Parisi, Fulvio
(2010)
NonLinear Seismic Analysis of Masonry Buildings.
[Tesi di dottorato]
(Unpublished)
Item Type: 
Tesi di dottorato

Language: 
English 
Title: 
NonLinear Seismic Analysis of Masonry Buildings 
Creators: 
Creators  Email 

Parisi, Fulvio  fulvio.parisi@unina.it 

Date: 
30 November 2010 
Number of Pages: 
335 
Institution: 
Università degli Studi di Napoli Federico II 
Department: 
Scienze fisiche 
Doctoral School: 
Scienze fisiche 
PHD name: 
Rischio sismico 
PHD cycle: 
23 
PHD Coordinator: 
name  email 

Zollo, Aldo  aldo.zollo@unina.it 

Tutor: 
name  email 

Augenti, Nicola  augenti@unina.it 

Date: 
30 November 2010 
Number of Pages: 
335 
Uncontrolled Keywords: 
Masonry Buildings, NonLinear Seismic Response, Spread Plasticity MacroElements, Static Pushover Analysis. 
MIUR S.S.D.: 
Area 08  Ingegneria civile e Architettura > ICAR/09  Tecnica delle costruzioni 
Date Deposited: 
13 Dec 2010 17:39 
Last Modified: 
30 Apr 2014 19:46 
URI: 
http://www.fedoa.unina.it/id/eprint/8417 
DOI: 
10.6092/UNINA/FEDOA/8417 
Abstract
Nonlinear analysis is the most viable tool to get accurate predictions of the actual response of masonry structures under earthquake loading. Analytical methods based on the idealisation of masonry walls with openings as systems of macroelements allow not only to capture the main failure modes observed after past earthquakes, but also to ensure a limited computational demand in engineering practice.
The present thesis deals with nonlinear incremental static (pushover) analysis on masonry buildings modelled through evolutionary spread plasticity macroelements.
In the first part of the work, fundamentals of structural analysis, seismic risk, and performancebased seismic design are reviewed along with nonlinear static procedures and macroelement methods for seismic analysis of masonry buildings.
The second part of the work deals with theoretical advances in nonlinear seismic analysis of masonry buildings. In particular, an evolutionary spread plasticity macroelement has been developed and static pushover procedures for individual masonry walls, as well as entire buildings, are presented and discussed in detail.
The proposed macroelement has been defined as ‘evolutionary’ because its inner reacting domain changes as the lateral drift demand increases. Such an evolution is caused by the spreading of cracking and yielding within the masonry. Namely, tensile cracking of masonry induces significant reductions in the effective width of crosssections, which then depends on the magnitude of the given lateral drift (geometrical nonlinearity). Yielding of masonry develops near the extreme parts of the macroelement, which are subjected to maximum bending moment. Mechanical nonlinearity of masonry in compression is also taken into account through a deformationbased approach. In fact, the mechanical behaviour of the macroelement is characterised for different constitutive laws of masonry, by means of (1) two and threedimensional flexural strength domains (to be coupled with classical strength domains), (2) momentcurvature relationships, and (3) forcedisplacement diagrams.
Twodimensional strength domains derived from strength degrading constitutive models allow to account for more real characteristics of masonry. The comparison between flexural strength domains corresponding to different constitutive models have shown that current simplified formulas lead to higher values of ultimate shear force and bending moment, if the given axial force is not significantly higher than onehalf of the allowable axial force. The implementation of full nonlinear stressstrain relationships (which have been obtained by recent uniaxial compression tests in the direction orthogonal to mortar bed joints of masonry) has been found to provide more conservative estimations of ultimate shear force corresponding to flexural failure of macroelements (i.e., toe crushing). Flexural strength domains have been defined at cracking, elastic, and ultimate limit states of masonry crosssections and panels, in both cracked and uncracked conditions. The explicit consideration of strain ductility of masonry has allowed to assess the evolution in strength domains. In this regard, less significant variations in both ultimate shear force and bending moment have been detected for a given axial force lower than onefourth of the allowable axial force. Finally, flexural strength of macroelements has been also investigated for any boundary condition through the development of threedimensional strength domains corresponding to elastic and ultimate limit states, in both cracked and uncracked conditions.
