Behavior Of Masonry Walls Research Articles

Numerical Evaluation of Mechanical Parameters Role in GFRP Strengthened Cobblestone Masonry Walls

The use of a GFRP (Glass Fiber Reinforced Polymers) mesh, embedded as a reinforcement in a mortar coating on both wall sides, proved to be effective and reliable in increasing the masonry wall resistance and the plastic deformation capacity.In this study, a NL finite element model, developed to predict the in-plane behaviour of masonry walls strengthened by means of this technique, is refined and used in an extensive parametric study. Numerical results were compared with diagonal compression test data on URM and RM cobblestone masonry samples, showing good agreement. The masonry panel and the mortar coating were modelled as isotropic homogeneous materials with a smeared crack approach, whereas the GFRP reinforcement was modelled as a mesh of truss elements. Properties assigned to materials were derived from experimental tests.The parametric study performed before on some involved mechanical properties, considering a standard range of variation, is now extended to other parameters. Moreover, the combined variation of different properties is considered. The actual contribute of each component (masonry, GFRP mesh, mortar) on some macroscopic parameters (strength and ductility of the specimen) is evaluated.The parametric analysis highlights the important role of the GFRP mesh not only on the peak load increment but also on the post-peak behavior and, in particularly, on the ductility increment of the reinforced masonry panel. These results can address the optimization of the intervention technique and the deliverable of operative guidelines for practitioners.

Experimental and Numerical Investigations on the Behaviour of Masonry Walls Reinforced with an Innovative Sisal FRCM System

An experimental and numerical investigation on an innovative composite reinforced with sisal fibers for masonry strengthening is presented in this paper. A FEM numerical approach is also developed, based on diagonal compression test results, to simulate the shear in-plane response of unreinforced masonry panels (URM) and masonry strengthened with a Fibre Reinforced Cementitious Matrix (FRCM) composite system made with sisal fibers (RM-SISAL).

Mechanical in-plane behaviour of masonry walls reinforced by composite materials: Experimental and analytical approaches

Masonry is a traditional building system in most countries of the world, including France. However, in recent decades, earthquakes have caused significant damage to masonry structures. The possibility of using textile-reinforced concrete or fibre-reinforced polymers to strengthen masonry structures has been recently assessed. This article addresses the effectiveness of externally bonded composite materials, particularly those based on newly developed cementitious matrices, to strengthen masonry structures. Experimental tests were performed in a previous study on six masonry walls, five of which were strengthened on both sides with either textile-reinforced concrete or fibre-reinforced polymers. This experimental campaign has been supplemented to determine the mechanical properties of the materials involved in design models, and it is used to check the potential of analytical models to predict lateral strength. This study identifies the interests and the restrictions governing the use of traditional empirical design approaches (employed for fibre-reinforced polymer-strengthened walls) when next-generation textile-reinforced concrete composites are used as strengthening materials. Adjustments taking into account the specificities of textile-reinforced concrete behaviour have been introduced, and their impact on the relevance of the models has been quantified.

Effect of FRP strengthening on the flexural behaviour of calcarenite masonry walls

The use of fiber-reinforced polymers (FRP) for structural strengthening has become increasingly popular in recent years. Several applications of FRP have been proposed and applied, depending on the target of the technique, kind and/or material of the structural member. In particular, because of their great tensile strength, FRP materials are commonly used to enhance the out-of-plane behaviour of masonry walls, allowing to increase their strength, ductility and improving safety against overturning. For these reasons, FRP laminates are often applied in vulnerable ancient buildings in seismic areas to reinforce facades and walls with poor structural features. However, some issues arise when adopting composites in historical constructions, the most related to the aesthetical impact of laminates and compatibility between FRP and masonry. Consequently, a correct evaluation of the reinforcement percentages for strength and ductility purposes is crucial, as well as the effective increase of structural performances. This paper presents a numerical-analytical approach able to reproduce the flexural behaviour of out-of-plane loaded masonry walls. The model is based on a simplified representation of the member, the latter modeled as a cantilever beam. Mechanical non-linearity is introduced by means of moment–curvature relationships, deduced with proper constitutive laws of masonry and by taking into account the ultimate debonding strain of FRP. Second order effects are considered by adopting an iterative step-by-step procedure. Comparisons are made in terms of moment–curvature and load–displacement curves with experimental data available in the literature and with non-linear finite element analyses, showing both good agreement. Finally, parametric considerations on the reinforcement percentages are made in terms of strength and ductility.

