EFFECTIVE RETROFIT PLANNING FOR MASONRYHOUSING USING STEEL MESH
Daniel Felipe ESCALANTE MARINO *Supervisor: Dr. AZUHATA Tatsuya * *ABSTRACT
The city of Lima located on the coasts of the ocean and belonging to the ring of fire of the Pacific; It has
a high probability of a high intensity earthquake, in Lima lives a third of the population of Peru, due tothe high concentration of people, low-rise housing and low cost are very common, the 70% of the houses
in Lima are of masonry. The seismic code recommends buildings with this system and gives us valuesof their results to be able to use them. The Pandereta brick is a type of masonry that was created forpartitions for rooms because they are lightweight and low cost.
Some people of low-income use these bricks to build their homes, some of which are self-built without
engineering because those materials are not adequate to resist an earthquake.
The retrofitting of masonry walls of homes is a method which is rarely used due to the high price in thestructural evaluation. In this research, experimental wall data is used, and the typical distribution of a
two-level house is used.
To obtain better values, three models were analyzed. The first analysis one is the housing without
retrofitting; the second analysis is with all walls retrofitted and the third is in the housing with 50% of
the total walls retrofitted. With three points we interpolate the percentage of retrofitting of the house.
Keywords: Masonry housing, performance point, retrofitting, and steel mesh.
1. INTRODUCTION
In the years of 1966 and 1974, Lima was the scene of great earthquakes where it destroyed more than
50% of houses and 500 people lost their lives. Today the population has increased five times more sincethe 70's. While the masonry housing in Peru began their construction in the 80's and the 90's, it grew
without control extending all around the capital.
Many seismologists predict that an earthquake of 8.5 MW in the coming years would destroy almost allof these homes. The central government together with universities and research centers are investigating
and developing methods to strengthen these homes so that they can resist the coming earthquake.

Figure 1. Typical masonry housing in thesurroundings of the city of Lima.

*Figure 2. Types of masonry brick units: solidbrick, King Kong brick and tubular brick.

Japan-Peru center of earthquake engineering research and disaster mitigation, Peru.
Chief research engineer, Building Research Institute, Japan.

**1

1.1.

••

Objectives
To improve non-engineering and selfconstruction masonry houses byapplying steel mesh method as shownin Figure 3.
Reduce damages in the homes ofmasonry in the city of Lima producedby the earthquake.
2.

Figure 3. Coatings of steel mesh withmortar.

INTRODUCTION MASONRY WALLS IN LIMA-PERU

2.1.
Masonry homes
Generally, masonry housings are of confined walls, which means that the wall is first constructed,
leaving some grooves in each of ends the Wall. Then the steel of the two columns is placed at the endsof the Wall, while concrete is placed posteriorly and the beam is finally constructed.
The masonry of Lima presents mainly three types of brick: (1) Pandereta brick, commonly
known as tubular with horizontal hole. This brick presents a low cost and also has a very low weight.
That is why many houses use these bricks. (2) Industrial solid is known as King Kong of 18 holes,
because they present 18 holes oriented vertically. These types of units are used in the first floor. (3) thesolid bricks are hand-made, completely solid bricks made manually, these bricks are found in the wallsof the first floor.
2.2.
Previous studies
The laboratory of structures of the Japan-Peru center of earthquake engineering research and disastermitigation (CISMID) together with the National Training Service of the Industrialization ofConstruction (SENCICO) belonging to the central government tested masonry walls in real scale ofsolid handmade bricks and Pandereta bricks (known as tubular brick) in the years 2016-2017.
2.3.
Calibration of experimental data
The data obtained after the test is processed by filtering values in the experiment. The data obtained
from the experiment are displacement and Load, and they form several loops or hysteretic curves. The
area formed by these loops is obtained by the damping, and the maximum values are obtained by therigidity for each distortion.
To verify the good performance of the house, we will use the performance levels according to the seismiccode FEMA356 according to the code the levels are classified into three levels of structural performanceand two structural performance ranges. See Figure 4 to Figure 6.

