  
Finite Element ◽  
Coefficient Of Variation ◽  
Coefficient Matrix ◽  
Loading Frequency ◽  
Stochastic Finite Element ◽  
Deflection Analysis ◽  
Equivalent Mass ◽  
Subgrade Modulus ◽  
Pavement Structures ◽  
Surface Deflections

The effect of random variations in layer properties of a pavement-subgrade system on surface deflections is investigated. This is done by using a stochastic finite-element framework based on the perturbation method. The Taylor's expansion scheme is used. The variations of the surface deflections are related to the variations of layer moduli via a coefficient matrix, thereby allowing an investigation of the sensitivity of measured deflections to the variation of pavement and subgrade moduli. The analyses confirm that surface deflections are not very sensitive to variations of modulus within the pavement structure. Using the Boussinesq-Odemark approximation, it is concluded that, for the sample problem analyzed, the effect of higher-order terms on variation estimates of displacement is negligible when the coefficient of variation of subgrade modulus is less than 15 percent. The effect of inertia on the coefficient of variation of displacement due to variations in layer moduli is also briefly addressed. It is demonstrated that the variation in displacement under the load is sensitive to both the loading frequency and the equivalent mass of the pavement-subgrade system, particularly in the vicinity of the natural frequency of the system.

Representative Volume Element for Mechanical Properties of Carbon Nanotube Nanocomposites Using Stochastic Finite Element Analysis

2020 ◽  
Vol 142 (3) ◽  
Author(s):  
Seyed Hamid Reza Sanei ◽  
Randall Doles
Keyword(s):  
Mechanical Properties ◽  
Finite Element ◽  
Representative Volume Element ◽  
Volume Element ◽  
Length Scale ◽  
Stochastic Finite Element ◽  
Element Analysis ◽  
Representative Volume ◽  
Element Approach ◽  
Stochastic Finite Element Analysis

Abstract The aim of this study is to present a representative volume element (RVE) for nanocomposites with different microstructural features using a stochastic finite element approach. To that end, computer-simulated microstructures of nanocomposites were generated to include a variety of uncertainty present in geometry, orientation, and distribution of carbon nanotubes. Microstructures were converted into finite element models based on an image-based approach for the determination of elastic properties. For each microstructure type, 50 realizations of synthetic microstructures were generated to capture the variability as well as the average values. Computer-simulated microstructures were generated at different length scales to determine the change in mechanical properties as a function of length scale. A representative volume element is defined at a length scale beyond which no change in variability is observed. The results show that there is no universal RVE applicable to all properties and microstructures; however, the RVE size is highly dependent on microstructural features. Microstructures with agglomeration tend to require larger RVE. Similarly, random microstructures require larger RVE when compared with aligned microstructures.

Curvilinear Behavior of Base Layer Moduli from Deflection and Seismic Methods

2000 ◽  
Vol 1716 (1) ◽  
pp. 55-63
Author(s):  
Kamal Tawfiq ◽  
John Sobanjo ◽  
Jamshid Armaghani
Keyword(s):  
Surface Deformation ◽  
Low Frequency ◽  
Field Testing ◽  
Base Layer ◽  
Falling Weight Deflectometer ◽  
Seismic Methods ◽  
Extensive Field ◽  
Curvilinear Relationships ◽  
Falling Weight ◽  
Surface Deflections

The reality of curvilinear relationships of stiffness versus deformation is usually neglected when moduli values from seismic methods are compared with those of deflection methods. On the basis of extensive field testing, results showed that moduli values for the base layers from deflection methods did not conform to those of seismic methods. Deflection testing techniques were signified by the falling weight deflectometer (FWD) and the Dynaflect methods. Seismic testing was carried out by use of the seismic pavement analyzer (SPA) method. The SPA test results yielded moduli values higher than those obtained from the deflection methods. Utilizing pavement parameters obtained from the SPA data, researchers determined surface deflections by use of frequency response functions of signals from the two groups of sensors used in the testing setup. Because of the types of hammers in the SPA testing, two different deflection basins were obtained at each testing point. Comparison of surface deflections from these methods indicated that deflection amplitudes from the FWD method were about 100 times higher than those obtained from the high-frequency hammer of the SPA. At certain pavement sections, deflections from the Dynaflect method were comparable to those obtained with the SPA low-frequency hammer. Accordingly, curvilinear relationships between surface deformation versus stiffness values were derived. These relationships can be used to determine moduli values at all surface deflections, including those from service loads.

