Comparison of Behaviors of Non-Engineered Masonry
Tubular Block Walls and Solid Engineered Walls

Paper:

Comparison of Behaviors of Non-Engineered Masonry
Tubular Block Walls and Solid Engineered Walls
Carlos Zavala, Luis Lavado, Jenny Taira, Lourdes Cardenas, and Miguel DiazJapan-Peru Center for Earthquake Engineering Research and Disaster Mitigation (CISMID),
Faculty of Civil Engineering, National University of Engineering (UNI)
Av. Tupac Amaru 1150 Puerta 7 Campus UNI, Lima, Peru
E-mail: czavala@uni.edu.pe[Received August 2, 2014; accepted October 10, 2014]

In Peru, the most commonly used structural system
for housing construction is based on confined masonrywalls. Solid engineered walls are regulated by the
NTE-E070 standard, which lays down a required degree of earthquake resilience. However, around 60%of the population lives in non-engineered houses that
use tubular blocks for their walls. This paper presents
a comparison of the behaviors of non-engineered tubular block walls and solid engineered walls. Tests were
performed on a tubular brick wall by subjecting it tohorizontal cyclic loading to examine the effects undera constant axial load of 20 tf. Then, the test results
were compared with those for walls in the CISMID
Structural Lab database. The resistance of the tubular
brick wall in terms of shear stress was found to be relatively low, having an average value of 4 kg/cm2 , while
the solid walls can withstand a shear stress in excess of
5.5 kg/cm2 .
Keywords: masonry, tubular brick, solid brick, nonengineered wall, engineered wall

1. Introduction
Masonry buildings first appeared in Peru in the seventeenth century, where most housing had until then been
built using adobe or stone. However, the use of thismaterial was a privilege of the rich, the authorities, andwealthy traders. Modern masonry became commonplacein the twentieth century, when it came to be used by
the general population. Many people dreamed of a masonry house in the wake of the May 24th , 1940 Lima
Earthquake, in which adobe houses collapsed but masonryhouses remained standing after the quake. People cameto accept that masonry was the stronger material, especially in the case of confined masonry structures. A wallbuild with bricks confined with concrete elements in theirfour edges is called confined masonry. Since confined
masonry was not so popular at that time, most builders
provided a strong support for the roof of a building byusing solid handmade bricks. Since then, bricks have
evolved, incorporating holes to attain a 25% reduction in

Journal of Disaster Research Vol.9 No.6, 2014

Fig. 1. Handmade, factory-made, and tubular bricks.

Fig. 2. Non-engineered house.

the amount of material used. According to Peruvian masonry standard NTE-E070, a standard brick should notexceed this maximum hole area. Then, factory-madebricks appeared and, considering the maximum amountby which the area could be reduced, factories started producing 12-hole bricks. Then, in 1990, 18-hole and 24hole bricks appeared. All factory-made bricks are standard bricks that conform to the standards. However, due
to the high price of these bricks, the population in rapidly
expanding regions started to use the bricks intended forpartition walls as material for supporting walls, creating
non-engineered walls made of tubular brick. Fig. 1 shows
the three kinds of masonry bricks used in the rapidly expanding parts of Peruvian cities. The purpose of our studyof the behavior of walls made from tubular bricks was toshow how weak these components are, relative to the demands of the Peruvian standards.
One of the problems is the load capacity of tubular
brick walls under a lateral load, even though the construction of buildings of up to five stories is permitted by
the standards (see Fig. 2). These walls are prone to failabruptly.
1021

Zavala, C. et al.

30

30
330

2. Test with Tubular Bricks

220

30

240

220

One of our aims was to understand the yield level ofthe confinement elements due to the low strength in shearof the masonry. Confinement, horizontal and vertical concrete elements, will predominant start to work prematureon the wall. The relatively low stiffness of such walls
in comparison with that of solid walls will be presented.
This paper compares the behavior of both kinds of wall:
non-engineered walls constructed using tubular bricks andsolid engineered walls. A test is presented using cyclic
lateral loading under the action of a constant axial load.

90

Fig. 3. Specimen wall.