Figure 4. Immediate occupation, Figure 5. Life safety, in this Figure 6. Collapse prevention,
cracking initiates in the lower step the lengths of the diagonal increase of the cracks in thecracks increase.
part of the walls.
diagonal. At the same time thethickness of cracks.
In previous figures, it presents the levels of performance that are going to consider in thestudio. For the immediate occupation performance level (IO) is 0.07% of story drift angle, for the life
safety performance level (LS) is 0.18% of story drift angle, and for the collapse prevention performance1level (CP) is 0.25% of story drift angle is obtained. The Peruvian code specifies a maximum story drift
angle for masonry of 0.50%, but this type of material known as Pandereta brick is not recommended tosupport gravity load or lateral loads.
2.4.
Retrofitting method for masonry walls
Reinforcement of masonry walls with steel mesh consists of the following steps:• Cleaning of wall impurities, such as dust, paint, concrete, etc.
• Cut the steel mesh to the suggested size for both sides• Make perforations to the masonry wall to be able to pass wire of 8mm of diameter to each 45
centimeters of distance between them to each other.
• Place the steel mesh on both sides and fasten them with wires, keeping in mind that the steel
mesh must be separated from the wall 0.5 cm• Prepare a mixture of water with cement and rub against the wall, so that the mortar adheres tothe walls.
• Cover the steel mesh with mortar 1: 4 in volume (cement-sand) cover it completely with amaximum thickness of 2.5 centimeters.
3.

TARGET MODEL

As a typical housing of the city of Lima, the house has an area of 50.8 m2 of two levels, whose model
was tested in the CISMID laboratory. In this study we will use the distribution of housing, changing thebehavior of masonry walls with non-linear properties of the typical walls used in the district of Lima.
3.1.
Test of the masonry wall
The tests of masonry walls were carried out to know their non-linear behavior. In this informationcollection, we will show the curve of masonry walls with and without retrofitting.
Comparison of the story drift vs. load curve of the specimens was tested for the first load(black line) and the second load (red line) of the target distortion of Pandereta brick wall without
retrofitting (left) and with retrofitting (right). See Figure 7.
400

150

ML2CCA-2 (1)100

ML2CCA-2 (2)50Load (kN)

Load (kN)200

0-50-100

300

MRL2-3 (1)200

MRL2-3 (2)100
0-100-200-300-150-400-200-15-10-5051015

Story drift (mm)-15-10-5051015

Story drift (mm)Figure 7. Comparison of the story drift vs. load curve of the specimens tested.
4.

EVALUATION OF RETROFIT EFFECTS BY CAPACITY SPECTRUM METHOD

4.1.
Demand curve
To find the demand curve we have to refer to the Peruvian standard of earthquake resistance. Thendemand curve is the spectrum of acceleration vs. period expressed in spectral acceleration (Sa) andspectral displacement (Sd).
Response spectrum reduction factor (Fh)Acceleration reduction factor Fh is the response spectrum reduction factor due to the damping effect ofthe building. Where h is equivalent viscous damping, 𝜇𝜇 represents the ductility factor of the building.
See the Eq. (1) to Eq. (3).

2𝐹𝐹ℎ =

1.5
1 + 10 ∙ ℎ(1)ℎ = 𝛾𝛾 ∙ �1 −1
� + 0.05√𝜇𝜇(2)

𝜇𝜇 =𝛿𝛿𝑚𝑚𝑚𝑚𝑚𝑚
𝛿𝛿𝑦𝑦(3)

4.2.
Capacity curve and performance point
From the STERA 3D program, we did obtain the curve of sdx and sfx (shear force vs. story drift). To
restrict the maximum displacement, we made use of the Peruvian seismic code, which restricts us thedrift for masonry of 0.5%. The limit point is assumed as the starting point, with this point it is determined
the performance point assumed, this step is repeated until obtaining a curve of assumed points. Then theassumed point is intersected with the capacity curve to obtain the performance point.
4.3.
Analysis of masonry housing
For the analysis of the housing, the STERA 3D program was used. The walls of the house were designedwith passive damper elements whose data were obtained from the tests. See Figure 8 and Figure 9.

Figure 8. Plans of distribution of the housing.

Figure 9. A Mathematical model in STERA 3D.

