Luca Pelà

Comparison of seismic analysis methods applied to a historical church struck by 2009 L’Aquila earthquake

This paper presents the seismic assessment of a historical church by means of different analysis methods. The church of San Marco, seriously damaged by 2009 L’Aquila earthquake, Italy, is chosen as case-study. The analysis tools adopted and compared are linear and non-linear kinematic analysis, FEM pushover analysis and FEM nonlinear dynamic analysis. The different methods are evaluated regarding their ability to predict the damage and collapse mechanisms actually caused by the earthquake. The accelerograms of the main shock of the 6th April 2009 L’Aquila earthquake are considered for nonlinear dynamic analysis. The influence of relevant construction features, as original disconnection between parts or RC additions, is analysed into detail. Limit analysis is carried out to understand some of the critical collapse mechanisms which are not clearly revealed by FE analysis. The comparison of the analysis methods indicates advantages and limitations of each approach.

Viscoelasticity and Damage Model for Creep Behavior of Historical Masonry Structures

This paper presents a continuum model for the simulation of the viscous effects and the long-term damage ac- cumulation in masonry structures. The rheological model is based on a generalized Maxwell chain representation with a constitutive law utilizing a limited number of internal variables. Thanks to its computational efficiency, this approach is suitable for the analysis of large and complex structures. In the paper, the viscous and damage models are presented and their coupling is discussed. The FE simulation of the construction process of the representative bay of Mallorca Cathedral is presented, together with the analysis of the long-term effects. The parameters of the model are tentatively calibrated on the basis of the time-dependent viscous deformations detected during the cathedral monitoring. detailed. The application of the model to the numerical study of a representative bay of Mallorca Cathedral is discussed. The procedure to identify the parameters that define the vis- cous and damage model, starting from the experimental monitoring activity, is also described. The parameters of the model have been calibrated using a 5-year monitoring pe- riod. In spite of it, the study has mostly a tentative character given the important uncertainties and difficulties involved. One of the main difficulties is found in the estimation of the initial deformation of the structure after construction. In the present study, an attempt towards an estimation of this de- formation is carried out through a sequential analysis involv- ing two construction phases suggested by the historical re- search carried out on the building. The structure shows significant deformation which, ac- cording to previous studies (12), can be related with the combined effects of construction process undergoing delicate intermediate stages, long-term deformation and geometric non-linearity. The research presented aim to explore the vi- ability of a numerical simulation of deformation and damage taking into account these combined effects.

Mechanical Characterization of Historical Masonry by Core Drilling and Testing of Cylindrical Samples

ABSTRACT This article presents an experimental study aimed at the characterization of the mechanical behavior of existing masonry. The research proposes a methodology based on the in situ core drilling of existing masonry members, made of clay brick and low-strength lime mortar. The obtained cylindrical samples, with different diameters, are tested in the laboratory to derive the compression and frictional response of the composite material and the components (units, mortar). This article addresses the main issues related to the extraction of cylindrical specimens: the testing and the interpretation of results. The proposed minor destructive technique is suitable for existing masonry structures and especially for those of the built cultural heritage, since a direct estimation of the mechanical parameters can be obtained without damaging excessively the historical structure.

Review of Different Pushover Analysis Methods Applied to Masonry Buildings and Comparison with Nonlinear Dynamic Analysis

This article presents the comparison among different nonlinear seismic analysis methods applied to masonry buildings, i.e., pushover analyses with invariant lateral force distributions, adaptive pushover analysis and nonlinear dynamic analysis. The study focuses on the influence of lateral force distribution on the results of the pushover analysis. Two simple benchmark case studies are considered for the purpose of the research, i.e., a four-wall masonry building prototype without floor rigid diaphragms and a two-wall system with a cross-vault. The comparative study offers a useful review of pushover analysis methods for masonry structures and shows advantages and possible limitations of each approach.

Analysis of the Effect of Provisional Ties on the Construction and Current Deformation of Mallorca Cathedral

ABSTRACT This article presents the analysis of the structure of Mallorca Cathedral taking into account the influence on the structural behavior of auxiliary iron ties used during the construction process. Recent studies (Roca et al. 2012, 2013) presented some hypotheses about the construction process of the cathedral. This article complements the previous results by considering the use of auxiliary ties as temporary stabilizing device during the construction. Evidence of the use of ties during the construction has been recognized after a comprehensive survey. The study of the role of such ties and the effect of their later removal are studied by a FE analysis carried out on a representative bay of the structure. The study includes a time-dependent FE analysis after the removal of the ties to assess the long-term structural behavior. The results of the numerical analysis are compared with the deformation trends identified by means of a recent monitoring campaign.