To investigate the behavior of a tubular brick wall, aseries of experiments was performed, with tubular bricks
being used to construct a specimen wall.

2.1. Outline of the Specimen
The specimen wall measured 2400 mm long by
2300 mm high and 120 mm thick. The walls have confining reinforced concrete columns at the corners, witheach column incorporating four #4 bars with #2 stirrups
every 250 mm. Fig. 3 shows the configuration of the specimen. The specimen was built on a foundation measuring
900 mm by 300 mm.
The construction was done in such a way as to replicate, as closely as possible, the actual environment of aconstruction site. To that end, the wall was built up tohalf of its full height on one day, with the remainder being completed on the following day. After masonry wallis completed, confined elements reinforce bars are set, tofinally put the concrete on site. The three stages of theconstruction are presented in Fig. 4.
2.2. Loading Test
For the test, four jacks were installed to apply a loadto the wall. An axial load equivalent to 20 tf could beapplied, thus simulating the load applied by four stories
bearing down on the wall.
During the test, an axial load was applied at the beginning of the loading process and, after reaching 20 tf,
the load was kept constant throughout the duration of theexperiment. To simulate a lateral load like that imposedby an earthquake, cyclic loading with controlled displacement was applied to the specimen. Fig. 5 shows a plot of
the cyclic displacement applied to the wall. The displacement was applied using a new hydraulic jack system provided by JICA as part of the SATREPS project. This jacksystem had a capacity of 500 kN and a stroke of 400 mm.
As shown in Fig. 6, transducers were installed to measure the displacement at different points on the walls. The
sensors were installed diagonally, vertically, and horizontally in order to reproduce the displacement in all directions. To measure the strains, strain gauges were glued tothe surfaces of the concrete and the reinforcing bars. Allof the sensors and gauges were connected to a scanningbox and a Tokyo Sokki TDS 530 data logger.
1022

Fig. 4. Three stages of specimen construction.

Fig. 5. Cyclic displacement.

The test setup of the specimen is shown in Fig. 7. To
apply the axial load, two jacks were installed vertically.
Another two jacks were used to simultaneously apply alateral load. Strain gauges were also installed to investigate the yielding of the reinforcing bars at each corner ofthe confinement elements.

Journal of Disaster Research Vol.9 No.6, 2014

Comparison of Behaviors of Non-Engineered Masonry
Tubular Block Walls and Solid Engineered Walls

Table 1. Characteristics of comparison specimens.
σ
σo
fm
L
t
h
No
Specimen(kg/cm2 ) (mm) (mm) (mm) (kg/cm2 ) (tf)M-ART
33.20 2500
115 2300
4.13 11.88
M-IND
22.10 2500
115 2300
4.13 11.88
WALL C2-HM
59.26 2200
140 2300
2.76 8.50
WALL C2-FM
70.24 2200
140 2300
2.76 8.50
WALL-SP-1
30.87 2400
120 2300
6.94 20.00

CISMID/FIC/UNI Structural Lab
Comparison of Tubular and Structural Masonry
Hysteresis Curve30

Fig. 6. Locations of displacement transducers.

Lateral Load (Tf)

20

10

0

WALL C2-HM
WALL C2-FM-10

WALL-SP-01
M-ART

-20

M-IND
-30
-30

-20

-10

0

10

20

30

lateral deformation (mm)Fig. 8. Hysteresis curves of WALL-SP-1 wall and others.

Fig. 7. Test setup for masonry wall test.

