Deliverable 5.1 Review on the experimental in-plane and...

DEVELOPING INNOVATIVE SYSTEMS FOR REINFORCED MASONRY WALLS

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Experimental and numerical characterization D5.1 of 57

Deliverable 5.1

Review on the experimental in-plane and out-of-plane testing

Due date: October 2006

Submission date: October 2006 Issued by: UMINHO

WORKPACKAGE 5: Experimental and numerical characterization (Leader: UMINHO)

PROJECT N°: COOP-CT-2005-018120

ACRONYM: DISWall

TYTLE: Developing Innovative Systems for Reinforced Masonry Walls

COORDINATOR: Università di Padova (Italy)

START DATE: 16 January 2006 DURATION: 24 months

INSTRUMENT: Co-operative Research Project

THEMATIC PRIORITY: Horizontal Research activities involving SMEs

a) b)

2828

80,8

2828

101,

4

520

222,

8

Reaction wall

Reaction slab

120

Steel beam

Concrete beam

Concrete beam

c)

Test setup for the in-plane cyclic tests: a) UNIPD; b) TUM; c) UMINHO

Dissemination level: PU Rev: final


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INDEX

INDEX................................................................................................................................................................ 2 1 INTRODUCTION........................................................................................................................................ 3 2 STRUCTURAL BEHAVIOR OF MASONRY WALLS................................................................................. 3

2.1 IN-PLANE BEHAVIOUR....................................................................................................................... 4 2.2 OUT-OF-PLANE BEHAVIOUR............................................................................................................. 7

3 EXPERIMENTAL INVESTIGATIONS ...................................................................................................... 10 3.1 IN-PLANE TESTS............................................................................................................................... 12 3.2 OUT-OF-PLANE TESTS .................................................................................................................... 18 3.3 COMBINED TESTS............................................................................................................................ 21

4 CONCLUDING REMARKS ...................................................................................................................... 23 5 PLANNING OF THE EXPERIMENTAL RESEARCH............................................................................... 24

5.1 PERFORATED CLAY BOCKS........................................................................................................... 24 5.1.1 Typology of reinforced masonry walls – brief overview ............................................................. 24 5.1.2 Design criteria for in-plane masonry walls ................................................................................. 25 5.1.3 Material properties for in-plane masonry walls .......................................................................... 27 5.1.4 Geometry of the in-plane masonry walls ................................................................................... 31 5.1.5 Design criteria, material properties and geometry for out-of-plane masonry walls ................... 33 5.1.6 Test setup .................................................................................................................................. 36 5.1.7 Experimental program................................................................................................................ 37

5.2 HOLLOW CLAY BLOCKS .................................................................................................................. 38 5.2.1 Types of hollow clay blocks ....................................................................................................... 38 5.2.2 Geometry of the reinforcement .................................................................................................. 39 5.2.3 Test Set-Up................................................................................................................................ 40 5.2.4 Tests on small specimens.......................................................................................................... 43

5.3 CONCRETE HOLLOW BLOCKS ....................................................................................................... 44 5.3.1 Typology of reinforced masonry walls – brief overview ............................................................. 44 5.3.2 Design criteria of masonry panels ............................................................................................. 46 5.3.3 Material properties ..................................................................................................................... 48 5.3.4 Geometry of the walls ................................................................................................................ 50 5.3.5 Test setup .................................................................................................................................. 52 5.3.6 Experimental program................................................................................................................ 54

REFERENCES ................................................................................................................................................ 55


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1 INTRODUCTION The mail goal of this report is the presentation of an overview of the most common experimental approaches

used in the characterization of the in-plane and out-of-plane behaviour of masonry walls. In a first phase it

aims at reviewing the characteristics related to the in-plane and out-of-plane behaviour of unreinforced and

reinforced masonry walls and in a second phase the main issues regarding the experimental setup and

procedure most commonly cited in the literature. This intends to be an introductory work for planning the

experimental program foreseen in the Work package 5 dealing with the analysis and validation of the

different solutions proposed for reinforced masonry walls.

Besides, for a better clarification of the different experimental approaches proposed for the different partners

and to promote the good progress of the work of this work package, and additional section is included, where

the preliminary work related to the design of the masonry walls to be tested as well as the test program to

characterize the constitutive behaviour of masonry are pointed out.

2 STRUCTURAL BEHAVIOUR OF MASONRY WALLS Structures are often subjected to lateral loads from wind or, in zones of moderate or high seismicity, from

seismic actions, meaning that structural systems have to be designed to resist these types of loading. In

masonry buildings, the walls are the main structural elements that carry on these actions, which can be in-

plane loads and out-of-plane loads. Due to the cyclic random nature of these actions any wall in a building

can be subjected to in-plane and out-of-plane loads, as shown in Figure 1. Besides lateral loads, the walls

are submitted to vertical loads since they constitute the main supports of slabs, vaults and domes, which

lead that a complex stress develops.

Figure 1: Behaviour of the walls due to cyclic random nature of the loading.

Masonry is an excellent structural system when compressive stresses are preponderant. Though, it is well

known that the low tensile strength of masonry becomes it inadequate to use when lateral forces can reach

high values. Therefore, the use of steel reinforcement appears to be a good solution to increase the tensile

strength and thus to improve the mechanical behaviour of masonry under lateral loading.


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Although several investigations have been performed in the scope of unreinforced masonry, mainly due to

the need of preserving historical constructions, its behaviour under lateral forces is not still completely clear.

The complexity of the behaviour of the walls increases when the presence of steel reinforcement is

considered. Besides the material properties of the components (units and mortar) and its interaction (tensile

bond and shear bond behaviour), the interaction between masonry material and reinforcement has to be

analyzed.

Therefore, further experimental studies are required in order to better understand the factors that influence

the in-plane and out-of-plane response of reinforced masonry walls under biaxial loading. A brief overview of

the structural masonry behaviour under in-plane and out-of-plane loading is given in the next sections.

2.1 IN-PLANE BEHAVIOUR

The walls subjected to in-plane loading are known as “shear walls” because the predominance of the shear

effort. A shear wall acts as vertical cantilever and its stiffness depends basically on its aspect ratio defined as

the relation between the height and the length of the wall. As observed by several authors (Anthoine and

Magonette, 1995; Kikuchi et al., 2003; Schultz et al., 1998), the aspect ratio has a great influence in the

failure mode of the walls. Low aspect ratios generate shear failure, while high values lead to the flexural

behaviour of the wall. The failure mode of a particular shear wall also depends on the combination of applied

loads, wall geometry, properties of the materials and as recently pointed out by Vasconcelos (2005), of the

bond masonry. Besides, in reinforced masonry walls, the details of the reinforcement also influence its in-

plane behaviour. Figure 2 shows the distinct crack patterns associated to different stress states exhibited by

shear walls.

Axial load

Lateral load

Tension Failure

Diagonal Failure

Comression Failure

Figure 2: Typical failure modes of shear walls (Page, 1988).

According to Tomaževič (1999), in case of low axial load the lateral loading may cause shear failure by the

horizontal sliding of the joints. This failure usually happens in upper storeys of buildings, where high seismic

accelerations are associated to low axial loads. If the axial load is within moderate values, the wall may

failure by shear or flexure. In shear mode, diagonal cracks occur at the unit-mortar interface or both at the

unit-mortar interface and through units as result of a biaxial tension-compression stress state, which

generally mean the collapse of the wall. In flexure mode, horizontal cracks opens at the unit-mortar

interfaces as a result of its reduced tensile bond strength. This crack pattern is only an intermediate failure


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mechanism since isolated failure of wall does not develop if it occurs. However, these cracks reduce the

resisting cross section, leading to a concentration of compressive stresses and to the failure of the wall by

toe crushing. The axial compression load has a significant influence on the shear strength. In case of

unreinforced masonry, it is widely accepted that axial compression increases the shear strength according to

a Coulomb failure criterion until a limit value, see Figure 3, being the failure mode mainly characterized by

diagonal staffed cracks at the unit-mortar interface. After this point, the increase on the axial compression

leads only to a slight increase on the shear strength. Diagonal shear cracks can be followed by the reduction

of the shear strength with the increase on the axial compressive stress (Drysdale et al., 1999).

µ

τ

σne

d

c

b

a

τ oshearbond

Combinedshear-tension

Biaxialtension-compression

Sliding shearτ = τ + µσo n

Slidingfailure

Diagonalfailure

Compressivefailure

Tensilefailure

MasonryCompressive strength

σn

τ

Figure 3: Behaviour of unreinforced masonry under combined shear and normal stresses (Drysdale et

al., 1999).

The brittleness of the failure of unreinforced masonry shear walls, which is more remarkable with high axial

loads, may be reduced by the use of steel reinforcement. This procedure ensures the increase of the ductility

due to redistribution of lateral load, and provides better energy dissipation under seismic loading. This is very

important in areas with high seismicity. According to Tomaževič (1999), when an unreinforced masonry

shear wall is subjected to lateral loading a diagonal crack opens producing a severe deterioration in wall

strength and a brittle collapse. The horizontal reinforcement prevents the separation of the wall’s cracked

parts at shear failure and provides the load transfer between the edges of the cracks; see Figure 4a. Schultz

et al. (1998) reported that the bed joint reinforcement allowed the masonry carry stresses after initial cracks.

The horizontal reinforcement is subjected to tensile stresses and a tendency for its pull-out from the joint

because the separation of the two parts of the wall occurs. This mechanism enables the redistribution of

lateral loads improving the resistance and energy dissipation capacity of the wall when subjected to repeated

reversal lateral loads. Therefore, the walls that are reinforced horizontally present smeared cracking in

opposition to the localized shear crack of unreinforced masonry walls. Yoshimura et al. (2003) observed that

specimens with horizontal reinforcement uniformly distributed along the length of the wall and specimens

with the reinforcement located only at the corners of the wall presented similar behaviour. In both cases

higher ductility and the ultimate load are obtained in relation to unreinforced masonry. The resisting

mechanisms of vertically reinforced masonry shear walls are quite different, see Figure 4b.


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H

N

H

N

(a) (b)

Figure 4: Resisting mechanisms of reinforced masonry walls: (a) horizontal reinforcement and (b)

vertical reinforcement (Tomaževič, 1999).

