A recursive-faulting model of distributed damage in confined brittle materials

We develop a model of distributed damage in brittle materials deforming in triaxial compression based on the explicit construction of special microstructures obtained by recursive faulting. The model aims to predict the effective or macroscopic behavior of the material from its elastic and fracture properties; and to predict the microstructures underlying the microscopic behavior. The model accounts for the elasticity of the matrix, fault nucleation and the cohesive and frictional behavior of the faults. We analyze the resulting quasistatic boundary value problem and determine the relaxation of the potential energy, which describes the macroscopic material behavior averaged over all possible fine-scale structures. Finally, we present numerical calculations of the dynamic multi-axial compression experiments on sintered aluminum nitride of Chen and Ravichandran [1994. Dynamic compressive behavior of ceramics under lateral confinement. J. Phys. IV 4, 177–182; 1996a. Static and dynamic compressive behavior of aluminum nitride under moderate confinement. J. Am. Soc. Ceramics 79(3), 579–584; 1996b. An experimental technique for imposing dynamic multiaxial compression with mechanical confinement. Exp. Mech. 36(2), 155–158; 2000. Failure mode transition in ceramics under dynamic multiaxial compression. Int. J. Fracture 101, 141–159]. The model correctly predicts the general trends regarding the observed damage patterns; and the brittle-to-ductile transition resulting under increasing confinement

Implication of the overlap representation for modelling generalized parton distributions

Based on a field theoretically inspired model of light-cone wave functions, we derive valence-like generalized parton distributions and their double distributions from the wave function overlap in the parton number conserved s-channel. The parton number changing contributions in the t-channel are restored from duality. In our construction constraints of positivity and polynomiality are simultaneously satisfied and it also implies a model dependent relation between generalized parton distributions and transverse momentum dependent parton distribution functions. The model predicts that the t-behavior of resulting hadronic amplitudes depends on the Bjorken variable x_Bj. We also propose an improved ansatz for double distributions that embeds this property.Comment: 15 pages, 8 eps figure

Development of a nonlinear macro element for URM walls

Masonry is a widespread method of construction to this day and has proven particularly successful in the construction of office and residential buildings. This is mainly due to the fact that masonry has physical advantages over reinforced concrete. With the currently used linear calculation methods, it is not possible to exploit the load bearing capacity of a masonry wall. Therefore non-linear static calculation methods are developed, which should make this possible. In the present work, several of these calculation methods are presented and compared. A macro model, based on the work of Jin Park, will be further developed and generally implemented in the OpenSees software environment to make the model easy to use and shorten the calculation times. Then, in this software environment, calculations are performed on the macro model to verify its effectiveness. With the element it is possible to show the stress state over the wall height, in every joint. This macro model consists of a series of rigid body spring elements, which are connected by springs connected in series. These springs serve to depict the axial, shear and rotational behavior of a masonry wall. Each of these springs is described with its own spring law. These spring laws not only make it possible to determine the stiffness, but also the load capacity and ductility.Masonry is a widespread method of construction to this day and has proven particularly successful in the construction of office and residential buildings. This is mainly due to the fact that masonry has physical advantages over reinforced concrete. With the currently used linear calculation methods, it is not possible to exploit the load bearing capacity of a masonry wall. Therefore non-linear static calculation methods are developed, which should make this possible. In the present work, several of these calculation methods are presented and compared. A macro model, based on the work of Jin Park, will be further developed and generally implemented in the OpenSees software environment to make the model easy to use and shorten the calculation times. Then, in this software environment, calculations are performed on the macro model to verify its effectiveness. With the element it is possible to show the stress state over the wall height, in every joint. This macro model consists of a series of rigid body spring elements, which are connected by springs connected in series. These springs serve to depict the axial, shear and rotational behavior of a masonry wall. Each of these springs is described with its own spring law. These spring laws not only make it possible to determine the stiffness, but also the load capacity and ductility