BIOSCUST-17

Comparative Study on Reinforced Masonry with Polymer Grids

CALBUREANU POPESCU MADALINA XENIA, CODITA ALINADepartment of Applied Mechanics and Civil Engineering

University of CraiovaAddress 107 Calea Bucuresti st.,200512 CRAIOVA - Dolj

[email protected], [email protected]

Abstract: This paper concerns a comparative study, in terms of energy, on two types of masonry pillars: simpleunreinforced masonry and reinforced masonry with polymer grids. Energy issues relate to mechanical work,embedded caloric energy and strain energy. Is also highlighted the bearing capacity increase in case of themasonry reinforcement with polymer grids.Key-Words: masonry, reinforcement, embedded energy, polymer grills, bearing capacity, ergonomics

1 IntroductionThe article relates to the use of polymeric grids forthe brickwork reinforcement, in order to improve itsperformances.On this line, the paper approaches two models ofmasonry (pillars), with dimensions 375x375x874mm, both of them made of double pressed brickswith lime-cement mortar. One model is simple,unreinforced masonry and other is reinforcedmasonry with polymeric grids at 3 rows.The approach is in terms of ergonomics, embeddedenergy, strength and stiffness.

2 MaterialsMaterials used are: bricks, mortar and polymergrids.

2.1. The Bricks and the MortarThe solid bricks dimensions are: 240x120x60 andthe strength is 7.5 MPa.The mortar for joints is M10Z lime-cement.

2.2. The Polimeric ReinforcementAs polymer reinforcement, three types of gridsmade under the license of Tensar InternationalLimited in England [1] have been used: RG 20, RG30 and RG 40. [2]The three types of grids differ in the resistancecharacteristics.

Fig. 1. The geometrical characteristics of polymergrids (source: [1])

3. ErgonomicsErgonomics synthesize principles of other sciences,for their application in labors optimization and forthe growth of work productivity. [7]In order to determine the amount of energy requiredto construct masonry pillars (375x375x874), themechanical work is calculated considering thematerials movement for 1m distance.The masonry volume is 0.123 m3.The specific weight of solid brick masonry withlime-cement mortar is 18 kN/m3.The mechanical work for building a pillar is:

W = 18 kN/m3 x 0,123 m3 = 221,2 J (1)

Mass of the polymer grids: 1 m2 weighs:

RG 20 - 0,2 kgRG30 - 0,3 kgRG40 - 0,45 kgFor reinforcing at 3 rows are used 0,54 m2 ofpolymer grids.The result is in the following table:

Table 1 The mechanical work for the pillarsreinforced with three types of polymer gridsType of grid Mechanical work

(J)RG 20 222.2

Recent Advances in Environmental and Biological Engineering

ISBN: 978-1-61804-259-0 123

RG 30 222.7RG 40 223.4

Fig. 2. The mechanical work for the two situations:unreinforced masonry and reinforced masonry with

three types of grids

4. Embedded Energy in Materials

4.1. The BricksFrom the point of view of the embedded energy, thevalues extend over a wider range, depending on themanufacturing technology. [3] The table belowpresents the amount of power calculated for 1 m3 ofsolid bricks.[4]

Table 2. The solid bricksBricks specific

weight(kN/m3)

Bricksdensity(kg/m3)

The medium energycontent of solid brick

(MJ/m3)

18 1834,9 4506

4.2. The MortarThe amount of raw energy required to manufacturea cubic meter of mortar is obtained as sum of thequantities of primary energy embodied in thematerials that make up the mortar, with the addedenergy required to transport and mix thecomponents.For the mortar M10Z is necessary an averageprimary embedded energy of 2237 MJ/m3.

4.3 The MasonryThe total amount of primary energy embedded in acubic meter of masonry was obtained by summingup the bricks energy content with the energyembedded in mortar.

In masonry, bricks occupies 85% of the totalvolume, and the mortar 15%.