3. Test Results and Comparison
3.1. Test Results
To compare the results of the test with those of previous experiments, the CISMID Structural Lab database ofexperiments, generated as part of the SATREPS project,
was used. For comparison with the test results (WALLSP-01), four walls were selected: one built with handmade tubular bricks (M-ART), one built using factorymade tubular bricks (M-IND), one built using solid handmade bricks (WALL-C2-HM), and finally one built using
factory-made bricks (WALL-C2-FM).
Table 1 lists the geometrical characteristics of the comparison specimen, where fm is the maximum compression
stress on the masonry, L is the length, t is the thickness, his the height, σo is the confined axial stress, and No is thetotal axial load applied vertically. It can be seen that the
specimen (WALL-SP-1) was subjected to almost double
the axial load of the other specimens.
The relationship between the displacement and shear
force applied to the walls is shown in Fig. 8, where thedisplacement of wall WALL-SP-1 reaches a maximum of
13.85 mm, corresponding to a maximum drift of 1/160.
The specimens were subjected to different maximum
Journal of Disaster Research Vol.9 No.6, 2014

loads, due to differences in the axial confinement and variations in the quality of the materials. For WALL-SP1 and
M-ART, shear cracks appeared at basically the same displacement. Table 2 shows that the maximum load (Qu )is the lowest of all the measured values, and the displacement at the maximum load (dmax ) is the smallest. WALLSP-1 is subjected to more confinement stress and this has
a major influence on the displacement. From the table, it
is possible to conclude that the confinement will yield before the other walls, due to the low material strength andhigh axial load on the wall.
Initial cracks appeared in the masonry at a drift of
1/1500, and diagonal cracks started propagating at a driftof 1/1075. Finally, diagonal crack openings appeared ata drift of 1/200 with shedding of the brick surface. The
final state of specimen WALL-SP-1 is shown in Fig. 9.
The backbone curves of the relationships between thedisplacements and shear forces are shown in Fig. 10. Table 3 lists the maximum shear stresses, together with thecorresponding drifts. It can be seen that the stress for the
SP-01 wall is lower because of the action of the strong
axial load and the low strength of the material, producing a shear stress of 4.44 kg/cm2 . The M-IND and MART walls exhibit the second-lowest level of shear stressamong the specimens. Since WALL C2-FM is an engineered wall, it exhibits a higher shear stress.
Also evident is the great difference in the maximum
capacity of the engineered wall and that of the M-ART
and M-IND walls.
1023

Zavala, C. et al.

CISMID/FIC/UNI Structural Lab
Comparison of Tubular and Structural Masonry
Stiffness Degradation

Table 2. Comparison of test results.
Qy
dy
Qc
(tf)
(cm)
(tf)
14.27 0.2493 9.794
17.23 0.2869 10.659
14.90 1.1613 9.305
17.99 0.2708 13.924
13.34 0.2780 9.617

16
14
12
Keq (Tf/mm)

dmax
du
Qu
(tf)
(cm) (cm)M-ART
18.86 0.7242 1.042
M-IND
20.76 0.5548 1.086
WALL C2-HM 17.45 2.1340 2.337
WALL C2-FM 22.79 0.9010 0.901
WALL-SP-1
13.88 0.3070 1.474
Specimen

10

WALL C2-HM

8

WALL C2-FM
WALL-SP-01

6

M-ART
M-IND

4
2
0
0

1

2

3

4

5

6

7

8

9

10

Ductility Factor

Fig. 11. Comparison of equivalent stiffness relative to ductility factor.

Figure 11 presents a comparison of the equivalent stiffness relative to the ductility factors of the specimens. The
engineered walls (WALL C2-FM) exhibit a higher equivalent stiffness while the tubular walls (M-ART, M-IND,
WALL-SP-01) have an average stiffness that is around
60% of the initial stiffness of the engineering wall. In
all these cases, the tubular brick walls exhibit the lowest
levels of stiffness.

Fig. 9. Final state of wall (1/150) – WALL-SP-1.

CISMID/FIC/UNI Structural Lab
Comparison of Tubular and Structural Masonry
Envelope Curves

4. Conclusions

10
8• In Peru, tubular bricks intended for partition walls

Shear Stress (kg/cm2)

64
2
0-0.015-2-0.010-0.005

0.000

0.005

0.010

0.015

WALL C2-HM-4

WALL C2-FM-6

Wall-SP-01
M-ART

-8

M-INT

-10

Drift

Fig. 10. Comparison of behavior curves.