The vertical reinforcement is subjected to transversal efforts resulting in its bending, which is known as the

dowel action mechanism, see Figure 5. Part of the shear capacity of the wall can also be attributed to this

mechanism. Dhanasekar and Haider (2004) studied the influence of the spacing ratio of vertical

reinforcement (defined as the ratio of spacing of vertical reinforcement at the central region to the end region

of the wall). The authors concluded that shear walls with approximately uniform spaced vertical

reinforcement exhibited good level of shear capacity and ductility. These specimens degraded gradually

when compared with the walls with non-uniform distribution of the vertical reinforcement. The normalised

shear capacity of the shear walls exhibited gradual reduction with the increase on the spacing ratio of vertical

reinforcement.

rebar

crack

Rrv

Rrv

L/3 Rrv

Rrv

R /3rv

R /3rv

L

LMmáx

contactstresses

bendingmoments

0.577 L

Figure 5: Dowel mechanism of vertical reinforcement at shear failure of a reinforced masonry wall

(Tomaževič, 1999).

On the other hand, as assessed in post-earthquake damage observations and through experimental

indications, only vertical steel reinforcement is not capable of contributing to the shear resistance of

masonry. Walls reinforced with vertical reinforcement fail in shear, despite their predicted flexural behaviour

(Tomaževič, 1999).

Experiments performed by this author confirmed the idea that the shear resistance of reinforced masonry

walls can be more easily assessed as a sum of contributions of the masonry wall panel and reinforcement.


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The behaviour of shear walls has been studied by many researchers mainly for unreinforced masonry.

However, the amount of variables that influence the in-plane behaviour is not completely understood until

now. With respect to reinforced masonry shear walls, more experimental research is required in order to get

a better insight on the influence of the bed joint and vertical reinforcement on the shear strength and ductility.

This is absolutely essential, when new constructive solutions of reinforced masonry walls are to be

proposed.

2.2 OUT-OF-PLANE BEHAVIOUR

The walls subjected to out-of-plane loading are known as “flexural walls” because the flexure is the

predominant effort. The out-of-plane behaviour is considerably more complex than in-plane behaviour of

walls. The walls may be subjected to flexure in two directions which becomes statically indeterminate, as

shown in Figure 6. The analysis of these walls is extremely complicated because the tensile strength in

horizontal flexure can be several times greater than strength in vertical flexure (Drysdale et al., 1999). This

difference can occur because the vertical flexure depends basically on the tensile bond strength of the unit-

mortar interface of the bed joints, whereas the horizontal flexure depends on the friction resistance of the

bed joints and on the tensile bond strength at vertical joint interface (Lourenço, 2001).

Figure 6: Flexure in two directions of a wall subject to out-of-plane loading.

The behaviour of flexural walls depends mainly on the boundary conditions of the masonry panel. In

unreinforced masonry walls supported on four sides, the vertical bending moment at mid-height of the wall

induces tensile stresses perpendicular to the bed joints. When these stresses are higher than the tensile

strength, a horizontal crack initiates and the behaviour of the cracked wall depends upon the orthogonal

flexural strength of the masonry. If the vertical flexure strength is equal to the horizontal flexure strength,

there is no additional strength. The crack propagates along the bed joint and the mechanism is immediately

formed with only a small residual strength due to the self-weight. In general case, in which the horizontal

flexural strength is greater than its vertical strength, a crack propagates along the bed joint under constant

load and a stable state is reached. The panel (ideally) consists of two sub-panels, each simply supported

along three sides and free along the cracked bed joint. As load is further increased, each sub-panel behaves


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as described previously until diagonal cracks occurs, see Figure 7. These cracks immediately propagate to

form a mechanism leading to the collapse of the wall (Drysdale et al., 1999).

Wall supported on four sides

Wall supported on three sides

(a)

(b)

(c)

Figure 7: Crack pattern at failure for walls supported on three and four edges.

The boundary conditions may increase substantially the out-of-plane resistance of masonry walls because

they induce additional compressive forces in the wall panel associated to the denominated “arching” effect,

see Figure 8. When a wall is built between and in tight contact with supports that are restrained against

outward movement, elongation of the tensile face due to bending cannot occur without inducing a

compressive force. Under lateral load, this induced in-plane compressive force results on developing arching

mechanism (Drysdale et al., 1999).

Applied load

Rigid supports

PP

P = Induced compressive force Figure 8: Arching mechanism of masonry behaving under out-of-plane loading.

As pointed out by Moxon (2004) apud Liu et al. (2004), the increase on the axial load increases the out-of-

plane strength but also reduces the ductility, see Figure 9.


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Figure 9: Mid-height deflection vs. lateral pressure measured in reinforced masonry walls (Moxon

apud Liu et al., 2004).

As in shear walls, the tensile strength of masonry is a central property in the flexural behaviour of walls

submitted to out-of-plane loading. The brittle nature of unreinforced masonry due its low tensile strength

makes it as an inadequate material to stand lateral loads as in seismic active regions. In these areas

reinforced masonry is needed. As with in-plane behaviour, the steel reinforcement provides the load transfer

between the edges of the cracks enabling the redistribution of stresses improving the resistance and energy

dissipation capacity of the wall. Abboud et al. (1996) studied the flexural behaviour of reinforced concrete

masonry walls under out-of-plane monotonic loads. The vertical reinforcement was one of the parameters

observed in their study. The results showed that specimens with steel percentage less than 0.2% result in

the increase of the ultimate deformation, being the ductility ratio higher than 4, which is adequate to seismic

areas. The vertical reinforcement led to the increase of the ultimate load but no significant differences were

recorded in the cracking load level. The failure modes were characterized by yielding of reinforcements. The

location of the vertical reinforcements reveals as negligible in the behaviour of the walls.

With respect to experimental investigations on the out-of-plane behaviour of masonry walls, few results have

been pointed out. Therefore, more researches should be performed not only on the out-of-plane behaviour of

masonry walls but also on the combined, in-plane and out-of-plane behaviour since both actions act together

in a real building.


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3 EXPERIMENTAL INVESTIGATIONS

The in-plane and out-of-plane behaviour of masonry walls have been evaluated through different

experimental approaches such as quasi-static monotonic or cyclic tests, dynamic shake-table tests and

pseudo-dynamic tests. According to Gerardin and Negro (2000) the dynamic shake-table tests are the most

realistic way of subjecting a structural model to any particular base motion (Bennet et al. (1993) apud

Handerson et al., 2003; Modena et al, 2004; Reneckis et al., 2004; Wight et al., 2004). These tests simulate

the seismic action with more accuracy because test structure is subjected to real earthquake acceleration

records. However, the unavailability of the equipment in most laboratories leads to other types of tests.

Nevertheless, several dynamic results have been found in literature. Reneckis et al. (2004) studied the out-

of-plane behaviour of brick veneer walls on wood frame construction under dynamic lateral loading by

performing shaking table tests. A full-scale one-story wall was designed to represent a portion of the wall

system in a single-family home, see Figure 10.

Figure 10: Wall test structure setup on the shaking table (Reneckis et al., 2004).

Another approach that provides realistic dynamic results consists of performing pseudo-dynamic tests. They

are more simple than shaking table tests. This test is a conjunction of a quasi-static test with a computer

model which calibrate the load level to considerate the dynamic responses. Paquette and Bruneau (2003)

carried out pseudo-dynamic tests on a full-scale one-story unreinforced brick masonry specimen having a

wood diaphragm subjected to earthquake excitations by using the test setup displayed in Figure 11. The

objective of this research was to better understand the flexible-floor/rigid-wall interaction, the impact of wall

continuity at the building corners and the effect of a relatively weak diaphragm on the seismic behaviour.

The masonry walls were submitted to a real earthquake excitation at a relatively slow speed, which enabled

the observation of the evolution of damage. The dynamic characteristics of the structure, equivalent mass

and damping, were numerically simulated on a computer model, while the characteristics of the restoring

force were directly measured in the tested specimens.


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Figure 11: Test setup used by Paquette and Bruneau (2003).

The quasi-static monotonic/cyclic tests are the most common technique used to evaluate the behaviour of

shear walls. They are simple, relatively inexpensive, and do not require special apparatus. Static tests are

generally carried out in single elements or simple subassemblages. The test is performed by controlling the

displacement due to the larger uncertainties in predicting the restoring forces in the nonlinear regime.

According to Gerardin and Negro (2000) the main limitation of the static tests concerns the impossibility of

simulating the inertial forces. Distinct lateral displacement histories may be used to simulate the seismic

loads as shown in Figure 12.

Figure 12: Typical lateral displacement time histories used to simulate seismic loading (Tomaževič,

1999).

Tomaževič et al. (1996) investigated the influence of the distinct displacement time histories on the in-plane

behaviour of masonry walls by comparing the results obtained for each procedure in the same type of

specimens. The results showed that in-plane behaviour depends on the displacement time history.

Monotonic loading led to the highest lateral resistance and displacement capacity. Masonry walls exhibited a

more brittle behaviour under real earthquake and sinusoidal loading.

Other factor that have a strong influence in the structural behaviour of the masonry walls are the boundary

conditions. In real buildings the walls are generally restrained in three or four sides: in up and bottom face,


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by slabs/wood diaphragms and in lateral faces by other walls. Abrams (1986) and Modena et al. (2004)

tested two-story reinforced masonry building systems in a real scale, which enabled to simulate the real

connection between the structural elements. Nevertheless, these types of specimen are expensive and need

special apparatus to be tested. Therefore, a single wall is the most common system for in-plane and out-of-

plane tests. These specimens are commonly cantilever walls or fixed-fixed ends. Lateral restraints can be

simulated by flanged panels (Zhang et al., 2001; Yoshimura et al., 2003; Modena et al., 2004) as shown in

Figure 13. However, the interaction between walls is still a subject not well understood. Thus, this type

specimen is particularly used when the main aim is the assessment of the influence of the level of

connection between walls on the in-plane or out-of-plane behaviour.

Figure 13: Lateral restraints simulated by flanged walls.

The boundary conditions are generally simulated in different ways as concerns in-plane or out-of-plane tests.

Therefore, there are some specific features intrinsic to in-plane and out-of-plane tests, which lead that the

evaluation of both tests should be made separately.

3.1 IN-PLANE TESTS

As mentioned in the last section, the dynamic tests are the most real approach when seismic behaviour of

masonry walls is required. However, due to the unavailability of shaking tables in the most laboratories, the

static cyclic/monotonic tests are preferred. In this section, a brief overview of the major issues to be taken

into account in static cyclic/monotonic tests is given. The Figure 14 shows the typical test configuration for

shear walls. This led that some changes can be introduced in the configuration of the test setup used to

analyze the in-plane behaviour of walls.


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Lateral Load

Axial Compression

Concrete Header Beam

Panel Wall

Concrete Footer Beam

Figure 14: Typical test configuration of shear walls.

Typically, the wall is submitted to combine in-plane horizontal and vertical loading. The masonry walls have

to be tested under an axial load in order to simulate the effect of the upper storeys. According to Tomaževič

(1999), in a real situation the axial compression load in a structural wall changes during earthquake because

of stresses that develop due to restraints that prevent the rotation of the wall at large displacements.