4.4.
Analysis results
To know the good behavior of the housing in front of an earthquake we rely on the determination of theperformance point, used by many engineers when they retrofit an existing building. For this study it
proceeded to determine the performance point of the house for three models: the first is the housewithout retrofitting, the second model is the one with some walls retrofitted with steel mesh method
until it becomes very close to the level of performance (69% retrofitting) and the third model is thebuilding totally retrofitted. See the result in Table 1.
Table 1. Story drift and capacity curve.
Model

Story drift (cm)

Shear force (kN)

1. Original (0%)
2. Retrofit (69%)
3. Retrofit (100%)

1.06
0.45
0.34

888.7
923.3
1007.9Spectrumdisplacement (cm)
1.37
0.78
0.64

Spectrum
acceleration (gal)
753.3
852.0
896.0

4.5.
Result comparison
The Figure 10 it shows the results of the three analyses, in which the increase in resistance is observedwith the increase in the ratio retrofitting. The decrease of the performance point, in which it is observedthat after several iterations, the minimum ratio retrofitting was obtained (69%). The blue line represents
the minimum displacement according to the ones proposed for this type of masonry (Life safetyperformance level). See Figure 11.

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1/200 , ( 0.5%Limit Code )

600

1000

1/400 , ( 0.25% )500

1/550 ( Life Safety0.18% )800

1/550 , ( 0.18% )400

1/400 ( Collapse
Prevention 0.25% )300

1/200 ( LIMIT
Peruvian CODE0.5% )First model (0%)

Height of the housing (cm)

Shear force (kN)

12001/1500 , ( 0.07% )600

0% Retrofit

400
69% Retrofit

200
100% Retrofit

00.0

0.2

0.4

0.6

0.8

1.0

1.2200
Second model(69%)

100Third model(100%)

01.4

0.0

Story drift (cm)

1.0

2.0

3.0

Story drift (cm)Figure 10. Comparison of performance points ofthe three analyzed models.
5.

1/1500 ( Immediate
Occupancy 0.07% )Figure 11. Story drift vs. shear force for the firstand second floor.

EVALUATION OF RETROFIT EFFECTS BY JAPAN BUILDING DISASTER
PREVENTION ASSOCIATION (JBDPA) METHOD

Seismic evaluation method uses the Japanese method JBDPA to evaluate old buildings to be able toretrofit. In this method, the seismic demand index should be greater than the seismic index of thestructure.
Seismic demand index 𝑰𝑰𝒔𝒔𝒔𝒔 : The seismic demand index Iso, is calculated with the Eq. (4).
Seismic index of structure 𝑰𝑰𝒔𝒔 : Seismic performance of the building is represented by Is, the index isevaluated by the following Eq. (5), at each story.
𝐼𝐼𝑠𝑠𝑠𝑠 = 𝐸𝐸𝑠𝑠 ∙ 𝑍𝑍 ∙ 𝐺𝐺 ∙ 𝑈𝑈(4)𝑛𝑛 + 1∙ (𝐶𝐶𝑤𝑤 + 𝛼𝛼1 ∙ 𝐶𝐶𝑐𝑐 ) ∙ 𝐹𝐹𝑤𝑤
𝑛𝑛 + 𝑖𝑖(6)

𝛽𝛽𝑚𝑚 ∙ 𝑣𝑣′𝑚𝑚 ∙ 𝐿𝐿𝑤𝑤 ∙ 𝑡𝑡𝑤𝑤 ∙ 𝜆𝜆𝑜𝑜𝑜𝑜∑ 𝑊𝑊(8)𝐼𝐼𝑠𝑠 = 𝐸𝐸𝑜𝑜 ∙ 𝑆𝑆𝐷𝐷 ∙ 𝑇𝑇(5)𝐴𝐴𝑜𝑜𝐴𝐴𝑜𝑜𝜆𝜆𝑜𝑜𝑜𝑜 = 0.6 ∙ ( )2 − 1.6 ∙ � � + 1𝐴𝐴𝑤𝑤
𝐴𝐴𝑤𝑤

(7)