Direct Method for Evaluating Structural Needs of Flexible Pavements with Falling-Weight Deflectometer Deflections

2003 ◽  
Vol 1860 (1) ◽  
pp. 41-47 ◽  
Author(s):  
Mario S. Hoffman
Keyword(s):  
Direct Method ◽  
Flexible Pavements ◽  
Falling Weight Deflectometer ◽  
Simple Method ◽  
Traffic Demand ◽  
Structural Evaluation ◽  
Overlay Design ◽  
Subgrade Modulus ◽  
Simple Equations ◽  
Falling Weight

A direct and simple method (YONAPAVE) for evaluating the structural needs of flexible pavements is presented. It is based on interpretation of measured falling-weight deflectometer (FWD) deflection basins using mechanistic and practical approaches. YONAPAVE estimates the effective structural number (SN) and the equivalent subgrade modulus independently of the pavement or layer thicknesses. Thus, there is no need to perform boreholes, which are expensive, time-consuming, and disruptive to traffic. Knowledge of the effective SN and the subgrade modulus together with an estimate of the traffic demand allows the determination of the overlay required to accommodate future needs. YONAPAVE’s simple equations can be solved using a pocket calculator, making it suitable for rapid estimates in the field. The simplicity of the method, and its independence from major computer programs, make YONAPAVE suitable for estimating the structural needs of a road network using FWD data collected on a routine or periodic basis along network roads. YONAPAVE can be used with increased experience and confidence as the basis for nondestructive testing structural evaluation and overlay design at the project level.

Pavement displacement sensitivity to layer moduli

2002 ◽  
Vol 39 (6) ◽  
pp. 1395-1398
Author(s):  
Dieter Stolle
Keyword(s):  
Finite Element ◽  
Surface Displacement ◽  
Falling Weight Deflectometer ◽  
Contribution Ratio ◽  
Displacement Sensitivity ◽  
Stiffness Characteristics ◽  
Element Technique ◽  
Falling Weight ◽  
The Relationship ◽  
Displacement Measurements

The backcalculation of layer moduli using falling weight deflectometer data has proven to be challenging owing to the insensitivity of displacement measurements to the stiffness characteristics of some layers. This note describes a rigorous, yet simple, finite element technique for identifying the relationship between surface displacement and the elastic modulus of each layer. An example is given to demonstrate the application of the procedure.Key words: pavements, subgrade, backcalculation, contribution ratio.

A practical approach to falling-weight deflectometer (FWD) data reduction

2005 ◽  
Vol 42 (2) ◽  
pp. 641-645 ◽  
Author(s):  
Dieter Stolle ◽  
Peijun Guo
Keyword(s):  
Mechanical Properties ◽  
Shear Modulus ◽  
Falling Weight Deflectometer ◽  
Layer System ◽  
Surface Loading ◽  
Back Calculation ◽  
Pavement Response ◽  
Subgrade Modulus ◽  
Falling Weight

The authors present a simplified methodology for preprocessing falling-weight deflectometer (FWD) data, which identify a pseudo-static pavement response to surface loading. This allows one to employ static analysis to back-calculate the mechanical properties of the pavement–subgrade system. It is shown that the subgrade modulus can be identified, independent of the details of the pavement structure itself, at least for a two-layer system. The quality of the effective shear modulus is sensitive to the value of Poisson's ratio selected.Key words: pavement–subgrade system, subgrade modulus, back-calculation, FWD.

