José M. Sancho

Modeling Quasibrittle Material Cracking with Cohesive Cracks: Experimental and Computational Advances

Fracture processes in concrete and other quasibrittle materials can be realistically described by means of the cohesive crack model which, as introduced by Hillerborg in his celebrated fictitious crack model, can be viewed as a constitutive assumption for the fracturing behavior of the material [1].

An experimental and numerical method to investigate the oxide behavior in corrosion of reinforced concrete

In the prediction of corrosion-induced cracking of reinforced concrete, the mechanical behavior of the oxide has been proved to be crucial. However, there is a lack of experimental information, and the values of the oxide parameters have to be assumed in the models. In this work, a methodology is presented for indirect determination of the mechanical parameters of the oxide layer. It combines the results from accelerated corrosion tests, carried out in concrete prisms reinforced with a tube equipped with special instruments, and numerical simulations using a model that reproduces the cohesive fracture of concrete and the expansive behavior of the oxide. From the joint analysis of the experimental and numerical results, relevant conclusions about the oxide behavior have been disclosed, and values for the oxide parameters are proposed. With those, the experimental results reported by other authors have been simulated, with satisfactory results, which supports the model.

Modelling of non-uniform corrosion-induced cover cracking in reinforced concrete

Cover cracking and spalling in concrete due to corrosion of reinforcement bars is one of the major concerns for durability of reinforced concrete structures and has been widely researched during recent years. Most approaches to the problem are based on a uniform corrosion and expansion pressure around the rebar. However, corrosion rust tends to accumulate around the steel circumference that faces the concrete cover. From this outer part of the rebar, the corrosion front gradually advances to the inner, which entails a non-uniform expansive pressure around the rebar. The purpose of the study is to simulate the effect of non-uniform rust distribution around the corroded rebar, taking advantage of an embedded cohesive crack finite element. The objective is to develop more realistic models for the estimation of the service life of reinforced concrete structures

Mixed Mode Fracture of Brickwork Masonry

The brickwork masonry, especially walls, often shows cracking ought to differential settlements and excessive deflections of the slabs. In these circumstances the cracks are induced by a combination of tensile and shear stresses, under static loading. Until now the study of the brickwork masonry failure under static loading has been focussed on the compression and compression/shear failure mechanisms, and minor effort has been devoted to study the tensile/ shear failure (mixed mode I/II fracture) [1],[2]. This is the reason because there are not enough experimental data for a good knowledge of the mixed mode fracture of the brickwork masonry. The experimental results are needed for a better knowledge of the failure mechanisms of the brickwork masonry under tensile/shear loading and to supply a benchmark to validate the analytical and numerical models for the mixed mode fracture of the brickwork masonry.

Simulation of the Mixed Mode Fracture of Concrete with Cohesive Models

Considerable effort has been devoted to developing numerical models to simulate the mixed mode fracture of quasi-brittle materials. Traditionally, the numerical methods based on the Finite Element Method were classified into two groups [1]: smeared crack approach and discrete crack approach.