International Journal of Masonry Research and Innovation (32 papers in press)
LIMIT ANALYSIS OF MASONRY ARCH BRIDGES THROUGH AN ADAPTIVE GA-NURBS UPPER-BOUND APPROACH
by Andrea Chiozzi, Nicola Grillanda, Gabriele Milani, Antonio Tralli
Abstract: This paper investigates the application of a fast and reliable NURBS-based kinematic limit analysis approach for the assessment of the collapse behavior of masonry bridges. This approach relies on the description of the geometry of the bridge structure by means of NURBS approximating functions. Starting from the known geometry, an assembly of rigid bodies can be generated, composed by very few elements which still provide an exact representation of the original geometry. The main properties of masonry material are accounted for through homogenization and a upper-bound formulation for the limit analysis of the obtained mesh is devised. The approach is capable of accurately predicting the load bearing capacity of masonry bridges with arbitrary geometry and load configuration, provided that the initial mesh is adjusted by means of a suitably meta-heuristic approach (i.e. a genetic algorithm) until element edges correctly approximate the actual yield lines of the collapse mechanism.
Keywords: Masonry Bridges; NURBS; Limit Analysis; Genetic Algorithms;.
BOND BEHVIOUR OF FRP STRENGTHENING APPLIED ON CURVED MASONRY SUBSTRATES: NUMERICAL STUDY
by Ernesto Grande, Gabriele Milani, Antonio Formisano, Bahman Ghiassi, Francesco Fabbrocino
Abstract: Aim of the present paper is to numerically investigate the bond behaviour of FRP strengthening systems externally applied on curved masonry specimens. In particular, considering the simple spring-model approach proposed by the authors in previous research, a new constitutive law derived from the work of Thorenfeld et al. (1987) is here proposed by also considering the coupled behaviour between shear and normal forces at the reinforcement/masonry interface. Numerical analyses are developed with reference to case studies deduced from the literature and consisting of shear-lap bond tests of curved masonry specimens characterized by different values of the geometric curvature and different strengthening configurations. The obtained results show the ability of the proposed modelling approach in capturing some effects, such as the beneficial friction effect when compression normal stresses develop at the interface level.
Keywords: FRP; debonding; masonry curved structures; spring-model.
In-plane Shear Testing of Unreinforced Masonry Walls and Comparison with FEA and NZSEE Predictions
by Milon Howlader, Mark Masia, Michael Griffith
Abstract: Unreinforced masonry (URM) constructions are vulnerable to seismic loading due to their high mass and stiffness and low ductility and tensile strength. It is important to be able to predict the seismic resistance and the governing failure modes of URM walls and components in order to evaluate the seismic hazard for existing URM structures. If local out-of-plane failure mechanisms are restrained via suitable detailing, the capacity against collapse under seismic loading for URM buildings is typically limited to the in-plane shear capacity of the URM walls. Based on observations of damage suffered from previous earthquakes, the present study was conducted to investigate the global and local in-plane response of perforated URM walls under earthquake loading. Full-scale cyclic in-plane testing of URM walls with an arched opening which were designed to represent walls in heritage URM structures in Australia was performed. The study investigated the behaviour of both pier and spandrel elements within the walls. Emphasis was also given to the position of walls within a multi-storey building by varying the pre-compression loads (representing gravity loads) on the walls. The tested walls were then simulated using nonlinear Finite Element analyses (FEA) where simplified micro-modelling (crack-shear-crush) approaches were used to analyse the wall behaviour. Finally, the shear capacities and the failure modes of the walls obtained from the experimental tests and FE analyses were compared to the proposed New Zealand Society for Earthquake Engineering (NZSEE) predictions.
Keywords: Unreinforced masonry (URM); In-plane shear behaviour; cyclic testing; FEA; NZSEE.
The new foundation system of the Basilica di Collemaggios transept
by Marco Zucca, Pietro Crespi, Nicola Longarini, Manuela Scamardo
Abstract: In the seismic retrofitting of historical churches, the realization of new foundations of collapsed elements represents an important aspect for the interaction with both the underground pre-existing structures and the new structural elements to be rebuilt.rnFor the specific case study of the Basilica di Collemaggio, after an accurate geometrical survey and on-site geotechnical tests, a specific mixed structure foundation system is proposed in order to fulfil the seismic safety requirements and the Cultural Heritage Offices conservation prescriptions.rnNonlinear analyses are performed considering the interaction between the soil and the foundation system, together with the new couple of main pillars and the triumphal arch. The analyses are aimed to verify the capabilities of the new foundation system to bear the transversal seismic actions.rnThe analyses are also completed by some experimental tests on micropiles, which represent the main underground-to-elevation connection elements.rn
Keywords: Foundation system; Historical building; Seismic retrofitting.
