Behavior Of Masonry Walls Research Articles

Modelling micro-structure aspects of masonry walls by a simplified approach

A specific simplified rigid element approach is proposed to model the elasticplastic behaviour of masonry walls subjected to in-plane loadings. This proposal originates from the consideration that the evaluation of seismic vulnerability of masonry monuments requires peculiar procedures since their responses to earthquakes often differ substantially from those of ordinary buildings. In particular, the effective characterisation of the masonry material requires a special attention because the global mechanical behaviour of this composite material depends strongly on the different textures, as well as on the elastic-plastic characteristics of the component materials. Numerical analyses are made with the objective of evaluating the importance of the micro-structure effects in the response of masonry walls with special attention to the fact that mechanical degradation tends to concentrate in the weaker component according to a well defined pattern. The paper is limited to the case of monotonic loadings as a first step in the formulation of a rigid element model that is suitable for performing complete dynamical analyses.

Modified estimation method of fundamental periods of historic buildings with masonry shear walls in Taiwan

Thls study focused on the applicability of the fundamental period formula on historic buildings with masonry shear walls based on the building code in Taiwan. In order to verify the empirical formula proposed in the building code, ambient vibration measurements were conducted on 28 historic buildings with masonry shear walls to yield their hndamental periods, and then compared those measured periods with periods estimated by the original formula. Two disadvantages were shown in the original formula, poor correlation between estimated and measured periods and unconservative estimation of the earthquake force. To overcome these disadvantages, a new formula was estimated by only taking into account the shear behavior of masonry walls. In order to assure the feasibility of this modified formula, the evaluation on the origin formula in the building code by considering the normalized response spectrum coefficient was carried out. The results show that the modified formula not only shows conservative performance in the short-period region of these hstoric buildings but also have good correlation between measured and estimated periods.

Cyclic Flexure Tests of Masonry Walls Reinforced with Glass Fiber Reinforced Polymer Sheets

The research work reported here investigates the out-of-plane flexural behavior of masonry walls reinforced externally with glass fiber reinforced polymer (GFRP) sheets and subjected to cyclic loading. A full-scale test program consisting of eight wall specimens was conducted. Nine tests were performed, in which three parameters were studied. These included the level of compressive axial load, amount of internal steel reinforcement, and amount of externally bonded GFRP sheet reinforcement. Of the three parameters studied, varying the amount of GFRP sheets was the only parameter that significantly affected the behavior of the walls. The GFRP sheet reinforcement governed the linear response of the bending moment versus centerline deflection hysteresis. Increasing or decreasing the amount of GFRP sheet reinforcement either increased or decreased both the wall stiffness and the ultimate strength, respectively. Except for visible cracks, the walls maintained their structural integrity throughout the out-of-plane cyclic loading. The unloading/reloading paths for successive loading cycles were similar, indicating little degradation. Thus, the general behavior of the walls was very predictable. The system, therefore, could be used to advantageously rehabilitate older masonry structures that are inadequately reinforced to withstand seismic events. A simple model of the behavior is also presented to allow for the evaluation of the strength and deformation characteristics of these elements.

Modélisation jusqu'à rupture de murs en maçonnerie chargés dans leur plan

ABSTRACT This paper deals with modeling of mechanical behaviour of masonry walls submitted to in-plane loading. The adopted strategy consists of modelling separately the appropriate local failure mechanisms of thoug elements and mortar joints. A particular attention is dedicated to brick crushing mechanisms which were captured with strong displacement discontinuities within the framework of incompatible mode method. A perfect plasticity model including di-latancy has been employed for the joints modeling. This model has been compared with two experimental results. We show that we are able to well reproduce the global behaviour of such structure (stiffness and peak load) and thus construct reliable predictive model of the masonry walls by using only the experimental characteristics of their components.

Modélisation jusqu'à rupture de murs en maçonnerie chargés dans leur plan

ABSTRACT This paper deals with modeling of mechanical behaviour of masonry walls submitted to in-plane loading. The adopted strategy consists of modelling separately the appropriate local failure mechanisms of thoug elements and mortar joints. A particular attention is dedicated to brick crushing mechanisms which were captured with strong displacement discontinuities within the framework of incompatible mode method. A perfect plasticity model including di-latancy has been employed for the joints modeling. This model has been compared with two experimental results. We show that we are able to well reproduce the global behaviour of such structure (stiffness and peak load) and thus construct reliable predictive model of the masonry walls by using only the experimental characteristics of their components.

