Paper No. TS-7-1

CICLIC BEHAVIOR OF LOW DUCTILITY WALLS CONSIDERINGPERPENDICULAR ACTION
Carlos ZAVALA1, Patricia GIBU2, Luis LAVADO3,
Jenny TAIRA4, Lourdes CARDENAS5, Luis CEFERINO6

SUMMARY
Low ductility wall buildings became part of the Peruvian construction boom of the first decade of the
21st century. Government promote under the Program named "Mi Vivienda" (My house in English),the construction of low rise buildings of 5 stories using walls with wire mesh reinforcement, provide
part of a solution of an apartment, with reasonable cost. However, the height of the buildings started
to grow and grow, reaching 12 to 16 stories. In the design of this walls, provisions recommend theconfinement of the corners of the walls, due the action of the walls ensemble will provide a limited
ductility under seismic behavior. In this paper the comparison of the action of perpendicular wall witha one plane wall is presented. Here experimental test has been performed by a cyclic loading test
considering the action of a constant axial load of 40 kN, where the elastic stiffness of H shape wall ishigher than one plane wall. Also resistant of the H shape wall increase, however ductility remains
almost similar in both walls.
INTRODUCTION
On 1997 as initiative of Professor A. Galvez, his idea of replace the masonry wall bricks by a thinconcrete wall, bring the opportunity to CISMID Structural Lab to start the study of low ductility walls.
The purpose of study the behavior of this walls using low strength concrete (f'c=100 kg/cm2) and thereinforce of a wire mesh Q62 became a benchmark of the study for walls to be used on 4 stories
buildings. On that research the walls with very light reinforcement and low compressive stress, areconsidered a low limit for this kind of walls. Investigations like performed by UNICON-PRODAC at
PUCP Structural Lab, were used as basic material for discussion among the members of the Peruvian
Concrete Standards committee to fill the empty space for the design of this kinds of walls produced
between 1997 to 2003. On 2003 Peruvian Concrete Standards committee publish an addenda that
include recommendations for the design of low ductility walls. By that time new research on Wall andfull scale test were performed on the study of Eng. Gabriela Medina at CISMID Structural Lab, under
the support of UNICON-FORSA-PRODAC. This study produced parameters considered as a highlimit of stress for this walls. Since that time low ductility walls are widely used on middle and low risebuildings in Peru. Since in low rise buildings, the behavior of these walls had a predominant shear
failure, however during the empty space on the standards, buildings of 12, 14 and 16 stories were build
under unknown criteria.
1 Professor, FIC - UNI. email: czavala@uni.edu.pe
2 Associate Professor, FIC -UNI. email: pgibu@uni.edu.pe
3 Assistant Professor, FIC - UNI. email: lmlavado@hotmail.com
4 Assistant Researcher, CISMID-FIC-UNI. email: jenny_taira@hotmail.com
5 Assistant Researcher, CISMID-FIC-UNI. email: lamcardenas@gmail.com
6 Researcher student, CISMID-FIC-UNI. email: lceferinor@uni.pe

One of the worries is to understand when flexural behavior will be predominant and under which
number of stories. Also how is the influence in the stiffness of a perpendicular wall against one planewall. In this paper the comparison of the action of perpendicularperpendicular wall with a one plane wall ispresented. Here experimental test is presented by a cyclic lateral loading considering the action of aconstant axial load.

Figure 1: Low ductility wall
MAIN DIFFERENCES OF A LOW DUCTILITY WALL AND STANDARD WALL
On Figure 2 two off the main differences between a low ductility wall and an standard concrete wallare presented. The first is the thickness of the wall, were low ductility wall could have 100 mm. oreven 80 mm. against the 150 mm. which is minimum thickness of an standard conc
concrete wall. The
second difference is the reinforcement showing deformed ductile bars at the edges of the walls andelectro welded wire mesh on the web of the wall, also connection with dowels tied to basement orconnection between stories is produce using ddowels,
owels, against the deformed bars on web of walls usedin standard concrete wall.

2 Low ductility wall reinforcement and configuration
Figure 2:

Figure 3 presents the difference in the construction where builders offer one day one story and slab as
an efficiency parameter. However this massive and continuous placement brings failures such cold
joint at base of wall or hole air bags inside the concrete. It increase time in the construction process
due to actions of repair this deficiencies. Some builders after a series of bad experiences propose theuse of fluid concrete with fibers in order to reduce total time of construction.