Basic seismic index of structure 𝑬𝑬𝒐𝒐 : The basic seismic index of structure Eo , shall be calculated foreach story with the following Eq. (6).
Reduction factor for openings in masonry walls 𝝀𝝀𝒐𝒐𝒐𝒐: Al-chaar (2002), proposed the reduction factor
due to opening that exist in the masonry walls, it can be estimated under the following Eq. (7):𝐸𝐸𝑜𝑜 =

Strength index of masonry 𝑪𝑪: The strength index C in the first level screening procedure shall becalculated approximately using the cross-sectional areas of walls and columns as follows. See Eq.
(8) and Eq. (9).
𝐶𝐶𝐶𝐶 =

𝐶𝐶𝐶𝐶 =𝛽𝛽𝑐𝑐 ∙ 𝜏𝜏𝑐𝑐 ∙ 𝐴𝐴𝑐𝑐
∑ 𝑊𝑊

(9)

Table 2. Seismic index of structure 𝐼𝐼𝑠𝑠 − Seismic demand index 𝐼𝐼𝑠𝑠𝑠𝑠 , checking
and required strength ΔQu.

2nd story
1st story

Is0.8520.551

Iso0.80
0.80

CheckRetrofit NOT requited
Retrofit required

Weight (kN)
356712Is0.852
0.551

ΔIs (Iso - Is)
00.249ΔQu (kN)
0177.28

4

6.

CONCLUSIONSThe behavior of the Pandereta masonry (tubular) is very brittle. At the beginning it has high resistance,then the resistance decreases rapidly, releasing small pieces of bricks which is dangerous for theresidents. It is recommended to retrofit these types of walls with any other mesh to avoid risks of collapse.
Based on the results presented in the tests, Maximum load on the housing without
retrofitting wall was 136 kN, and a displacement of 4.4 mm and in the case of the housing with aretrofitted wall is 310 kN and its displacement is 5.9 mm, it can be concluded that it is necessary to doa retrofitting to the houses that present this type of bricks to increase the resistance in front of anearthquake.
As the tubular brick is very brittle, its behavior is very different from bricks specified by
the seismic code, we verified it by comparing the tests of the unit, piles, and prism.
Test
NTE-070 Masonry
Test (tubular brick)

Unit f'b (MPa
5.4 (100%)
3.6 (67%)

Piles f'm (MPa)3.40 (100%)
0.92 (27%)

Prism v'm (MPa)0.50 (100%)
0.37 (74%)

The percentage of retrofitting of the capacity spectrum method is bigger than the result of the JBDPAmethod. To improve the results, it would be better to carry out more tests.
X-X (Capacity spectrum method)
11.75 ∗ 100
≅ 69%
16.70

X-X (JBDPA method)
8.00 ∗ 100
≅ 48%
16.70

ACKNOWLEDGEMENTS

I would like to express my sincere gratitude to Dr. Tatsuya AZUHATA, for the support I received
throughout this particular learning process as a thesis advisor.
I would also like to thank the Japanese government through GRIPS, IISEE and BRI and allits staff for the opportunity to open the doors of the world and to grow intellectually and above all
personally. I would like to express my gratitude to JICA for giving me a chance to follow this course byfinancial supporting.
I thank the doctors, engineers, and friends of the CISMID for the opportunity they gave me
to apply for the scholarship and to support me in many things since I joined CISMID. I always feel thesupport in many aspects.
I thank my family and friends who are always present anywhere in the world using theircalls, messages, likes and viewed on social networks.
REFERENCES
Japan Building Disaster Prevention Association (JBDPA), 2001, Standard for Seismic Evaluation ofExisting Reinforced Concrete Building. Guidelines for seismic retrofit of Existing Reinforced
Concrete Building.
Saito, T., 2017. STERA 3D (ver.9.6) Technical Manual. Toyohashi: Toyohashi University ofTechnology.
Web site: Japan-Peru center for earthquake engineering Research and disaster Mitigation CISMID National University of Engineering (UNI), http://www.cismid-uni.org
Zavala, C., Lavado, L., Taira, J., Cardenas, L. and Diaz, M.,” Comparison of behaviors of nonengineering masonry Tubular block walls and solid engineering walls,” Journal of disaster researchVol. 9 Dec.2014, Peru.

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