Giovanni Castellazzi

From Laser Scanning to Finite Element Analysis of Complex Buildings by Using a Semi-Automatic Procedure

In this paper, a new semi-automatic procedure to transform three-dimensional point clouds of complex objects to three-dimensional finite element models is presented and validated. The procedure conceives of the point cloud as a stacking of point sections. The complexity of the clouds is arbitrary, since the procedure is designed for terrestrial laser scanner surveys applied to buildings with irregular geometry, such as historical buildings. The procedure aims at solving the problems connected to the generation of finite element models of these complex structures by constructing a fine discretized geometry with a reduced amount of time and ready to be used with structural analysis. If the starting clouds represent the inner and outer surfaces of the structure, the resulting finite element model will accurately capture the whole three-dimensional structure, producing a complex solid made by voxel elements. A comparison analysis with a CAD-based model is carried out on a historical building damaged by a seismic event. The results indicate that the proposed procedure is effective and obtains comparable models in a shorter time, with an increased level of automation.

Seismic Vulnerability Assessment of a Historical Church: Limit Analysis and Nonlinear Finite Element Analysis

The seismic vulnerability of a historical Basilica church located in Italy is studied by means of limit analysis and nonlinear finite element (FE) analysis. Attention is posed to the failure mechanisms involving the facade of the church and its interaction with the lateral walls. In particular, the limit analysis and the nonlinear FE analysis provide an estimate of the load collapse multiplier of the failure mechanisms. Results obtained from both approaches are in agreement and can support the selection of possible retrofitting measures to decrease the vulnerability of the church under seismic loads.

Numerical insights on the seismic behavior of a non-isolated historical masonry tower

In this paper, numerical insights on the seismic behavior of a non-isolated historical masonry tower are presented and discussed. The tower under study is the main tower of the fortress of San Felice sul Panaro, a town located near the city of Modena (Italy). Such a tower is surrounded by adjacent structural elements and, therefore, is not isolated. This historical monument has been hit by the devastating seismic sequence occurred in May 2012 in the Northern part of the Emilia region (the so-called “Emilia earthquake”), showing a huge and widespread damage. Here, in order to understand the behavior of the structure, its interaction with the adjacent buildings and the reasons of the occurred damage, advanced numerical analyses (both nonlinear static and dynamic) are performed on a 3D finite element model with different levels of constraint supplied by the adjacent structural elements and a detailed comparison between the simulated damage and the actual one is carried out. The results of the conducted numerical campaign show a good agreement with the actual crack pattern, particularly for the model of the tower that considers the adjacent structural elements.

Prediction of stress waves propagation in progressively loaded seven wire strands

High tensile strength steel strands are widespread load carrying structural components in civil structures. Due to their critical role, several researchers have investigated nondestructive techniques to assess the presence of damage such as corrosion or the change in prestress level (prestress loss). Ultrasonic Guided Waves are known to be an effective approach for defect detection in components with waveguide geometry such as strands. However, Guided Wave propagation (dispersion properties) in steel strands is fairly complex partially due to the strand helical geometry and the influence of axial prestress. For instance, the strand axial stress generates a proportional radial stress between adjacent wires (interwire stress) that is responsible for inter-wire coupling effects. While experimental and numerical investigations have attempted to study and predict wave propagation in axially loaded strands, the propagation phenomenon is not yet fully understood. The present paper intends to improve the knowledge of dispersion properties in progressively loaded seven wire strands accounting for helical geometry and interwire contact forces. Full three dimensional Finite Element simulations as well as Semi-Analytical Models will be used to predict the dispersion curves in strands as a function of the axial stress.

A MESH GENERATION METHOD FOR HISTORICAL MONUMENTAL BUILDINGS: AN INNOVATIVE APPROACH

The numerical modeling of historical monumental buildings is a challenging task for contemporary civil engineers. One of the main reasons for this is that the use of traditional simplified structural schemes is inadequate due to the complex geometry of such historical structures. Therefore, it is necessary to resort to a fully 3D modeling technique that is performed using Computer Aided Design (CAD). In general, CAD-based modeling is an expensive and complex process and it is often performed manually by the user, which inevitably leads to the introduction of geometric simplifications or interpretations. In this study, an innovative mesh generation approach for the structural analysis of historical monumental buildings is presented. The method consists in a peculiar breakdown of the geometry starting from laser scanner or photogrammetric surveys. Moreover, this new approach involves a structural discretization that guarantees the generation of 3D finite element meshes as well as their mechanical characterization. The most relevant feature of the proposed method is the possibility to directly exploit 3D and detailed point clouds surveyed on historical buildings for structural purposes. As a result, a large reduction in the required time in comparison to CAD-based modeling procedures is achieved. A geometrical and structural validation of the method is carried out on a masonry tower application. The findings show good reliability and effectiveness of the mesh generation approach.