Non-linear modeling of masonry churches through a discrete macro-element approach

Seismic assessment and rehabilitation of Monumental Buildings constitute an important issue in many regions around the world to preserve cultural heritage. On the contrary, many recent earthquakes have demonstrated the high vulnerability of this type of structures. The high nonlinear masonry behaviour requires ad hoc refined finite element numerical models, whose complexity and computational costs are generally unsuitable for practical applications. For these reasons, several authors proposed simplified numerical strategies to be used in engineering practice. However, most of these alternative methods are oversimplified being based on the assumption of in-plane behaviour of masonry walls. Moreover, they cannot be used for modelling the monumental structures for which the interaction between plane and out-plane behaviour governs the structural response. Recently, an innovative discrete-modelling approach for the simulation of both in-plane and out of-plane response of masonry structures was proposed and applied to study several typologies of historic structures. In this paper the latter model is applied with reference to a real case study, and numerically compared with an advanced finite element modelling. The method is applied to the St.Venerio church in Reggiolo (Italy), damaged during the 2012 Emilia-Romagna earthquake and numerically investigated in the literature.

A full 3D rigid block model for the collapse behaviour of masonry walls

Abstract This paper presents and validates a non-commercial rigid block model code for performing pushover analysis of one leaf masonry assemblages with regular texture, in three dimensional field. Hypotheses of rigid blocks and joints modelled as interfaces are adopted for representing historic masonry behaviour, characterized by dry joints or weak mortar joints having negligible size with respect to block size. Masonry elastic and inelastic behaviour is concentrated at joints by defining their normal, shear, bending and torsion stiffness and strength, adopting a Mohr-Coulomb criterion for restraining interface actions. The proposed model is an extension to the field of material nonlinearity of an existing code, moreover nonlinear analyses follow an effective approach introduced by authors for the in-plane case, based on the determination and update of the stiffness matrix of the masonry assemblage during the incremental analysis, accounting for damage. A numerical experimentation is performed for determining limit load multipliers and collapse mechanisms of several masonry walls subject to in-plane actions generated by self-weight and out-of-plane actions that may cause tilting or toppling of masonry assemblage portions. Dry and mortar joints are considered and existing case studies are adopted for calibrating the proposed model and evaluating its effectiveness.

Methods and Approaches for Blind Test Predictions of Out-of-Plane Behavior of Masonry Walls: A Numerical Comparative Study

ABSTRACTEarthquakes cause severe damage to masonry structures due to inertial forces acting in the normal direction to the plane of the walls. The out-of-plane behavior of masonry walls is complex and depends on several parameters, such as material and geometric properties of walls, connections between structural elements, the characteristics of the input motions, among others. Different analytical methods and advanced numerical modeling are usually used for evaluating the out-of-plane behavior of masonry structures. Furthermore, different types of structural analysis can be adopted for this complex behavior, such as limit analysis, pushover, or nonlinear dynamic analysis.Aiming to evaluate the capabilities of different approaches to similar problems, blind predictions were made using different approaches. For this purpose, two idealized structures were tested on a shaking table and several experts on masonry structures were invited to present blind predictions on the response of the structures, aiming at evaluating the available tools for the out-of-plane assessment of masonry structures. This article presents the results of the blind test predictions and the comparison with the experimental results, namely in terms of formed collapsed mechanisms and control outputs (PGA or maximum displacements), taking into account the selected tools to perform the analysis.

