International Journal of Masonry Research and Innovation (11 papers in press)
INVESTIGATION OF THE STRUCTURAL BEHAVIOUR OF A MASONRY CASTLE BY CONSIDERING THE ACTUAL DAMAGE
by Maria Stavroulaki, Georgios Drosopoulos, Efstathia Tavlopoulou, Nikolaos Skoutelis, Georgios Stavroulakis
Abstract: The structural behaviour of an ancient masonry castle located in South Crete, Greece is studied in the present work. Frangokastello is a medieval castle built by the Venetians in 1371-74 in a narrow coastal zone at the southeastern part of the White Mountains, approximately 12 km east of Chora Sfakion. The structure presents several damaged areas, consisting of cracks and local failure of masonry. The finite element method is used in order to model the structure. In order to investigate the response of the structure, taking into account the real damaged state which is developed in the structure, unilateral contact interfaces are introduced. Along these interfaces opening (separation) and frictional (stick-slip) effects are considered. Then, non-linear time history analysis is considered to demonstrate how the existing failure of the structure affects its mechanical response.
First, an eigenvalue analysis of the structure without the cracks and a dynamic modal analysis are done. Then a non-linear constitutive model using a smear crack law is used to investigate the limit state of the structure under static and dynamic loading. Finally, unilateral contact interfaces are introduced, to simulate the cracks which appear in the structure. This model, which consists of several non-linearities, is tested under non-linear time history analysis.
Comparison of the results obtained when the damage of the structure is taken into account, with the results when no damage is considered in the analysis, demonstrates how the pathology of the structure affects its response. This procedure is necessary towards taking actions for the reinforcement of the structure.
Keywords: Masonry; Crack; Dynamic analysis; Unilateral contact.
EXPERIMENTAL INVESTIGATIONS ON THE INITIAL SHEAR STRENGTH OF MASONRY WITH EARTH MORTARS
by Patrick Fontana, Lorenzo Miccoli, Ulf Grünberg
Abstract: In this article, a comparative study on the initial shear strength of masonry with earth mortars is presented. Triplet tests were carried out to characterise the shear bond strength of five different types of earth mortar, three purely mineral and two with vegetable additives (wood and straw chaff), using calcium silicate blocks.
In spite of their lower bulk densities, mortars with chaffs reached a value of compressive strength comparable to the values shown by the purely mineral mortars. The results show that the organic additives have a positive influence on the initial shear strength. The characteristic initial shear strengths of all the tested earth mortars were between two and five times higher than the minimum values for initial shear strengths required by DIN 18946. To assess the influence of blocks pre-wetting, a comparison between calcium silicate blocks and earth blocks was carried out to evaluate the results obtained from the standard test procedure compared to the more common practice of using earth mortars in combination with earthen blocks. The additional triplet tests conducted with earth blocks showed that the pre-wetting of blocks before building up had a positive effect.
Keywords: earth mortar; sand-lime block; earth block; initial shear strength; triplet tests.
Creep failure of two historical masonry towers: analysis from material to structure
by Els Verstrynge, Dionys Van Gemert
Abstract: The sudden collapse of several historical masonry towers has been attributed to gradually increasing mechanical damage, such as creep cracking which occurs under constant stress levels. This paper reviews theoretical, experimental and numerical methods for analysing compressive creep in historical masonry. The investigations focus on creep behaviour in ferruginous sandstone, as results are applied to understand the collapse of two historical towers in Belgium that were both constructed in local sandstone. At the level of the material, cracking, creep strains and acoustic emissions are observed in small-to-medium scale sandstone samples under dry and saturated conditions. The advantage of performing acoustic emission-controlled creep tests is highlighted. Results indicate an acceleration of the degradation process when water absorption takes place during the secondary creep phase. At the structural level, numerical macro modelling is performed to investigate the case studies and study the effect of stress redistributions on creep behaviour of three-leaf masonry. Finally, experimental and numerical results are related to the collapse of two historical towers, and accelerating effects for the creep failure of these monuments are indicated.
Keywords: Historical masonry; creep; time-dependent damage; experimental research; numerical modeling; microCT; acoustic emission; three-leaf masonry; case studies.