3. Construction

Figure 3: Construction Process
During 1998 to 2003 non regulation was applied in the construction of this kind of wall due they were
not consider shear walls. The application was on 5 story buildings, however many constructors started
to build structures of 12, 14 and 16 stories, just like that, without confinement columns. On 2003 theNTE-060 Peruvian Concrete Standard include recommendations for construction of this kind of walls.
Stiffness contribution of the perpendicular wall is need in order if this will contribute on the inelastic
behavior under lateral load with and without perpendicular wall.
THEORETICAL INFLUENCE OF THE PERPENDICULAR WALL EFFECT
For the theoretical investigation of the influence of the perpendicular wall against the in plane wall,
we consider an H shape wall of 2500 mm. length, and 2600 mm. height and 100 mm. thickness. If wementioned the H shape wall as steel shape, the in plane wall is the web, and the perpendicular walls
are flange of the wall. Therefore, flange length is 2500 mm, with same height and thickness as the web.
Theoretically speaking, walls under perpendicular action and combined load demands will experimentprimary axial deformation, due to the axial forces, usually assigned as dead load and live load on thebuilding design process, produced a pattern of axial stresses. Then, seismic action appears, lateral
deformation will change the configuration of axial stresses and shear stresses will produce
concentration and also dissipation of stress on the wall flange.

100 kN
200 kN

Figure 4: Load condition for H wall and deformation under shear stress component
As an example, load configuration and the deformation of the H wall under lateral load with a constantaxial load is presented on Figure 4. Therefore if 200 kN axial load is applied, producing a confinement
axial stress of 8kg/cm2. This axial stress is reduced by the application of the lateral load to a level till
7.2 kg/cm2 on the web, and increase on the toe to 18 kg/cm2 on the toe intersection of web and flange.
Also horizontal stress on the flange wall shows average value of a level of 4.0 kg/cm2. Let´s consider
the variation on the geometrical parameter flange length, and produce the variation of the flange
length and web length ratio for the component of the horizontal stress. Results of the investigation arepresented on Figure 5.

Bf= 1750 mm. Bf/L=0.7
Bf = 1500 mm. Bf/L= 0.6
Bf=1250 mm. Bf/L= 0.522
σ 11 = 4.02 kg/cm
σ 11 = 4.15 kg/cm
σ 11 = 4.32 kg/cm2
Figure 5: Horizontal stress on perpendicular wall for different flange length - web length ratio.

Figure 6: Horizontal stress variation for Bf/L ratio
If the example is repeated to investigate the change of stress in the axial component on the H wall,considering that this kind of stress will have an initial level of axial stress of 18 kg/cm2, from thispoint, the stress change function with the Bf/L ratio is presented on Figure 8. Also Figure 7 presents
the stress distribution for each case. If we consider the division in elements and the amount of theelements on the flange wall, we can find that stresses have a similar level of axial stress for bf/4. It
means as long is the flange less increment on the axial stress is reached.

Wall Flange
Bf= 2500 mm. Bf/L=1.0

Wall Web
Wall Flange
Wall Webσ 22 = -15.85 kg/cm2 Bf= 1750 mm. Bf/L=0.7 σ 22 = -17.12 kg/cm2

Wall Flange
Wall Web
Wall Flange
Wall Web
Bf= 1500 mm. Bf/L=0.6 σ 22 =-17.89 kg/cm2 Bf= 1250 mm. Bf/L=0.5 σ 22 = -18.97 kg/cm2
Figure 7: Axial stress on perpendicular wall for different flange length - web length ratio.