The Introduction of Confined Semi-Interlocking Masonry System for Buildings to Improve Earthquake Performance
by Mehdi Hemmat, Yuri Z. Totoev, Mark J. Masia
Abstract: Confined masonry is a typical structural system for many developing countries with high risks of an earthquake and limited engineering expertise. Lack of a comprehensive design code for confined masonry buildings brings motivation to develop new efficient and economical confined masonry system with improved seismic performance. One such system is being developed in the Centre for Infrastructure Performance and Reliability at The University of Newcastle. The semi-interlocking masonry (SIM) is a system which has good structural and seismic performance as an energy dissipation masonry with increased displacement ductility. SIM allows relative sliding of brick courses in-plane and prevents out-of-plane relative displacement of bricks. SIM has already been studied as infill panels. This paper aims to combine semi-interlocking masonry with confined masonry system and introduce the new system; which is called confined semi-interlocking masonry (confined SIM or CSIM). CSIM is intended to be used in developing countries in which the construction facilities are simple. In this regard, after initial theoretical and analytical studies, design criteria are presented to verify the capability of buildings with confined SIM system as an alternative for buildings with conventional confined masonry system. It is believed that confined masonry and semi-interlocking system are complementary and their combination could be an improvement on the currently used confined masonry.
Keywords: confined masonry; semi-interlocking masonry; in-plane shear capacity; confining elements; and earthquake performance.
In-Plane Stiffening and Strengthening of Timber Floors for the Improvement of Seismic Behaviour of URM Buildings
by Margarida Nunes, Rita Bento, Mário Lopes
Abstract: The seismic vulnerability of unreinforced masonry (URM) buildings is strongly influenced by the strength and stiffness of timber floors. In fact, it is well-recognized that an adequate in-plane stiffness of the floors and of the connections between the floors and the walls can improve the three-dimensional response of masonry buildings.
In this work, a steel strengthening solution is proposed to improve the in-plane stiffness of timber floors. The solution consists of placing underneath the wooden floors a steel grid of thin plates and angles at the perimeter to connect to the walls of the existing building. The connections between steel elements were done with screws. The strengthening solution proposed was numerically modelled in SAP 2000. Furthermore, to check the performance of this solution an experimental investigation was conducted.
A cyclic shear test was carried out on a real scale timber floor strengthened with the steel structure proposed. This test allowed the evaluation of the failure mode, forcedisplacement diagrams, and of various behavioural parameters such as floor resistance and in-plane stiffness. The experimental cyclic test, showed that the strengthened timber floor considerably increased the floor resistance and in-plane stiffness.
A proposal to model the stiffening solution is offered.
Keywords: Horizontal diaphragms; Timber floor; Experimental test; In-plane stiffness; retrofit of URM buildings.
Numerical Analysis and Experimental Characterization of Brick Masonry
by Jamiu A. Dauda, Ornella Iuorio, Paulo B. Lourenço
Abstract: Simulating the mechanical behaviour of masonry structures by using numerical analysis is still a complex subject because the process is hindered by little knowledge of the properties of masonry constituents and the interface. In particular, the definition of mechanical properties of masonry components is a key issue when finite element analysis is adopted for the prediction of the mechanical behaviour of masonry walls under accidental and exceptional loads. In an attempt to develop a detailed micro-modelling of brick masonry under compression, where the brick unit, mortar and brick-mortar interface are defined by their corresponding mechanical properties obtained through experimental testing, this work presents experimental tests on brick units, mortar and small masonry cubic specimens. Hence, a detailed micro-modelling of brick masonry cubic specimen is developed in ABAQUS. The numerical model is calibrated and validated based on the results obtained from the experimental tests on masonry cubic specimens. The results show that the numerical model is able to predict the mechanical behaviour of the masonry specimen with a 95% accuracy in terms of compressive strength.
Keywords: brick masonry; characterization; finite element analysis; mechanical properties; micro-modelling.
Presentation and validation of a specific RBSM approach for the meso-scale modelling of in-plane masonry-infills in R.C. frames
by Giuseppina Uva, Vito Tateo, Siro Casolo
Abstract: In the last few years, the scientific community has been strongly involved in the development of approaches able to incorporate the contribution of infill walls in seismic vulnerability analysis of infilled RC framed buildings. The detailed meso-scale modelling of panels within global models as an alternative to equivalent strut models is still a challenge because of the difficulties in controlling constitutive parameters and the high computational effort. The potential of Rigid Body and Spring Models (RBSM) in this field is investigated by exploiting a specific code for the non-linear analysis of in-plane masonry with an efficient computational management. The reference benchmark is an infilled 1-bay 1-storey frame that was subjected to cyclic tests within an experimental campaign and has been here modelled by RBSM, performing a set of numerical parametrical analyses under lateral loads. A good general matching of results and effective computational performance have been found
Keywords: Infill masonry; Infilled RC frames; RBSM; pushover analysis; in-plane mechanisms.
