International Journal of Masonry Research and Innovation (13 papers in press)
Behaviour of block masonry under in-plane loading
by Roberto Capozucca, Erica Magagnini
Abstract: In the design of buildings, the 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. However, the performance of MURM is influenced by many parameters such as solid or perforated units and strength, deformability and thickness of mortar joints. In this paper, the strength of blockwork walls built with two types of perforated clay blocks, lateral surfaces toothed and smooth, and different mortar 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. The response of blockwork walls under diagonal tests have been analysed
comparing experimental data with that obtained with finite element method (FEM).
Keywords: blockwork masonry wall; experimental test; shear strength; FE analysis.
Macroelement and dynamic seismic analysis of the medieval government building of Perugia, Italy
by Marco Corradi
Abstract: This paper emphasizes the actual structural analysis of a multistory medieval building, located in Perugia, Italy, for seismic resistance. This is the local Governor building of the capital city of Umbria, known as Palazzo dei Priori, an iconic grade-I stone masonry construction. Strong emphasis is placed on specific issues, critical for the structural response of the building under the seismic action. Fundamental assessment methods are presented and discussed to find vulnerabilities and defects that affect its seismic response. The discussion includes the analysis by macro-elements (local analysis), leading to the identification to the most likely collapse mechanisms of the building under the seismic action. In addition to the macro-element method, a non-linear analysis is given for the whole building. All the used analyses are carried out with reference to the Italian guidelines for heritage protection and conservation and by considering the architectural and artistic assets of the building.
Keywords: Historic masonry; earthquake engineering; numerical modelling; seismic assessment.
Testing and Analysis of Masonry Hollow Clay Block Prisms Filled with Mortar
by Marcio Nascimento, Humberto Roman, Fernando Fonseca
Abstract: In some design situations, in construction systems with structural masonry, an increase in the capacity of the walls is required, which can be achieved with the filling of empty cells of masonry blocks with grout. The Brazilian technical standard for clay masonry blocks aiming at attaining greater agility and flexibility in the construction process allows the use of bedding mortar instead of grout to fill the cells of the blocks. In this context, the objective of this study was to evaluate the mechanical behavior of prisms filled with bedding mortar. Six classes of mortar and one type of clay block with nominal resistance of 6 MPa were studied. The results of the compressive strength of the prisms indicate the viability of using bedding mortar with the same structural function as grout.
This article presents also an analytical study to evaluate the mechanical behavior of clay block prisms filled with mortar. Analyses were conducted using a general-purpose, nonlinear finite element software that simulates structural behavior under different loading scenarios. A three-dimensional model of the prisms was developed using 8-node brick elements for both block and mortar with non-linear properties assigned to each material.
Keywords: structural masonry; compressive strength; clay blocks; FEA; numerical modelling.
Effect of Modified Fiber Flour Wood on the Fresh Condition Properties of Cement Based Mortars
by Fadhel Aloulou, Sabrine Alila
Abstract: Abstract: The effect of wood fiber flour in a studied Portland cement material shows interesting mechanical properties. The objective of this work is the elaboration new composite materials by emulsion. The dispersion of wood fiber and compressive strength was studied. The results showed an improvement in compressive strength of over 40% with 2% added wood fibers flour. The chemical modification of the wood fibers by grafting alkyl chains into their surfaces changes from the hydrophilic state to the hydrophobic state which makes it necessary to reduce the amount of water absorbed by the sample. The addition of anionic surfactant: Sodium dodecylbenzenesulfonate (SDBS) in the mixing water further improves the surface of the samples by minimizing the pore size, hence the reduced water absorption. The alkaline treatment of the fibers before their injection into the cement paste has a very remarkable effect on the mechanical behavior of the composites.
Keywords: Wood; Flour wood; Emulsion; surfactant ; cement.
Experimental assessment of large displacement cyclic in-plane shear behaviour of semi-interlocking masonry panels
by Md Akhtar Hossain, Yuri Z. Totoev, Mark J. Masia
Abstract: A Semi Interlocking Masonry (SIM) building system has been developed in the Centre for Infrastructure Performance and Reliability at The University of Newcastle, Australia for seismically vulnerable regions as an alternative to traditional masonry panels. This innovative masonry building system consists of mortar-less masonry panels with multiple sliding bed joints made of semi-interlocking units capable of relative sliding in-plane of a panel but interlocked against relative out-of-plane movement. The SIM panel can withstand large in-plane displacements without damage due to the sliding joints in the panel. These new panels are suitable for both infill and confined masonry. An experimental program was conducted to evaluate displacement ductility of the infill panels under large displacement. It used a special steel testing frame with pin connections, which allows application of in-plane shear distortion to the panel up to 120 mm. The study presented herein focused on the experimental investigation of large cyclic in-plane shear behaviour of three different types of panels: (i) panel with an open gap between the steel frame and the top of the panel, (ii) panel with foam in the gap, and (iii) panel with grout in the gap. This paper reports the results of this testing program with mechanically interlocking units with main focus on the force-displacement relationship and the energy dissipation capacity of panels. The structural performance of the SIM panels is also analysed, and potential displacement patterns are identified under large displacement.