Finite Element Thrust Line Analysis (FETLA) of Cracked Axisymmetric Masonry Domes Reinforced with Tension Rings
by Mahesh Varma, Siddhartha Ghosh, Gabriele Milani
Abstract: Masonry domes under self-weight are subjected to hoop tensile forces in their lower portion, which lead to vertical cracks appearing along the domes meridian planes. Almost always, a close inspection reveals such hoop tension cracks. At the final extent of cracking, the dome stands as a series of arches with a common key stone. Tension rings put around the perimeter close to the base of a dome are commonly used to arrest these cracks. However, the behaviour of domes with tension rings is not well understood. This paper presents an enhancement of the Finite Element Thrust Line Analysis in order to analyze masonry domes with tension rings. The development of a new element to include the effect of both hoop and meridian tension cracks, utilizing orthotropic material properties and a penalty approach, is discussed in detail. The case study for a hemispherical cupola with FRP hoop rings shows that the proposed method can accurately estimate the thrust line of the dome.
Keywords: Unreinforced Masonry; Domes; FETLA; Finite Element; Thrust Line; Tension Ring; FRP.
The gothic arcade of Santa Maria Incoronata in Naples. Equilibrium of gothic arches.
by Concetta Cusano, Claudia Cennamo
Abstract: The paper is an application of the structural theory for masonries to a historic building through a static analysis of the shape and stability of the arches of the Incoronata Church in Naples. The previous history of the interventions has been thoroughly investigated by checking the consistency of decisions made over time by engineers and architects who, despite not having modern tools of calculation, designed only by using geometric rules and professional experience. So, a stability analysis is centered on the Gothic Arcade, which has the singularity of a non-symmetrical front and has suffered restoration interventions whose results can be debatable. The analysis conducted is both analytical and graphical, by using the well-known concept of the line of thrust. The obtained equilibrium solution explains the suitability of the arches and the rationality of the intervention in the context of the history of constructions. Although limited to one building, the approach could be applied more generally, with the aim to afford a contribution to the structural knowledge of architectural heritage.
Keywords: masonry; gothic architecture; limit analysis; equilibrium approach.
Sensitivity analyses of seismic performance of ancient mixed masonry-RC buildings in Lisbon
by Jelena Milosevic, Serena Cattari, Rita Bento
Abstract: In the first half of the twentieth century, the mixed masonry-RC buildings were introduced in Lisbon; they were typically designed without strictly considering seismic-design requirements. To assess their potential seismic vulnerability, it is crucial to simulate adequately their actual response by: (i) explicitly considering their characteristics, and (ii) identifying the main parameters that affect their seismic performance. In this context, the aim of the paper is twofold. Firstly, the structural elements are characterized in detail. This first study includes the proposal of reference values for the main mechanical parameters, which are defined by combining various data available in the literature adopting a Bayesian approach. Secondly, to identify the main parameters that affect the seismic response of one type of the ancient mixed masonry-RC buildings, a sensitivity analyses is adopted and implemented; within this context, the influence of different material properties and the quality of connections among structural walls are considered.
Keywords: aleatory and epistemic uncertainties; Bayesian approach; mixed masonry-RC “Placa” buildings; nonlinear static; seismic performance; sensitivity analysis.
Approaches to strongly local phenomena in dry masonry structures
by Fernando Magdalena Layos, Julian Garcia Munoz
Abstract: Sliding collapse tests performed on dry-stack masonry structures show a statistical dispersion in the results that cannot be explained by the dispersion in the properties of its constituent materials, but may correspond to an uneven distribution of stresses at the contact surfaces or within the constituent elements. In order to study these local phenomena, a method of numerical analysis of rigid blocks in unilateral contact is implemented and confronted with two types of benchmark tests: load tests and photoelastic tests. Comparing the results will allow stating that the random irregularities in contact surfaces play an important role in local behaviour. The results are very encouraging and suggest that this type of approach, common in the field of granular media but not in orthotropic media, can provide interesting insights for the analysis of local phenomena in historical masonry structures.
Keywords: masonry structures; numerical analysis; discontinuous media photoelasticity; rigid blocks; unilateral contact; friction.