Table 3. Maximum values from drift-stress curves.
Test

Drift

M-ART
M-IND
WALL C2-HM
WALL C2-FM
WALL-SP-1

0.00300.00230.00890.00390.0013

Max Stress(kg/cm2 )6.04336.65295.59297.30354.4479are being used for load-bearing walls, despite thisbeing illegal in active seismic zones according to Peruvian standard NTE-E-070. The axial load capacityof tubular brick walls does not satisfy the minimum
requirement of the NTE-070 standard.
• A comparison of the cyclic behavior of engineering

walls and tubular walls was presented. Four walls
were selected for the comparison: one built withhandmade tubular bricks (M-ART), one built withfactory-made tubular bricks (M-IND), one built using solid handmade bricks (WALL-C2-HM), and one
built using factory-made bricks (WALL-C2-FM).
The last of these is regarded as being an engineered
wall, and exhibits the best backbone curve in thecomparison.
• The test results show that the tubular brick walls havethe lowest capacity.
• A reduction in the equivalent stiffness is attained

more quickly in the case of tubular brick walls. The
shedding of the surface of these walls would be dangerous for the inhabitants of housing built using thismaterial.
• The retrofitting of tubular brick walls is required to1024

Journal of Disaster Research Vol.9 No.6, 2014

Comparison of Behaviors of Non-Engineered Masonry
Tubular Block Walls and Solid Engineered Walls

avoid the possible collapse of housing built using
these materials and techniques.
Acknowledgements
The authors are grateful to the Ministry of Education of Japan,
through the Japan Science and Technology Agency (JST) and theJapan International cooperation Agency (JICA) for their supportof the Japan-Peru SATREPS Project. We also extend our gratitude
to Dr. Fumio Yamazaki, Principal Investigator of the SATREPS
project and promoter of this investigation.

References:[1] C. Zavala and T. Kaminosono, et al., “Construction Monitoring and
Improvement Techniques for Masonry Housing,” CISMID-IDI Report, 2003.
[2] R. Salinas and F. Lazares, “The Tubular Masonry and its Use on
Buildings in Seismic Zones,” CISMID-II-FIC/UNI, 2007.

Name:
Carlos Zavala

Affiliation:
Researcher, Laboratory of Structures, CISMID
Professor, Faculty of Civil Engineering, National
University of Engineering (UNI)

Address:
Los Ishipingos (Ex-Abetos) 245 Dpt. 202, Urb. El Remanso La Molina,
Lima 12, Lima, Peru

Brief Career:
1984 Undergraduate Course, Faculty of Civil Engineering, National
University of Engineering (UNI), Lima, Peru
1989 Master Course, Graduate School Faculty of Civil Engineering,
National University of Engineering (UNI), Lima, Peru
1995 Ph.D., Graduate School of Architecture, University of Tokyo, Japan
2001 Professor, Faculty of Civil Engineering, National University ofEngineering, Lima, Peru
2007-2012 Director of Japan Peru Center of Earthquake Engineering
Research & Disaster Mitigation CISMID

Selected Publications:• C. Zavala, K. Ohi, and K. Takanashi, “A general Scheme for
Substructuring On-line Hybrid Test on Planar Moment Frames (TheNeural Network Model),” Proceedings of 4th Pacific Steel Structures
Conference, Pergamom Press, October 1995.
• C. Zavala, “Improvement on low cost housing through non-conventional
construction systems,” Proceedings of the 12th World Conference on
Earthquake Engineering, Auckland, New Zealand, February 2000.
• C. Zavala, C. Honma, P. Gibu et. al, “Full Scale On Line Test On Two
Story Masonry Building Using Handmade Bricks,” Proceedings of the 13th
World Conference on Earthquake Engineering (WCEE), Vancouver,
Canada, August 2004.
• C. Zavala, Z. Aguilar, and M. Estrada, “Evaluation of SRSND Simulator
against Fragility Curves for Pisco Quake,” Proceedings of the 8thInternational Conference on Urban Earthquake Engineering Tokyo
Institute of Technology, Tokyo, Japan, 2011.

Academic Societies & Scientific Organizations:• Peru Engineering Association (CIP)

Journal of Disaster Research Vol.9 No.6, 20141025