However, since it would be difficult to simulate the real boundary conditions, the walls are tested at a

controlled level of vertical load that is kept constant during seismic resistance test, within the usual limits of

vertical loading in a real building. Usually the vertical axial load is applied by means of vertical actuators

whose reaction is often given by a steel frame. Maintaining the axial loading constant during whole test is a

difficult task since the progress of the wall deformation changes the initial characteristics of the test

arrangement. The main differences among various test apparatuses thus concern the boundary conditions

and the applied horizontal load or displacement history, as shown in previous section 3. Masonry specimens

can be tested as cantilever with centred vertical loading or as double fixed end walls, by preserving the

parallelism between the two bases of the specimen during the test (see Figure 15). The two possible tests

configurations, cantilever or double fixed ends, can be preferred respectively because they have determinate

force distribution or they better simulate the force distribution into a real wall (Manfredi et al. 1992).

Figure 15: Schematization of the two typical configurations for shear-compression tests (after Magenes,

2000).


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For the two boundary conditions, cantilever and double fixed end walls, a large variety of test rigs have been

designed and used. The cantilever is generally fixed at the base (see, for example, Figure 16), but can also

be fixed at the top, with rotations and horizontal displacements released at the lower edge of the specimen

and the vertical load easily controlled and applied by means of a lever (see, for example, Figure 17). In the

first case, the vertical load is generally applied by means of a single actuator placed centrally over a reaction

beam or by means of two actuators. Several systems are used to join the free-to-rotate edge of the

specimen to the apparatus applying the vertical load. This can be bolted, simply supported, or jointed by

means of roller bearings to the top reinforced concrete beam of the specimen. Each of these systems can

introduce forces at the free edge that have to be taken into account in the interpretation of the test results.

The horizontal load or displacement is generally applied laterally or centrally on the free edge through a steel

or concrete beam, whose stiffness should minimize differences arising from the possible configurations for

the load application.

Hydraulic pump

Strong floor

Concretefoundation

Specimen

Programable actuator 250 kN

Programmableactuator 1000 kN

Load cell

Strong steelbeam

Concreteelement

Rollerbearing

Testingframe

Cardan shaft

Load cell

Figure 16: Scheme of shear compression test on cantilever wall fixed at the base (after Bosiljkov et al.,

2004).

Figure 17: Scheme of shear compression test on cantilever wall fixed at the top (after Bosiljkov, 2001).

The double fixed end configuration has been typically obtained by means of kinematic constraints associated

or incorporated into heavy reaction frames or thanks to electronic control systems regulating in real time

forces and displacements of the vertical actuators. Anthoine and Magonette (1995) in an investigation about


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the in-plane behaviour of unreinforced brick masonry walls used two jacks to apply the axial load. The jacks

balanced their force levels during the test aiming to obtain a constant vertical displacement and preventing

the top rotation of the wall, which led that the axial load in each vertical actuator is not constant. However,

the total vertical load resulting from the sum of both forces measured by the jacks is kept constant, see

Figure 18.

Steel Beam

Reaction wall

AA

A

A = Actuator

Figure 18: Schematic view of the test setup of Anthoine and Magonette (1995).

Vermeltfoort et al. (1993) performed shear tests using a test setup that also intends to prevent top rotations.

These authors used three actuators to apply the vertical forces: two actuators in one side of the wall and one

actuator in the other side of the wall. Other different configurations have been used recently in order to

prevent top rotations (Kikuchi et al., 1999; Kikuchi et al., 2003 and Yoshimura et al., 2003). As is shown in

Figure 19, the vertical load is applied by only one actuator. However, an additional vertical actuator is used

to restraint top rotations. Besides it should be noted that the bending moment associated to horizontal load

applied at 0,55h also intends to reduce the trend for rotation.

Figure 19: Test setup of Kykuchi et al. (1999).


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The axial compression can be also applied through post-tensioned cables (Rodriguez et al., 1998; Chai and

Yaw, 1999). There are other several manners of applying the vertical load (Abdel-Halim and Barakat, 2003;

Miller et al., 2005; Manos et al., 2001), as shown in Figure 20. Generally, the different manners to apply the

axial load have as the main objectives a uniform distribution of the normal load on the wall and to reduce the

wall top rotation.

(a)

(b)

(c)

Figure 20: Different ways to apply the axial load: (a) Abdel-Halim and Barakat (2003), (b) Miller et al.

(2005) and (c) Manos et al. (2001).

In relation of the horizontal loading, is common to apply this force in only one of the sides. Though, the test

setup presented by few authors considers the using of two horizontal actuators to apply the horizontal cyclic

loading (Zhuge et al., 1996; Modena et al., 2004), being each actuator placed at each side of the wall, see

Figure 21. This procedure enables a symmetrical stress distribution during the cyclic test. It means that one

actuator applies the horizontal load pushing the wall in the positive direction, and the other actuator pushes


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the wall in the opposite direction producing a cyclic behaviour. There is not the push-pull action of the

actuator. This test setup allows that similar conditions can be considered in both directions which lead to the

total symmetry of the response. Another possibility to obtain a symmetrical response is to use a single

actuator, but centred into the header beam, such as in Figure 16.

In some cases the lateral load is applied with an eccentricity in order to reduce the flexure response of the

wall. This configuration intends to simulate a wall with a fixed-fixed ends. The boundary conditions constitute

a central issue for the achievement of a reliable response. In general cantilever or fixed-fixed ended walls

are tested. Modena et al. (2004) performed an experimental research on reinforced and unreinforced

masonry specimens subjected to lateral loading and used fixed-fixed boundary conditions. The equipment

used for the tests on masonry walls was made of an extremely rigid steel frame where the upper section of

the panel was fixed, while the lower section was supported on a double articulated quadrilateral, which

allows applying the horizontal displacement with no rotation, as shown in Figure 21.

Figure 21: Test setup used by Modena et al. (2004).

Usually, stiff concrete header and footer beam are used to fasten the specimens; however, it is very difficult

to assert that there will be no rotations at the level that the lateral load is applied. Chai and Yaw (1999) used

the test setup shown in Figure 22, where the top rotations of the wall were reduced through a reverse-

bending moment induced by vertical loadings transferred by the steel struts. A double-acting actuator was

mounted at mid-height of the wall to provide an in-plane reverse-curvature to the wall.


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Figure 22: Test setup used by Chai and Yaw (1999).

Besides the header beam can partially restrain the top rotations in case of reinforced masonry walls, their

use is extremely necessary as they are responsible for anchoring the vertical reinforcement, see Figure 23.

Independently of the presence of the reinforcement, the footer beam also acts as a foundation for the wall

and the header beam generates a better distribution of the horizontal loads. This is the reason by which

Schultz (1994) recommends it also when masonry is tested as a cantilever.

Figure 23: Specimens tested by Chai and Yaw (1999).

3.2 OUT-OF-PLANE TESTS

Performing out-of-plane tests in masonry walls is a difficult task since it requires special cares. The stability

conditions of the specimen during the test become a critical issue when the wall begins to be damaged.

Thus, the out-of-plane tests conducted on horizontal specimens, as is shown in Figure 24, have been

preferred in relation to the vertical specimens (Heeringa and McLean, 1990; Rodriguez et al., 1998).


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Figure 24: Test setup used by Heeringa and McLean (1990).

The most common specimens tested under out-of-plane loading have the top and bottom edges free to

rotate and with out-of-plane displacements fixed. The base of the wall is restraint for axial displacements and

the top is free for axial load application (Abboud et al., 1993; Abboud et al., 1994; Bhende and Ovadia,

1994), as shown in Figure 25.

8" Masonry wall

Distributor Beam

Swivel HeadSwivel Base

Bottom Pin Support

Top Roller Support

Spreader Beam

Load Cell MTS Hydraulic Jack

Figure 25: Test setup of Bhende and Ovadia (1994).

In out-of-plane tests, the header and footer beams are only used with the objective of anchoring the vertical

reinforcement. The header beam is also used to distribute the axial compression. The application of the axial

loading may be done in the same way showed for in-plane tests.

Another important issue concerns the application of the out-of-plane loading. A simple manner of applying

the out-of-plane loading is through one or two lines of force simulated by a set of steel profiles (Heeringa and

McLean, 1990; Abboud et al., 1993; Abboud et al., 1994; Bhende and Ovadia, 1994; Rodriguez et al., 1998),

see Figure 24 and Figure 25. However, this type of loading does not allow the evaluation of the out-of-plane

behaviour of the wall in its two directions. A uniformly distributed force would be a more real loading, but its

application is rather difficult because it involves special apparatus. In Figure 26 some possibilities of

simulation of uniformly distributed load, suggested by RILEM (1994) are shown.

Several recent experimental investigations have been using the air-bag to simulate the out-of-plane loading.

Moxon (2004) apud Liu et al. (2004) carry out the analysis of the out-of-plane behaviour of reinforced

masonry walls by considering the air-bag to simulate the loading case. The lateral pressure was applied by

means of an air bag, as shown in Figure 27.


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Zhang et al. (2001) and Henderson et al. (2003) also used air-bags to evaluate the behaviour of walls under

out-of-plane loading. The test setup, which is the basis for a successful out-of-plane test, constitutes the

main limitation and the cause for the scarce experimental results on the out-of-plane behaviour of masonry

walls.

(a)

(b)

(c)

Figure 26: Out-of-plane test setups suggested by RILEM (1994): (a) air-bag loading method, (b)

“Christmas tree” loading method and (c) direct air pressure loading method.


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Figure 27: Test setup of Moxon (2004) apud Liu et al. (2004).

3.3 COMBINED TESTS

The most realistic analysis of the behaviour of masonry walls under seismic or wind loads, would be

performed through the results obtained from combined tests. In these tests, vertical compressive loading, in-

plane and out-of-plane loading would be simultaneously applied. In this way, the interaction between both

solicitations could be both assessed. However, combined tests are rather difficult to be conducted in a

laboratory due to the large amount of equipment would be needed. It would be necessary three jacks for the

application of the normal, out-of-plane and in-plane loading, a stiffer reaction frame and a large amount of

instruments to record the deformations of the walls. This is the main reason by which, there is few works

considering the conjunct behaviour of normal, in-plane and out-of-plane loading.