Mechanistic-Based Approach to Utilize Traffic Speed Deflectometer Measurements in Backcalculation Analysis

2020 ◽  
Vol 2674 (5) ◽  
pp. 208-222
Author(s):  
Zia U. A. Zihan ◽  
Mostafa A. Elseifi ◽  
Patrick Icenogle ◽  
Kevin Gaspard ◽  
Zhongjie Zhang
Keyword(s):  
Asphalt Concrete ◽  
Traffic Control ◽  
Parametric Study ◽  
Complex Modulus ◽  
Falling Weight Deflectometer ◽  
Software Application ◽  
Traffic Speed ◽  
Definition Of ◽  
Falling Weight ◽  
Surface Deflections

Backcalculation analysis of pavement layer moduli is typically conducted based on falling weight deflectometer (FWD) deflection measurements; however, the stationary nature of the FWD requires lane closure and traffic control. In recent years, traffic speed deflection devices such as the traffic speed deflectometer (TSD), which can continuously measure pavement surface deflections at traffic speed, have been introduced. In this study, a mechanistic-based approach was developed to convert TSD deflection measurements into the equivalent FWD deflections. The proposed approach uses 3D-Move software to calculate the theoretical deflection bowls corresponding to FWD and TSD loading configurations. Since 3D-Move requires the definition of the constitutive behaviors of the pavement layers, cores were extracted from 13 sections in Louisiana and were tested in the laboratory to estimate the dynamic complex modulus of asphalt concrete. The 3D-Move generated deflection bowls were validated with field TSD and FWD data with acceptable accuracy. A parametric study was then conducted using the validated 3D-Move model; the parametric study consisted of simulating pavement designs with varying thicknesses and material properties and their corresponding FWD and TSD surface deflections were calculated. The results obtained from the parametric study were then incorporated into a Windows-based software application, which uses artificial neural network as the regression algorithm to convert TSD deflections to their corresponding FWD deflections. This conversion would allow backcalculation of layer moduli using TSD-measured deflections, as equivalent FWD deflections can be used with readily available tools to backcalculate the layer moduli.

Application of Falling Weight Deflectometer Data for Analysis of Superheavy Loads

1996 ◽  
Vol 1540 (1) ◽  
pp. 83-90 ◽  
Author(s):  
Dar-Hao Chen ◽  
Emmanuel Fernando ◽  
Michael Murphy
Keyword(s):  
Falling Weight Deflectometer ◽  
Pavement Condition ◽  
Percent Confidence Level ◽  
Significant Difference ◽  
Before And After ◽  
Transport Vehicle ◽  
Pavement Damage ◽  
The Cost ◽  
Falling Weight ◽  
Surface Deflections

Permitting superheavy loads may increase the rate of pavement damage and the cost of maintenance. An analysis of a proposed superheavy load route (FM519) to evaluate the potential pavement damage caused by a planned superheavy load move is presented. Falling weight deflection (FWD) tests and backcalculations of layer moduli were performed on the FM519. FWD tests and backcalculation of layer moduli were performed on the pavement before and after the superheavy load was moved. ELSYM5 and BISAR were used to evaluate the pavement responses using the backcalculated layer moduli from FWD data. The predictions of surface deflections from ELSYM5 and BISAR were close to (within 10 percent of) the measured deflections from FWD tests. The FWD data and analyses show that the existing pavement structure is adequate for the planned superheavy load move. Finally, the permit was issued with the condition that the transport vehicle should be kept within the travel lanes and away from the shoulder whenever possible. FWD tests were conducted after the superheavy load move and comparisons with before superheavy load move were made. T-tests were performed to check for significant difference at the 95 percent confidence level. T-tests showed that there is no significant difference between before and after superheavy load move. Also, no significant distresses due to this superheavy load were observed after the move, and the pavement condition is consistent with the analysis performed to issue the permit.

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