J M Roesset

Bio: J M Roesset is an academic researcher from Texas A&M University. The author has contributed to research in topics: Falling weight deflectometer & Deflection (engineering). The author has an hindex of 6, co-authored 8 publications receiving 766 citations.

Stiffness matrices for layered soils

Abstract: The Haskell-Thompson transfer matrix method is used to derive layer stiffness matrices which may be interpreted and applied in the same way as stiffness matrices in conventional structural analysis These layer stiffness matrices have several advantages over the more usual transfer matrices: (1) they are symmetric; (2) fewer operations are required for analysis; (3) there is an easier treatment of multiple loadings; (4) substructuring techniques are readily applicable; and (5) asymptotic expressions follow naturally from the expressions (very thick layers; high frequencies, etc) While the technique presented is not more powerful than the original Haskell-Thompson scheme, it is nevertheless an elegant complement to it The exact expressions are given for the matrices, as well as approximations for thin layers Also, simple examples of application are presented to illustrate the use of the method

Dynamic interpretation of dynaflect and falling weight deflectometer tests

Abstract: The Dynaflect and the falling weight deflectometer are commonly used for nondestructive testing of pavements. In both cases a dynamic load is imparted, and the determination of the mechanical properties of the pavement, the base, and the subbase is normally performed by comparing the measured deflections at various points along the surface to results of static analyses that consider the subbase as a homogeneous, elastic half-space. In this paper, the displacements obtained from dynamic analyses are compared to those provided by conventional static programs when the subbase is a homogeneous soil stratum of finite depth resting on a much stiffer rocklike material and when the soil properties increase smoothly with depth, as is often the case. The results of these comparisons indicate that for certain ranges of depth to bedrock a static interpretation of the Dynaflect and falling weight deflectometer tests may lead to substantial errors. Situations in which these errors are important are more likely to be encountered with the Dynaflect than with the falling weight deflectometer.

Nondestructive Dynamic Testing of Soils and Pavements

Abstract: Non destructive testing techniques based on the application of dynamic loads on the surface of a soil deposit or a pavement system, and the measurement of the resulting deflection basins or the phase difference between the motions recorded at various receivers have become powerful tools in civil engineering. In many cases, however, the interpretation of the recorded data relies on static analyses, ignoring entirely dynamic needed for a correct dynamic interpretation using wave propagation theory propagation in an elastic half space, a homogeneous layer of finite thickness resting on a rigid base, and a horizontally layered medium in general are presented with special emphasis on the interpretation of the data collected in the Falling Weight Deflectometer ( FWD ) and the Spectral Analysis of Surface Wave ( SASW ) tests.

Applications and limitations of the spectral analysis of surface waves method

Abstract: The spectral analysis of surface waves (SASW) method is an in situ seismic method for non destructively determining the modulus profiles of geotechnical, pavement, and structural systems. This method requires no boreholes and is performed entirely from the surface of the system being tested. Measurements are made at strains below 0.001 Per cent where elastic properties of the materials are independent of strain amplitude. The versatility and relatively easy deployment of this method represent two of the strengths of the method. By generating and measuring surface waves in the field, a dispersion curve, a plot of surface wave velocity versus wavelength, is constructed. This dispersion curve is then inverted in the office. Inversion is an analytical process for reconstructing the shear wave velocity profile from the field dispersion curve. Layering and the young's modulus of each layer are readily obtained from the shear wave velocity profile. Due to the complex nature of surface wave propagation, a half space with infinite lateral extent was assumed in the past for most theoretical analyses. As a result, the existence of reflected waves from any reflecting boundary was neglected. To understand the impact from the existence of reflecting boundaries in the real world such as joints or edges in a pavement system, a simplified model was developed. Field experiments were then performed to verify this model. Based on the results from both model and field studies, remedial measures for minimizing the effects of reflections in sasw testing are recommended. Several case studies are presented to illustrate the versatility of the sasw method, and a masscomp minicomputer was introduced in an attempt to automate the sasw method (a).