Experimental determination of masonry beam-column behaviour

An experimental program consisting of 36 reinforced concrete masonry wall specimens comprised of 400 × 200 × 150 mm standard units in two series of tests was carried out to investigate the behaviour of masonry walls under combined axial and lateral loading. W2R series specimens had a single layer of vertical steel, and W4R series specimens had a double layer of vertical steel. Test results show that the effective wall stiffness, (EI)eff, differs from currently specified code values in regions where compression failure tends to predominate. Overall test results presented graphically in the form of lateral load versus deflection, axial load versus moment, and (EI)eff versus eccentricity ratio, e/t, indicate that the current Canadian masonry design code underestimates the effective stiffness of walls with eccentricity ratios e/t < 0.4.Key words: beam–column, masonry, reinforcement, experimental, rigidity, moment magnifier.

Modelling the out‐of‐plane seismic behaviour of masonry walls by rigid elements

A computational model for evaluating the dynamical response and the damage of large masonry walls subjected to out-of-plane seismic actions is presented. During earthquakes, these actions are often the main cause of damage for the front wall and lateral walls of old masonry-built churches and monuments. Since the crack patterns often tend to subdivide the plane walls into a number of blocks, the model assumes such walls as a series of quadrilateral plane rigid elements connected to each other in the middle of their adjoining sides. Only the out-of-plane displacements are considered, and the connections are regarded as spherical elasto-plastic joints which allow rotations whose axis is in the plane of the undeformed wall. The hysteretic characteristics of these joints are defined so as to approximate the brittle behaviour of masonry material and the degradation due to cyclic loadings. The numerical results obtained using a limited number of elements show that the global out-of-plane response of the masonry walls and the mechanical degradation at each connection are in accord with the observed behaviour of real churches hit by strong earthquakes. Copyright © 2000 John Wiley & Sons, Ltd.

Reinforcing Masonry Walls with Composite Materials-Model

In this investigation, a procedure is developed for determining the effectiveness of composite materials in retrofitting masonry buildings to reduce seismic damage. The reinforcement considered is a thin layer of fiber-reinforced composite applied to the wall in a wallpaper-like fashion. Models were developed which predict the behavior of masonry walls reinforced in such a fashion and subjected to static, in-plane normal and shear loads. Solid walls, as well as walls with openings (such as windows and doors), were considered. The models estimate the load-deflection characteristic of the wall, the load set at which the wall fails, and the deflection of the wall at the instant of failure. Numerical results were also generated which indicate that composite reinforcement applied in a wallpaper-like fashion may increase substantially the load carrying capacities of masonry walls.

Modelling the out-of-plane seismic behaviour of masonry walls by rigid elements

A computational model for evaluating the dynamical response and the damage of large masonry walls subjected to out-of-plane seismic actions is presented. During earthquakes, these actions are often the main cause of damage for the front wall and lateral walls of old masonry-built churches and monuments. Since the crack patterns often tend to subdivide the plane walls into a number of blocks, the model assumes such walls as a series of quadrilateral plane rigid elements connected to each other in the middle of their adjoining sides. Only the out-of-plane displacements are considered, and the connections are regarded as spherical elasto-plastic joints which allow rotations whose axis is in the plane of the undeformed wall. The hysteretic characteristics of these joints are defined so as to approximate the brittle behaviour of masonry material and the degradation due to cyclic loadings. The numerical results obtained using a limited number of elements show that the global out-of-plane response of the masonry walls and the mechanical degradation at each connection are in accord with the observed behaviour of real churches hit by strong earthquakes. Copyright © 2000 John Wiley & Sons, Ltd.

Rigid element model for non-linear analysis of masonry façades subjected to out-of-plane loading

A simplified method for investigating the out-of-plane behaviour of masonry walls subjected to seismic loading is presented. A survey of the large walls of monuments hit by earthquakes reveals that in many cases the damage is mainly due to lateral actions, and the crack patterns often tend to subdivide the walls into a number of rigid blocks. In the present study such walls are modelled as a series of plane rigid elements in which only the out-of-plane displacements are considered. The elements are quadrilateral and are connected to each other in the middle of their adjoining sides by hinges that can be regarded as spherical joints at which all the deformation takes place. The mechanical characteristics of these connections are defined so as to approximate the brittle behaviour of masonry material. The results obtained using a limited number of elements are in accord with the observed out-of-plane response of masonry panels. Copyright © 1999 John Wiley & Sons, Ltd.

Seismic Behavior of Masonry Walls: Experimental Simulation

The influence of four different lateral displacement patterns used for experimental simulation of seismic behavior of masonry walls has been studied. Thirty-two equal reinforced-masonry walls have been tested by imposing monotonically increasing displacements; cyclic lateral displacements with amplitudes, stepwise increasing in predefined blocks of two different shapes and repeated three times at each amplitude peak; and simulated displacement seismic response. By imposing the same displacement pattern dynamically, higher values of lateral resistance and more rigid initial behavior of the walls has been obtained than statically. Higher resistance and larger ultimate displacements have been obtained by monotonic than by cyclic loading procedures of all types. At a higher level of vertical load, lateral resistance of the wall was improved, but deformability and ductility decreased at both, static, and dynamic types of loading at all load patterns.