Out-of-plane testing of masonry infills strengthened using Fibre Reinforced Matrix with prior in-plane damage
by Najif Ismail, Nouman Khattak, Tamer El-Maaddawy, Kevin Walsh, Jason Ingham
Abstract: Buildings constructed of reinforced concrete frames with in contact unreinforced masonry infill (referred to as RCFMI buildings hereafter) have been frequently observed to undergo damage during past earthquakes. Earthquake induced out-of-plane collapse of masonry fragments has been reported to cause collateral damage to surrounding properties and injuries to passers-by, whereas it has been widely acknowledged that masonry infills with prior in-plane damage are more susceptible to collapse out-of-plane but such interaction of bi-directional loading is far from well understood. Performance of fibre reinforced cementitious matrix (FRCM) strengthened masonry infills under sequential bi-directional lateral loading was therefore experimentally investigated. A total of eight single bay RCFMI assemblies were constructed with hollow concrete masonry infills, of these one was tested non-retrofitted and served as control specimen and the remainder were strengthened using diagonally oriented FRCM bands with varying widths onto both wall faces. The variables investigated were FRCM type and width of the applied FRCM band. The RCFMI assemblies were subjected to reversed cyclic displacement-controlled in-plane loading gradually increasing to 1% storey drift, replicating lateral loading due to a moderate earthquake. The RCFMI assemblies were then subjected to a gradually increasing one-directional out-of-plane loading until failure. Performance parameters that were observed and measured included damage patterns, failure mechanisms, force-displacement response, and stiffness characteristics. FRCM strengthening delayed the onset of out-of-plane cracking, instigated a more controlled failure mode, with FRCM strengthened infills exhibiting out of plane strength of 1.7-2.0 times that of the control specimen.
Keywords: out-of-plane; residual; strength; damaged; infill; fibre reinforced; matrix.
Macro Scale Material Characterization In Support Of Meso Scale Modelling Of Masonry Under Uniaxial In-Plane Loading
by Anastasios Drougkas, Leidy Bejarano-Urrego, Nathalie Van Roy, Els Verstrynge
Abstract: The amount of detailed experimental data on the mechanical properties of brick masonry available in the literature is limited as regards the cracking and crushing behaviour. These properties include both the strength and the fracture energy in the two modes of loading. Moreover, the quantification of the effect of the direction of the loading in relation to the bond pattern and the overall dimensions of the masonry samples has not been extensively studied. This paper attempts to determine the mechanical properties of the masonry composite as a function of the properties of its components. In this paper a combined experimental/numerical methodology is proposed for the derivation of the macro scale properties of masonry. The experimental aspect deals with the mechanical characterization of the individual materials, small masonry samples and, finally, masonry wallettes. Unknown properties are taken from the available literature. The numerical aspect is the calculation of the macroscopic properties of the masonry composite through calculations using discrete cracking models of the wallettes. The calculations are carried out in two orthogonal in-plane directions, both in tension and compression. For evaluation, material properties for the meso-models are taken from laboratory testing and from the literature. The results of the numerical analyses are compared with the experimental stress-strain results and Digital Image Correlation (DIC) analysis. Parameters such as the Youngs modulus, tensile strength and tensile fracture energy for the masonry composite are able to be derived. The results are analysed in view of the resulting anisotropy of masonry and the obtained failure modes. This paper is a revised and expanded version of a paper entitled Mechanical characterization of masonry on the macro scale from experimental testing and numerical meso scale modelling presented at the 10th International Masonry Conference, Milan, Italy, 9-11 July 2018.
Keywords: Numerical analysis; masonry; discrete cracking; meso-modelling; macro-modelling.
Seismic response evaluation of ten tuff masonry churches with basilica plan through advanced numerical simulations
by Marco Valente, Giuseppe Brandonisio, Gabriele Milani, Antonello De Luca
Abstract: Masonry churches with basilica plan represent a large portion of the cultural heritage and are highly vulnerable to seismic actions, as it has been proved by recent seismic events. This paper investigates the seismic behavior of ten tuff masonry churches with basilica plan, located in Southern Italy, through advanced numerical simulations. For each church, a detailed three-dimensional FE model with a damage plasticity behavior for masonry was developed and non-linear dynamic analyses were performed. The same masonry material was assumed for all the churches in order to have an insight into the seismic behavior of the structures only as a function of their geometry. The seismic response of the churches was evaluated in terms of damage distribution, energy density dissipated by tensile damage and maximum normalized displacements. The comparative study reveals considerable analogies and differences in the response of the various churches. From the extensive set of simulations performed, it is found that the geometrical characteristics of the macro-elements are the main parameters influencing the seismic performance of the churches.
