Numerical simulation of concrete block masonry under compression

Cement and Concrete Composites, 2007

The aim of this work is to critically assess the mechanical properties of hollow concrete masonry using experimental results from prisms constructed with blocks of two different strengths and four types of mortar. A key conclusion is that mortar is mostly responsible for the non-linear behavior of masonry. Moreover, a strongly non-linear relationship between masonry elasticity modulus and compressive strength is found, which contradicts the simple linear relation proposed by Eurocode 6 [CEN. Eurocode 6: Design of masonry structures -Part 1 -Common rules for reinforced and unreinforced masonry structures. EN-1996-1-1;. The porosity of mortar and the state of stress that mortar undergoes in the process of compressive loading can be responsible for changes in the mechanical properties, such as elasticity modulus and Poisson's ratio. Finally, different types of mortars induce different failure modes in the masonry prisms and there is clear evidence that the failure of hollow concrete masonry starts after onset of mortar crushing. In order to better reproduce the observed experimental behavior, a tentative model for the mortar Poisson's ratio variation upon loading is also presented.

A nonlinear three-dimensional finite element model was developed to study the complex behavior of ungrouted and grouted concrete block masonry prisms under axial compression. The model detects crack initiation and traces crack propagation in the masonry assemblage. Variable strengths for blocks, mortar, and grout were used to study the effect of the mechanical properties of prism constituents, and their combinations, on the prism strength and modulus of elasticity. The effect of the number of courses was also investigated. The results of the finite element analysis were used to develop simplified relationships to predict prism strength and modulus of elasticity. Good agreement was observed between the available experimental data and the predicted prism strengths.

A set of experimental tests to determine the compressive strength of masonry stack prisms has been numerically simulated using a combined plasticity-smeared crack constitutive law employed in three-dimensional analysis. Supported by an experimental campaign for the mechanical characterization of lime mortar masonry, a series of finite element analyses was performed in an attempt to assess the capacity of the model to reproduce the results obtained in terms of capacity, failure mode and global stiffness. The constitutive law used for the non-linear analysis of the masonry is a combination of a smeared cracking model in tension and a pressure dependent plasticity model in compression, which is capable of accounting for all failure mechanisms that may arise in concentric compression of masonry, both in the units and in the mortar. The purpose of this investigation is to establish whether a numerical approach based on the micro-modeling method is suitable for the simulation of the salient features encountered in masonry under compression as well as highlighting the main material properties necessary to be determined in order to properly model such experiments. The results are expanded upon through a parametric investigation.

2011

The main objective of this study is to verify, through compression tests on different prisms, the vertical and horizontal deformability and the failure modes of the components of concrete blocks under compression. In this study two mortar mixes were tested, according to the recommendations of BS-5628 1992, along with two types of prism, with and without the presence of a vertical joint. The conclusions were: the appearance of non-linearities of the masonry corresponds to an increase in the lateral strain due to extensive cracking of the material and a progressive increase in the Poisson ratio; the cracks in the three-block prisms built with the mortar type I were vertical, occurring symmetrically on both sides; the prisms built with mortar type II had, as a consequence of localized crushing, an association with vertical cracks due to the concentrations of stresses at some points; the presence of a vertical joint led to the appearance of separation cracks between the middle block and the vertical mortar joint, when the stress reached approximately 30% of the compressive strength of the set; the prisms with two whole blocks and one vertical joint (B) built with the mortars of mixes I and II had a compressive strength of the order of 42% and 66% of the prisms with three whole blocks (A), respectively.

Engineering Structures, 2015

The paper focuses on the numerical prediction of the compressive response of masonry by means of detailed micro-modelling techniques. In such a model, the material constituents (mortar and units) and the unit-mortar interfaces are separately described by means of specific constitutive equations. The available modeling choices are evaluated through a literature review of related case studies. A systematic approach is proposed and is corroborated by the numerical simulation of a large number of experimental cases from various sources. A total of fifty experimental results are simulated resulting in an overall good prediction of the compressive strength and elastic modulus of the masonry composite, as well as a realistic depiction of the failure mode. This study focuses on the numerical prediction of the compressive strength of masonry, extending to issues pertaining to global stiffness, failure mode, hardening and softening behavior of masonry and their numerical simulation. The masonry typology considered consists of solid units, primarily brick, and mortar of mostly lower strength and higher deformability.