Tabel3. Energy embedded in a cubic meter of solidbrick masonry with M10Z mortar

Embedded energy inmortarMJ/ m3

Embedded energyin the solid bricks

MJ/m3Total

MJ/m3

2237 4506 4193

4.4. The Reinforced Masonry with PolymerGridsIn the following table has been calculated energyembedded in a square meter of different polymericgrid types:

Table 4. Quantity of primary energy contained bythe polymer grid

Type ofpolymer

grid

Polymer gridweight

(kg/m2)

The total amount ofembedded primary energy

(MJ/m2)RG 20 0,2 100,8RG 30 0,3 109,2RG 40 0,45 121,8

To determine the amount of primary embeddedenergy in reinforced masonry is totalized theembedded simple brickwork energy with the energyembedded in polymer grids. Result in the followingtable:

Table 5 The embedded primary energy for 1 m3 ofreinforced masoryType ofpolymer

grid

The amount ofembedded

primary energy(MJ/m2)

The amount of totalembedded primary

energy for thereinforced masory

(MJ/m3)RG 20 100,8 4248.2RG 30 109,2 4281.8RG 40 121,8 4332.2

4.5. Plain and Reinforced at 3 Rows MasonryPillarsThe amount of embedded energy in the unreinforcedmasonry pillar is 515.3 MJ.The amount of energy embedded in the reinforcedmasonry pillars with 3 types of grids in thefollowing table:

221,2 222,2 222,7 223,4

0

50

100

150

200

250

Unreinforcedmasonry

Reinforcedmasonry with

RG20


RG30


RG40

Mec

hani

cal w

ork

(J)


ISBN: 978-1-61804-259-0 124

Table 6 The embedded primary energy in thereinforced masonry pillarsType ofpolymer

grid

The amount ofembedded

primary energy(MJ/m2)

The amount of totalembedded primary

energy for thereinforced masory

(MJ/m3)RG 20 100,8 522.1RG 30 109,2 526.3RG 40 121,8 532.5

Fig. 3. The embedded energy in the masonry pillars

5. Laboratory Tests

The starting point of this study were the static testsperformed in the laboratory of EarthquakeEngineering of INCERC Iasi, using the AMSLER400 press with mechanical and electronictransducers. [5]Static tests were performed on several modelspillars of 375x375x874 mm.Execution was manually without supervision, so theusual standard of quality.The pillars were tested for axial compression asfollows:- Three simple masonry pillars, as witnesses- Three armed to 3 joints, namely, 2.6 and 10 joints.The polymer grid was RG40.The pillars were not plastered.All the six pillars were tried to the ultimate statelimit.Polymeric grids embedded in mortar in horizontaljoints reduce its lateral deformations but bricks arefree to deform under the vertical forces.The results have a wide range of spreading becauseof the uneven quality of materials and workmanship.Still, the six curves configurations show a typicalductile behavior of the pillars subjected to axial

compression, and about 30% increase of bearingcapacity.Axial compression results are presented in thefollowing figures:

Fig.4. Axial compression tests, unreinforcedmasonry

Fig. 5. Axial compression tests, reinforced masonry

6. StiffnessMasonry is an elastic-plastic material, whichtension-strain characteristic curve - for brick withcement mortar, has a characteristic aspect (Fig. 4).

515,3 522,1 526,3 532,5

0

100

200

300

400

500

600

Unreinforcedpillar

Reinforced pillarwith RG20



Ener

gy em

bedd

ed in

pill

ars

(MJ)


ISBN: 978-1-61804-259-0 125

The deformations of masonry due, in most part, tohe mortar in the horizontal joints; close tobreakage, 90% of deformation is due to the mortarand 10% to the blocks, although they cover about85% of the volume of the masonry. If moredeformable mortars (lime, mixed with low dosageof cement etc.) the contact with the blocks is moreuniform and masonrys deformations are mostlyinfluenced by the thick horizontal joints.The total specific deformation , corresponding to acompression stress , can be decomposed into twoparts, one elastic e, which is canceled after theremoval of external action, and other plastic,remanent p.