Keywords: masonry church; full 3D FE models; non-linear dynamic analysis; damage distribution.
Laboratory and numerical experimentation for masonry in compression
by Daniele Baraldi, Emanuele Reccia, Claudia Brito De Carvalho Bello, Antonella Cecchi
Abstract: In this paper, the initial part of a laboratory and numerical experimental campaign dedicated to historical masonry is described. One leaf masonry panels with regular texture are built in order to simulate a historical material characterized by strong resisting elements and weak mortar joints. Laboratory tests are first dedicated to masonry components and then to the behaviour in compression of masonry panels, which is applied both orthogonal and parallel to bed joints, in order to highlight the orthotropic behaviour of the material. First of all, the mechanical parameters of masonry constituents are calibrated and then a heterogeneous Finite Element Model is introduced and calibrated for reproducing the orthotropic behaviour of masonry, together with the initial elastic response and the initial nonlinear behaviour due to the first level of damage.
Keywords: masonry; compression tests; heterogeneous Finite Element Model; model calibration.
A continuum-based strength criterion for masonry: identification of parameters and validation
by Stan Pietruszczak, Mohammadreza Mohammadi
Abstract: This paper is focused on the formulation and verification of an anisotropic continuum-based strength criterion for structural masonry. In the approach followed here, the failure function incorporates a scalar anisotropy parameter whose value depends on the orientation of the principal stress system in relation to preferred material directions. An explicit identification procedure for the material parameters/functions is developed and a numerical study, including a set of simulations of biaxial compression-tension tests for different orientations of bed joints, is conducted to verify the predictive abilities of this criterion. The results are compared with the experimental data of Page (1983). In the last part, 3D finite element analysis of a shaking table test is performed involving reduced scale model of a four storey masonry building subjected to seismic excitation. A linear dynamic analysis is carried out and the plastic admissibility of the resulting stress field is assessed.
Keywords: Structural masonry; Anisotropy; Failure criterion; Finite elements.
Analysis of the stress and deformation states in the vertical flat jack test
by Corrado Chisari, Lorenzo Macorini, Bassam Izzuddin, Claudio Amadio
Abstract: Performing a realistic assessment of unreinforced masonry structures involves designing and executing appropriate experimental tests on masonry components for determining the material model parameters to be used in structural analysis. Considering recent developments in which inverse analysis was used as calibration framework, a vertical flat-jack test is investigated in this paper. Two simplified models are described for the analysis of the stress state in the masonry due to the pressure transferred by the flat-jack. Furthermore, with the aim of designing the sensor setup for the test, a POD analysis on the deformation state of the structure is carried out, highlighting the basic deformation modes which govern the response. The results show that high stresses and local modes can occur in the proximity of the flat-jack, and thus local use of FRP reinforcement is recommended to avoid undesired brittle crack propagation which may prevent accurate calibration of mortar joint mechanical characteristics.
Keywords: stress; deformation; vertical flat-jack; unreinforced masonry; structural assessment; Proper Orthogonal Decomposition; FRP reinforcement; sensor placement; mesoscale modelling; calibration; elastic properties; cohesion; friction coefficient; fracture energy.
SURVEY, EXPERIMENTAL TESTS AND MECHANICAL MODELING OF THE DOME OF PISA CATHEDRAL: A MULTIDISCIPLINARY STUDY
by Stefano Bennati, Danila Aita, Riccardo Barsotti, Gabriella Caroti, Giuseppe Chellini, Andrea Piemonte, Francesco Barsi, Caterina Traverso
Abstract: The present contribution illustrates the results obtained to date on an ongoing research study of the mechanical response and load capacity of the dome of Pisa Cathedral. A well-known feature of structural modelling is that it requires reliable data on the actual shape and material properties of the structure in question. Moreover, a comprehensive account of relevant historical and architectural aspects is needed as well. Hence, the starting point of our research work consisted of high-density, precision surveys. Both range-based (laser scanning) and image-based (3D photogrammetry) survey methodologies have been used to obtain different structural models. Furthermore, a set of experimental tests has been performed to evaluate the constituent masonrys properties. From the mechanical point of view, the research has focused mainly on structural analysis of the dome subject to vertical dead loads. The domes mechanical behaviour is described by means of both analytical and numerical analyses. The results obtained via these different methods are discussed.
