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International Journal of Numerical Methods for Calculation and Design in Engineering (RIMNI) contributes to the spread of theoretical advances and practical applications of numerical methods in engineering and other applied sciences. RIMNI publishes articles written in Spanish, Portuguese and English. The scope of the journal includes mathematical and numerical models of engineering problems, development and application of numerical methods, advances in software, computer design innovations, educational aspects of numerical methods, etc. RIMNI is an essential source of information for scientifics and engineers in numerical methods theory and applications. RIMNI contributes to the interdisciplinar exchange and thus shortens the distance between theoretical developments and practical applications.

Desde 1985 la Revista Internacional de Métodos Numéricos para Cálculo y Diseño en Ingeniería (RIMNI) contribuye a la difusión en castellano, portugués e inglés de los desarrollos teóricos y aplicaciones prácticas de los métodos numéricos, tanto en relación con su utilidad como instrumentos de cálculo y análisis para el ingeniero y el científico, como en aspectos que inciden en las nuevas tecnologías de diseño y proyecto de producción y procesos en ingeniería. La revista abarca áreas diversas, tales como: modelos matemáticos y numéricos de problemas de ingeniería, desarrollo y aplicaciones de los métodos numéricos, nuevos avances en temas de software, innovaciones en el campo del diseño por computador, aspectos didácticos de los métodos numéricos, etc. La revista constituye una fuente de información imprescindible para ingenieros y científicos sobre innumerables temas relacionados con los métodos numéricos y sus aplicaciones, contribuyendo a promover la transferencia de conocimiento interdisciplinar y, por consiguiente, a acortar la distancia que existe entre los desarrollos teóricos y las aplicaciones concretas.

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A constitutive model based on classical plasticity theory for non‐linear analysis of concrete structures using finite elements is presented. The model uses the typical parameters of non‐associated plasticity theory for frictional materials and a modified Mohr‐Coulomb yield surface is suggested. Onset and amount of cracking at a point are controlled by the values of the effective plastic strain and thus it can be studied by a posteriori postprocessing of numerical results. The accuracy and objectivity of the model is checked out with some examples of application.

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In the present paper, a new d+/d− damage model apt for quasi-brittle materials is described and its validation is carried out considering unreinforced concrete, reinforced concrete and masonry elements.

Two independent scalar damage variables, d+ and d−, in combination with the split of the reversible strain tensor into its positive and negative counterparts, are adopted in order to simulate the pronounced dissimilar response under tension and compression, typical of these materials. An energy-equivalent framework is considered for representing the orthotropy induced in the material by the degradation process, with the consequence that a thermodynamically consistent constitutive operator, positive definite, symmetric and strain-driven, is derived. In addition to the degradation parameters, the permanent strain tensor is also contemplated by the model and a modification of the exponential softening modulus is proposed in order to treat the evolution of the two causes of dissipation, damage and irreversible deformations, in a coupled way.

The formulation is integrated with a multidirectional damage procedure, addressed to extend the microcrack closure-reopening (MCR) capabilities of the model to shear cyclic conditions, characterized by orthogonal (or however intersecting) sets of cracks. Maintaining unaltered the dependence of the constitutive law from two scalar indeces, d+ and d−, this approach activates or deactivates a tensile(compressive) damage value on the base of the current maximum (minimum) principal strain direction. In correspondence with damage activation (crack opening) or deactivation (crack closure), a smooth transition is introduced, in order to avoid abrupt changes in stiffness and enhance the numerical performance and robustness of the multidirectional procedure. The adequacy of the proposed constitutive model in reproducing experimental results has been proven for both monotonic and cyclic loading conditions. The two examples of application involving cyclic loads, dominated by shear, constitute a validation of the multidirectional damage approach, showing how the suitable representation of unilateral effects and permanent deformations is essential to model the observed structural response in terms of maximum resistance, evolution of stiffness degradation and dissipation capacity.

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The paper presents a systematically numerical procedure based on the finite-element method for three-dimensional analysis of segmentally constructed prestressed concrete bridges using hexahedral elements including realistic tendon profiles. The enhanced assumed strain (EAS) is used in the formulation of the hexahedral element in order to improve the element performances. Both the geometric nonlinearity and time-dependent effects due to creep, shrinkage, and aging of the concrete and relaxation of the prestress are taken into account, while variations of the structural configuration due to changes of the structural geometry and boundary conditions during the construction process are also incorporated. To include realistic tendon profiles, the idealized prestressing tendon is represented by a system of piecewise linear prestressing segments. Several numerical examples in a wide range of prestressed concrete structures are presented to demonstrate the validity and efficiency of the proposed procedure. Finally, application to the erection of a segmentally erected prestressed concrete bridge is discussed at the end of the paper.

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