Keywords: Semi-interlocking masonry; sliding joints; in-plane cyclic testing; energy dissipation; damping capacity; large displacement.
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.
Natural properties of confined masonry buildings - experimental case studies and possible inferences
by Harshit Nema, Dhiman Basu
Abstract: Construction of faculty housing and student-s hostels in a fully-residential 400-acre academic campus of Indian Institute of Technology Gandhinagar (IITGN) in the State of Gujarat, India is the first large scale confined masonry construction in the country. Knowledge of dynamic properties of these buildings will provide valuable inputs to the seismic design recommendations of confined masonry buildings. Ambient and forced vibration tests (AVT and FVT) are conducted in some of the constructed buildings for the natural period and damping ratio. This paper presents the details of such case studies and compares the experimental results with general expectation considering reinforced concrete buildings with in filled masonry wall as the basis. Also recommended in this paper are some of the fines tunings in the experimental framework of conducting AVT and FVT, and processing the recorded data to identify the natural frequency with greater confidence level.
Keywords: ambient vibration testing; AVT; forced vibration testing; FVT; confined masonry buildings; dynamic properties.
A limit analysis approach for masonry domes: the basilica of San Francesco di Paola in Naples
by Claudia Cennamo, Concetta Cusano, Maurizio Angelillo
Abstract: The object of the present study is the basilica of San Francesco di Paola, an historical structure that well lends itself to use the graphic method of statics to analyse its stability for a two-fold reason: on the one hand, it is an interesting structure being dominated by a dome of considerable size with a solid appearance, and on the other, it is an entirely masonry structure for which no consolidation interventions with different materials have been necessary so far. This paper applies limit analysis based on the geometric equilibrium of the dome starting from detailed surveys of the church, from the knowledge of its history construction to the comprehension of the entire building. The study carried out enriches previous researches developed around the same case study, and the new contribution is integrated by the analysis of stability of the buttress system that completes the work on the vertical loads, providing a more detailed assessment of the safety level of the structure.
Keywords: masonry domes behaviour; limit analysis; safety evaluation.
Monotonic tests on masonry elements with different angles of inclination of the bed joints under uniaxial compression
by Marius Weber, Akanshu Sharma, Jan Hofmann
Abstract: This paper describes the results from monotonic tests performed on masonry elements with different angles of inclination of the bed joints relative to the horizontal under uniaxial compression. Two different types of bricks (calcium-silicate and clay bricks) were tested under uniaxial compression stress state. The main test parameter was the angle of inclination of the bed joints, which was varied between 0 and 90 degrees in the interval of 15 degrees. The tests were performed in displacement control in order to capture the post-peak response of the masonry elements as well. The applied displacements were increased monotonically. During the tests, main measurements were performed to measure the edge deformation, detection of strain on the masonry surface using a photogrammetric method, and documentation of the crack propagation and fracture behaviour. The strength and the stiffness properties, as well as stress-strain relationships as a function of the angle of inclination of the bed joints and the comparison between the principle directions of stresses and strains is reported here.
Keywords: compression test; inclined bed joints; monotonic loading; macromodel.
Validation of a two-step simplified compatible homogenisation approach extended to out-plane loaded masonries
by Elisa Bertolesi, Luis Carlos Silva, Gabriele Milani
Abstract: A two-step homogenisation model, formulated by the authors for the in-plane case, is herein extended for the nonlinear out-of-plane analysis of masonry structures. A rectangular running bond elementary cell is discretised by 24 elastic CST elements and inelastic zero-thickness interfaces. The mechanical meso-scale problem is briefly recalled, whereas the out-of-plane homogenised behaviour is evaluated by means of a simple on-thickness integration of the in-plane homogenised curves. At a macro-scale, the rigid body and spring model is slightly modified to allow both flexural and torsional failure mechanisms. The validation of the numerical approach is achieved comparing with some full-scale masonry panels tested in two-way bending up to failure. A series of nonlinear structural analyses are conducted considering different parameters, which have been varied during the experimental campaign. The numerical results are promising and demonstrate the capability to deal with different failure mechanisms as result of a combination of various experimental aspects.
Keywords: masonry; in-plane loads; out of plane loads; semi-analytical approach; compatible model of homogenisation.
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.