Keywords: Dome; Structural analysis; Limit analysis; FEM; Laser scanning; Photogrammetry.
Masonries and stone materials of Romanesque architecture (Northern Italy)
by Roberto Bugini, Luisa Folli
Abstract: Romanesque architecture (9th to 13th centuries) in Northern Italy was examined in order to classify the masonries and the stone materials employed in the costruction. Four kinds of masonry were identified: rubble of pebbles; rubble of stones; ashlar of stones, brickwork also mixed with pebbles or stones. The lithologies involved are: glacial deposits, coarse grained igneous rocks, gneisses, massive or thin bedded limestones and dolomites, conglomerates, sandstones. These stone materials were exploited in different areas of the Northern Italy and they had a long-lasting influence on the making of ma-sonries in the neighbouring territory. The lack of stone material in the Po plain was overcome using the clays of the alluvial deposits to make bricks. The use of mortar (lime binder and sandy aggregate) varies according to the shape and the size of the stones, pebbles and bricks.
Keywords: Stone; Brick; Masonry; Romanesque architecture; Northern Italy.
Evaluating Elastic Modulus and Thrust Force of Semi-Interlocking Masonry Panel
by Orod Zarrin, Yuri Totoev
Abstract: The Semi-Interlocking Masonry (SIM) system has developed in Masonry Research Group at the University of Newcastle, Australia. The main purpose of this system is to enhance the seismic resistance of framed structures with masonry panels. In this system, SIM panels dissipate energy through the sliding friction on bed joints of SIM units during earthquake excitation. To model the SIM panels behaviour numerically some key parameters need to evaluate experimentally. The main objective of this study is to investigate the elastic modulus of SIM prism and thrust force induced in SIM during out-of-plane deflection.
In this paper the relationship between the thrust force and the out-of-plane deflection was investigated experimentally for horizontal and vertical arching. Three types of bricks were used in tests: topological SIM, mechanical SIM, and without interlocking bricks. The dimensions of all units were 220
Keywords: SIM; Elastic Modulus; Slip Joints; Horizontal Arching; Vertical Arching; Out-Of-Plane.
Testing and Finite Element Modelling of Concrete Block Masonry Walls under Axial and Out-of-Plane Loading
by Andrea Isfeld, Anna Müller, Mark Hagel, Nigel Shrive
Abstract: The current Canadian masonry design standard, CSA S304-14 (2014), appears to underestimate the capacity of loadbearing masonry walls. This is compounded by the fact that most testing has been completed on walls with pinned base supports, a condition that is not achieved in practice. To understand the structural response of concrete block walls under eccentric axial and out-of-plane loads better, walls with height to thickness ratio of 12.6 were tested. The displacement profiles under pinned-pinned and pinned-fixed boundary conditions were obtained and were used with the constituent material properties to calibrate finite element models. Models were developed using micro-modelling approaches, modelling units, mortar, and grout as merged parts, or individually with friction contact interfaces, having rebar embedded in the grouted cells. The contact modelling approach showed broad agreement with the test results. Both the test results and the modelling showed a clear reduction in out-of-plane displacements, and change in the displaced profile, when a pinned connection was not forced at the wall base.
Keywords: concrete masonry walls; load eccentricity; out-of-plane loading; slenderness; finite element modelling.
Non-linear programming numerical formulation
to acquire limit self-standing conditions of circular masonry arches
accounting for limited friction
by Giuseppe Cocchetti, Egidio Rizzi
Abstract: The modern rational Limit Analysis (LA) of masonry arches typically takes off from classical three Heyman hypotheses, a main one of them assuming that sliding failure shall not occur, like linked to unbounded friction. This allows for the computation of the least thickness of circular masonry arches under self-weight (Couplet-Heyman problem) and of the associated purely rotational collapse mode, by different analytical and numerical approaches. The aim of this work is to further investigate the collapse of circular masonry arches in the presence of limited friction. Here, the normality of the flow rule may no longer apply and the whole LA analysis shall be revisited. A new computational methodology based on non-linear programming is set forward, toward investigating all possible collapse states, by jointly looking at admissible equilibrium configurations and associated kinematic compatibility, in the spirit of the uniqueness theorem of LA. Critical values of friction coefficient are highlighted, marking the transitions of the arising collapse modes, possibly involving sliding. Uniqueness of critical arch thickness is still revealed, for symmetric arches of variable opening, at any given supercritical friction coefficient allowing the arch to withstand, despite the visible role of friction in shifting the final appearance of the collapse mode.
Keywords: Computational Limit Analysis (LA); circular masonry arches; minimum thickness; collapse mechanisms; limited friction.