Nonlinear effects in falling weight deflectometer tests

Abstract: The falling weight deflectometer (FWD) has been used in the evaluation of material properties of pavement systems for many years. The load amplitude and frequency content are intended to provide deformation levels similar to those induced by truck wheel loads. Interpretation of the in situ measured data is normally based on an elastic solution and therefore does not take into account the possible existence of localized nonlinearities. The objective of this work was to develop some understanding of the potential for nonlinear behavior in the FWD test. Analytical studies were conducted using both a linear iterative solution and a nonlinear solution with the generalized cap model to reproduce the nonlinear soil behavior. Three pavement sections in Texas were considered using the finite discrete model. By varying the level of loads FWD deflection basins, induced strains, and inelastic material properties were obtained. The results of this study indicate that material nonlinearities are localized and are important for FWD tests on flexible pavements where the subgrade is relatively soft or the pavement is thin. In these cases, nonlinear effects increase peak displacements by at least 50% under a 20,000-lb load but are negligible for receivers at 3 ft or more from the source. In general, a FWD test with a load of 2,000 lb or less would not result in any apparent nonlinear effects at any pavement site. For FWD tests on rigid pavements or flexible pavements with a relatively stiff subgrade, nonlinearities are also less pronounced.

Exact Solution for Simply Supported and Multilayered Magneto-Electro-Elastic Plates

Abstract: Exact solutions are derived for three-dimensional, anisotropic, linearly magneto-electroelastic, simply-supported, and multilayered rectangular plates under static loadings. While the homogeneous solutions are obtained in terms of a new and simple formalism that resemble the Stroh formalism, solutions for multilayered plates are expressed in terms of the propagator matrix. The present solutions include all the previous solutions, such as piezoelectric, piezomagnetic, purely elastic solutions, as special cases, and can therefore serve as benchmarks to check various thick plate theories and numerical methods used for the modeling of layered composite structures. Typical numerical examples are presented and discussed for layered piezoelectric/piezomagnetic plates under surface and internal loads.

Surface-wave analysis for building near-surface velocity models — Established approaches and new perspectives

Abstract: Today, surface-wave analysis is widely adopted for building near-surface S-wave velocity models. The surface-wave method is under continuous and rapid evolution, also thanks to the lively scientific debate among different disciplines, and interest in the technique has increased significantly during the last decade. A comprehensive review of the literature in the main scientific journals provides historical perspective, methodological issues, applications, and most-promising recent approaches. Higher modes in the inversion and retrieval of lateral variations are dealt with in great detail, and the current scientific debate on these topics is reported. A best-practices guideline is also outlined.

Surface-wave method for near-surface characterization: a tutorial

Abstract: Surface-wave methods (SWMs) are very powerful tools for the near-surface characterization of sites. They can be used to determine the shear-wave velocity and the damping ratio overcoming, in some cases, the limitations of other shallow seismic techniques. The different steps of SWM have to be optimized, taking into consideration the conditions imposed by the small scale of engineering problems. This only allows the acquisition of apparent dispersion characteristics: i.e. the high frequencies and short distances involved make robust modelling algorithms necessary in order to take modal superposition into account. The acquisition has to be properly planned to obtain quality data over an adequate frequency range. Processing and inversion should enable the interpretation of the apparent dispersion characteristics, i.e. evaluating the local quality of the data, filtering coherent noise due to other seismic events and determining energy distribution, higher modes and attenuation. The different approaches that are used to estimate and interpret the dispersion characteristics are considered. Their potential and limits with regard to sensitivity to noise, reliability and capability of extracting significant information present in surface waves are discussed. The theory and modelling algorithms, and the acquisition, processing and inversion procedures suitable for providing stiffness and damping ratio profiles are illustrated, with particular attention to reliability and resolution.

Effects of Multiple Modes on Rayleigh Wave Dispersion Characteristics

Abstract: The effects of multiple modes on Rayleigh wave dispersion are discussed to reduce the ambiguity of uniqueness of shear wave velocity (Vs) profiles estimated by the surface wave method. Based on a review of previous studies, dispersion curves of multiple‐mode Rayleigh waves induced by harmonic vertical point loading are derived for both vertical and horizontal particle motions. Also presented is the variation with frequency of the amplitude ratio between horizontal and vertical particle motions. Numerical studies indicate that a stiff soil layer overlying a softer soil layer induces a higher mode or multiple modes, leading to an inversely dispersive characteristic. Consideration of the effects of higher modes is strongly recommended in the inverse process when the observed data show an inversely dispersive trend. The ambiguity of uniqueness of the inverted soil profiles may be reduced by using either the dispersion data of horizontal motion or the amplitude ratio of particle motions in addition to the disp...