Abstract

A finite element thermomechanical analysis of a concrete arch dam has been carried out to predict the extent of cracking due to temperature variations. A linear elastic analysis allows us to find out the areas exceeding the tensile strength of the concrete. Then, a smeared crack approach based on a non-local damage model is used to accurately predict the pattern of the damage at the dam. Additionally, joint elements are introduced in the damaged regions of the wall to analyze the evolution of the crack aperture over the year.

Abstract

The static and seismic analysis of Janneh arch-gravity dam (157 m) is carried out by considering a combination of self-weight, hydrostatic, uplift and seismic loads. Linear and nonlinear analyses are performed for both static and seismic cases. Nonlinear behavior is studied by means of joint elements in the contact between the rock foundation and the dam following a bilinear cohesive law. The hydrodynamic effects derived to seismic loads are also considered. Hydrodynamic Westergaard’s approach is applied in the pseudo-static analysis, and the Westergaard’s generalized added mass is used for time-history case.

Abstract

Double curvature arch dams feature geometrical complexity with a significant amount of parameters involved. Different criteria exist to assist in the design task, from simplified geometrical approaches to optimization procedures. However, most of them present a lack of flexibility and are not integrated in computer-aided design tools. In this contribution, an interactive and flexible software tool is presented to support the complete design process: geometrical definition, FEM model generation (including the mesh, the loads and the boundary conditions) and thermo-mechanical analysis. The design can be performed with different levels of detail to adapt to the information available in each stage of the project. The tool allows defining the shape of the reference cylinder, the excavation depth and slope along the foundation, the crown cantilever thickness and curvature, the shape and location of horizontal arcs; all these steps were described in former contributions. Here, special attention is paid to the introduction of additional features such as joints, spillways, abutments of varying shape and outlet works. All steps have been defined with a high degree of flexibility in the design process. The tool is integrated with the pre and post process software GiD, which allows taking advantage of its functionalities, such as mesh generation and results analysis. It is also coupled with a specific application for thermo-mechanical analysis of dams, developed in Kratos Multiphysics – a framework for building parallel multi-disciplinary simulation software. The whole design process can be followed in a unique environment, because the structural response of preliminary designs can be computed and the results considered to refine the dam geometry.

Abstract

Progressive fracture in quasi-brittle materials such as concrete, rocks, soils, is often treated as strain softening in continuum damage mechanics. Such constitutive relations favour spurious strain localization and ill-posedness of boundary value problems, and call for some kind of regularization. In the present work, two different approaches are presented: a partially regularized local damage model that adjusts the softening part of a stress-strain law depending on the size of the element, and a fully regularized non-local damage model that introduces the characteristic length as an additional material parameter controlling the size of the fracture process zone.In addition, the strain softening of such models usually results in highly complex structural responses, including the snap-back type, and thus in this work we will be discussing non-linearity associated to damage modelling, and a global arc-length method for tracing the equilibrium path will be exposed.Furthermore, in the context of non-local damage models it is crucial to work with fine spatial discretizations at the damage progress zone, so that elements are smaller than the characteristic length. In this regard, a mesh-adaptive technique has been implemented with the purpose of enhancing the efficiency of the numerical analysis.Finally, two classical examples, the three-point bending test, and the single-edge notched beam test, are performed in order to analyse the mesh objectivity of the implemented integral-type non-local damage model, and assess the strengths and limitations of the mesh-adaptive procedure.