PRODUCTION OF STYROFOAM BRICKS USING STRENGTHENING ADMIXTURE
by H.M.A. Mahzuz, Ikhtiar Uddin Ahmed, Khoirom Kameshwar Singha, Rifath Sharmin
Abstract: The aim of this study is to make eco-friendly lightweight Styrofoam bricks of higher compressive strength. To achieve that strengthening admixture was used. Sixteen different mix ratios of Cement: Sand: Styrofoam is taken to make standard size (240mm
Keywords: Compressive strength; lightweight; Styrofoam; brick; admixture; water absorption rate.
Simplified micro-modelling of masonry cross vaults: stereotomy and interface issues
by Angelo Gaetani, Nicoletta Bianchini, Paulo B. Lourenço
Abstract: The importance and the relevance of masonry cross vaults is evident in churches, palaces and cloisters of almost all European countries. However, despite their relevance and long-lasting history, which prove an accurate design with respect to gravitational loads, their seismic behaviour is still poorly understood. In this regard, the present work deals with the Finite Element micro-modelling analysis of masonry cross vaults subjected to horizontal loads.
Assuming the blocks rigid-infinitely resistant, the interface represents the only source of physical nonlinearities. Consequently, block interlocking assumes a capital importance, here discussed in the light of the ancient rules of thumb. From the computational point of view, the mechanical properties of the interface are assessed by means of a sensitivity analysis. Comparisons between numerical and experimental results available in literature are presented in terms of ultimate strength capacity and failure mechanisms.
Keywords: cross vaults; masonry vaults; Finite Element; block interlocking; interface; micro-modelling; stereotomy.
Seismic protection of unreinforced masonry buildings by means of low cost elastomeric isolation systems
by Ahmad Basshofi Habieb, Gabriele Milani, Tavio Tavio, Federico Milani
Abstract: Thousands of rural houses in developing countries with high seismicity were built without adequate seismic protection. Unreinforced masonry and non-engineered concrete frame buildings are widely used in developing regions due to economical reason. This paper discusses a possibility to improve the seismic protection of typical unreinforced masonry buildings in developing regions using low cost base isolation devices. The proposed isolation system involves fiber reinforced elastomeric isolators (FREIs) having small dimensions and few layers of rubber pads to reduce the fabrication cost. A series of 3D finite element (FE) simulations are carried out to investigate the performances of the proposed FREIs utilized in the isolation of a one room/one story masonry house prototype. The model is assumed subjected to several accelerograms to have an insight into the sensitivity of the isolation system against different earthquakes in terms of top acceleration response, tensile damage of masonry elements, and isolator displacements. In the nonlinear time history (NLTH) analyses, a single isolator is modeled at a structural level as a nonlinear spring model with damper in order to decrease the computational cost. The results reveal that the proposed low cost FREI system provides significant damage mitigation to the masonry house with good applicability of the FREI devices.
Keywords: Masonry housing; low cost seismic isolation; rubber isolators; advanced FE modelling; Non-linear dynamic analyses.
Special Issue on: 6th ICAAC Performance and Reliability of AAC Masonry against Seismic Hazard
Seismic out-of-plane behaviour of unreinforced AAC walls
by Moritz Lönhoff, Hamid Sadegh-Azar
Abstract: Autoclaved aerated concrete (AAC) is a building material widely used in many countries around the world. In addition to the design for static loads, unreinforced masonry (URM) walls must also be designed for earthquake scenarios. In this load case, the out-of-plane loads (transverse to the plane) often have a significant impact on the load-bearing capacity. In most practical applications, simplified analytical methods are used to determine the out-of-plane capacity of URM walls. The estimations of these models are often inaccurate since essential parameters are neglected. To determine the out-of-plane capacity realistically, parameters like vertical stiffness of the support, geometry, constraints, vertical loads and dynamic effects must be taken into account. To investigate the influence of these parameters, shaking-table tests were performed at the [to be added after review]. Real earthquake time histories were applied and the amplitude has been increased until collapse of the wall. For the simplified numerical analyses of the deformation response of the wall, robust nonlinear single-degree-of-freedom systems are used. In addition, results from analytical models are compared with experimentally determined maximum acceptable earthquake accelerations. The comparison shows that the out-of-plane capacity is much higher than predicted by analytical models. The experimental, analytical and simplified numerical investigations on unreinforced AAC walls will be used to develop a simple and practical applicable engineering model in the next phase of the project.
Keywords: out-of-plane behaviour; shaking-table tests.
