The aim of this study was to model the mechanical behavior of interfaces in masonry structures. In the first part, the characteristics of the materials and interfaces involved are determined experimentally. In the second part, a model based on the adhesion intensity is developed. This model can be used to describe the interfaces between mortar and full or hollow bricks and to describe the damage occuring in the mortar. The mechanical behavior predicted by this model is compared with previously obtained experimental data. The model is then tested in the case of some classical masonry structures (small walls, diagonal compression tests).

Contribution to the modelling of interfaces in masonry

Application of tack coat in pavement engineering

Performance evaluation of modified asphalt based trackless tack coat materials

Asphalt mixture is a type of textured composite material made of aggregates and mastic part. Overall strength and failure behavior in such materials depends on the texture or heterogeneity of the mixture. In particular, the crack growth mechanism from the tip of the pre-crack is significantly affected by the texture of the asphalt composite and environmental conditions. The crack can extend through the soft mastic, tight aggregates or interface of the mastic/aggregates. In this research, by performing some fracture tests on a typical asphalt mixture with different test specimens under mode I, mixed mode I/II and mixed mode I/III, the fracture resistance and trajectory of propagating crack is studied at two low and medium temperatures (i.e., −15 and +15 °C). The load bearing capacity and the fracture resistance of the tested asphalt samples increases by decreasing the temperature. It is also shown that a significant part of fracture plane passes through the soft mastic and boundary of aggregates (i.e., the interface of aggregates and mastic) and only about 10–15% of the fracture surface of the propagating crack passes via the tight aggregates by breaking them. This percentage decreases for mode II and III loading conditions and higher testing temperatures. Compared to brittle and isotropic materials, the fracture path of the asphalt mixture shows more deviation, and this deviation increases for those mixtures containing coarser aggregates in the ligament and tested under medium temperature conditions.

Contribution of Interface Fracture Mechanism on Fracture Propagation Trajectory of Heterogeneous Asphalt Composites

The objective of this study is to evaluate the performance of the artificial neural network (ANN) approach for predicting interlayer conditions and layer modulus of a multi-layered flexible pavement structure. To achieve this goal, two ANN based back-calculation models were proposed to predict the interlayer conditions and layer modulus of the pavement structure. The corresponding database built with ANSYS based finite element method computations for four types of a structure subjected to falling weight deflectometer load. In addition, two proposed ANN models were verified by comparing the results of ANN models with the results of PADAL and double multiple regression models. The measured pavement deflection basin data was used for the verifications. The comparing results concluded that there are no significant differences between the results estimated by ANN and double multiple regression models. PADAL modeling results were not accurate due to the inability to reflect the real pavement structure because pavement structure was not completely continuous. The prediction and verification results concluded that the proposed back-calculation model developed with ANN could be used to accurately predict layer modulus and interlayer conditions. In addition, the back-calculation model avoided the back-calculation errors by considering the interlayer condition, which was barely considered by former models reported in the published studies.

Assessing artificial neural network performance for predicting interlayer conditions and layer modulus of multi-layered flexible pavement

Pavement interface damage behavior in tension monotonic loading

The mechanical behaviour of the first interface under a surface layer is critical to pavement durability. Several of the distresses observed are mainly due to traffic loading or repetitive loading;...

Surface roughness: a key parameter in pavement interface design

This paper dealt with the characterization of opening mode fracture using Digital Image Correlation, coupled with a kinematic approach. Tests were carried out using a Wedge Splitting sample made in asphalt concrete AC12. The asphalt concrete was provided in the RILEM-SIB. The samples were a bi-layered asphalt concrete with or without a carbon fiber grid at interface. During experimentation, the sample deformation was recorded by using Digital Image Correlation. Based on the optical measurements coupled with the analytical approach, the energy release rate was performed by means the crack relative displacement and stress intensity factors. Using an adjustment procedure, based on an iterative Newton–Raphson algorithm, the crack relative displacement factor was calculated from optical measurements. the stress intensity factor was estimated from an analytical approach. Furthermore, the crack opening displacement was measured from the mark tracking method. This approach allowed the assessment of fracture parameters for the real structures to be considered.

Analyzing of Wedge Splitting Test on Asphalt Pavement Using Optical Measurements

Even if, for composite materials, many experimental studies as well as behavior laws have been developed, evaluation of the behavior of interfaces between pavement layers is an actual scientific lock. The current French design method only takes into account interfaces, as conventional perfect bonding or slipping plane. In order to understand the behavior of the interface or interphase, the photomechanical tools are unavoidable. The feasibility of this approach is presented for a direct tensile test on double-layered asphalt pavement specimen t. The results (rugosity, adhesion) will be input parameters of a damage model interface. Mots clefs: Interface, analyse d’images, mesure de champs, rugosite, modele d’endommagement.

http://documents.irevues.inist.fr/bitstream/handle/2042/52216/a_9U8RCCI4.pdf;sequence=1

Interfaces de chaussées : de la caractérisation du comportement mécanique de l'interface à sa modélisation

The interface mechanical behavior in asphaltic pavement structures represents a key parameter for the computational design. Several degradation mechanisms are observed in surface layers due to the de-bonding despite the implementation of tack coats or reinforcing systems. The interface modeling becomes more important in the pavement field during the last ten years, even if this concept is widely studied in composites, masonry structures… Furthermore, the experimental research highlights the sensitivity of the imperfect interface behavior in respect to the underlayer roughness. Due to these concerns, parametrical studies are proposed in this paper, by using a macro scale cohesive zone model. This model allows taking into account the damage behavior of the interface, in pure or mixed mode. Damage mechanisms are governed by internal variables. The numerical results based on a finite element method are compared with experimental tensile and shear data. The geometrical periodic roughness (triangular, crenel) and the mixed mode failure are investigated under monotonic loading. A parametric numerical analysis is presented and shows clearly the roughness influence of these structures.

Rahma Ktari

Papers

Pavement interface damage behavior in tension monotonic loading

Surface roughness: a key parameter in pavement interface design

Analyzing of Wedge Splitting Test on Asphalt Pavement Using Optical Measurements

Interfaces de chaussées : de la caractérisation du comportement mécanique de l'interface à sa modélisation

Damage modeling of asphaltic pavement rough interfaces under tensile and shear loading