Simplified Modeling of Rectangular Concrete Cross-Sections Confined by External FRP Wrapping

The goal of this research project is to model the effect of confinement by means of fiber reinforced polymer (FRP) externally bonded wrapping, hence to provide a simplified closed form solution to determine directly the ultimate confined concrete strength. Common cross-section shapes for reinforced concrete (RC) columns are considered herein, namely square and rectangular. The simplified model is derived from a more refined iterative confinement model proposed by the same authors to evaluate the entire stress-strain relationship of confined concrete. Based on a detailed analysis of the stress state through Mohr's circle, a simplified closed form solution is proposed to account for the non-uniformly confined concrete performance exhibited in non-axisymmetric sections. The non-uniform confining stress field exhibited in such cross-sections is explicitly considered by means of the mean value integral of the pointwise variable stress state over the cross-section. The key aspect of the proposed methodology is the evaluation of the effective equivalent pressure to be inserted in any triaxial confinement model, to account for the peculiarities of square and rectangular cross-sections. Experimental data, available in the literature and representative of a wide stock of applications, were compared to the results of the theoretical simplified model to validate the proposed approach, and satisfactory results were found

Comparison of Two Parameters Models for clay brick masonry confinement

Masonry elements are often strengthened in order to improve their structural capacity. Generalized methods to assess the behavior of confined masonry columns are not available in the technical literature. They have been usually derived from concrete confinement models. However, concrete and masonry present several crucial differences due to their physical and mechanical properties. In fact, generalized models to assess the axial capacity of masonry columns were limited by the strong variability and heterogeneity of physical and mechanical properties. However, the recent scientific researches provided relevant information on the experimental behavior of confined masonry columns. In this paper, a confinement model has been proposed to assess the axial capacity of clay brick masonry strengthened using several strengthening systems. The model has been validated by means of comparisons with experimental results. In order to assess the potential of the proposed model, the comparison was carried out also with other available mechanical models

RC deck - stiffened arch existing bridges: simulated design and structural analysis

The 20th century is known as the age that gave birth to the largest reinforced concrete structures. Many applications of this new material were realized at that time, both from a theoretical and practical point of view. With reference to bridges, the engineer Robert Maillart achieved a new concept of arched bridges, characterized by very stiff deck beams and slender and wide vaults, i.e., the "Deck-Stiffened Arch". The paper deals with the study of such bridge typology, particularly widespread in Italy around the 50s of the 20th century. While, nowadays, calculation tools allow developing very refined structural modelling, in the past very simple structural schemes were adopted in the design phase in order to simplify the calculation effort. The study starts from a "simulated design" of such a bridge typology adopting a reliable geometry and following the design rules and the simplified structural schemes of the time and, then, by means of a refined three-dimensional model, the performance of a typical "Maillart-Type Arch" bridge is analysed

Masonry walls retrofitted with natural fibers under tsunami loads

AbstractIn the last decades, several tsunamis hit international coasts and engaged scientific awareness to the retrofit of coastal buildings against tsunami loads. Structural design under tsunami loads is difficult due to the high uncertainties of the phenomenon. Local collapse mechanisms of masonry walls, like as out of plane mechanisms, have an high probability due to flexural actions; a higher flexural capacity can be reached using specific retrofit systems; in particular, this paper aims to deepen the behavior of masonry walls retrofitted with innovative retrofit systems like as natural fibers applied with inorganic mortar matrices. The retrofit of structures under tsunami actions could be an innovative research topic for international research community dealing with coastal buildings located in areas characterized by a high tsunami risk. Recent engineering applications demonstrated the innovative strengthening systems to be effective for the retrofit of existing masonry buildings. These strengthening systems are of great interest in the practical applications due to the low costs and their sustainability. In fact, the lower costs compared to the synthetic fibers allow their diffusion in emerging countries. In a first part the impact of constituents on the structural capacity of masonry elements strengthened with natural systems has been discussed. Important results have been provided in order to improve the knowledge and encourage the development of these systems in many engineering applications. Finally, the effects of retrofit systems on masonry walls under tsunami loads will be discussed in terms of critical inundation depth variations before and after the interventions

Repair of composite-to-masonry bond using flexible matrix

The paper presents an experimental investigation on an innovative repair method, in which composite reinforcements, after debonding, are re-bonded to the substrate using a highly deformable polymer. In order to assess the effectiveness of this solution, shear bond tests were carried out on brick and masonry substrates within two Round Robin Test series organized within the RILEM TC 250-CSM: Composites for Sustainable strengthening of Masonry. Five laboratories from Italy, Poland and Portugal were involved. The shear bond performance of the reinforcement systems before and after repair were compared in terms of ultimate loads, load-displacement curves and strain distributions. The results showed that the proposed repair method may provide higher strength and ductility than stiff epoxy resins, making it an effective and cost efficient technique for several perspective structural applications

Shake‑table testing of a stone masonry building aggregate: overview of blind prediction study

City centres of Europe are often composed of unreinforced masonry structural aggregates, whose seismic response is challenging to predict. To advance the state of the art on the seismic response of these aggregates, the Adjacent Interacting Masonry Structures (AIMS) subproject from Horizon 2020 project Seismology and Earthquake Engineering Research Infrastructure Alliance for Europe (SERA) provides shake-table test data of a two-unit, double-leaf stone masonry aggregate subjected to two horizontal components of dynamic excitation. A blind prediction was organized with participants from academia and industry to test modelling approaches and assumptions and to learn about the extent of uncertainty in modelling for such masonry aggregates. The participants were provided with the full set of material and geometrical data, construction details and original seismic input and asked to predict prior to the test the expected seismic response in terms of damage mechanisms, base-shear forces, and roof displacements. The modelling approaches used differ significantly in the level of detail and the modelling assumptions. This paper provides an overview of the adopted modelling approaches and their subsequent predictions. It further discusses the range of assumptions made when modelling masonry walls, floors and connections, and aims at discovering how the common solutions regarding modelling masonry in general, and masonry aggregates in particular, affect the results. The results are evaluated both in terms of damage mechanisms, base shear forces, displacements and interface openings in both directions, and then compared with the experimental results. The modelling approaches featuring Discrete Element Method (DEM) led to the best predictions in terms of displacements, while a submission using rigid block limit analysis led to the best prediction in terms of damage mechanisms. Large coefficients of variation of predicted displacements and general underestimation of displacements in comparison with experimental results, except for DEM models, highlight the need for further consensus building on suitable modelling assumptions for such masonry aggregates

Il comportamento degli aggregati in muratura

Il comportamento degli aggregati in muratur

Il rinforzo di volte con materiali compositi e validazione sperimentale mediante tavola vibrante

Il rinforzo di volte con materiali compositi e validazione sperimentale mediante tavola vibrant