EFFECT OF CONCRETE BLOCK HEIGHT VARIATION TO THE SHEAR BOND STRENGTH OF THIN LAYER MORTARED MASONRY
by Julian Thamboo, Manicka Dhanasekar
Abstract: Thin layered masonry employs 1 mm 3 mm thick mortar joints laid using simple tools with minimal skilled masons and hence achieve significant saving in the cost of construction. However, the applicability of this masonry system relies on units made with tighter control of their height. Currently unit height variation is tolerated up to
Keywords: Unit height tolerance; thin layer mortared masonry; Shear bond strength; polymer-cement mortar; digital image correlation.
Behaviour of block masonry under in-plane loading
by Roberto Capozucca, Erica Magagnini
Abstract: Knowledge about the behaviour of masonry has increased during the last decades so that codes of practice adopted in many countries allow designing masonry structures on the base of well-defined principles and rules. In the design of buildings, strength of modern masonry under compression and shear is crucial for safety in seismic areas. Modern unreinforced masonry (MURM) built with perforated clay blocks may also be considered adequate in terms of withstanding seismic action without relevant damages. However, the performance of MURM is influenced by many parameters such as solid or perforated units and strength, deformability and thickness of mortar joints. rnIn this paper, the strength of blockwork walls built with two types of perforated clay blocks, lateral surfaces toothed and smooth, and different mortar joints - unfilled vertical joints, shell bedded joints and continuous joints - has been experimentally tested under loading in-plane. An extensive investigation based on compression tests and diagonal compression tests of blockwork walls has been carried out. The experimental results are presented and discussed. In particular, the response of blockwork walls under diagonal tests have been analysed comparing experimental data with that obtained with finite element method (FEM) by macro and micro-modelling, assuming masonry both as an isotropic and orthotropic linear elastic material. rn
Keywords: Blockwork masonry wall; experimental test; shear strength; FE analysis.
Rigid block models for masonry structures
by Maurizio Angelillo, Antonio Fortunato, Antonio Gesualdo, Antonino Iannuzzo
Abstract: The study of masonry mechanics and the modelling of masonry structures requires a methodological approach radically different from the ones used for metallic and concrete structures. The main criteria adopted for the design of the latter, such as strength, stiffness and elastic stability, have a minor role when dealing with masonry structures. Even if this peculiar behaviour, confirmed though a careful historical critique by several authors, such as Heyman with his seminal work of 1966, followed in the 80s and 90 by Di Pasquale, Como, Benvenuto, Huerta, is rather evident, this point of view is far from manifesting itself among structural architects and engineers. Indeed the theory of Heyman, giving a modern turn to the old approach to masonry design by means of clear cut simplifications, is in sharp contrast with the sophisticated constitutive theories made possible by Finite Element methods and the use of super-computers. In these notes, the basic ingredients of a new method based on unilateral equilibrium and rigid block kinematics, which may allow the implementation of Heymans model for masonry on a computer, is introduced. In particular we describe a simple method based on energy minimization allowing the evaluation of the combined effect of loads and settlements on real masonry structures.
Keywords: masonry structures; unilateral constraints; unilateral materials; multi-body structures; contact and friction.
Special Issue on: Seismic Analysis and Rehabilitation Methods of Monumental Masonry Constructions From Past Procedures to Future Advances
Numerical modeling of a Composite pentamode comprising a shear-thickening fluid
by Federico Cecchini, Valeria Cherubini, Francesco Fabbrocino, Francesca Nanni
Abstract: In this work, we developed a novel numerical approach for the analysis of the displacement field of a Composite pentamode material. Two different approaches to the solution of the equations system are taken into account: the first is an exact iterative approach, the second is a discrete one, based on finite element modeling.rnThe single beam elements that materialize the composite pentamode are hollow and comprise a Non-Newtonian fluid (NNF) Core. In particular, Shear-thickening fluids (STFs) were selected as the materials for the core, as they are capable of converting a large quantity of the kinetic energy deriving from the forces applied to the structure into heat.rnIn order to analyze the rheological properties of the material considered, we carried out a two-step rheological analysis.rnFinally, the previous equations were solved and the results obtained for the various solution approaches were compared.rn
Keywords: pentamode; seismic; metamaterial; shear-thickening fluids; constrained layer damping; FEM; viscoelastic damping.