On the seismic behavior of the main tower of the San Felice sul Panaro (Italy) fortress

The medieval fortresses are a very common and distinctive type among the Emilian historical constructions and the earthquakes of May 20th and 29th, 2012 underlined their high vulnerability. Among those heavily damaged, there is the fortress of San Felice sul Panaro located between the two epicenters. This study presents some FE results regarding the behavior under seismic actions of the main tower (Mastio tower). The Mastio has peculiar geometric features and represents a typical example of non-isolated tower. In fact, it is constrained in very different ways by the surrounding parts of the fortress along two of its sides: on the north side it is constrained by the perimeter wall until one third of his high, while a stiffer building constrains it on the west side. In order to remodel the entire fortress, a multidisciplinary project involving the Municipality of San Felice sul Panaro and four Universities of the Emilia- Romagna (Bologna, Ferrara, Parma and Modena) together with the University of Genoa is g...

Computation of leaky guided waves dispersion spectrum using vibroacoustic analyses and the Matrix Pencil Method: a validation study for immersed rectangular waveguides.

The paper aims at validating a recently proposed Semi Analytical Finite Element (SAFE) formulation coupled with a 2.5D Boundary Element Method (2.5D BEM) for the extraction of dispersion data in immersed waveguides of generic cross-section. To this end, three-dimensional vibroacoustic analyses are carried out on two waveguides of square and rectangular cross-section immersed in water using the commercial Finite Element software Abaqus/Explicit. Real wavenumber and attenuation dispersive data are extracted by means of a modified Matrix Pencil Method. It is demonstrated that the results obtained using the two techniques are in very good agreement.

Finite Element Modelling Tuned on Experimental Testing for the Structural Health Assessment of an Ancient Masonry Arch Bridge

This paper presents the structural health assessment of a railway ancient masonry arch bridge located in Bologna, Italy. A three-dimensional finite element model of the entire bridge, tuned on in situ experimental tests, has been used for the assessment. In particular, the finite element model has been employed to evaluate the structural health of the bridge both in its actual state and in the hypothesis of a structural strengthening intervention.

Assessment of the Effect of Natural and Anthropogenic Aquatic Noise on Vaquita (Phocoena sinus) Through a Numerical Simulation

Phocoena sinus (vaquita) is a small marine harbor porpoise endemic to the Gulf of California that is believed to be the most endangered cetacean in the world as reported by the International Union for Conservation of Nature (IUCN) red list (see Rojas-Bracho et al. 2008). Simultaneous use of the same habitat by fishermen and Phocoena sinus has led to the precipitous decline of the porpoise. Phocoena sinus is easily entangled in fishing nets, resulting in drowning.

SEISMIC ASSESSMENT OF COMPLEX ASSETS THROUGH NONLINEAR STATIC ANALYSES: THE FORTRESS IN SAN FELICE SUL PANARO HIT BY THE 2012 EARTHQUAKE IN ITALY

!This!paper!proposes!a!procedure!for!the!seismic!assessment!of!unreinforced!ma2 sonry! complex! structures! together!with! a! first! application! to! the! case! of! fortresses.! The! proposal!of!such!procedure!arises!from!different!reasons:!firstly,!Standards!suggest!proce2 dures!mainly!addressed!to!ordinary!structures;!furthermore,!even!those!Recommendations,! which!are!more!specifically!addressed!to!monumental!assets,!state!only!general!principles,! without!specifying!operational!targeted2procedure!for!their!seismic!assessment.!The!dam2 age!occurred!after!past!earthquakes,!and!in!particular!the!one!hit!the!Emilia!region!in!Italy,! highlighted! that! fortresses! are! characterized! by! an! aggregation! of! bodies! with! an! own! seismic!behavior!which,!however,! is!strongly!affected!by!their!dynamic! interaction!due!to! the! mutual! boundary! conditions.! Hence,! the! adoption! of! a! numerical! three2dimensional! model!of!the!whole!structure!is!necessary!to!take!into!account!explicitly!the!effect!of!such! interactions.! The! proposed! procedure! requires! the! execution! of! a! modal! analysis! of! the! whole!structure!in!order!to!define!the!modes!involving!the!dynamic!response!of!each!units! and!their!modal!shapes.!Then,!fitting!the!modal!shapes,!proper!load!patterns!are!defined!to! pass! to! the! execution!of!pushover!analyses.! In!particular,! one! load!pattern! is!applied! for! each!unit!but!considering!the!whole!numerical!model.!The!pushover!curve!of!each!unit! is! then! converted! in! the! capacity! curve! to! finalize! the! seismic! assessment! and! verification.! The!proposed!procedure!is!applied!in!the!paper!to!the!case2study!of!San!Felice!sul!Panaro! fortress,!significantly!hit!by!the!Emilia!earthquake,!2012!allowing!the!comparison!between! the!occurred!damage!and!the!one!simulated!by!the!nonlinear!static!analyses!and!to!vali2 date!the!procedure.!The!potentialities!of!the!proposed!procedure!seem!relevant!in!order!to! provide!a!reliable!seismic!assessment!also!of!other!typology!of!complex!structures.! Available online at www.eccomasproceedia.org Eccomas Proceedia COMPDYN (2017) 2291-2300