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 assessment of an existing RC framed structure: a case study on a collapsed building

The total collapse of a building in L’Aquila, Via D’Annunzio (D’Annunzio Street), located at about 6 km from the epicenter of the earthquake of April 6 2009, is here analyzed. The reinforced concrete moment-resisting frames were designed in the 1961 according to the Italian Seismic Code of 1937, and failed with a “pancake-type collapse”, with a very high death toll of 13 casualties. At the beginning of 2013, the first Author was appointed by the legal authority to investigate the reasons for the collapse. Studies were partly based on the on-site investigations performed during the summer 2009, including tests on the concrete properties, analysis of the ground properties and exam of parts of the collapsed structure recovered from the debris. Due to the lack of a complete set of design blueprints, the dimensions and positions of the columns, as well as the geometry of the reinforcement, were obtained by an on-site series of measurements during 2013. The range of variation of natural periods and modal shapes depending on the modeling assumptions have been determined through numerical analyses. The seismic excitation at the site, determined from the earthquake records and the ground properties coming from down-hole tests, has been provided in terms of time history and response spectrum. When all the factors affecting the seismic behavior are taken into account, the collapse of the building can be explained; the collapse mechanism resembles the modal shape of the first mode. The flaws of the original design, brought to light with this study, can be assumed as typical for the design time and provide clear indications on the critical points to be checked when assessing an RC frame of the sixties

A study of the apse of the cathedral of Milan

The Apse is the most ancient part of Milan's cathedral, which originated in 1386 and presents a complex geometry. According to measurements made since 1960, consulted in the archives of the Veneranda Fabbrica del Duomo, the outer buttresses display an out of plumb of east buttresses. Therefore a first analysis of the structural response and state of conservation of the structure in relation to its construction configuration has been carried out. The static approach of limit analysis is used, providing synthetic results. A geometric model was set up based on the available survey drawings. The loads of each structural element were calculated as the first step for analysis of the internal forces. For the semi-dome above the choir, the membrane theory is used, adapting it to the existing geometry. The double exterior and interior vaulting system is analyzed, highlighting its role in the global structural response. The relevant role of the Lombard buttressing system [20] is analyzed, with radial and circumferential walls, bearing on piers and buttresses. Foundation structures were considered too, and the stability of the structure was verified. The comparison between the results obtained by limit analysis and the experimental observations of the damage, shows a correct geometric and structural conception, historically challenged by external factors, mainly soil subsidence, causing structural deformation and damage. The study shows the effectiveness of the analytical method in three-dimensional statics, under simplifying hypotheses