Earthquake-proof system for masonry infills in RC frame structures
by Marko Marinković, Christoph Butenweg
Abstract: Reinforced concrete (RC) structures constitute a significant portion of the building inventory worldwide. The need to arrange infill walls in framed structures naturally arises by the necessity to create a separation between internal space of buildings and external environment. Therefore, the use of masonry infill walls in RC frame structures is common in many countries all over the world, even in seismically active areas. Due to the complexity of the problem and the absence of a realistic, yet simple analytical model, infill walls within frame buildings have been generally considered as non-structural elements and thus have been typically neglected in the design process. However, the observations made after strong earthquakes have shown that masonry infills can modify the dynamic behaviour of the structure significantly. The consequences were total collapses of buildings and loss of human lives. The innovative system called INODIS (Innovative Decoupled Infill System) was developed within the European research project INSYSME (Innovative Systems for Earthquake Resistant Masonry Enclosures in RC Buildings), with the aim to improve the behaviour of infilled RC frames by decoupling the frame and the masonry infill. This paper presents the tests conducted to investigate the effectiveness of the INODIS system. First, properties and characteristics of system components are examined followed with the full scale tests on RC frames with masonry infills subjected to in-plane and out-of-plane loading. Finally, a micro model was developed to simulate the in-plane behaviour of RC frames infilled with AAC blocks with and without application of the INODIS system.
Keywords: Experimental tests; numerical model; INODIS; in-plane and out-of-plane failure; simultaneous loading; decoupling.
In-plane strength and stiffness of AAC floor without concrete topping in buildings with AAC masonry infill walls - experimental tests and numerical analyses
by Roberto Scotta, Lorenzo De Stefani, Sara Brandolese
Abstract: The diaphragm action of floors strongly influences the local and global seismic response of a masonry building. The American (ASCE 7-16) and European (EC8) Codes provide few and contrasting indications to classify the floor as rigid or flexible. Moreover, there is limited experience regarding the in-plane behavior of diaphragms made of Aerated Autoclaved Concrete (AAC) panels, and no specific regulations are available for AAC floors. The assessment of in-plane strength and stiffness of AAC floors without a concrete topping is still an open topic. In this work, in-plane diagonal compression tests on AAC precast panels without a collaborating slab are performed to evaluate the behavior of AAC floors. Panels have a different thickness and depth of the shear key were considered for testing. The experimental results are then applied to two case-study buildings to verify through numerical analyses if they behave as rigid or flexible.
Numerical results showed an almost rigid behavior in terms of stiffness, but the in-plane strength is not always assured in conditions of marked irregularities of the building and high seismic-prone areas.
Keywords: AAC floor; in-plane behaviour; diagonal compression tests; numerical analyses.
Effect of Openings on the Seismic Response of AAC Infilled Frames and an Innovative Method to Improve Performance
by Lana Todorovic, Ismail Ozan Demirel, Baris Binici
Abstract: Autoclaved aerated concrete (AAC) is an attractive building material with lightweight, good insulation, fireproofing, and durability characteristics. The seismic response of AAC requires an in-depth understanding as its use as infill walls is gaining popularity in seismically active regions of many countries in Europe, Middle East, and Asia. Recent studies on the seismic response of AAC infill walls were mostly conducted on solid AAC walls without considering openings and simulated earthquake loading was applied in the plane of the frame. In this study, recent tests on the out-of-plane and in-plane seismic response of AAC infill walls with openings were investigated experimentally. The door opening was considered for the purposes of the study. The limited deformation capacity of the AAC infill walls was observed. An
innovative system to improve the performance of AAC infill walls was briefly discussed.
Keywords: infill wall; seismic performance; in-plane; airbag; drift capacity; out-of-plane; OOP.
Damage assessment of autoclaved aerated concrete buildings: some Italian case studies
by Daniele Ferretti, Elena Michelini, Nicola Pongiluppi, Roberto Cerioni
Abstract: The present work deals with the damage assessment of some Italian case studies of structures/walls realised in autoclaved aerated concrete (AAC)blocks. Initially, examples of static damage of walls caused by excessive deformability of the slabs, differential loads on walls, and foundation settlements, are shown. Then, the seismic behaviour of AAC masonry buildings is analysed. In particular, the behaviour of two pre-seismic code buildings damaged by the Emilia 2012 earthquake is described and compared with modern engineered buildings. Then, the behaviour of non-structural walls
damaged by the Central Italy 2016 earthquake is reported. Very few case studies focusing on the damage assessment of AAC masonry buildings during real seismic events can be found in the literature. This work provides an opportunity to advance our knowledge on the behaviour of this material.
Keywords: autoclaved aerated concrete; AAC; damage assessment; 2012 Emilia’s earthquake; 2016 Central Italy’s earthquake; masonry; AAC partitions and infills; shear cracks; sub-vertical cracks; vulnerability; seismic design.