= e + p (2)

6.1. The Strain Energy Calculation forUnreinforced MasonryThe specific deformation limit lim corresponding tothe normalized resistance Rn is obtained byintegration:

nR

Ed

0

lim )(

(3)

where

ddE )(

is the modulus of elasticity,variable in relation to the loading step.

Relation (3) becomes:

9,0

0000lim 19,09,01

1

xdx

ER

R

dE

nR

n

n

(4)

It appears:

0lim 56,2 E

Rn(5)

The initial modulus of elasticity E0expresses as afunction of the masonry resistance Rn, asfollows:

nRE 0 [MPa] (6)where is the feature of the masonrys elasticity,depending to the blocks and the type of mortar,with values ranging between 400 and 2000.According to the characteristic of elasticity ,equation (5) becomes:

4,0

156,2lim r

(7)The equation of the characteristic curve - of thecompressed masonry is obtained analytically in oneof the following forms:

n

n

RE

R

9,0

1

1ln

9,0 0 (8)

nR

9,0

1

1ln

9,0

1

(9)

From the previous relations for simple masonry with6.5 MPa limit strength obtains:

Table 7 The theoretical calculation for the curve- of simple masonry

Rn Eo=Rn E() ()6.5 4875 0 4875 0

0,5 4537,5 0,1062871 4200 0,220793

1,5 3862,5 0,3448972 3525 0,480355

2,5 3187,5 0,6294573 2850 0,795261

3,5 2512,5 0,9819884 2175 1,195691

4,5 1837,5 1,4455025 1500 1,746156

5,5 1162,5 2,1237746 825 2,63184

6,5 487,5 3,4112377 150 5,157393

7,2 15 8,568637,22 1,5 11,97987

Fig.6 Simple masonry - curve for 6.5 MPalimit resistance

Using MATHCAD program, it was determined thearea bounded by the curve - and axis. This is thespecific strain energy for the curve calculated above.


ISBN: 978-1-61804-259-0 126

According to Clapeyron's theorem, for a solid bodyat rest, the deformation potential energy stored inthe body is equal to the work of external forces dueto deformation of the body.The area bounded by the graph and axis is thedeformation energy.

= 6.50.9 4875 11 0.9 6.5. = 7.166 10(10)

where w is the specific deformation energy ofsimple masonry with Rn = 6.5 MP.

6.2. The Strain Energy Calculation for theReinforced Masonry with Polymer Grids

Heterogeneous materials may be studied usinghomogenization techniques that permit thedefinition of a homogeneous body, equivalent to astrongly heterogeneous one in its geometry and inthe properties of its constituent materials [7].In order to determine the strain energy for thereinforced masonry with polymer grids arenecessary the following elements:a - the half thickness of the structural element(pillar)a (mm) [50, 150], a = 10 mm;b - the half thickness of the mortar in a jointb (mm) [1, 20], b = 1 mm;n - number of grids in the mortar,n [1, 25], n = 1P - axial compressive forceP (kN/m) [1, 1000], P = 1 kNR gridsendurance

Fig.7 Reinforced masonry with polymer grids

Considering

a = 187,5 mm, b = 5 mm, n = 3RG20, RG30, RG40E0 = 5,710 GPaResults = 37,5 and the following values for the

compressive force: RnP2

(11)where ba / is a raport,

R (kN/m) [20, 30, 40] RG20, RG30, RG40(RG=RichterGard)[6]

Table 8 Values for the compressive forcen E0

(GPa)RG

(kN/m)P

(MN/m)p=P/a(MPa)

3 5,71 20 1,2 6,5

30 1,8 9,8

40 2,4 13,0

Takeing into consideration the variation of -equation by the same law as the simple brickwork(homogeneous material), can obtain:

n

n

RE

R

9,0

1

1ln

9,0 0 (12)

