Testing low strength concrete of collapsed frame buildings

Within the scope of measurement of in-situ material properties, the paper presents results of two studies carried out by the Authors for forensic investigations of concrete properties in existing reinforced concrete frame structures collapsed during the 2009 Aquila earthquake. The two edifices were built in the 1960s; the results provide data on low-strength material property measurement. Cores were extracted: 53 specimens in two series for the first building and 16 in the second. Compression tests were carried out following EN12390-3, providing data on density, compression strength and ultrasound velocity. Non-Destructive Testing with SONREB measurements were also carried out in the first building. The test results are analyzed and discussed in relation to the design documents and the Italian code specifications at the time of the design of the building. The conclusions show that the concrete quality was very poor in relation to low quality construction practices

The structural life of a Cathedral and the worksites of the Duomo di Milano

The life of Milan Cathedral is described with the evolution of the structural system and the restorations carried out throughout the centuries. The organization of the Veneranda Fabbrica del Duomo di Milano is outlined, with the latest restoration interventions. The case study of the construction and restorations of the Tiburio with its supporting pillars is analyzed, from the initial design to the dramatic damage in the 20th century. The rebirth of the Cathedral was the fruit of restorations preserving the structural identity of the monument up to the present. The conclusions address the study of damage and maintenance and repair operations of mon-umental heritage buildings within a life cycle perspective, in relation to the underlying socie-tal values

DIGITAL MODELLING AND ANALYSIS OF MASONRY VAULTS

The focus of this paper is to discuss the peculiarities of the digital modelling of masonry cross vaults. The proposed methodological approach for a multidisciplinary study of masonry vaults will be focused on: geometrical survey, crack pattern, geometrical modelling, and safety assessment based on structural analysis.Automatic reconstruction procedures recently proposed in the literature for ribbed masonry vaults, are used to overcome time-consuming modelling tasks. The created digital models take into consideration the different aspects of the three-dimensional geometry, the internal divisions with variations of material properties in different parts, and a suitable discretization for finite element analysis. Moreover, the same model can be used in BIM (Building Information Modelling), judged as a suitable environment in which to combine different aspects of the restoration works such as: documentation, intervention design, and the data system in an unique model. The same model is then used to perform finite element analysis. Each of these aspects is clarified with examples of different vaults typology coming from case studies as that of the church of St. Bassiano in Pizzighettone (Cremona) or the notable Milan Cathedral.</p

INTEGRATED APPROACH COMBINING DIRECT SURVEY AND OBSERVATION IN DAMAGE ANALYSIS IN CASE OF SOIL SETTLEMENT

Nowadays, different methods are used to study historical masonry buildings. Among these, for the study of architectures with complex geometry, the effectiveness of an integrated approach, that is a method of analysis combining different disciplines, is increasingly evident.The aim of this paper is to show the importance of combining direct observation with structural analysis in order to understand the level of safety in buildings with composite geometries.This paper describes the analysis executed in the XX century parish church of San Bernardino in Sesto Calende (Va), which displays serious cracks and damage caused by soil settlements.The integrated approach starts with historical analysis, by consulting all available documents and drawings. To understand the geometry of the structure a new survey has been made and a three-dimensional digital representation was modeled, by which better deriving the weight of all the elements in the construction, and to find the correct actions and thrust on arches, columns, bases and foundation. All this data was used in the structural analysis based on the static method of limit analysis. For the material behavior the model proposed by J. Heyman (1966) is used, considering the “no tension” failure criterion. The static theorem of minimum reactions for settled states enunciated by M. Como (2010) is employed for the analysis of soil settlement effects on the building’s response.The work shows how direct survey of geometry and damage of a complex building has an effective importance in the structural analysis to ensure Cultural Heritage preservation and safety.</p

The technical causes of the collapse of Annone overpass on SS.36

The paper presents the technical causes of the collapse of Annone overpass, which occurred in October 2016. The tests carried out to identify the characteristics of the materials used for the construction, the verification calculations that led to the identification of the critical mechanism in the collapse and the test on the structural element deemed critical at the time of collapse are summarized. The paper highlights the critical issues occurring concurrently with the passage of the exceptional transports, the safety coefficient in relation to the project loads at the time of construction and that at the time of the passage of the exceptional convoy. The note also highlights some critical aspects of the national infrastructural system, with particular reference to exceptional transports and the methods that could be used to prevent future accidents in the absence of macro-design mistake

Analytical model for residual bond strength of corroded reinforcement in concrete structures

Bond strength deterioration in corrosion-damaged reinforced concrete structures significantly affects serviceability and load-carrying capacity in their remaining service life. This paper presents a new analytical model for predicting the cracking development in the surrounding concrete and the residual bond strength of rebar in concrete structures due to reinforcement corrosion. The proposed analytical method adopts the thick-walled cylinder model for the cover concrete and considers the realistic properties of the corrosion-induced cracked concrete such as anisotropic behavior, residual tensile strength, and reduced tensile stiffness. As corrosion progresses, three phases for bond strength evolution associated with concrete cracking development are defined and the corresponding corrosion levels in each phase are determined. By using the constructed new governing equation, the crack width growth in the concrete cover and the radial bursting pressure at the bond interface are evaluated. The ultimate bond strength is then estimated from the contributions of adhesion, confinement, and corrosion pressure as a function of corrosion level. Finally, the effectiveness of the proposed analytical model is demonstrated by comparing the predicted results with experimental data available, and the results show that the proposed model is useful for predicting the bond strength evolution of the corroded rebar in concrete structures