Seismic resistant AAC infill masonry: state-of-the art and future developments
by Lorenzo Miccoli
Abstract: This paper aims to provide an overview on the seismic behaviour of infill walls made by blocks of aerated autoclaved concrete, according to the available literature. Experimental results on the in-plane cyclic performance of infill walls are presented. In addition, numerical simulations of the infill-structure response according to linear and non-linear static methods are reported. In the last section, experimental and numerical studies on how the infill walls influence the structural behaviour are shown.
Recent studies on seismic isolated masonry infills have shown that damages are more serious for fully infilled test samples than for the isolated ones. Although the discussion on out-of-plane stability and strength of isolated infill is still open, the development of solutions able to assure the isolation of infill walls respect to structural frame seem to be the most promising in terms of damage prevention of the building.
Keywords: aerated autoclaved concrete; in-plane behaviour; infill-structure interaction; dynamic behaviour; finite element modelling.
Special Issue on: 10IMC Masonry Research in the Third Millennium From Theory to Practical Applications
Four years of Structural Health Monitoring of the San Pietro Bell Tower in Perugia, Italy: two years before the earthquake versus two years after
by Pier Francesco Giordano, Filippo Ubertini, Nicola Cavalagli, Alban Kita, Maria Giovanna Masciotta
Abstract: This paper addresses the Structural Health Monitoring (SHM) of the bell tower of the Basilica of San Pietro in Perugia, Italy, which is located in a seismic area. Known as one of the landmarks of the Umbrian capital, the tower belongs to a monumental complex of exceptional historical and cultural value. Therefore, its protection with respect to earthquakes is an important issue. To this purpose, a vibration-based SHM system able to detect anomalies in the structural behaviour by means of statistical process control tools has been installed in the tower and is under continuous operation since December 2014. The effects of the 2016-2017 Central Italy seismic sequence were clearly detected by this system, even if earthquakes took place at relatively large distance from the bell tower. The large amount of SHM data collected over four years allowed to assess the modifications in the structural behaviour of the bell tower in post-earthquake conditions.
Keywords: structural health monitoring; operational modal analysis; post-earthquake assessment; heritage structures; preservation of architectural heritage.
Performance assessment of a bio-inspired anomaly detection algorithm for unsupervised SHM: application to a Manueline masonry church
by Alberto Barontini, Maria Giovanna Masciotta, Paulo Amado Mendes, Luis Ramos
Abstract: Vibration-based techniques are commonly used in Structural Health Monitoring (SHM) to assess the condition of structural systems and identify the presence of damage. Negative Selection Algorithms (NSAs) are bio-inspired methods which allow to automatize the damage detection process by classifying the monitored systems features as normal or abnormal. In this paper, an NSA with a non-random strategy for detector generation is tested on the monitoring data of a remarkable masonry church in Portugal. The work aims to make users aware of NSA potential, contributing to a diligent application of the method in terms of best algorithm instance definition. Different setting approaches for the algorithm parameters are discussed and compared, exploiting artificial outliers of the features distribution to assess the NSA performance. Such a strategy allows the optimization of the algorithm in most of the civil engineering applications where no information about the features belonging to unhealthy scenarios is available.
Keywords: Structural Health Monitoring; Anomaly Detection; Damage Identification; Classification problems; Negative Selection Algorithm.
Structural and constructive analysis of San Juan de Dios basilica dome, in Granada (Spain).
by Javier Suárez Medina
Abstract: St. Juan de Dios Basilica, in Granada was built between 1734 and 1757, by design of architect Jos
Keywords: timber dome; timbrel dome; structural analysis; constructive analysis; San Juan de Dios; Fray Lorenzo.
Observation of crack initiation zone in brick masonry couplets under compression using X-ray microfocus computed tomography and digital image correlation
by Naveen Shetty, Georgios Livitsanos, Els Verstrynge, Dimitrios G. Aggelis, Danny Van Hemelrijck, Koen Van Balen, Martine Wevers
Abstract: The constituent materials of masonry include different brick and mortar types with various properties. The difference in the stiffness properties of these materials influence the observed failure modes under compression. The general hypothesis of the failure mechanisms in brick masonry under compressive loading relies on the difference between the relative elastic modulus of brick and mortar. The aim of this paper is to visually examine the above theory about the behaviour of masonry under compression using a high resolution X-ray micro-CT scanner. Additionally, full-scale couplets have been tested under compression with the application of stereo-vision Digital Image Correlation (DIC). The failure progression in masonry which evolves from the initiation of micro cracks, over the propagation into macro cracks has been clearly evidenced. Overall, the results from DIC positively confirm the observation from X-ray micro-CT.
Keywords: masonry; compression; failure mechanisms; X-ray computed tomography; digital image correlation.