Modelo numérico y verificación experimental del comportamiento en servicio de estructuras de hormigón

Abstract

A model for the non-linear analysis under serviceability conditions of plane concrete frames (suitable for composite concrete - steel structures) taking into account segmental construction has been developed. The model is based in an extension of the classical matrix theory for the analysis of frames (Generalized Matrix Formulation - GMF). The contribution of the tensioned concrete between cracks (tension stiffening) is simulated by a modified constitutive law for concrete in tension. A detailed study of the model for both instantaneous and long - time behavior has been performed, and a proposal to determine the coefficients defining the uniaxial tensioned concrete constitutive relationship from sectional characteristics is presented. Segmental construction (sectional and structural), load history and temporal changing in material properties are considered in the model. The generality of the proposal allows simulating the materials time - dependent behavior using several formulations. In future development, non - linear constitutive laws for the steel and for the compressed concrete will be incorporated. The model has been able to adequately reproduce the results obtained from analytical procedures, other models and from experiments available in benchmarks. Likewise good agreement has been obtained with results from specific tests carried out for this work. An objective of the thesis was to develop a scaled - up model suitable to analyze structures with many elements and with diverse construction processes. The examples included show it as well as the possibility to make parametrical studies to analyze the influence of several variables. The experimental part of the work has consisted in the construction, instrumentation and testing of a two - span continuous reinforced concrete beam with concentrated loads at the center of each span. Three phases can be distinguished: loading until serviceability conditions, unloading and strengthening and, finally, loading until collapse. Strengthening consists in bonded steel plates using epoxy resins. The installed instrumentation and the manual measurements have allowed registering the variation of stresses, strains and displacements. The results have showed a good agreement with those obtained from the numerical model.