An alternative mode of performing these tests consists in inducing a certain level of in-plane damage and a

subsequent out-of-plane testing. Flanagan and Bennett (1999) and Henderson et al. (2003) investigated the

possible influence of a previous damage induced by out-of-plane behaviour on the in-plane behaviour. It was

concluded that no influence seemed to exist in the in-plane lateral resistance. However, when the level out-

of-plane damage was severe enough, it may eliminate the in-plane diagonal cracking limit state and to

reduce the in-plane stiffness. On the other hand, the same authors noted a decrease on out-of-plane lateral

strength caused by prior in-plane damage. Besides, it was noticed that the arching effect could still form

resulting in a substantial capacity.

Bennet et al. (1993) apud Handerson et al. (2003) analysed the combined in-plane and out-of-plane

behaviour through dynamic shake-table tests. The tests were previously carried out with the walls submitted

to out-of-plane accelerations. The specimen was then rotated 90º on the shaking table and the second set of

tests were carried out under in-plane loading. After the in-plane tests were completed, two additional in-plane

sinusoidal sweep tests were performed on the specimen. The dynamic out-of-plane tests indicated that the

structure’s stiffness decreased slightly.


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Flanagan and Bennett (1999) performed combined tests and noted that interaction between out-of-plane and

in-plane forces appeared to be insignificant. The authors believe that the tests results justify the

determination of in-plane and out-of-plane capacities independently. On the other hand, the tests performed

by Fricke et al. (1992) apud Handerson et al. (2003) showed that in-plane forces that developed during the

out-of-plane loading enhance the ability of the wall to resist lateral pressure. According to the authors, this

effect was responsible for increasing the strength of walls.

Since there are little researches about this subject, further experimental studies are required in order to

better understand the combined behaviour of the in-plane and out-of-plane loading.


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4 CONCLUDING REMARKS

In the former sections a summary of the main features of the in-plane and out-of-plane behaviour of

unreinforced/reinforced masonry walls was given. Moreover, an overview of the experimental investigation

on the mechanical characterization of the in-plane and out-of-plane tests, including the most usual

experimental setup, boundary conditions, test procedure were analysed.

As has been referred, there are several variables that influence the in-plane and out-of-plane behaviour of

the walls: aspect ratio of the wall, level of axial compression, steel reinforcement, boundary conditions and

history of lateral load. In walls with low aspect ratios or submitted to high axial compression levels, the in-

plane behaviour is more brittle, which is essentially related to the predominant shear failure mode. The use

of steel reinforcement may also contribute to increase the ductility of the wall.

Regarding the experimental work, it could be seen that usually, single walls are used in experimental

programs, although they do not represent the real behaviour of the structure because it is not possible to

model the interaction of walls in a three-dimensional state. However, it should be stressed full scale

specimens are very expensive and requires special equipment. On the other hand, the obtained results are

difficult to analyze.

Therefore, single walls are more frequently used since it is possible to test a large amount of specimens and

it is easier to follow its behaviour. The basic configuration of the test depends mainly of the scope of the

research. However, shear tests (monotonic/cyclic tests) conducted on masonry panels can be considered

the most used test configuration to analyse the in-plane seismic behaviour of reinforced/unreinforced

masonry walls. Concerning this test setup, different ways of simulating the boundary conditions (cantilever,

fixed-fixed ends), or of applying the horizontal loading were shown.

Although less information of out-of-plane experimental testing is available, it was possible to note also that

different test setups can be used.

It is stressed that there is not a specific standard that rules the experimental procedure to be followed in the

experimental characterization of the in-plane/out-of-plane behaviour masonry walls. This is the main reason

by which several test setups, with distinct characteristics, have been reported in the scope of the analysis of

in-plane and out-of-plane behaviour of walls.


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5 PLANNING OF THE EXPERIMENTAL RESEARCH

This section aims at indicating the plan for the experimental work to be carried out on the characterization of

the in-plane and out-of-plane behaviour of reinforced masonry walls (design of masonry panels to be tested

and test setup) during work package 5. Additionally, the plan of tests on the materials characterization

(mortar, concrete and masonry) is also pointed out.

5.1 PERFORATED CLAY BOCKS

5.1.1 Typology of reinforced masonry walls – brief overview In the scope of work package 4, two distinct constructive systems have been proposed.

The first one is a system of reinforced masonry with concentrated vertical reinforcement, similar to confined

masonry, made by using a special unit with horizontal holes and recesses for the placement of the horizontal

reinforcement for the reinforced masonry panel and an ordinary unit with vertical holes for reinforced

masonry for the confinement columns. The unit width is 30 cm. Two types of horizontal reinforcement are

studied: one is made with ordinary steel rebars, the other is made with prefabricated steel trusses provided

by Bekaert. The mortar developed for the construction of the reinforced masonry system is a premixed M10

cement mortar, with 0÷4 mm grain size and additives to improve plasticity and adhesion properties. Figure

28 shows the developed masonry system.

Figure 28: Constructive system defined by the use of horizontally perforated clay units. Front views and

cross sections.


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The system, which makes use of horizontally perforated clay units that is a very traditional construction

technique for all the countries facing the Mediterranean basin, has been developed mainly to be used in

small residential buildings. For this reason, considering the use of rigid slabs, the small height of the floors

and the short spans of walls generally used for this type of buildings, the main problem related to the use of

such type of masonry is to obtain proper in-plane behaviour of walls exposed in the direction of the seismic

action. Hence, the test program has been developed keeping in mind the main objective of understanding

the in-plane behaviour of the developed masonry system.

The second construction system, conversely, is a system of reinforced masonry, made by using the

perforated clay units with vertical holes, developed and aimed at building mainly tall, load bearing reinforced

masonry walls for factories, sport centres, etc., which have to resist out-of-plane actions in particular when

they are in the presence of a deformable roof. For this system, the main objective of the test program is thus

that of understanding the out-of-plane behaviour. This system is based on the use of a ‘C’ shaped unit, which

can be easily put in place after the vertical reinforcement has been already placed. Figure 29 shows the

developed masonry system.

Figure 29: Constructive system defined by the use of vertically perforated clay units. Front views and

cross sections.

5.1.2 Design criteria for in-plane masonry walls

The definition of the geometry and dimensions of the masonry walls is based on the estimation of the

experimental in-plane horizontal load considering the possible distinct failure modes that can occur in the

reinforced masonry walls: shear and flexural failure mechanisms.


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The prediction of the horizontal in-plane load was made following the procedure indicated in the Eurocode 6

(2005), the procedure followed by Tomazevic (1999) and that followed by Tassios (1988). The evaluation of

shear capacity by means of the Eurocode 6 has been obtained as explained in the following section 5.3.2.

The formulation proposed by Tomazevic (equation 1) is:

321 RdRdrhRds VVCVH +⋅+= (1)

where:

1RdV is the shear resistance of an unreinforced masonry wall, evaluated in this case by applying the

Turnesek-Cacovic criterion:

t

twRd fb

fAV 0

1 1σ

+= (2)

where Aw is the horizontal cross sectional area of the wall, ft is the referential tensile strength of masonry, b is

the shear stress distribution factor and σ0 is the compressive stress during the test execution;

2RdV is the contribution of the shear reinforcement that in the equation (1) is multiplied by the horizontal

reinforcement capacity reduction factor Crh which can be taken equal to 0.3 (Tomazevic (1999)), 2RdV is

given by:

s

ykSwRd

fAV

γ⋅= 902 . (3)

3RdV is the contribution of the dowel action effects of the vertical reinforcement given by:

=3RdV ykmkrv ffnd ⋅⋅ 28060. , (4).

In the previous equations Asw is the total area of horizontal shear reinforcement, n and drv are respectively

the number and the diameter of vertical rebars, fmk is the characteristic compressive strength of embedding

mortar or grout, fyk is the characteristic yield strength of reinforced steel.

The formulation proposed by Tassios provides more consistent results for higher compressive strength of

masonry and higher percentage of horizontal reinforcement. However, it has been applied to obtain a

reference value of shear strength. The shear capacity of a reinforced masonry wall is found by multiplying

the cross sectional area of the wall times τu,sh (equation 6):

shuwS AH ,τ⋅= (5)

where τu,sh is given by:


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⎪⎭

⎪⎬⎫

⎪⎩

⎪⎨⎧

⎟⎟⎠

⎞⎜⎜⎝

⎛−++= 3

20

0 10130150411

hk

tkts

shu ffff

aρ

σστ ,,, (6)

VdMas = (7)

σ0 is the constant compressive stress during the test execution, fk is the characteristic compressive strength

of masonry, ft is the tensile strength of masonry, ρh is the percentage of horizontal reinforcement and a is the

shear ratio.

The determination of the in-plane moment of resistance Mrd, related to the flexural failure, has been

evaluated on the basis of the same hypothesis exposed in the following section 5.3.2, which are the

recommendation provided by EC6. Moreover, the evaluation of the in-plane moment of resistance has been

made considering the different mechanical characteristics of the two typologies of block (with horizontal

holes for the masonry panel and with vertical holes for the confining columns) involved in the new reinforced

masonry system. This concept it is widely explained in section 5.1.4.

5.1.3 Material properties for in-plane masonry walls

As regard the materials properties, the clay unit developed for the purpose of the research can be seen in

Figure 30.

Figure 30: Clay units developed for the horizontally perforated masonry.

The units can be classified as Group 4 masonry units as pointed out by the EC6 (2005), whereas the units

used for the vertical confining columns can be classified as Group 2 masonry units, see


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Table 1. The units produced are full scale units.


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Table 1: Requirements for the units (EC6, 2005)

Blocks Property

Ver. hol. Hor. hol.

Requirements For Group 2 (ver. holes)

Requirements For Group 4 (hor. holes)

Size (l x w x h) (cm) 250x300x190 250x300x200 No req. No req.

Percentage of holes (%) <45 45 > 25; ≤ 55 > 25; ≤ 70

Thickness of webs (mm) 8 11 ≥ 5 ≥ 5

Thickness of shells (mm) 10 12.2 ≥ 8 ≥ 6

In the absence of detailed experimental information about the mechanical properties of materials, in

particular mortar and the masonry as a composite material, which will be gained during the experimental

phase of the research itself, approximate values are calculated according to the EC6 based on the

classification of the units and a required M10 mortar. Conversely, the adopted values of compressive

strength of the units are experimentally found, and are equal to 9.45 N/mm2 for the unit with horizontal holes,

and 21 N/mm2 for the unit with vertical holes. The normalized compressive strength of the units is estimated

starting from the experimental values according to EN 772-1, by considering the characteristic mean

compressive strength over the gross cross section of the units multiplied by a shape factor respectively equal

to 1.1 and to 1.15 in order to take into account the size of the masonry units.

