Jan G. Rots

Bio: Jan G. Rots is an academic researcher from Delft University of Technology. The author has contributed to research in topics: Masonry & Unreinforced masonry building. The author has an hindex of 24, co-authored 132 publications receiving 3558 citations. Previous affiliations of Jan G. Rots include Norwegian University of Science and Technology.

Multisurface Interface Model for Analysis of Masonry Structures

Abstract: The performance of an interface elastoplastic constitutive model for the analysis of unreinforced masonry structures is evaluated. Both masonry components are discretized aiming at a rational unit-joint model able to describe cracking, slip, and crushing of the material. The model is formulated in the spirit of softening plasticity for tension, shear and compression, with consistent treatment of the intersections defined by these modes. The numerical implementation is based on modern algorithmic concepts such as local and global Newton-Raphson methods, implicit integration of the rate equations and consistent tangent stiffness matrices. The parameters necessary to define the model are derived from microexperiments in units, joints, and small masonry samples. The model is used to analyze masonry shear-walls and is capable of predicting the experimental collapse load and behaviour accurately. Detailed comparisons between experimental and numerical results permit a clear understanding of the walls structural behavior, flow of internal forces and redistribution of stresses both in the pre- and post-peak regime.

Continuum model for masonry: parameter estimation and validation

Abstract: A novel yield criterion that includes different strengths along each material axis is presented. The criterion includes two different fracture energies in tension and two different fracture energies in compression. The ability of the model to represent the inelastic behavior of orthotropic materials is shown, and a set of experimental tests to characterize the constitutive behavior of masonry is proposed. The capability of the model to reproduce the strength behavior of different masonry types is demonstrated through a comparison with available experimental data in masonry panels subjected to uniform biaxial loading conditions. Finally, the model is validated against experimental results on masonry shear walls and good agreement is found. A clear understanding of the behavior of masonry shear walls, and the nonlinear phenomena involved in its collapse, is presented with the help of a detailed comparison between numerical and experimental results.

Modeling Strategies for the Computational Analysis of Unreinforced Masonry Structures: Review and Classification

Abstract: Masonry structures, although classically suitable to withstand gravitational loads, are sensibly vulnerable if subjected to extraordinary actions such as earthquakes, exhibiting cracks even for events of moderate intensity compared to other structural typologies like as reinforced concrete or steel buildings. In the last half-century, the scientific community devoted a consistent effort to the computational analysis of masonry structures in order to develop tools for the prediction (and the assessment) of their structural behavior. Given the complexity of the mechanics of masonry, different approaches and scales of representation of the mechanical behavior of masonry, as well as different strategies of analysis, have been proposed. In this paper, a comprehensive review of the existing modeling strategies for masonry structures, as well as a novel classification of these strategies are presented. Although a fully coherent collocation of all the modeling approaches is substantially impossible due to the peculiar features of each solution proposed, this classification attempts to make some order on the wide scientific production on this field. The modeling strategies are herein classified into four main categories: block-based models, continuum models, geometry-based models, and macroelement models. Each category is comprehensively reviewed. The future challenges of computational analysis of masonry structures are also discussed.

A plane stress softening plasticity model for orthotropic materials

Abstract: A plane stress model has been developed for quasi-brittle orthotropic materials. The theory of plasticity, which is adopted to describe the inelastic behaviour, utilizes modern algorithmic concepts, including an implicit Euler backward return mapping scheme, a local Newton-Raphson method and a consistent tangential stiffness matrix. The model is capable of predicting independent responses along the material axes. It features a tensile fracture energy and a compressive fracture energy, which are different for each material axis. A comparison between calculated and experimental results in masonry shear walls shows that a successful implementation has been achieved. © 1997 John Wiley & Sons, Ltd.

Non-Linear Finite Element Analysis of Solids and Structures: de Borst/Non-Linear Finite Element Analysis of Solids and Structures

Abstract: Built upon the two original books by Mike Crisfield and their own lecture notes, renowned scientist Rene de Borst and his team offer a thoroughly updated yet condensed edition that retains and builds upon the excellent reputation and appeal amongst students and engineers alike for which Crisfield's first edition is acclaimed. Together with numerous additions and updates, the new authors have retained the core content of the original publication, while bringing an improved focus on new developments and ideas. This edition offers the latest insights in non-linear finite element technology, including non-linear solution strategies, computational plasticity, damage mechanics, time-dependent effects, hyperelasticity and large-strain elasto-plasticity. The authors' integrated and consistent style and unrivalled engineering approach assures this book's unique position within the computational mechanics literature.

Numerical simulation of mixed-mode progressive delamination in composite materials

Abstract: A new decohesion element with the capability of dealing with crack propagation under mixed-mode loading is proposed and demonstrated. The element is used at the interface between solid finite elements to model the initiation and non-self-similar growth of delaminations in composite materials. A single relative displacement-based damage parameter is applied in a softening law to track the damage state of the interface and to prevent the restoration of the cohesive state during unloading. The softening law is applied in the three-parameter Benzeggagh-Kenane mode interaction criterion to predict mixed-mode delamination propagation. To demonstrate the accuracy of the predictions, steady-state delamination growth is simulated for quasi-static loading of various single mode and mixed-mode delamination test specimens and the results are compared with experimental data.

Nonlocal integral formulations of plasticity and damage: Survey of progress

Abstract: Modeling of the evolution of distributed damage such as microcracking, void formation, and softening frictional slip necessitates strain-softening constitutive models. The nonlocal continuum concept has emerged as an effective means for regularizing the boundary value problems with strain softening, capturing the size effects and avoiding spurious localization that gives rise to pathological mesh sensitivity in numerical computations. A great variety of nonlocal models have appeared during the last two decades. This paper reviews the progress in the nonlocal models of integral type, and discusses their physical justifications, advantages, and numerical applications.

Finite element interface models for the delamination analysis of laminated composites: mechanical and computational issues

Abstract: The finite element analysis of delamination in laminated composites is addressed using interface elements and an interface damage law. The principles of linear elastic fracture mechanics are indirectly used by equating, in the case of single-mode delamination, the area underneath the traction/relative displacement curve to the critical energy release rate of the mode under examination. For mixed-mode delamination an interaction model is used which can fulfil various fracture criteria proposed in the literature. It is then shown that the model can be recast in the framework of a more general damage mechanics theory. Numerical results are presented for the analyses of a double cantilever beam specimen and for a problem involving multiple delamination for which comparisons are made with experimental results. Issues related with the numerical solution of the non-linear problem of the delamination are discussed, such as the influence of the interface strength on the convergence properties and the final results, the optimal choice of the iterative matrix in the predictor and the number of integration points in the interface elements. Copyright © 2001 John Wiley & Sons, Ltd.