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Falling-Weight Deflectometer data from three in-service pavement sections has been used to analyze dynamic response characteristics. The Analyzed data will be used later in the project along with computer predictions of pavement response to back-calculate engineering properties of pavements. The pavements had thicknesses of 1.5 in., 9 in., and 12 in., and two load levels were tested. The full pulse data is presented for the dropweight force and all seven surface displacement sensors. The analysis was performed in the frequency domain using frequency response functions computed from the pulse data. The frequency response functions were computed by dividing the Fast Fourier Transform (FFT) of the displacements by the FFI of the force. Magnitude and phase angles of the frequency response functions are presented. An undesirable oscillation was present in the frequency response functions. This was attributed to a discontinuity in the displacement pulses resulting from zero-packing in the FFT Program. The pulses have a non-zero "tail" value at the end of the 60 msec sample period which causes the discontinuity. The pulse "tail" may be due to drift, permanent deformation of the pavement, or premature truncation before the transient response had died out. A linear correction to the pulses that eliminated the discontinuity was applied to one test case. This eliminated the undesirable oscillation, giving the responses a more regular behavior similar to predicted theoretical responses. This correction should facilitate comparison studies of computed versus measured FWD responses.
As with the previous two symposia, the 32 papers from the June/July, 1999, Seattle symposium present advances in the nondestructive testing of pavements using conventional falling weight deflectometer techniques and other promising techniques such as ground penetrating radar, rolling weight deflecto
Bearing Capacity of Roads, Railways and Airfields includes the contributions to the 10th International Conference on the Bearing Capacity of Roads, Railways and Airfields (BCRRA 2017, 28-30 June 2017, Athens, Greece). The papers cover aspects related to materials, laboratory testing, design, construction, maintenance and management systems of transport infrastructure, and focus on roads, railways and airfields. Additional aspects that concern new materials and characterization, alternative rehabilitation techniques, technological advances as well as pavement and railway track substructure sustainability are included. The contributions discuss new concepts and innovative solutions, and are concentrated but not limited on the following topics: · Unbound aggregate materials and soil properties · Bound materials characteritics, mechanical properties and testing · Effect of traffic loading · In-situ measurements techniques and monitoring · Structural evaluation · Pavement serviceability condition · Rehabilitation and maintenance issues · Geophysical assessment · Stabilization and reinforcement · Performance modeling · Environmental challenges · Life cycle assessment and sustainability Bearing Capacity of Roads, Railways and Airfields is essential reading for academics and professionals involved or interested in transport infrastructure systems, in particular roads, railways and airfields.
Structural evaluation can be very useful at the network level for project prioritization purposes. In the project priority ranking procedure of the Kansas Department of Transportation (KDOT), a pavement rating attribute, Pavement Structural Evaluation (PSE), is used. These ratings are subjective. his study outlines an approach based on the classical multiple regression analysis resulting in a better estimation of the PSE values using the results from the Falling Weight Deflectometer (FWD) tests and network-level distress survey. The regression models proposed in this study predict the decrease in PSE values by taking into account the FWD data, age, thickness, and distress levels of pavements, and very closely approximate the current PSE ratings obtained at the district level.
This report describes the efforts undertaken to review the status of falling weight deflectometer (FWD) equipment, data collection, analysis, and interpretation, including dynamic backcalculation, as they relate to the models and procedures incorporated in the Mechanistic-Empirical Pavement Design Guide. The work conducted in this project resulted in the following: Development of a backcalculation scheme (BACKLAVA) in the time domain using a quasi-static model (LAVA) as its forward solution and genetic algorithm (GA) as its search engine. BACKLAVA is a backcalculation algorithm for a constant asphalt concrete (AC) layer temperature. Development of a backcalculation scheme (BACKLAVAP) in the time domain using a quasi-static model (LAVAP) as its forward solution and GA as its search engine. BACKLAVAP is a backcalculation algorithm for a temperature profile in an AC layer. Development of a backcalculation scheme (BACKLAVAN) in the time domain using a quasi-static model (LAVAN) as its forward solution and GA as its search engine. BACKLAVAN is a backcalculation algorithm for a viscoelastic AC layer and a nonlinear base layer. Development of a backcalculation scheme (DYNABACK-VE) in the time domain using a time-domain viscoelastic dynamic model (ViscoWave-II) as its forward solution and a hybrid approach (GA and Levenberg-Marquardt algorithm) as its search engine. DYNABACK-VE is a backcalculation algorithm for a viscoelastic AC layer with temperature profile and linear unbound layers. Short list of recommendations for FWD equipment enhancements. The tools developed in this project are standalone applications that could be used on most computers.
Non-destructive testing of pavement structures can be achieved by accurately measuring and interpreting deflection data. this paper describes a computer program designed for simple and fast processing of deflection data collected using a falling weight deflectometer (fwd). a set of diagnostic parameters are calculated: first, maximum horizontal strain in the asphalt concrete (ac) under the test load, directly via the corresponding maximum curvature; next, the elastic stiffness (or young's modulus) of the subgrade; and finally, the vertical stress, strain and deflection on top of the subgrade, by means of an improved method of equivalent layer thickness. the actual stresses, strains, and deflections at test conditions can be normalized for standard ac temperature and standard test load. diagnostic and design applications are discussed. comparisons are made with parallel elastic layer analysis computations. for the covering abstract of the conference see irrd 807201.