Based on the properties of masonry units (Group 4 for the masonry panels, Group 2 for the confining

columns) and on the estimated properties of mortar, and considering that a general purpose mortar is used

for laying the masonry units, the characteristic compressive strength of masonry, fk, can be calculated from

the expression:

3.07.0mbk ffKf ××= (8)

where K takes the value of 0.35 (Group 4, general purpose mortar, masonry laid with horizontally perforated

units), and takes the value of 0.45 (Group 2 and general purpose mortar), fb is the normalized mean

compressive strength of concrete masonry units and fm is the compressive strength of mortar. Hence, the

characteristic compressive strength of masonry, fk, takes the value of 3.60 N/mm2 for the masonry panels,

and 8.31 N/mm2 for the confining columns.

The characteristic shear strength of masonry, fvk, for the calculation of the shear capacity of the masonry

specimens, is estimated by the expression:

nvkkv ff σ⋅+= 400 . (9)

where fvk0 is the characteristic shear strength under zero compressive strength and σn is the normal

compressive stress during the execution of the tests. The value of fvk0 is considered to be 0.3N/mm2 (clay

masonry units and general purpose mortar M10) according to the EC6.


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Furthermore, considering that the collapse of masonry panels under combined vertical and horizontal loads

generally occurs with the development of a diagonal crack passing through the units, also the Turnsek and

Cacovic criteria (1971) has been taken into account for the evaluation of the shear capacity of the masonry

specimens under testing. In this case, a value of referential tensile strength ft for the masonry has to be

taken into account. Based on previous experiences and on the data available in literature, an average value

equal to 0.25 N/mm2 has been taken into account.

A characteristic tensile strength fyk equal to 430 N/mm2 was considered in the calculations for the

reinforcement. The summary of the characteristic mechanical properties of masonry required for prediction of

the lateral shear strength of clay block masonry walls are indicated in Table 2.

Table 2: Mechanical properties adopted of the masonry and masonry materials

Property Masonry panels (N/mm2) Confining columns (N/mm2)

fb 10.40 24.11

fm 10.00 10.00

fk 3.60 8.31

fvk0 0.3 -

ft 0.25 -

fyk 430 (horizontal reinf.)

430 (vertical reinf.)


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5.1.4 Geometry of the in-plane masonry walls

The geometry of the walls, and the corresponding height to length (slenderness) ratio (h/l), was obtained

based on the comparison of horizontal in-plane load associated to different possible failure modes. In order

to simulate the different failure mode of masonry piers under seismic loading, it was decided to choose

different slenderness ratio in order to force both the shear failure and the flexural failure response in two

different types of specimens. These two types of specimens respectively have a slenderness ratio equal to

1,09 and 1,64 (see Figure 31).

1550

16902510

12

34

56

78

400

420

2000

1030

16902510

12

34

56

78

400

420

2000

Figure 31: View of the two geometry to be tested: wall with slenderness 1,09 (left) and 1,64 (right) .

Shear and flexural horizontal loads were calculated based on the procedure indicated in Section 5.1.2 for

different height to length ratios and for variable values of the applied compression stresses (0<σn <2.3). The

result of the parametric studies is shown in Figure 32 and Figure 33.

It has to be noted that the evaluation of the in-plane moment of resistance Mrd have been made differently for

the two considered slenderness. For the 1.09 slenderness specimens, the Mrd has been evaluated by

considering the difference of the mechanical characteristics of the vertically perforated units in respect to the

horizontally perforated units. For the 1.64 slenderness specimens, Mrd has been evaluated by considering

the base section reacting only where the vertically perforated units are placved, since the presence of the

horizontally perforated units is negligible.


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Shear Specimen Design (h/l=1,09)

Shear failure (EC6)

Shear failure (Tassios)

filed 2 field 3

Flexural failure

Shear failure (Tomazevic)

0

50000

100000

150000

200000

250000

300000

350000

400000

450000

500000

0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1 1,1 1,2 1,3 1,4 1,5 1,6 1,7 1,8 1,9 2 2,1 2,2 2,3

σ0 (MPa)

Vru (N)

Figure 32: Design curves for slenderness 1.09 and variable values of applied compressive strength

Shear Specimen Design (h/l=1,64)

Shear failure (EC6)

Shear failure (Tassios)

Flexural failure

Shear failure (Tomazevic)

field 2 field 3 field 40

50000

100000

150000

200000

250000

300000

350000

400000

450000

500000

0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1 1,1 1,2 1,3 1,4 1,5 1,6 1,7 1,8 1,9 2 2,1 2,2 2,3

σ0 (MPa)

Vru (N)

Figure 33: Design curves for slenderness 1.64 and variable values of applied compressive strength

The evaluation of shear resistance is very variable in respect to the applied formulations, but considering the

limitation in the use of the method proposed by Tassios and considering the high values obtained with the

EC6 method, it seems to be more realistic in this case the evaluation of shear resistance by means of the

method proposed by Tomazevic. The verification of the compressed strut following the EC6(2005) procedure

confirmed that there is not hazard of this type of failure.


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The carried out parametric study, has confirmed that the choice to apply an axial load variable between 0.2

and 0.4 N/mm2, leads towards shear failure for the 1.09 slenderness specimen and to flexural failure for the

1.64 slenderness specimen. The axial loads to be applied during the tests have been chosen considering the

actual serviceability loads for the low rise building typology for which the present reinforced masonry system

has been developed.

5.1.5 Design criteria, material properties and geometry for out-of-plane masonry walls

The definition of the geometry and dimensions of the masonry walls is based on the estimation of the

possible distinct failure modes that can occur in tall, out-of-plane loaded, reinforced masonry walls due to the

different structural configurations of the building where they are located. One of the two possible structural

configurations consists in buildings made with deformable roofs, thus the walls can be tentatively considered

as cantilevers with a vertical load applied at the top and a horizontal load due to the masses of both the roof

and the wall itself. If the roof is stiff, the horizontal action is mainly distributed to the in-plane loaded walls.

The out-of-plane walls, in case of seismic action, are mainly loaded by the action coming from their own

mass, where the roof can be considered a very stiff elastic restraint and act only for its dead-load. The two

static schemes of the reinforced masonry walls are represented in Figure 34.

Figure 34: Static schemes for out-of-plane walls: with deformable roof (left), with rigid roof (right)

The definition of the wall geometry and loading condition has thus been based on actual building geometry.

To do this, a review of possible industrial, commercial and sport centre building dimensions and roof

typologies have been taken into account. Generally, the building span ranges between 10÷15 m and the

masonry wall height ranges between 6÷8 m. As significant P-∆ effects can rise when the walls are subjected

to out-of-plane loading, together with the different roof typologies also the dead load coming from these

types of roofs has been evaluated. Among the deformable roofs, three main typologies have been found:

gluelam beams with metallic cover, precast reinforced concrete double T-beams, precast reinforced concrete

sheds. The roof dead load plus the load from snow per linear meter of wall, for larger spans of 15 m, ranges

from 21 to 34 kN/m, or from 13 to 26 kN/m if the snow is taken into account with the probabilistic factor

related to seismic events (ψ2 = 0,2). A view of these three roof typologies can be seen in Figure 35.


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Gluelam beams and metallic cover

Precast RC double T-beams

Precast RC shed

Figure 35: Sketch of the three deformable roof typologies

Among the rigid roofs, other three main typologies have been found: common concrete slabs with lightening

clay units, composite steel-concrete slabs, steel beams with collaborating concrete slabs. The roof dead load

plus the load from snow per linear meter of wall, for larger spans of 15 m, ranges from 30 to 49 kN/m, or from

23 to 42 kN/m if the snow is taken into account with the probabilistic factor related to seismic events (ψ2 =

0,2). A view of these three roof typologies can be seen in Figure 36.

RC slabs with lightening clay units

Composite steel-concrete slabs

Steel beams and collaborating RC slab

Figure 36: Sketch of the three rigid roof typologies

Two types of tests will be thus carried out: for the first configuration, a real scale structure will be built and

tested by applying a horizontal load at the top (see Figure 40 left and centre). For the second structural

configuration, considering that the behaviour is more similar to the usual flexural behaviour (generally tested

as in Figure 40 rigth), flexural test on normal and eventually pre-stressed specimens will be carried out.

For the first typology of structural configuration and test type, as the wall geometry play an important role, it

has been decided to fix the overall specimen dimension on the basis of realistic building conditions. The

specimens will be thus 6 m high, with a width of 2,07 meters in order to allow for a minimum plate effect to

develop, and also to allow for a minimum 2 meters spacing of the reinforced masonry columns (minor

spacing would be unrealistic). The specimen thickness is 0,38 m, equal to the unit thickness. The specimens

will be loaded with a constant vertical load corresponding to the average compressive stresses coming from

different types of deformable roofs, varying between 0,055 and 0,089 N/mm2 or between 0,034 and 0,068

N/mm2 if the snow is taken into account with the probabilistic factor related to seismic events (ψ2 = 0,2).

Finally, a horizontal load will be applied at the top of the specimen.

The determination of the out-of-plane moment of resistance, Mrd, has been evaluated under the basic

hypothesis that plane sections remain plane; the reinforcement is subjected to the same variations in strain

as the adjacent masonry; the tensile strength of the masonry is taken to be zero and it is based on the


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rectangular stress distribution. The maximum compressive and tensile strains of the masonry and the

reinforcement are 2‰ and 10‰ respectively. According to the expected characteristic compressive strength

fb of the units of about 14,5 N/mm2, the value of characteristic compressive strength for masonry has been

taken equal to 5,83 N/mm2 by applying equation (8) with K=0,45 (Group 2 units) and a mortar M10. A

characteristic tensile strength fyk equal to 430 N/mm2 was considered in the calculations for the

reinforcement. The stress and strain distribution of the wall section can be seen in Figure 37. The resisting

section is shown in Figure 38 together with the Bending Moment-Axial Force domain and Neutral Axis

position at the ultimate limit state considering the application of an axial force equal to 50 kN (corresponding

to load equal to 25 kN/m). For the field of Axial forces expectable from the roof dead load, the failure is

expected to happen in the field 3 (concrete side with yielded steel).

Figure 37: Stress and strain distribution of the wall section (from the EC6)

2070

7015

515

5

70155

120

140

120

RIEMFLUI

Dominio M-N (setto RM 2000 mm x 380 mm)

0

20

40

60

80

100

120

140

160

180

200

-1000 -500 0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000

N [kN]

M [k

Nm

Figure 38: Wall resisting section (top left), neutral axis position at ULS (bottom left), and M-N domain

(right)

For the second typology of structural configuration and test type, the main parameter governing the failure of

the wall is the flexural strength having a plane of failure parallel to the bed joints. To obtain this specific

parameter, simple tests in accordance with EN 1052-2 can be carried out, so no specific issues are related

to the design of the masonry panels. In case that the influence of dead load from the roof has to be analyzed

also experimentally, the specimens will be loaded with a constant vertical load corresponding to the average

compressive stresses coming from different types of rigid roofs, varying between 0,078 and 0,128 N/mm2 or

between 0,060 and 0,111 N/mm2 if the snow is taken into account with the probabilistic factor related to

seismic events (ψ2 = 0,2).