Analysis of In-plane Deformation of Walls Made Using AAC Blocks Strengthened by GFRP Mesh

Masonry walls are considered to be structures most vulnerable to irregular deformation of the substrate of different origin. Such activities generate static or dynamic shearing forces responsible for the most typical masonry damage – diagonal cracking. Recently, various composite materials (FRP) have become very popular as external strengthening used to improve the shear resistance of unreinforced masonry load-bearing walls. Many laboratory tests were conducted to show the positive influence of the application of CFRP, GFRP or BFRP laminates on the shear behavior of masonry walls, but because of the huge diversity of masonry components, to date there are no universal procedures to evaluate the effectiveness of strengthening. This situation imposes a need of separate analyses of individual problems, supported by some laboratory tests, especially if using non-typical masonry elements and erecting techniques. In this article, a detailed in-plane deformation process of unstrengthened and strengthened (by different GFRP meshes) walls made using AAC blocks with thin bed joints and unfilled head joints is shown and discussed. The laboratory tests were conducted because of the growing problems with severely cracked buildings, featuring walls built using AAC blocks, located in Silesian region. The present article is a continuation of the conducted research on the improvement of the shear parameters of walls made using AAC blocks.

Modelling the nonlinear behaviour of masonry walls strengthened with textile reinforced mortars

Textile Reinforced Mortars (TRMs) have found extensive attention for externally bonded reinforcement of masonry and historical structures. However, only few information is available regarding their mechanical properties and effectiveness in improving the seismic performance of strengthened structures. This paper presents an extensive numerical investigation on the effect of TRM composites on the nonlinear response and failure modes of masonry walls. The effect of boundary conditions and the TRM type on the performance of strengthened walls are critically discussed and presented. It is shown that the performance and failure mode of the walls can significantly change after strengthening, an important issue that should be considered at the design stage. Finally, the effect of TRM application on the nonlinear response of a large historical masonry façade in Macau is investigated and presented.

Numerical simulations of tests masonry walls from ceramic block using a detailed finite element model

This article deals with an analysis of the behaviour of brick ceramic walls. The behaviour of the walls was analysed experimentally in order to obtain their bearing capacity under static loading and their seismic resistance. Simultaneously, numerical simulations of the experiments were carried out in order to obtain additional information on the behaviour of masonry walls made of ceramic blocks. The results of the geometrically and materially nonlinear computations were compared to the results of the performed tests.

Effect of Uncertainty of Tensile Strength of Mortar Joints on the Behavior of Masonry Walls under Lateral Loads

AbstractAnalyzing the behavior of a masonry structure is a complex issue due to the complicated nature of masonry. Moreover, random spatial variation of masonry properties due to workmanship quality makes the prediction of its behavior even harder. This paper studies the effect of random spatial variability of mortar joint properties on the lateral strength of masonry walls under in-plane loads. Tensile strength of mortar joints is considered a random variable whose variation represents different quality of workmanship. Using a 3D nonlinear FE model, the influence of the random spatial variability of bed joint and head joint properties on the performance of unreinforced masonry walls is investigated. Results show the considerable effect of random spatial variability of bed joint properties on the performance of masonry walls under in-plane loads, while similar variation in head joint properties has a negligible effect on the wall response. The influence of correlation in bed joint properties on the wall s...

Influence of special plaster on the out-of-plane behavior of masonry walls

The present study aimed at investigating the effect of a special plaster on the out-of-plane behavior of masonry walls. A reference specimen, plastered with conventional plaster, and a specimen plastered with a special plastered were tested under reversed cyclic lateral loading. The specimens were identical in dimensions and material properties. The special plaster contained an additive, which increased the adherence strength of the plaster to the wall. The amount of the additive in the mortar was adjusted based on the preliminary material tests. The influence of the plaster on the wall behavior was evaluated according to the initial cracking load, type of failure, energy absorption capacity (modulus of toughness), and crack pattern of the wall. Despite having limited contribution to the ductility, the special plaster increased the ultimate load capacity of the wall about 25%. The failure mode of the wall with special plaster resembled the plastic failure mechanism of a reinforced concrete slab in the formation of yielding lines along the wall. The deflection at failure and the modulus of toughness of the wall with special plaster were measured to be in order of 60% and 75% of the corresponding values of the reference wall.