Figure 8: Maximum axial stress variation for Bf/L ratio

Wall Flange

Wall Webτ 12 = 3.30 kg/cm2

τ 12 = 6.96 kg/cm2

Bf = 2500 mm

Wall Flangeτ 12= 2.93 kg/cm2
Bf = 1500 mm

Wall Flangeτ 12 = 3.07 kg/cm2

Bf/L= 1.0

Bf = 1750 mm

Wall Webτ 12

Wall Flange= 6.55 kg/cm2

τ 12

Bf/L= 0.6

τ12 = 6.70 kg/cm2
Bf/L= 0.7

Wall Web= 2.73 kg/cm2

τ 12 = 6.31 kg/cm2

Bf = 1250 mm

Bf/L= 0.5

Figure 9: Shear stress on wall and web walls(a)Wall Web(b)Figure 10: Shear stress variation for Bf/L ratio
In the opposition of the case of axial stress, let´s consider the variation on the shear stress underconstant axial and shear force. Figure 9 presents the patterns of the shear stress for different values of
Bf/L. We must take into account that 6.85 kg/cm2 is the starting point, since value will decrease as the
Bf/L ratio decrease as is presented at Figure 10a.
Also the ratio between Bf/L and shear stress for the web wall is presented on Figure 10b, where thelevel of shear stress on the flange wall are almost have of the shear stress of the web stress. Tendencyof the stress are almost the same, stress decrease as Bf/L ratio decrease. It means less flange less stress.
EXPERIMENTAL TEST CONSIDERING PERPENDICULAR WALL EFFECT
In order to investigate in experimentally the influence of the perpendicular wall on and H shapeconfiguration against one plane wall, two experiments were performed: an experiment on a one planewall, and an experiment with a perpendicular wall that produce an H shape wall.
About The Specimens
Both walls (one plane and H wall) will has the same dimensions: 2500 mm. length with 2600 heightand 100 mm. thickness. In the case of H wall, a flange with a total dimension (Bf) of 2500 mm. isincorporated to the one plane wall, in order to investigated it influence by the measured stresses.

The walls have a reinforce on the corners as confinement 3 bars #4. Wire mesh appears as
reinforcement of the web and flange with electro welded mesh Q-158 (5.5 mm. diameter @ 0.15m
As=1.58 cm2/m). Is common use of 600 mm. dowels between stories on buildings, but in the case of
the specimens dowels are same growing from the footing base. Figure 11 presents the configuration ofboth specimens, one plane and H shape wall, notice that there is a horizontal border beam of 300 mm.
by 300 mm. section on the top of each beam. Also foundation of 900 mm. by 300 mm. is on thebottom part of the specimen.

Figure 11: Test specimen configuration for H shape wall
The construction process tried to replicate as near the real environment on the site area. So wire meshfrom the footing was fixed with the wire mesh of the wall and three ductile bars #4 were placed on thecorners of the specimens. Wood forms were used to encase the reinforcement and set the fluid mix ofconcrete inside to produce the concrete wall. On the top of each wall a loading beam is build to be use
for setting of the loading steel frame. Figure 12 presents four stage of the constructions of thespecimens.

Figure 12: Four stages on the construction of the specimens
ABOUT THE TEST EXECUTION
For the execution of the test 2 jacks and one actuator were used for the application of the loads. Axial
load equivalent to 200 kN that approximately represents the load of four stories over the wall. During
the execution of the test, this load will be applied at the beginning of the load process, and after
reaching 200 kN, the load will remain constant during the whole test. To simulate the lateral action
such a earthquake movement, an increasing cyclic displacement will be applied to the specimen inorder to start the movement of the wall and measure in each step the load. Figure 13 present thehistory of the cyclic displacement applied on the wall. The displacement were applied using the new
jack system provided by JICA under the SATREPS project. This jacks (Rikken System) had capacityof 500 kN and 400 mm. stroke.

Displacement (mm)

20
10
0
0

500

1000

1500

2000

2500

3000

-10
-20

Number of cyclic

Figure 13: History of cyclic displacement on test
For the measure of the displacements a set of transducer were placed to measure displacement indifferent locations on the walls. In the one plane wall and web wall (on H shape specimen),
displacements transducers were set on the positions presented on Figure 14, here sensors on the bodyof the wall were setting on the diagonal, vertical and horizontal in order to reproduce the displacementon all directions. For the measure of the stress on points strain gauges were glued to the surface of theconcrete and to the reinforce bars. All the sensors and gauges, were connected to an scanning box anddata logger Tokyo Sokki TDS 530.

Figure 14: Displacement transducer setting

Figure 15: Test set up for one plane wall and H shape wall.
On Figure 15 the test setup of both specimens are presented. Here is possible to notice the difference
on the setup due to need of application of the axial load and lateral load simultaneously in special in
the case of the H shape wall were space is quite narrow to applied both loads. In the case of H shapewall the perpendicular wall (flange wall) has three lines of sensors in order to investigated thedisplacement on that positions and the dissipation of the stress. Also strain gages were set for the same
purpose.