Finally, these types of wall can be prone to instability problems deriving from the high slenderness (height to

thickness ratio). The Eulero critic load has been thus evaluated taking into account the most unfavorable


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boundary condition (cantilever wall) for the specimens characterized by a height of 6 m. The critic load is

equal to 1,62 kN/m, corresponding to a compressive stress of 4,26 N/mm2. Thi stress is equal to the 85% of

the assumed characteristic compressive strength (5 N/mm2), it is anyway sensitively higher than the working

stresses corresponding to the test execution.

5.1.6 Test setup A preliminary view of the test setup to be used for in-plane cyclic tests can be seen in Figure 39. The

masonry specimens will be built between a bottom and an upper concrete reinforced beam in order to

anchor the vertical reinforcements. The concrete beam at the base of the wall will be directly connected to

the reaction slab by means of steel tie-rods. The vertical load will be applied by means of two actuators

connected to a steel beam for load redistribution. The free rotation of the upper part of the specimen will be

assured by coupling the steel beam to the upper concrete beam by means of linear guides, and by keeping

the load constant and equal to half of the total vertical load in each of the two actuators. The horizontal

displacement will be applied by the horizontal actuator directly to the centre of the upper concrete beam. The

horizontal actuator will be linked to the specimen by means of two cylindrical connecting rods, departing from

a forked beam for load distribution. The rods will be jointed to a steel pin placed in a hole at the centre of the

top end reinforced concrete beam.

Figure 39: View of the test set-up for the in-plane cyclic tests

The static monotonic out-of-plane tests will be carried out on real-scale specimens. For the first structural

configuration (cantilever wall with applied constant vertical load and horizontal load applied at the top) the

test will be carried either on a small frame consisting of two walls connected by a simply supported slab

created to provide adequate dead load and transfer the displacements from the load application point also to

the second wall, or on singular walls if it will be possible to apply a sufficient dead load by means of a loading

beam placed on the top of it. The frame or the singular wall will be build above reinforced concrete beams


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that will be connected to the reaction floor, the horizontal load will be applied to the top of the specimens by

means of an actuator placed against a reaction frame (see Figure 40 left and centre).

For the second structural configuration, considering that the behaviour is more similar to the usual flexural

behaviour, common flexural tests on wallettes, according to the scheme of Figure 40 right or by applying a

pre-stress (compressive stress) as in Figure 25, will be carried out.

Figure 40: View of the test set-up for the out-of-plane monotonic tests simulating the deformable roof

(left and centre) and simulating the rigid floor (simple flexural tests, right, after EN 1052-2)

5.1.7 Experimental program The detailed description of the experimental program of characterization of the constitutive behaviour of

masonry materials and masonry as a composite will be given in deliverable D5.5. However, for a better

planning of the work package, the summary of the test on masonry materials and on masonry assemblages

is given in the Table 3 for both the walls made for residential housing (walls mainly developed to resist in-

plane loads) and the walls made for tall buildings (walls mainly developed to resist out-of-plane loads).

Table 3: Experimental tests to be conducted on Work package 5

Type of masonry For in-plane loads For out-of-plane loads

Materials Tests Tests

Blocks

- Uniaxial compression

- Modulus of elasticity

- Indirect tension



- Indirect tension

Mortar



- Poisson's ratio

- Three-point load tests



- Poisson's ratio


Reinforcements - Uniaxial tensile tests - Uniaxial tensile tests

Masonry walls



- In-plane cyclic tests



- Four point load tests

- Out-of-plane tests on a structure


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Experimental tests conducted on masonry materials follows standard procedures. The characterization of the

behaviour of masonry walls are to be made taking into account the geometry, test setup described in the

previous sections and a test procedures to be defined. Combined tests on masonry walls depend on the

results of the in-plane cyclic tests.

5.2 HOLLOW CLAY BLOCKS

5.2.1 Types of hollow clay blocks

Basically the construction of masonry in Germany that consists of hollow clay blocks can be divided into two

different systems of masonry. The first system consists of clay blocks with large hollow cells only in the

vertical direction (Figure 41: Large hollow clay units: (a) unfilled; (b) filled with erected vibrated concrete).

These cavities are filled with mortar or concrete after the wall has been built. In most cases the filling is done

with concrete over the complete height of the wall.

The application and the design of these units are regulated by general inspection approvals in conjunction

with the German standard for masonry (DIN 1053). The valid design code allows presently only the

consideration of the load bearing capacity of the clay blocks, the concrete inside is not taken into account.

Also reinforcement is not considered for the calculations of the bearing capacity.

(a)

(b)

Figure 41: Large hollow clay units: (a) unfilled; (b) filled with erected vibrated concrete

The second system looks quite similar to the first. It differs to the first by recesses in the cross web of the

hollow clay units (Figure 42) and by the filling of the holes. In this case only concrete is valid. Like the first

system the application and the design of these units are regulated by general inspection approvals in

conjunction with the German standards for design. In contrary to the system without horizontal gaps, the

design of this masonry is based on the load bearing capacity of the concrete and the vertical and horizontal

reinforcement. The load bearing capacity of the bonded materials and the interaction is not considered.


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(a) (b)

Figure 42: Large hollow clay units with horizontal recesses: (a) square gap; (b) rounded gap;

5.2.2 Geometry of the reinforcement Within the scope of the testing program in work package 5, different types of experiments are planned to

carry out to characterize the behavior of masonry built of hollow clay units. For these experiments only the

second system of hollow clay blocks is tested, as a significant better behavior under combined loadings is

expected due to the activations of reinforcement.

The geometry of the units and of the concrete has been optimized in work package 3. In the context of this

work package, the geometry of the cross webs of the clay units have been developed by several numerical

studies to optimize the load bearing capacity of the masonry. The result was a new geometry of the clay unit.

For this unit an applicable reinforcement system has to be developed. The reinforcement should consist

easy to install, economically priced prefabricated system for the horizontal and vertical direction for which the

accurate position inside the units can be ensured. According to the reinforcement system Murfor RE of

BEKAERT the following system is proposed, see Figure 43:

Figure 43: Reinforcement system

The geometry (diameter, number of bars in vertical respectively horizontal direction, concrete cover, etc.) of

the reinforcement will be optimized within the experiments.


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5.2.3 Test Set-Up

5.2.3.1 In-Plane loading of complete masonry walls

The in-plane load application on shear walls is done by a horizontal shear force and a vertical compression

force with a corresponding and variable eccentricity, to simulate the stress state in whole structures.

The horizontal force may be applied in both directions, i.e. with positive and negative sign, describing cyclic

loadings appearing e.g. under seismic actions. The eccentricity of the vertical load covers the elastic restraint

of shear walls in (concrete)-slabs when bending deformations, i.e. rotations, of the shear walls appear. The

product of eccentricity and compression force is equivalent to the restraint moment.

Figure 44: Mechanical idealization of the load application and corresponding stress state on a shear

wall

The application of the horizontal force at the top of the wall should be done in a manner, where all points

along the wall get the same horizontal displacement. Therefore a stiff cap beam should be applied at the top

of the wall with a rigid connection to the masonry, e.g. a reinforced concrete beam placed in a cement mortar

bed. For the connection and anchorage of a possible vertical reinforcement into the beam further details of

the construction have to be investigated in dependency of the used type of reinforcement and the amount of

reinforcement. Generally the use of epoxy glue, welding or mechanical fixations is possible.

The action of a vertical force with possible eccentricity can be characterized by a linear distribution of the

compressions stresses. Generally here has to be differentiated between joints with and without tension

strength.

As the application of tension forces by the vertical hydraulic actuators is very complex and not suitable, the

joint directly below the actuators can be described without any tension strength. In contrary the joint between

the top of the wall and the cap beam directly above applying the horizontal load can be described with an

certain tension strength, when reinforcement running from the masonry wall to the cap beam.

Therefore, at the top of the masonry wall two beams have to be applied. Between these elements as soft

layer of elastomeric stripes or springs ensures the linear distribution of the compression stresses.

ebase R (=resulting force)

lwall

hwall

Mcap H N

σ τ

R ecap


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Figure 45: Idealized system for the load application of the horizontal load, the vertical load and the cap

moment

Figure 46: Proposed test set-up for the application of combined action on shear walls

5.2.3.2 Three point-loading

The three point-loading of masonry beams is carried out to investigate the failure behavior and the

performance and suitability of the used reinforcement system. The tests are carried out under out-of plane

loadings perpendicular to the wall. The thickness of the beam is correspondingly the thickness of the

masonry wall resp. of the units.

Generally a slenderness of about 8 (ratio between span length and thickness) ensures a dominating bending

loading impact. The determination of the width of the beam has to done in respect of the amount of

elastomeric stripes as soft interface between cap beam A and B

Hydraulic actuators with roller bearings

upper cap-beam A

application of the horizontal load via a hinge

lower cap beam B (mortar layer at the cap of the masonry wall / possible vertical reinforcement running from the wall into the beam)


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reinforcement and its distribution along the height of the wall, e.g. application only in each horizontal bed

joint. Generally a width of 3 times of the thickness resp. 3 times of the height of a unit can be taken to be

high enough.

Figure 47: System of a three point-loading test on a masonry beam (load application perpendicular to

the wall plane)

Additional tests on a corresponding beam under in-plane loadings can be performed to investigate the

behavior under constant strain over the thickness of the wall.

5.2.3.3 Out-of-plane loading

The out-of plane loading is relevant for walls under earth-pressure or wind-loadings. Here the load transfer

under bending can be carried out in horizontal, in vertical or in both directions. The uniaxial load transfer can

be tested simple by the above mentioned three point-loading tests. The biaxial load transfer can be simply

considered as a combination of the horizontal and vertical direction.

Generally a vertical compression force leads to a higher bending stiffness and also to a higher load bearing

capacity, especially at systems with low or without any reinforcement.

The main interest here is paid not on the combination of vertical compression and out-of-plane-loadings but

on the combination of these types of actions with additional in-plane loadings. As a result of the out-of-plane-

loadings the compressed part of cross section of the wall is reduced and therefore the load bearing capacity

under in-plane loadings (shear wall) is affected significantly.