Revista IBRACON de Estruturas e Materiais, 2011

The main goal of this work is to investigate the nonlinear behavior of concrete block masonry prisms under compression, with an emphasis in the prism deformability and the failure modes. A total of 18 stack-bonded prisms have been tested, using hollow blocks of a single geometry and two different mortar types. To investigate the effect of vertical joints, the bond pattern-stack and running bond-in the prism was varied, by using half units. Finite element analysis of hollow masonry prisms was done utilizing a commercial non-linear finite element code DIANA. The numerical simulation were carried out using non-linear two dimensional 8-node elements and the biaxial stress state material was modeled by a combination of the yield conditions of Rankine and Drucker-Prager. The numerical and experimental results were compared to validate the ability to predict deformation and peak load. The results show that an analytical model cannot be formulated without understanding the interaction between block and mortar. It was observed that: the non-linearities of the masonry correspond to an increase in the lateral strain due to extensive cracking of the material and a progressive increase in the ratio between lateral and axial strains.; the cracks in the three block stacked prisms constructed with a stronger mortar were vertical on both sides; the prisms constructed with a weaker mortar had, as a consequence of localized crushing, also vertical cracks due to stress concentration at some points; the presence of a vertical joint in the prism led to the appearance of separation cracks between the middle block and the vertical mortar joint.

Matéria (Rio de Janeiro)

For decades, prisms and wallette have been used to explore masonry's strength and deformation capabilities under uniaxial compression; moreover, the link between these two main test methods needs to be better established. Using standard masonry design expressions and data, the prism or wallette test can determine compression qualities. The researchers compared the standards and came to judgments on their conservatism or lack thereof, independent of how the rules for those design standards were formed. As a result, an attempt was made to link the behaviour of the enormous masonry prism to the wallette pressure behaviour. Prisms and wallette were made and tested by three different types of units and three mortar compositions. According to test results, the compressive strength of prism tests is consistently higher than that of identical wallette samples. It has remained demonstrated that a linear relationship concerning the compressive strengths of prisms and wallette is tolerable. To test data from the prisms and wallette, a simplified analytical model for the deformation properties of masonry is given.

2nd Pak-Turk International Conference on Emerging Technologies in the field of Sciences and Engineering, 2019

In this study numerical modeling of unconfined masonry is carried out using finite element analysis software Abaqus. The model selected for this study is concrete damaged plasticity which has the ability to describe compression and tension behavior in plastic range. Modeling of masonry structure is done in three diverse ways i.e. Micro-mechanical, Simplifiedmicro mechanical and Macro-mechanical, out of which macro-mechanical modeling was chosen, where the constituents of masonry is homogenized as an isotropic or anisotropic continuum. Testing of model for different pre-compression ratios is carried out and its load displacement curve and energy versus time curve are plotted. At different limit state the numerical and experimental results are compared in term of drift ratio. The results of numerical modeling and experimental modeling are in good agreement at some point and deviates from each other at other points.

Journal of Engineering Sciences, 3 (2), 2014

This paper presents the behavior of load-bearing masonry wallettes built up of hollow concrete blocks systems, loaded by axial compression until failure. The test specimens consist of wallettes (small walls) which built in two types by a hollow concrete blocks. Experimental tests, in order to obtaining a basic mechanical characterization of the construction system, were also performed on raw materials and also on the masonry constituents such as block unit and mortar. Characteristics of the masonry constituents are important to be defined to conclude a complete description for the system behaviour under loading. Linear and Non-linear behavior of loaddeformation and stress-strain relationships, were observed from results of experimental tests for those models that were built in the laboratory. In particular, this paper describes: (a) results of axial compression tests on mortar, unit hollow concrete block, and complete masonry system; (b) comparison of walletts built in two patterns; (c) The results of experimental test of specimens such as elastic modulus and Poisson's ratio; (d) Behavior of failure mode and (d) the linear and Non-linear behavior of load-deformation and stress-strain relationship.

Jurnal teknologi, 2012

This paper presents the numerical verifications of the experimental investigation on the effect of mortar joint thickness on compressive strength characteristics of axially loaded brick-mortar prisms. The three dimensional micro modeling of the prisms was based on two approaches: firstly, models were assumed to be made of homogeneous material; the second approach envisaged the models as composite material made of brick and mortar. The later modeling approach, which assumed the prism to be made of composite material, gave more accurate prediction of the stress distribution in the prisms, and also the failure loads predictions were in good agreement with the experimental results, suggesting that this modeling approach with composite material assumption is more appropriate than the homogenous material assumption. In the present work, a strength magnification factor has also been proposed for the design purposes, which can be used to assess the experimental compressive strength of the brick masonry from its finite element analysis results.