Seismic Behavior of Masonry Walls: Modeling of Hysteretic Rules

A method of modifying the lateral load–lateral displacement relationship obtained by a simple monotonic racking test to represent the skeleton hysteresis curve of an arbitrary dynamic response of a reinforced-masonry wall is proposed. The results of tests of 32 equal reinforced-masonry walls, tested by imposing monotonically increasing displacements, cyclic lateral displacements of two different shapes, and simulated displacement seismic response, have been used as a basis for the development of the procedure of modification. The amount of input energy, defined as the actuator work done to deform the specimens during the test, has been taken into account as the decisive parameter for carrying out this modification. On the basis of experimental results, correlation factors between the monotonic and cyclic hysteresis envelope curves, as well as stiffness and strength degradation parameters, which define the hysteretic rules, have been evaluated. Good agreement between predicted and experimental cyclic behavior of the walls has been obtained.

Thermal behaviour of masonry walls: Mathematical modelling and field monitoring

This Canadian study shows that the potential use of their procedure is very broad since the data computed can be used to investigate deterioration problems, to check risks associated with any proposed thermal upgrading and to perform stress analysis. The variation between the computed data and recorded data is small, except at peaks where the maximum differences occur.

Finite Element Model for Masonry Subjected to Concentrated Loads

A finite element model for brick masonry subjected to in-plane loading is presented. The proposed model reproduces the nonlinear characteristics of masonry caused by material nonlinearity and progressive local failure. Bricks and joints are modeled separately, allowing for nonlinear deformation characteristics of the two materials as well as failure of the bricks, the mortar, or the mortar joints by bond. Because of its ability to model local effects, the model is capable of reproducing the behavior of masonry walls in which high local stresses and stress gradients are present (e.g., walls subjected to concentrated loads from beam supports or prestressing anchorages). The material properties for the model are determined from tests on small samples of brickwork and its constituents. Concentrated load tests on brick masonry are used as a basis for comparison between predicted theory and experimental evidence.

A linear mathematical model for the seismic inplane behaviour of brick masonry walls part 1: Theoretical considerations

AbstractIn this study two mathematical models are presented for the linear dynamic behaviour of masonry walls. The study is completed in three stages: experimental observations, selection of a mathematical model and the determination of model parameters through optimization analysis. In the present paper (Part 1) the theoretical analysis used in the development of the mathematical models is presented. Part 2 is devoted to the optimization analysis.Evaluation of the experimental data, which is described in detail in Part 2, indicates that the first two modal frequencies of the wall specimen are close to each other. This may be attributed, on physical grounds, to strong interaction between the brick and mortar phases of the wall. Accordingly, a two‐phase mathematical model, namely a mixture model (MM), is chosen to describe the wall behaviour because it can differentiate between the two phases of the wall and take into account the interaction between them. The equations of MM are put into a discrete form to simplify the optimization analysis. As a special case, MM contains a simple one‐phase model called the effective modulus model (EMM). The equations of EMM are also established. Finally, the theoretical complex frequency response functions (CFRF) predicted by MM and EMM are obtained. CFRF relates the top acceleration of the wall to its base acceleration and is the response quantity chosen to be matched in the optimization analysis.

Cracks In Historic Masonry Walls Due ToSettlement - Experiments And MechanicalModelling

Many walls -of brick or natural stoneof buildings exhibit cracks through the entire thickness of wall. Such cracks are often caused by historic and also by recent differential settlement along the base of wall. Thereby, restraint actions arise in the wall, which are the response to the interaction of the wall with the foundation and ground. In many cases, the causes of cracks must be clarified in order to assess the load carrying capacity of the damaged wall and to decide on eventual structural repair. On the other hand, the possibility of future cracks must be known if additional settlement is to be expected, if repair of foundations and consolidation of ground are to be planned etc. For such tasks, the development of a predictive mechanical model of the interaction is necessary. This report presents first results of this problem. Wall strips of single and triple leaf natural stone masonry were built for experiments (L:H:D = 4.5 nr.l.O m:0.45 m). In a heavy test set-up, a hollow with a bending radius of R ~ 400 m was forced upon the specimen. Forces, deformations and cracks were measured, fracture phenomena were observed. The mechanical model includes the description of the critical settlements and the leading to cracks structural behaviour of masonry walls in bending and shear. Furthermore, strengthening measures and their effects on the behaviour are considered in the model. Transactions on the Built Environment vol 39 © 1999 WIT Press, www.witpress.com, ISSN 1743-3509 750 Structural Studies, Repairs and Maintenance of Historical Buildings