For the experimental investigation of these effects the above mentioned test set-up can be modified and

expanded to the additional application of horizontal out-of-plane loadings, see Figure 48.

soft support

application of the horizontal load

thickness of the beam resp. the wall

soft support

span length

width of the beam


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Figure 48: Side view of the expanded test set-up of shear walls to horizontal out-of-plane loadings

5.2.3.4 Indirect actions

The effect of indirect actions, namely shrinkage of the concrete infill and (rarely observed) expansion of clay

masonry is only relevant at high lengths of the walls. The effect is reduced significantly when cracks appear

and the stiffness of the wall decreases. For the design of masonry walls these effects are covered generally

by construction rules, e.g. maximum lengths of walls in respect of the material.

The experimental investigations can be carried out on a cantilever wall without any external loadings to avoid

unintentional effects, e. g. elastic deformations or creeping. Here the deformations of the several materials

have to be measured independently.

5.2.4 Tests on small specimens The tests on small specimens will be conducted on masonry units and specimens taken from these as well

as on concrete, see Table 4. In these tests first of all a commonly used hollow clay block and a vibrated

concrete will be investigated, to be able to formulate possible approaches for the further development of the

blocks and the achieve reference properties. Afterwards tests on the further developed hollow clay block and

the developed self-compacting concrete will be carried out.

Most of the tests will be carried out deformation controlled to achieve information about the post-peak

behaviour of the test specimens. For example the compression tests on masonry units filled with concrete

test frame for in-plane-loadings

(N, M , H)

horizontal fixation in lateral direction

Add

ition

al fr

ame

with

hor

izon

tal

fixat

ion

of th

e ca

p be

am A

an

d th

e fo

unda

tion

beam

horizontal fixation in lateral direction fo

rce

ap

plic

atio

n by

ac

tuat

ors

or

ai

r bag


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and on concrete specimens will be conducted with a constant crosshead speed. The fracture mechanical

properties and the load bearing behaviour under tensile stresses will be determined inversely by

recalculating three-point bending tests using the finite-element-method. The three-point-bending tests will be

carried out deformation controlled to achieve almost complete load-deflection curves.

In compression tests, at first, four storey high wall panels made of commonly used hollow clay blocks and

vibrated concrete will be investigated. By means of these tests the influence of the use of mortar in the bed

joints on the compressive strength of hollow clay block masonry will be tested and reference values will be

determined. The test will be conducted controlled by a constant cross head speed to investigate the stress-

strain-curve as far as possible. On the basis of the results of the aforementioned tests it will be decided, if

mortar will be used in the bed joint in two additional compression tests on masonry panels made of the

further developed hollow clay unit and self-compacting concrete.

Table 4: Tests on small specimens

specimens determined properties

1 2

taken from

the units

- load bearing behaviour under compressive stresses perpendicular to the bed joints

- load bearing behaviour under tensile stresses tangential and parallel to the bed joints

- load bearing behaviour under tensile stresses and fracture mechanical properties

masonry units

filled with

concrete

- load bearing behaviour under both tensile and compressive stresses perpendicular as well as tangential to the bedjoints

- bonding properties

concrete - load bearing behaviour under compressive stresses - load bearing behaviour under tensile stresses and fracture mechanical

properties

5.3 CONCRETE HOLLOW BLOCKS

5.3.1 Typology of reinforced masonry walls – brief overview

As Portugal is a country with very different seismic risk zones with low to high seismicity, two distinct

constructive systems for reinforced masonry walls to be used in general masonry buildings located in zones

with moderate to high seismic hazards within the scope of the DISWall project were proposed (work package

4). Both constructive systems are based on concrete masonry units, whose geometry and mechanical

properties have to be specially designed to be used in structural purposes. It is foreseen that two and three

hollow cell concrete masonry units (CB3c) are developed in order to vertical reinforcements can be properly

accommodated. The concrete masonry block with two vertical hollow cells (CB2c) is quite similar to the

typical blocks used for non-load bearing walls. The concrete block with three hollow cells is especially

formulated to accommodate uniformly spaced vertical reinforcement. It should noticed that the easy

acceptance of the proposed novel constructive systems by the contractors requires that minimal changes on

the traditional workmanship are needed. The Constructive system CS1 is composed by two hollow cell


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concrete masonry units, being the vertical reinforcements inside a continuous vertical joint filled with the

general purpose mortar used for the bed joints, see Figure 49.

Murfor RND Z

Murfor RND Z

(a)

Murfor RND Z

Murfor RND Z

(b)

Figure 49: Constructive systems defined by two hollow cell concrete masonry units; (a) vertical

reinforcements inside a continuous vertical joint; (b) vertical reinforcement inside the hollow cells

This system enables that vertical reinforcements can be fixed before the masonry wall construction, being

the construction technique rather similar to the traditional one used in unreinforced masonry walls. An

alternative to this construction it to place the vertical reinforcements into the vertical hollow cells filled with a

proper bed joint mortar. The features of the two hollow cell concrete masonry units imply that reinforcement

overlap should be used.

It is foreseen that both horizontal bed joint and vertical reinforcements are prefabricated galvanized welded

wire steel meshwork (truss type) provided by Bakaert, see Figure 50. According to EN 845-3, the minimum

wire size of the longitudinal wires is of 3mm.

Figure 50: Prefabricated truss type reinforcements

The Constructive system CS2 is composed by the three hollow cell concrete masonry units, where the

vertical reinforcements can be placed inside a continuous vertical joint defined by the external shells of the

masonry units, see Figure 51a, or placed inside the hollow cell formed by the webs, see Figure 51b.

Also in this constructive system, the hollow cells with the vertical reinforcements are to be filled with general

purpose bed joint mortar. Similarly to previous constructive system, prefabricated struss reinforcements are

to be used both for vertical hollow cells and bed joints. A reinforced masonry wall composed by three hollow

cell masonry units and Murfor RND reinforcements is to be considered, see Figure 52.


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Murfor RND Z

Murfor RND Z

(a)

(b)

Figure 51: Constructive systems defined by three hollow cell concrete masonry units; (a) vertical

reinforcements inside the vertical joint formed by the lateral shells; (b) vertical reinforcement placed into the

internal webs

Murfor RE

Murfor RE

Figure 52: Constructive systems defined by three hollow cell concrete masonry units with Murfor RE

reinforcements

5.3.2 Design criteria of masonry panels The definition of the geometry and dimensions of the masonry walls is based on the estimation of the

experimental in-plane horizontal load considering that two main possible distinct failure modes can occur in

the reinforced masonry walls: diagonal shear and flexural mechanisms.

As discussed previously, the failure mode of a reinforced masonry shear wall depends on the vertical normal

stress, wall geometry (height to length ratio), properties of the materials (units, mortar), properties of the unit-

mortar interface (tensile and shear bond strength), the tension of the horizontal steel, the dowel action of the

vertical steel as well as the interlocking between the parts of the walls diagonally cracked.


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The prediction of the horizontal in-plane load was made following the procedure indicated in the Eurocode 6

(2005) and by using procedures followed by Tomazevic (1999).

According to EC6 (2005), the shear resistance of a reinforced masonry wall is calculated as:

s

yksw

m

vkRdRds

fs

AltfVVH

γγ9.021 +=+= (10)

where VRd1 is the shear resistance of an unreinforced masonry wall and VRd2 is the contribution of the shear

reinforcements (Asw). Also in the formula, fvk is the characteristic shear strength of masonry, l and t are

respectively the length and the thickness of the wall, fyk is the characteristic strength of steel reinforcement,

and γm and γs are the partial safety factors of masonry and reinforcements respectively.

Tomazevic (1999) accounts for the dowel action by considering an additional strength, VRd3, calculated as:

mkykRd ffnV ×××= 23 806.0 φ (13)

being fmk the characteristic compressive strength of masonry and fyk the characteristic strength of steel

reinforcement, n the number of reinforcing bars and φ their diameter.

As an indication, it should be noticed that the contribution of the vertical steel reinforcement to the shear

strength is considered in the EC6 (2005) (Annex J) by calculating the value of Vrd1 calculated from a

characteristic shear strength given by:

7.05.1735.0 ≤+= ρvkf (11)

being ρ given by:

tdAs=ρ (12)

where As is the cross sectional are of the primary reinforcement, t is the thickness of the section and d is the

effective depth.

The in-plane bending strength of reinforced masonry walls was calculated based on the bending moment of

resistance, Mrd, of the section of the reinforced masonry walls and considering the wall as a cantilever:

hMH rd

f = (14)

The determination of the in-plane moment of resistance, Mrd, is carried out based on the rectangular stress

distribution, assuming the composite behaviour of masonry in compression, see Figure 53. This calculation

takes into account that plane sections remain plane, the tensile strength of the masonry is taken to be zero,


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the maximum compressive and tensile strains of the masonry and the reinforcement are 2‰ (masonry units

of group 2) and 10‰ respectively.

A

A εsc

εstst

sc

εm

X

fdFsc

Fst

Fm0.8 X

H

B

d

s

N

MR

Figure 53: Stress and strain distribution of the wall section (EC6)

5.3.3 Material properties

As referred previously, within the scope of the work packages 3 and 4, two types of concrete hollow blocks

have been designed: the concrete block with two vertical hollow cells (CBc2), quite similar to the typical

blocks used as infill, and a block with three hollow cells (CBc3), see Figure 54. In view of the experimental

limitation to carry out full scale in-plane and out-of-plane tests on masonry walls, it was decided to scale the

geometry of the blocks. Reduced of approximately 1:2 was adopted.

(a)

(b)

Figure 54: Concrete blocks that will be used in masonry panels; (a) Block 1: two cells; (b) Block 2: 3

cells.

Considering the vertical holes to gross volume ratio, both concrete blocks can be classified as Group 2

masonry units as pointed out by EC6 (2005), see Table 5. Blocks CB2c and CB3c have a percentage of

holes of 50.50 % and 52.56 % respectively. This classification is essential in order to make the design of the

masonry walls to be tested. Taken into account that the blocks are reduced scale masonry units, it can be

seen that both of them also fulfil the requirements related to the thickness of the webs and shells, see

Table 5.

Table 5: Requirements for the units (EC6, 2005)

Blocks

CB2c CB3c Requirement

50.5% 52.6% Group 2 – 25< vertical holes ≤60

20.0 13.0 Webs ≥ 15

15.0 14.0 Shells ≥18


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In the absence of detailed experimental information about the mechanical properties of materials, units and

mortar and of the masonry as a composite material, approximate values are calculated according to the EC6

based on the classification of the units and a required M10 mortar. A compressive strength ranging from 20

to 25N/mm2 is expected to be obtained in the concrete blocks and a compressive strength of 10N/mm2 is

considered for the mortar.