TEST RESULTS
The cyclic displacement versus base shear on the experimented walls are presented on Figure 16,
where hysteresis curves of the development of each test are present. It is possible to read that both
specimens had almost the same level of maximum stress, but in different failure mode. In the case of
the one plane wall, shear cracking appears on the base of the experiment. Then flexural cracks starts toappear on both borders elements, propagation horizontally. Finally diagonal cracks appear and a
combination of shear failure with slip failure of the base, is the final failure pattern.
CISMID/FIC/UNI-JICA SATREPS Project
Low ductility concrete wall - H- Wall 03
04/06/2012

CISMID/FIC/UNI-JICA SATREPS Project
Low ductility concrete wall - Wall 02
18/02/2012

500

-20

400

400

300

300

200

200

100
-15

-10

0 -2.185, 7.25
-5
0
5
-100

10

15

20

Base shear (kN)

Base Shear (kN)

500

100
0
-20

-15

-10

-5

0

5

10

15

20

-100

-200
-200

-300

-300

-400

-400
Displacement (mm)-500
Displacement (mm)Figure 16: Hysteresis curves of one plane wall and H shape wall
CISMID/FIC/UNI-JICA SATREPS Project
Comparison Low ductility concrete wall - Wall 02 vs Wall 03
Lareal Load (kN)

500
400
300
200
100

-20.00 -16.00 -12.00 -8.00

0-4.00 0.00
-100

4.00

8.00

12.00 16.00 20.00

-200
-300
-400
-500
One Plane Wall - M2

displacement (mm)Wall - H - M3

Figure 17: Comparison of behavior curves of low ductility walls.
In the case of the H shape wall, the starting crack was a diagonal crack that appears in the intersection
zone between both walls. A continue diagonal shear cracks on the intersection of both walls appears
during the test. Then shear cut of the basement appears, together with an up light of the toe. Final stageof both specimens are presented on Figure 18.

Figure 18: Final stage of one plane wall and H type wall
A resume of the results of both test is summarized on Table 1. Here we can read that in the case ofwall-H stiffness is increased due to the perpendicular wall action. Also the end of the elastic zone in
the specimens are presented on Table 1. Here is possible to read that as more stiff is the wall less isthe ductility. Maximum drift value for one plane walls is 0.004 against the maximum drift on the H
shape wall of 0.0015. Therefore, more rigid the wall less ductile is the wall.
Table 1: Test results on walls
Specimen

Initial Stiffness

End Elastic

Limitτmax Stress

One Plane Wall
Wall - H(kN/mm)
185.2
192.0

Drift
0.000340.00040

Drift0.00400.0015(kg/cm2)
14.5
14.5

Shear Stress (kg/cm2 )CISMID/FIC/UNI-JICA SATREPS Project
Comparison Low ductility concrete wall - Wall 02 vs Wall 03-0.008-0.006-0.004

16
14
12
10
8
6
4
2
0
-0.002 -20.000
-4
-6
-8
-10
-12
-14
-16
One Plane Wall - M2

0.002

0.004

0.006

0.008

Drift
Wall - H - M3

Figure 19: Comparison of shear stress on low ductility walls

On Figure 19 the comparison at shear stress behavior curves is presents in terms of drift and shear
stress on the web wall on both specimens. Wall H has a limit drift prior the case of one wall specimen,
where the values are presented on Table 1. Both walls reach the same level of maximum shear stress
but with different drift.

CONCLUSIONS.
 Contribution of the perpendicular action of a wall to one plane wall has been presented
theoretically on this paper. The influence of the flange size of the wall shows and spreading of thestress for L/4 to low levels. It is necessary to continue the study using experimental test of different
flange length.
 One case of flange length has been studied experimentally with the execution of two test: first testwith one plane wall, and another test with and H shape wall with flange length of 250 mm. Heightof the walls is 2600 mm. and 100 mm. thickness. Both walls have been reinforce on the corners asconfinement 3 bars #4. Wire mesh appears as reinforcement of the web and flange with electro
welded mesh Q-158 (5.5 mm. diameter @ 0.15m As=1.58 cm2/m).
 Test results are summarized on Table 1. Here we can read that in the case of wall-H stiffness isincreased due to the perpendicular wall action. Maximum drift value for one plane walls is 0.004
against the maximum drift on the H shape wall of 0.0015. Therefore, more rigid the wall lessductile is the wall.
 We need to continue the study in order to verify the spread of stress on perpendicular flange wall
and web wall. At this time we need to process data from strain gauges to investigate this spread ofstress.
REFERENCES
1. CISMID Report. Experimental test on walls to investigated lateral load Behavior AGV System
CISMID/FIC/UNI, 1998 (in Spanish).
2. Zavala C. ,et al. Behavior under lateral load of low concrete strength walls with electro welded wire
mesh reinforcement. – Material Bank of Peru – AGV & Association – CISMID Report. 1999 – 2000.
3. G. Medina – Study of the behavior of low ductility and one story scale model reinforce withelectrowelded wire mesh – Graduate Thesis FIC/UNI – Research supported by UNICON-FORSA –PRODAC- CISMID/FIC/UNI 2004-2005.