Rocking analysis of masonry walls interacting with roofs

This paper investigates the out-of-plane behavior of masonry walls interacting with roofs. Often, collapses of masonry portions supporting roofs may occur due to the roof thrust, which generates a destabilizing effect over motion. Nevertheless, the roof weight can produce a positive stabilizing effect for rotation amplitudes smaller than the critical value. The dynamics of a rocking masonry block interacting with roofs is discussed, by properly modifying the Housner equation of motion of the free-standing single degree-of-freedom block. The dependence of the restoring moment on the rotation angle is investigated and the minimum horizontal stiffness is calculated so that the same ultimate displacement as the system without roof thrust is obtained. Two case studies are presented as applicative examples of the proposed method: an unreinforced masonry structure tested on shaking table and a spandrel beam subjected to roof thrust that survived the Emilia Romagna earthquake. Inertia moments and radius vectors of different failure mechanisms are also provided to solve the equation of motion for different block shapes. Finally, a parametric analysis of a trapezoidal rocking block has been carried out by changing its geometrical shape. This analysis shows that the influence of the shape is relevant for the calculation of the failure load, although is not possible to determine an a priori most critical shape.

Modelling of the in-plane behaviour of masonry walls strengthened with polymeric grids embedded in cementitious mortar layers

The seismic reinforcement of masonry walls needs to be carried out through appropriate and effective techniques aiming at providing both adequate strength and displacement capacity. The present research concerns experimental results about the in-plane behaviour of masonry walls strengthened through an innovative technique employing polymeric grids embedded in cementitious mortar layers applied on the wall surface. The behaviour of strengthened masonry walls subjected to cyclic shear-compression tests is examined in order to quantify the strength and displacement capacity increment provided by the reinforcement. A Finite Element Model of the unreinforced and reinforced panels has been developed and parameters defining masonry and strengthening materials have been calibrated by means of comparisons with the experimental results. The effectiveness of the strengthening system has been then numerically investigated through a wide parametric analysis varying the masonry strength, the wall shape, the axial stiffness of the strengthening grid and the strength of the mortar. Finally, a comparison of the effectiveness of the polymeric grid with a traditional steel one embedded in the same mortar layer is also reported.

Implementation and validation of a strain rate dependent anisotropic continuum model for masonry

A newly developed strain rate dependent anisotropic continuum model is proposed for impact and blast applications in masonry. The model presented adopts the conventional approach of considering different yield criteria in tension and compression. The analysis of unreinforced block work masonry walls subjected to impact was performed to evaluate model performance. Comparison of the numerical predictions and test data revealed good agreement. Next, a parametric study was conducted to evaluate the influence of the tensile strengths in the three orthogonal directions and of the wall thickness on the global behavior of masonry walls.

Strengthening of Masonry Walls Using Fiber Reinforced Polymer (FRP) Materials

The paper presents the behavior of masonry walls built up using ceramic blocks with hollows tested in bear state and then strengthened using FRP materials. A number of two masonry walls are subjected to cyclic in-plane horizontal loads and constant vertical loads, in order to determine the efficiency of the strengthening solutions compared with the shear resistance of the walls in bear state. Also, the experimental program is useful to observe the failure modes of the strengthened walls and also to determine if such strengthening solutions is earthquake-resistant.