Table 9. The specific deformation () of a thethree joints reinforced pillar with RG20, RG30

and RG40

(MPa)

(RG20)

(RG30)

(RG40)0 0 0 0

0,5 0,09074 0,08965 0,0891

1 0,1885 0,18375 0,1815

2 0,41008 0,38721 0,377

3 0,67889 0,61512 0,5889

4 1,02064 0,8742 0,8202

5 1,49031 1,17431 1,0747

6 2,24551 1,53096 1,3578

6,5 2,90928 1,73803 1,5121

7 1,9705 1,6765

8 2,54351 2,0413

9 3,36827 2,4676

9,5 3,97113 2,7111

9,75 4,36391 2,8423

10 2,9806

12 4,491

13 5,8186


ISBN: 978-1-61804-259-0 127

Fig.8 - curve of reinforced masonry in threerows, with three types of polymer reinforcement

By integrating the curve () between 0 andmaximum resistance:

= 10.8 11 0.9 10.80.9 3440. = 0.028(13)

= 16.3 11 0.9 16.30.9 3440. = 0.064(14)

In case of reinforcement with three types of grids,differences between deformations are large. Thusbetween reinforcement with RG20 and with RG30,for an increase of maximum effort by 34%,maximum deformation capacity increases by about35%.

= 21.7 11 0.9 21.70.9 3440. = 0.113(15)

Fig. 9 The deformation energy in the masonrypillars

Comparing between RG30 and RG40reinforcements, the increase of the maximum

deformation capacity is 25%, while the maximumstress increases by 25%.

7. CONCLUSIONS

The following conclusions can be drawn:1. In terms of ergonomics, by comparing theresulting values of mechanical work, can beobserved an increase by 0.4% for the reinforcedpillars with RG 20, 0.7% for the reinforced pillarswith RG 30 and 1% for the reinforced pillars withRG 40 versus unreinforced pillars.2. From the point of view of embedded caloricenergy, results an increase of 1.3% in the case ofRG 20 reinforced pillars, 2.1% in the case of RG30reinforced pillars and 3.3% in the case of RG 40reinforced pillars, compared to the energyembedded in unreinforced pillars.3. Laboratory tests showed an increase bearingcapacity by approximately 30% by reinforcingpillars with polymeric grille.4. Compared to the unreinforced pillars, theincreasing of deformation energy was by 290%when reinforcing with RG20, by 793% whenreinforcing with RG30 and by 1477% whenreinforcing with RG40.In conclusion, one can notice the improvement ofstrength and stiffness properties of reinforcedmasonry with polymer grids in the context of arelatively small increase in energy embodied inmaterials and workmanship.

References:[1] http://tensar.co.uk[2] Sofronie, R., Feodorov, V. Procedeu de armare

si consolidare a zidriilor cu grile sintetice.Brevet de invenie OSIM nr. 112373 B1 (1995)

[3] Radu, A. si colab. Contribuii la stabilireaconsumului de energie n sectorul deconstrucii, Construcii, nr. 10/1980, pp.3-9.

[4] Codi Alina, The performances of thereinforcement procedures with polymeric gridsof brick masonries, Doctoral thesys, 2011

[5] Sofronie, R. Manual RichterGard. TOTALPublishing, Bucharest 2004.

[6] Sofronie, R. Performances in seismicstrengthening of masonry. The 13th World Conf.on Earthquake Engineering. Vancouver, B.C.,Canada August1-6, 2004. Paper No. 182.[7] A. Barbieri, A. Cecchi - Analysis of masonrycolumns by a 3D F.E.M. homogenization procedure,2nd IASME/WSEAS Int. Conf. on ContinuumMechanics (CM'07), Portoroz, Slovenia, May 15-17,2007

0,007166

0,028

0,064

0,113

0

0,02

0,04

0,06

0,08

0,1

0,12

Unreinforcedpillar




Def

orm

atio

n en

ergy

(M/m

3)


ISBN: 978-1-61804-259-0 128

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