Momentcurvature relationships have been defined for rectangular unreinforced masonry crosssections by means of an incremental iterative procedure. Their development has allowed to assess key parameters of sectional behaviour, such as flexural overstrength, strength degradation due to strain softening of masonry, yielding and ultimate curvatures, and curvature ductility. Such parameters have been estimated for a number of constitutive laws and the relationship between curvature and strain ductilities has been also investigated. The implementation of empirical stressstrain relationships presented in the first appendix of this thesis has let to derive momentcurvature relationships where both yielding and ultimate strains of masonry, as well as strain softening, are explicitly considered. It has been found that, if the applied axial force does not exceed onehalf of the allowable axial force, the ratio between curvature ductility and strain ductility is greater than unity and does not depend on the magnitude of the applied axial force.
In order to define forcedisplacement diagrams of macroelements, a specific incremental iterative procedure has been developed; it is based on the monitoring of the maximum axial strain over the crosssection(s) subjected to the maximum bending moment. It has been shown that forcecontrolled procedures can lead to significant underestimations of displacement capacity of masonry panels and to underestimations of both lateral stiffness and maximum resisting shear force.
Forcebased pushover procedures in response control have been developed for individual walls with openings and entire masonry buildings, separately, in order to predict also their nonlinear softened response. Such procedures have been implemented in a novel computer program named RAN CODE, which is specifically devoted to structural analysis of masonry buildings. Amongst several numerical applications aimed at validating the developed procedures, the outcomes of a series of global pushover analyses on a masonry building designed in compliance with Eurocode 8 and Italian building code are discussed.
The pushover procedure developed for single masonry walls with openings could be employed in the case of existing buildings (either single buildings or building units within aggregates), which have often flexible floor diaphragms and lacking, or poor, connections between diaphragms and walls, as well as between orthogonal walls.
The procedure developed for global pushover analysis of masonry buildings accounts for torsional effects due to both inherent (i.e., structural) and accidental eccentricities between centres of mass and centres of stiffness. The use of spread plasticity macroelements which change with the given deformation state allows to relate the ‘local’ response of masonry panels to the ‘global’ response of the structure.
Finally, three appendices include results and empirical models obtained through experimental programs aimed at supporting nonlinear modelling and analysis of masonry buildings.
Appendix A deals with mechanical characterisation of masonry under uniaxial compression along directions parallel and orthogonal to mortar bed joints. Such a characterisation is consisted in the definition of mechanical parameters and constitutive models able to simulate nonlinear behaviour of masonry up to large inelastic strains.
Appendix B deals with mechanical characterisation of masonry in sliding shear along mortar bed joints. Also in this case, both classical and advanced mechanical parameters have been defined and empirical models have been derived. Such models include shear stress versus shear strain relationships and a shear response surface, which allows to simulate nonlinear shear behaviour of unitmortar interfaces over the whole range of allowable strains (that is, from elastic to inelastic range).
Appendix C summarises the main results of three quasistatic lateral loading tests on a fullscale masonry wall with a opening and no tensileresistant elements (e.g., reinforced concrete bond beams, steel ties), which is the typical case of existing masonry buildings. Namely, the first monotonic test allowed to investigate nonlinear behaviour of the wall up to the first significant damage to the spandrel panel above the opening. The second test was carried out on the predamaged wall under cyclic displacements, in order to assess residual properties and to reach some hints on seismic performance of masonry walls subjected to earthquake sequences. The last test was performed under cyclic displacements on the wall after repairing and upgrading of the spandrel panel with an inorganic matrixgrid composite system. The aim of that test was to assess the effectiveness of the strengthening system for seismic retrofit of masonry structures and rapid remedial works during seismic emergency scenarios. Data processing for all lateral loading tests has shown that the damage to the spandrel panel affected both loadcarrying capacity and strength degradation of the wall, whereas rocking behaviour of piers produced large displacement capacity and low residual drifts (that is, high recentring capacity).
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