1,721,110 research outputs found
Modello diffusivo e di danno per l'analisi del degrado di strutture di calcestruzzo armato
No full textA model for the evaluation of the strength decrease in reinforced concrete structures subjected to the degradation phenomena caused by the interaction with the external environment is presented. In particular the degradation due to the chemical attacks by chlorides, sulphates and CO2 is focused keeping into account the reaction between the chemicals species and the concrete components and the steel corrosions. The concept of coupled damage parameter is introduced to consider both the mechanical and the environmental effects. The stress-strain analyses of a r.c. beam and of a frame subjected to chemical attack and mechanical loads are presented
An Orthotropic Fourth-Rank Damage Model for Masonry Structures
No full textAn orthotropic damage model suitable for the modeling of orthotropic material, e.g. masonry, under plane stress conditions is presented. In the proposed formulation the natural axes of the masonry are assumed coincident to the principal axes of the damage parameters. Then in each direction two independent damage parameters are used, one for compression and one for traction, allowing the crack closure effect to be adequately described. The shape of the admissible field is a double pyramid with rectangular base where the inclinations of the faces correspond to the internal friction angle of the material. The field of the damaged stress is obtained as an homothetia of the admissible field. A comparison between numerical and experimental results in masonry shear walls shows that, when a macro-modeling approach can be used, the proposed damage model is able to well predict the behavior of masonry structures
Shear behaviour of r.c. structures analyzed by means of two-parameters damage model
No full textA local isotropic two-parameter scalar model able to simulate the mechanical behavior of quasi-brittle materials, such as concrete, is described. The constitutive law needs the mechanical characteristics and the fracture energy of concrete to be completely addressed. The damage parameters are obtained directly from the value of two equivalent elastic undamaged stresses in order to reduce the computational effort. Due to the two damage parameters, this model is suitable for the study of both static and dynamic problems, involving arbitrarily variable loads. In this work the model was enriched further with the introduction of a shear retention factor that accounts for the friction between the two surfaces of a crack. This new feature assures a real improvement of the damage model, maintaining nevertheless its simplicity and low computing cost and making it suitable for the practical solution of large-scale problems. Several numerical simulations of experimental tests made on reinforced concrete beams, with or without shear reinforcement, failing in shear, have been carried out. The main results from the numerical analyses are described and compared with the experimental ones to demonstrate the effectiveness of the numerical method
Reliability of Reinforced Concrete Structures under Chemical-Physical Attack
No full textBoth the concrete deterioration and steel corrosion are major problems affecting an increasing number of reinforced concrete structures. In this paper an unified approach, based on a coupled damage model, which is able to evaluate the strength reduction and the reliability of the structures is presented. The effects of chemical attack on concrete (e.g. expansive sulphate/chloride reaction) are investigated and considered in the numerical model. Moreover the deterioration of reinforced concrete structure due to reinforcement corrosion is included in the analysis
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