First Evaluation of the Structural Performance of Traditional Brickwork after Standard Fire Exposure

The paper addresses the issues of fire behavior of masonry walls made of traditional/historical component materials (bricks and mortar). There are reasons for coupling investigations on the residual mechanical properties to fire resistance data, aiming at a more complete knowledge of the behavior of a masonry member during and after fire exposure. The paper is part of a research that aims at investigating the relationship between fire and post-fire (i.e. residual) mechanical behavior of masonry walls, paying attention to scale-related problems and to the possible exploitation of numerical tools to establish simplified approaches. The goal is to establish relationships between fire resistance ratings under exposure and decay in mechanical properties after exposure; the parameter of wall thickness is especially investigated, by choosing four different values (i.e. 12, 25, 38 and 51 cm). This is performed by means of FEM analysis with DIANA 9.4.4 software, simulating a standard ISO 834 fire resistance test followed by a mechanical compressive failure test on each investigated type of wall. The approach, successfully tested against experimental data already available, features a preliminary transient heat flow analysis which gives a numerical prediction of fire resistance after violation of I (Insulation) criterion; then, a staggered heat flow - stress analysis repeats the heating of the wall up to insulation failure and calculates the thermal strain accounting for cracking; finally, a ‘cold’ structural analysis in compression is performed on the thermally-deformed model after cooling. The paper also addresses a way for the extended application of the research outcomes, relying on a simple approach based on the concept of equivalent fire severity.

Residual Mechanical Parameters of Masonry Exposed to Fire: A New Numerical Approach

The paper is part of a research that aims at investigating the relationship between fire and post-fire (i.e. residual) mechanical behaviour of masonry walls, paying attention to the possible exploitation of numerical tools for simplified approaches. The goal is to establish relationships between exposure severity under ISO834 conditions and decay in mechanical properties after exposure; the parameter of wall thickness is especially investigated, by choosing four different values (i.e. 12, 25, 38 and 51 cm). This is performed by means of FEM analysis with DIANA 9.4.4 software, simulating a standard ISO 834 fire resistance test followed by a mechanical compressive failure test on each investigated type of wall. The FE analyses’ outcomes allow to draw exponential expressions of the decay in compressive strength as a function of the exposure severity.

Shear behaviour of masonry walls strengthened by external bonded FRP and TRC

This experimental study focuses on the behaviour of hollow concrete brick masonry walls, especially walls reinforced with composite materials under in-plane loading conditions. This work is a step towards defining reliable seismic strengthening solutions. Indeed, in France, more stringent seismic design requirements for building structures have been considered with the replacement of old design codes. Thus, an experimental program has been performed at the laboratory scale. Six walls have been submitted for shear–compression tests – five walls are reinforced by (1) – fibre-reinforced polymer (FRP) strips using E-glass and carbon fabrics and/or (2) a textile-reinforced concrete (TRC), and the last wall acts as a reference. It is noted that the composite strips are mechanically anchored into the foundations of the walls to improve their efficiency. All of the walls share the same boundary and compressive loading conditions, which are representative of a seismic solicitation. Nevertheless, masonry wall performances and anchor efficiency are only evaluated under monotonic lateral loadings. A comparative study on global behaviour and on local mechanisms is performed and, in particular, highlights that the mechanical anchor systems play an important role in improving the behaviour of reinforced walls (by FRP and TRC) and that the solutions for strengthening by TRC permit the upgrade of the walls’ ductility with a lower strength compared with the solutions with FRP.

Comparison between rocking analysis and kinematic analysis for the dynamic out‐of‐plane behavior of masonry walls

SummaryThis paper provides a contribution to the rocking analysis of masonry walls by making a comparison with the kinematic analysis suggested by the Italian code. It is shown that the latter approach is generally over‐conservative and therefore potentially inappropriate for historic buildings, where rehabilitation can be expensive and can affect their cultural value. The equation of motion given by the Housner formulation, corresponding to the movement of a rigid block, is here modified to account for different boundary conditions at different heights of the wall. These boundary conditions or horizontal restraints can represent vaults, transverse walls, or retrofitting devices such as steel tie‐rods. A systemic analysis of walls having different dimensions and slenderness is performed, and the results from the Italian code and rocking analysis are compared. Finally, the improvement in the response offered by retrofitting devices is discussed in terms of reduction of amplitude ratio. Copyright © 2015 John Wiley & Sons, Ltd.