Climent Molins i Borrell

Micro-mechanical modeling of masonry: parametric study

Masonry structures, usually being composed of a repeating geometric pattern, lend themselves well to analysis using periodic unit cells. Based on stress and strain equilibriums and rational assumptions concerning the interaction of the components of the cell, one may propose micro-mechanical models using simple analytical expressions which simulate well the behavior of masonry. Models describing the nonlinear behavior of masonry constituent materials may be implemented in such models and used to simulate the failure modes anticipated to arise in the composite. In this way, the nonlinear behavior of masonry composites may be derived, as defined by the interaction of its two main material phas-es: units and mortar. Taking advantage of the low computational cost of models based on analytical expres-sions, which is only a fraction of those based on finite element simulations, wide and in-depth parametric analyses can be performed with ease. In this paper, a model for the nonlinear behavior of masonry is presented and used in a parametric study, investigating the influence of various material properties on its compressive strength. The results indicate a strong dependence of the compressive strength of masonry on material parameters that are difficult to measure accurately or are often ignored, particularly in existing and historic masonry structures.

Experimental and analytical study of the structural response of segmental tunnel linings based on an in situ loading test: part 1: test configuration and execution

During the last years the use of segmental linings in tunnels bored with tunnel boring machines (TBMs) have increased considerably. Despite this, uncertainties remain on the structural behavior of segmental tunnel linings. To overcome them, a new methodology for an in situ real scale test on this kind of tunnels was developed and applied on an experimental section placed at the new Line 9 (L9) of the metro of Barcelona. nThe main particularity of this test falls on its performance in the definitive placement of the rings and, therefore, in the real work conditions of the tunnel. The main advantage to previous real scale test nexperiences was the consideration of the real ground–structure interaction. The experimental section was composed by 15 rings built using steel fibers as a unique reinforcement. Significant loads were applied to the tunnel crown (max 3000 kN) by means of three hydraulic flat jacks embedded at the extrados of the loaded ring. A complete set of internal and external instrumentation was placed on the experimental section to obtain the necessary measurements to characterize the lining behavior. Such measurements were intensively treated and its main results are presented and analyzed in detail in this paper. This in situ test provides significant evidences of the structural response of SFRC segmental tunnel linings in hard ground conditions.