Seismic Risk Assessment and Mitigation at Emergency Limit Condition of Historical Buildings along Strategic Urban Roadways. Application to the “Antiga Esquerra de L’Eixample” Neighborhood of Barcelona

ABSTRACT This article presents a management tool for the large-scale assessment and mitigation of the seismic risk of urban systems. The research introduces a new perspective for a scientifically tackled holistic approach. The proposed methodology considers multiple objectives, from the identification of the most vulnerable buildings whose collapse may hinder the operationality of strategic urban roadways after the occurrence of an earthquake, up to the proposal of proper interventions to improve their functionality. The approach uses a performance-based approach founded on the concept of urban Emergency Limit Condition. Plotting maps of geo-referenced scenarios by means of GIS software have revealed to be extremely useful to detect the weak points of the urban network and to plan suitable strategies of seismic risk mitigation and appropriate enhancement of reliability. The proposed methodology is applied to the “Antiga Esquerra de l’Eixample” neighborhood of Barcelona that hosts the strategic route to the hospital and is characterized by high levels of seismic vulnerability of existing buildings and exposition of its high-density population.

Combined In-Situ and Laboratory Minor Destructive Testing of Historical Mortars

ABSTRACT Mortar is of all masonry components the most difficult to be experimentally characterized in heritage buildings. This article investigates the possibility of combining different in-situ and laboratory minor destructive testing (MDT) techniques to assess the strength of mortar in historical brickwork. Lime mortar and clay brick walls were built in the laboratory and then tested in order to derive empirical correlation rules among three different MDT techniques: double punch test (DPT), helix pull-out test (HPT), and pin penetration test (PPT). The outcomes of this activity were used eventually to assess the mortar properties of an important historical heritage structure, Casa Puig i Cadafalch, located near Barcelona. The research is intended to promote the use of MDT in studies and conservation works on built cultural heritage by providing criteria for the evaluation of the strength of existing mortar with respectful sampling and testing techniques.

An Enhanced Finite Element Macro-Model for the Realistic Simulation of Localized Cracks in Masonry Structures: A Large-Scale Application

ABSTRACT Finite element macro-modeling approaches are widely used for the analysis of large-scale masonry structures. Despite their efficiency, they still face two important challenges: the realistic representation of damage and a reasonable independency of the numerical results to the used discretization. In this work, the classical smeared crack approach is enhanced with a crack-tracking algorithm, originating from the analysis of localized cracking in quasi-brittle materials. The proposed algorithm is for the first time applied to a large-scale wall exhibiting multiple shear and flexural cracking. Discussion covers structural aspects, as the response of the structure under different assumptions regarding the floor rigidity, but also numerical issues, commonly overlooked in the simulation of large structures, such the mesh-dependency of the numerical results.

Seismic Assessment of the Milano Centrale Railway Station

This study of the Milano Centrale railway station aimed at assessing the seismic vulnerability of the monumental building. The work was carried out on the occasion of a big project to refurbish the station, including both the restoration of certain areas of high artistic value and the improvement of functionality with the current railway services. The seismic analysis is focused on the monumental part of the building, including the Coaches Gallery, the Tickets Hall, and the Head Gallery. The safety level of the structure was assessed on the basis of comprehensive historical investigation, survey, testing, and finite element analysis. The issue of checking the seismic safety of a large number of members is addressed using a step-by-step verification strategy. The results of the study show that the overall safety level of the structure is acceptable, although some local structural deficiencies need to be handled with a proper strengthening design.

Building survey forms for heterogeneous urban areas in seismically hazardous zones. Application to the historical center of Valparaíso, Chile

ABSTRACT Building survey is an essential data-collection procedure to feed large-scale seismic vulnerability assessment. The available strategies usually consider survey forms to gather information about the urban buildings. The application of the available survey forms poses important challenges for the case of the heterogeneous urban centers including different structural typologies. This work proposes four specific survey forms for traditional structural typologies constructed with masonry, reinforced concrete, mixed steel-reinforced concrete, and timber. The proposed forms request essential information on the parameters necessary for seismic vulnerability assessment, by evaluating the lateral-load resistant system, regularity, condition of conservation, and existing damages. The survey forms were applied to the study of 111 buildings of the historical center of Valparaíso, Chile. The proposed methodology was complemented with the use of Geographic Information Systems to obtain a complete database with the structural characterization of the most representative typologies for future works of large-scale seismic vulnerability assessment.