1,720,973 research outputs found
Studying the equilibrium of oval-base pointed masonry domes: the case of Pisa Cathedral
No full textThis paper addresses the equilibrium problem of an oval-base, pointed masonry dome, that of famous Pisa Cathedral. Set within the framework of the safe theorem of limit analysis, the analysis involves searching for compressive-only statically admissible internal actions for the dome under vertical loads by using the concept of 'thrust surface'. According to Heyman's hypotheses, it is assumed that no in-plane tensile stresses can be transmitted within the thrust surface. The equilibrium problem is tackled by finding an explicit solution for the stresses within a suitable collection of thrust surfaces having the shape of ellipsoids, all contained within the dome thickness. The dome intrados and extrados surfaces have been carefully reconstructed by laser scanner survey and approximated by regular surfaces. The analytical expressions used for both the stress field and the intrados and extrados surfaces have enabled determining estimates of the safety level by means of an expressly developed optimisation procedure
Addition and overflow handling in a class of redundant RNS with magnitude index
No full textNota interna IEI-CNR B4-33, Pisa. dicembre 1987
Admissible shell internal forces and safety assessment of masonry domes
No full textThe present paper illustrates a methodology for the safety assessment of masonry domes. The dome is modelled as a thin shell made of a material satisfying Heyman's hypotheses. Based on the static theorem of limit analysis, the method searches for statically admissible distributions of internal forces within the shell, suitably combining membrane forces and bending moments, by solving a convex optimisation problem. The solution is pursued numerically by means of an expressly developed collocation method that enables obtaining the analytical expressions for each internal force component. In its present formulation the method can be applied to domes of any shape, as well as to arbitrary load distributions. After validation against the benchmark case of the spherical dome under its self-weight, the paper illustrates application of the method to the dome of Pisa Cathedral under vertical loads as a first real case study
STATICALLY ADMISSIBLE SHELL INTERNAL FORCES FOR THE STABILITY ANALYSIS OF THE DOME OF PISA CATHEDRAL LOADED BY VERTICAL AND HORIZONTAL LOADS
No full textThe present contribution illustrates some recent results concerning the stability analysis of the oval-based pointed masonry dome of the renowned Pisa Cathedral subjected to both vertical and horizontal loads. The study is aimed at determining lower bounds of the horizontal collapse load by making use of the static theorem of limit analysis. Heyman's hypotheses are adopted, i.e., masonry is assumed to have unlimited compressive strength and zero tensile strength while collapse due to sliding is assumed to be prevented. The structural analysis is carried out by modelling the dome as a thin shell; an ad-hoc solution procedure is enforced which is able to define optimised statically admissible stress fields. The results in terms of stress distribution and safety factor are discussed
Studying a masonry sail vault by Antonio da Sangallo the Elder in the Fortezza Vecchia in Livorno
No full textThe present contribution aims to illustrate some first results obtained from ongoing research on a 16th-century masonry sail vault in the Fortezza Vecchia (the Old Fortress) in Livorno (Italy). A multidisciplinary research is currently ongoing. The information collected by means of geometric surveys and experimental tests are being used as input data for the different analytical and numerical models expressly developed to study the vault’s structural response. The structural analysis has been performed using two analytical models set within the framework of limit analysis. The first considers the vault as a thin shell, and suitable sets of statically admissible stresses are built; the second model is a modern reinterpretation of Durand-Claye’s method for domes. As an additional term of comparison, numerical analyses are carried out by means of FE models. The study is still under development, and a first set of results has been obtained by limiting the analysis to vertical loads accounting for the self-weight of the vault and that of the overlying soil layers
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
- …