Based on the estimated properties of masonry units (Group 2) and mortar and considering that a general

purpose mortar is used for laying the masonry units, the compressive strength of masonry, fk, can be

calculated from the expression:

3.07.0mbk ffKf ××= (6)

where K takes the value of 0.45 (Group 2 and general purpose mortar), fb is the normalized mean

compressive strength of concrete masonry units and fm is the compressive strength of mortar. The

normalized compressive strength of the units is estimated according to EN 772-1, by considering the

characteristic mean compressive strength over the gross cross section of the units multiplied by a shape

factor of 0.8 in order to take into account the size of the concrete masonry units (100mm height, 200mm

width).

The characteristic shear strength of masonry, fvk, is estimated by the expression:

nvkkv ff σ×+= 4.00 (7)

where fvk0 is the characteristic shear strength under zero compressive strength and σd is the design normal

compressive stress. The value of fvk0 is considered to be 0.2 (aggregate concrete masonry units and general

purpose mortar M10).

The summary of the characteristic mechanical properties of masonry required for prediction of the lateral

shear strength of concrete masonry walls are indicated in Table 6.

Table 6: Mechanical properties adopted for masonry and for masonry materials.

Property Value (MPa)

fb 10.00

fm 10.00

fk 4.50

fyk 500.0

As the concrete masonry units are to be considered in reduced scale (approximately 1:2), the truss type

prefabricated reinforcements has also to be adjusted. The standard pitch of the cross-wire of the

reinforcements provided by Bakaert has to be reduced from 400mm to 200mm in order to ensure similar

bond conditions.


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In spite of tensile tests on prefabricated are to be carried in the scope this work package, a characteristic

tensile strength of 500 MPa was considered in the calculations of the horizontal lateral strength of reinforced

masonry walls.

5.3.4 Geometry of the walls

The geometry of the walls, and the corresponding height to length ratio (h/l), was obtained based on the

comparison of horizontal in-plane load associated to different possible failure modes. Two loading

configurations were analysed, see Figure 55. The configuration shown in Figure 55a considers the

application of the horizontal cyclic loading at the top of the wall, and the loading configuration shown in

Figure 55b is constituted by a lateral load applied at mid-height of the wall.

Lateral Load

Axial Compression

(a)

Lateral Load

Axial Compression

(b)

Figure 55: Position of the horizontal load. (a) at the top of the wall and (b) at mid-height of the wall.

The latter configuration changes the moment’s diagram along the height of the wall and aims at reducing the

tendency of the walls to exhibit a flexural response, by decreasing the bending moment at the base of the

wall. The normal stress considered in the calculations is about 30% of the compressive strength of masonry,

corresponding to a vertical load of approximately 162kN.

Shear and flexural horizontal loads were calculated based on the procedure indicated in Section 6.3.2 for

different height to length ratios. As expected, flexural behaviour governs the lateral response for high height

to length ratios. The flexural and shear strength of different types of masonry walls and for a height to length

ratio of 0.67, corresponding to a height of 0.808m and a length of 1.2m, are summarized in Table 7.

An example of the resistant in-plane bending resistant section is given in Figure 56. From the values

indicated in Table 7, it can be observed that even for a height to length ratio of 0.67, if the loading

configuration CF1 is adopted, the flexural lateral load is lower than the shear loading, which means that the

wall predominantly behaves in flexure. However, if the lateral load is applied at mid height of the walls, it is

expected that, with the exception of model 8, all the walls fail in shear.


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Table 7: Flexural and shear load for different types of walls and for two distinct loading test

configuration.

Load configuration

CF1 Load configuration CF2

Model Shear (kN) Flexural (kN) Shear (kN) Flexural (kN)

1(unreinforced masonry wall) 122,52 61,96 86,00 123,92 2 (ρv= 0.104% - φv=5mm; ρh= 0.132% - φh=4mm) 123,34 68,42 127,26 136,85 3 (ρv= 0.104% - φv=5mm; ρh= 0.132% - φh=4mm) 123,34 68,42 127,26 136,85 4 (ρv= 0.0982% - φv=5mm; ρh= 0.124% - φh=4mm) 122,52 69,15 128,55 138,30 5 (ρv= 0.0982% - φv=5mm; ρh= 0.124% - φh=4mm) 122,52 69,15 128,55 138,30 6 (ρv= 0.0982% - φv=5mm; ρh= 0.124% - φh=4mm) 122,52 69,15 128,55 138,30 7 (ρv= 0.0982% - φv=5mm; ρh= 0.07% - φh=3mm) 122,52 69,15 109,00 138,30 8 (ρv= 0.0982% -φv=5mm; ρh= 0.194% -φh=5mm) 122,52 69,15 154,23 138,30 9 (ρv= 0.0628% -φv=4mm; ρh= 0.124% -φh=4mm) 122,52 66,71 125,47 133,41 10 (ρv=0.126% -φv=4mm; ρh= 0.124% -φh=4mm) 122,52 70,76 125,47 141,52 11 (ρv= 0.0%; ρh= 0.07%-φh=3mm) 122,52 61,96 100,45 123,92 12 (ρv= 0.0982% -φv=5mm; ρh= 0.0%) 122,52 69,15 94,55 138,30

Model 1 is a reference unreinforced masonry wall, Models 2 and 3 are masonry walls built according to the

constructive system CS1 and models 4, 5 and 6 are the distinct masonry walls constructed according to the

constructive system CS2, as mentioned in section 6.3.1. Models 7 to 12 are reinforced masonry walls with

three hollow cell concrete masonry units, but with different ratios of horizontal and vertical reinforcement. The

in-plane and out-plane tests on masonry walls intends to access the performance of the constructive system

and the influence of the percentage of vertical and horizontal bed joint reinforcement on the strength,

deformational features and on the ability of the walls to dissipate energy of shear walls.

10

50 50

120

x = 38,09 cm

εm = 0,00200

ε 3 = 0,00145ε2 = 0,00113

ε1 = 0,00375

Figure 56: Resistant section for out-of-plane bending

The out of plane tests will be carried out for the geometry obtained for the shear tests. Considering that the

height to length ratio adopted for the in-plane masonry specimens is close to the typical dimensions found in

walls of usual buildings, where reinforced masonry can be applied, the results of out-of-plane behaviour

would represent the actual out-of plane behaviour of such walls. Depending on the results of the in-plane

tests, this procedure can also facilitate the evaluation of the influence of in-plane damage on the out-of-plane

performance of the same type of walls. A prediction of the lateral flexural resistance is obtained by means of

the assumptions given in EC6 regarding the design of masonry members subjected to bending and


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mentioned in section 5.3.2. Based on the material masonry properties used in the prediction of the in-plane

bending moment, an example of the resistant section is given in Figure 57. For the calculations, the same

normal stress was taken into account. It can be observed that a low value of the out-of-plane resistance

should be expected.

10

x = 3,43 cmε m

ε sc

ε st

= 0,00200

= 0,00054

= 0,0023750 50

120

Figure 57: Resistant section for out-of-plane bending

5.3.5 Test setup

In this section, a preliminary description of the test setup used in the shear tests is carried out, see Figure 58

and Figure 59. The masonry walls will be built between a bottom and an upper concrete reinforced beam in

order to anchor the vertical reinforcements, see Figure 58. The upper beam enables also that an

enhancement of the uniformity of the vertical load to be applied on the wall. The concrete beam at the base

of the wall will be connected to the steel profile that in turn is connected to the reaction slab through a set of

steel cables anchored in the slab by means of steel plates. In order to prevent horizontal displacements at

the base, the cantilever wall is fixed to the steel profile with two adjustable clamping angles. A steel beam is

connected to the upper concrete beam in order to transmit the horizontal load. The horizontal load is

transferred by means of a vertical steel profile, to which the horizontal actuator is connected. The horizontal

actuator is fixed to the reaction wall by means of a two-dimensional hinge, which enables the possible

rotation of the upper concrete beam. A stiff steel beam is used for the distribution of the vertical loading from

the vertical actuator and a set of steel rollers were placed to allow relative displacement of the wall with

regard to the vertical actuator. Both upper and bottom concrete beams are connected to the steel profiles by

means of steel bars and anchor plates. The vertical pre-load applied by the vertical actuator found the

reaction trough a set of four steel cables anchored to the reaction slab.

The static monotonic out-of-plane tests are to be conducted on the same type of reinforced masonry walls,

by using the test setup indicated in Figure 59. The upper and bottom fixed-fixed boundary conditions are

ensured by the connection of the bottom concrete beams to the reaction slab as described previously and by

using the braced steel structure at the top. In this case, the steel roller has to be properly fixed to the

concrete beam. The out-of-plane tests are conducted as four point load tests. The load is applied by means

of an horizontal actuator to two steel profiles that defines the line out-of-plane loads.


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2828

80,8

2828

101,

4

520

222,

8

Reaction wall

Reaction slab

120

Steel beam

Concrete beam

Concrete beam

Figure 58: Test setup for the in-plane cyclic tests (dimensions in mm)

75

101,

4

200

100

100

20

Steel cables

Figure 59: Test setup for the monotonic out-of-plane tests (dimensions in mm)


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5.3.6 Experimental program

The detailed description of the experimental program of characterization of the constitutive behaviour of

masonry materials and masonry as a composite will be given in deliverable D5.5. However, for a better

planning of the work package, the summary of the micro-tests and tests for the characterization of the

constitutive behaviour of masonry is given in the Table 8. Experimental tests conducted on masonry

materials and masonry as a composite follows standard procedures.

The flexural tests carried on masonry intend to be an indirect method of evaluating the bond between the

reinforcements and masonry and of the unit-mortar interface as well as to assess the influence of bed joint

reinforcements on the increase of ductility of masonry submitted to in-plane flexure.

The characterization of the behaviour of masonry walls are to be made taking into account the geometry, test

setup described in the previous sections and a test procedures to be defined. Combined tests on masonry

walls depend on the results of the in-plane cyclic tests. The analysis of damage associated to a given lateral

force a lateral displacement induced by cyclic loading could be performed. In this case, the combined tests

will be composed by two phases: (a) in-plane cyclic tests up to a certain damage level: (b) out-of-plane

monotonic tests on the damaged wall.

Table 8: Experimental tests to be conducted on Work package 5

Materials Test

Blocks



- Direct tension

Mortar



- Poisson's ratio


Unit-mortar interface - Tensile bond tests

- Shear bond tests

Reinforcements - Uniaxial tensile tests

Masonry



- Diagonal compression

- Four point load tests on masonry beams

Masonry walls

- In-plane cyclic

- Out-of-plane monotonic tests

- Combined tests


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