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To prevent premature failures of rehabilitated concrete pavements, transportation authorities need tools to characterize the prerehab pavement condition of its load carrying capacity, and to determine the resistance of the overlay material to underlying crack/joint movements. Two quantitative methods, the rolling dynamic deflectometer (RDD) and overlay tester (OT), along with field performance data were employed in rehabilitation studies involving reflective cracks. The RDD is able to continuously assess vertical differential movements at joints/cracks that represent the potential for reflective cracks on existing pavements. The OT has the ability to determine the resistance of the overlay material to underlying crack/joint movements. The RDD W1-W3 deflections were used to determine areas that have a high potential for reflective cracking due to poor load transfer across joints and cracks. This paper documents results from the RDD and OT on the following five rehabilitation projects: (1) SH225; (2) US96; (3) SH12; (4) SH342; and (5) IH35W. Based on the available test results from these five projects, it was observed that the W1-W3 threshold values of 5.5 mils (0.140 mm) for exposed concrete pavement and 6.5 mils (0.165 mm) for composite pavement with existing hot mix asphalt overlay and an OT threshold value of 700 cycles correlated well with the field performance. Ignoring either of these critical factors may lead to premature reflective cracking. [ABSTRACT FROM AUTHOR]

In this work, closed-form expressions for the buckling loads of a weakened column with different boundary conditions are presented. The cracked-column model is based on the well-known method consisting of dividing the column into two segments connected by a rotational linear spring whose flexibility is related to the crack size and the geometry of the cross section. For the formulation of closed-form expressions, the perturbation method is used and the results are compared with those found by directly solving the eigenvalue problem. [ABSTRACT FROM AUTHOR]

The objective of this paper is to study the deformation behavior of moist-compacted soil liners with and without inclusion of discrete and randomly distributed fibers for waste containment systems at the onset of nonuniform settlements in a geotechnical centrifuge. First, scaling considerations pertaining to simulation of discretely mixed fibers in a centrifuge are presented. A series of centrifuge tests were carried out by varying aspect ratio and dosage of fibers in a soil liner of 1.2 m thick and compacted at its standard Proctor compaction. Controlled in-flight simulation of nonuniform settlements in a centrifuge was carried out using a trap-door arrangement at 40 g. It was observed that the aspect ratio and fiber content has a significant affect in restraining cracks for a randomly reinforced soil liner at the onset of nonuniform settlements. In addition to centrifuge test results, flexural behavior of soil beams with and without discrete and randomly distributed fibers was evaluated in the laboratory to bring out significance of fiber content and aspect ratio. The analysis and interpretation of test results indicate the significant potential for fiber reinforcement to decrease and to retard soil crack potential in a randomly reinforced soil liner while retaining its hydraulic performance. [ABSTRACT FROM AUTHOR]

Web holes are often made in wood I-joists to allow passage of services. Design properties of wood I-joists with a web hole are commonly developed through testing which leads to empirical design information. This paper describes a mechanics-based method to predict the strengths of wood I-joists with a circular web hole that is suitable for implementation as a design tool. Curved beam theory is used to compute stresses around a hole. Peak tensile stresses obtained from curved beam analysis agree well with those predicted using the finite-element method. Failure load is attained by the application of fracture mechanics based finite area method. The method developed is used to predict failure loads of wood I-joists of different depths with different web hole sizes. Simplification of the method leads to the development of a simple expression that can be used for engineering design. It is found that the predicted strengths are in a good agreement with the corresponding test results. The calculation method developed can potentially replace the testing approach generally adopted by the wood I-joist industry. [ABSTRACT FROM AUTHOR]

A multiscale virtual internal bond (VIB) model for isotropic materials has been recently proposed to describe material deformation and fracture under quasi-static and dynamic loading situations. Fracture simulation using an isotropic VIB model is made possible by incorporating a cohesive type law, inspired by atomistic-level interaction among particles into a hyperelastic framework at the continuum level. Thus, fracture is built directly into the constitutive formulation. The numerical implementation of the material model for brittle materials into a finite-element scheme and the determination of model parameters has been previously researched. In this paper, the VIB model is applied to the dynamic fracture simulation of plain concrete. The experimental study on the dynamic tensile failure of concrete by Gran et al. is used to determine the VIB model material parameters for plain concrete. Simulations and results of comparisons with the concrete–VIB model with the experimental results are presented in this paper. [ABSTRACT FROM AUTHOR]

This paper presents a general strategy to select the numerical values of the coefficients defining an uniaxial tensioned concrete equivalent constitutive relationship to simulate, under serviceability conditions, the instantaneous and time-dependent flexural behavior of reinforced and prestressed concrete members. Such values are determined by a least-squares algorithm aiming to minimize the differences between the moment–curvature diagrams obtained with two fiber models: The first one uses the proposed stress–strain law and the second one follows suggestions from the Comité Euro-International du Béton. To obtain general conclusions, a numerical parametric analysis is performed on a number of reinforced and prestressed concrete rectangular and T beams undergoing bending moments and axial compressive forces. Closed-form solutions providing the sought values of the coefficients are given for reinforced concrete rectangular cross sections. These analyses yield a better understanding of the influence of the main considered parameters in the tension-stiffening effect. The proposed equivalent constitutive law is suitable to be incorporated into global models of concrete structures. Some examples on multistory plane frames are shown to highlight this capability. As well, various benchmark tests have been satisfactorily simulated. [ABSTRACT FROM AUTHOR]

Presents information on a study which investigated the use of Rayleigh waves for crack detection in structural elements. Theory of the Rayleigh-Lamb frequency equation; Description and measurement configuration; Application of two signal-processing techniques; Measurement elements.

Presents a study which discussed an evidence to show that a size and geometry dependence is observed in the shrinkage cracking behavior of restrained concrete structures. Effect of cracking in concrete structures; Types of concrete mixture compositions; Results; Conclusions.