In the past few years, a concern is observed internationally regarding the seismic mechanical behavior of reinforced concrete walls, especially against their transverse instability under extreme seismic loads.

1. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print),
ISSN 0976 – 6316(Online), Volume 5, Issue 6, June (2014), pp. 101-107 © IAEME
INTERNATIONAL JOURNAL OF CIVIL ENGINEERING
AND TECHNOLOGY (IJCIET)
ISSN 0976 – 6308 (Print)
ISSN 0976 – 6316(Online)
Volume 5, Issue 6, June (2014), pp. 101-107
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101
IJCIET
©IAEME
OUT-OF-PLANE BUCKLING OF HIGHLY REINFORCED SEISMIC
WALLS: DISPLACEMENTS AND MODE OF FAILURE
Theodoros A. Chrysanidis*1, Ioannis A. Tegos2
*1Aristotle University of Thessaloniki, School of Engineering, Department of Civil Engineering,
Division of Structural Engineering, 54124 Thessaloniki, Greece.
(T. A. Chrysanidis, Dr. Civil Engineer, MSc, MSc DIC).
2Aristotle University of Thessaloniki, School of Engineering, Department of Civil Engineering,
Division of Structural Engineering, 54124 Thessaloniki, Greece.
(I. A. Tegos, Professor)
ABSTRACT
In the past few years, a concern is observed internationally regarding the seismic mechanical
behavior of reinforced concrete walls, especially against their transverse instability under extreme
seismic loads. The present work is experimental and examines the influence of tensile strain on out-of-
plane buckling of reinforced concrete seismic walls. The experimental work herein consists of 5
scaled test specimens simulating the end regions of structural walls. These specimens were
reinforced with the same high longitudinal reinforcement ratio (3.68%). The degree of tensile strain
applied was different for each specimen and it took values equal to 0‰, 10‰, 20‰, 30‰ and 50‰.
The present work tries to investigate the influence of the degree of tensile strain to the displacements
(horizontal and vertical) and the modes of failure of test specimens.
Keywords: Buckling, Seismic Walls, Out-of-Plane, Tensile Strain.
1. INTRODUCTION
A sufficient number of reinforced concrete walls is good to be utilized during the process of
seismic design of reinforced concrete buildings. Buildings with a large number of structural walls,
have demonstrated exceptional behaviour against seismic action, even if these walls had not been
reinforced according to the modern perceptions [1]. Structural walls designed to be in a high ductility
category according to modern international codes such as EC8: 2004 [2] and NZS 3101: 2006 [3] or
designed with increased ductility requirements according to .... 2000 (Greek Concrete Code
2000) [4], are expected to present extensive tensile deformations, especially in the plastic hinge

2. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print),
ISSN 0976 – 6316(Online), Volume 5, Issue 6, June (2014), pp. 101-107 © IAEME
region of their base. According to Chai and Elayer [5], tensile deformations up to 30‰ are expected
at the walls of the bottom storey height depending on their geometric characteristics and the level of
ductility design of the walls. These tensile deformations, depending on their size, can cause out-of-plane
102
buckling of walls. Prominent researchers, like Paulay [6], propose the use of flanges or
enlarged boundary elements in the extreme regions of walls, which provide protection to the bending
compression regions against transverse instability. Moreover, these elements are easier to be
confined. New Zealand Concrete Code (NZS 3101: 2006) [3] and other modern international codes
propose the construction of such elements. The phenomenon of lateral buckling of R/C walls
depends basically on the size of tensile deformations which are imposed at the extreme regions of
walls at the first semi-cycle of seismic loading and not so much on the size of flexural compression
which is imposed at the reversal of seismic loading, according to Paulay and Priestley [7].
The authors of the present work have conducted an initial research work on the phenomenon
of lateral buckling of reinforced concrete structural walls strained under seismic action [8][9]. The
progress of research resulted to some promising results regarding the influence of the factor of
elongation degree to the maximum failure load of seismic walls [10] and to the displacements of
seismic walls [11]. The work presented herein focuses on the influence of the degree of tensile strain
to the wall displacements. The present work on the phenomenon of out-of-plane buckling constitutes
a small part of an extensive research program that took place at the Laboratory of Reinforced
Concrete and Masonry Structures of the Department of Civil Engineering of Aristotle University of
Thessaloniki. It has to be noted the fact that degree of tensile strain, degree of elongation and degree
of tensile deformation refer to the same thing (meaning the size of the tensile deformation that
longitudinal reinforcement is subjected to) at the present paper.
2. EXPERIMENTAL INVESTIGATION
2.1. Test specimen characteristics
The test specimens were constructed using the scale 1:3 as a scale of construction. The
dimensions of specimens are equal to 7.5x15x90 cm. The reinforcement of specimens consists of 4
bars of 10 mm diameter and 2 bars of 8 mm diameter. The total number of specimens is equal to 5.
Each specimen was submitted first in tensile loading of uniaxial type up to a preselected degree of
elongation and then was strained under concentric compression loading. The differentiation of
specimens lies in varying degrees of elongation imposed on each one of them. Fig. 1 presents their
front view both for tensile and compressive loading, while all specimen characteristics are brought
together in Table 1.
Table 1: Test specimens’ characteristics
Name of specimens -4Ø10+2Ø8-368-0-1 -4Ø10+2Ø8-368-10-2 -4Ø10+2Ø8-368-20-3 -4Ø10+2Ø8-368-30-4 -4Ø10+2Ø8-368-50-5
Dimensions
(cm)
15x7.5x90 15x7.5x90 15x7.5x90 15x7.5x90 15x7.5x90
Longitudinal
reinforcement
4Ø10+2Ø8 4Ø10+2Ø8 4Ø10+2Ø8 4Ø10+2Ø8 4Ø10+2Ø8
Transverse
reinforcement
Ø4.2/3.3cm Ø4.2/3.3cm Ø4.2/3.3cm Ø4.2/3.3cm Ø4.2/3.3cm
Longitudinal
reinforcement ratio
(%)
3.68 3.68 3.68 3.68 3.68
Concrete cube
resistance at day of
compression test
(MPa)
25.78 25.78 25.78 25.78 25.78
Degree of elongation
(‰)
0.00 10.00 20.00 30.00 50.00

3. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print),
ISSN 0976 – 6316(Online), Volume 5, Issue 6, June (2014), pp. 101-107 © IAEME
103
Fig. 1: Sketch of front view of specimens having longitudinal reinforcement 4Ø10+2Ø8 for:
(a) Tension test, (b) Compression test
2.2. Loading of specimens
The experimental setups used in order to impose to the specimens in the first semi cycle of
loading a uniaxial tensile load and in the second semi cycle of loading a concentric compressive load
are shown in Fig. 2.
Fig. 2: Test setup for application of: (a) Tensile loading, (b) Compressive loading

4. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print),
ISSN 0976 – 6316(Online), Volume 5, Issue 6, June (2014), pp. 101-107 © IAEME

5. !

6. 104
3. EXPERIMENTAL RESULTS
Fig. 3 refers to the concentric compression test and shows the change of transverse
displacement relative to the applied compressive load this time, while Fig. 4 depicts the residual
transverse displacement in relation to the normalized specimen height. Finally, Fig. 5 shows the
various failure modes of all specimens after the completion of the compressive loading.

7. Fig. 3: Diagram of compressive load [P(kN), P/(fc’·Ag)] – transverse displacement at the
midheight of test specimens [m/b, m(mm)]

8. Fig. 4: Diagram of normalized specimen height [z/h] – residual transverse displacement
[(mm), /b]

14. #

15. #
!

16. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print),
ISSN 0976 – 6316(Online), Volume 5, Issue 6, June (2014), pp. 101-107 © IAEME
105
Fig. 5: Modes of failure of specimens after the completion of the compression test: (a) -
4Ø10+2Ø8-368-0-1, (b) -4Ø10+2Ø8-368-10-2, (c) -4Ø10+2Ø8-368-20-3, (d) -
4Ø10+2Ø8-368-30-4, (e) -4Ø10+2Ø8-368-50-5
4. ANALYSIS OF RESULTS
The observations from the conduct of the experimental investigation are as follows:
1. It becomes readily apparent that there is substantial variation of the maximum failure load by
varying the degree of elongation. It is generally observed that increasing the degree of
elongation results to a decreased maximum failure load. This trend, however, is valid under
certain conditions.

17. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print),
ISSN 0976 – 6316(Online), Volume 5, Issue 6, June (2014), pp. 101-107 © IAEME
2. The evaluation of maximum residual transverse displacements indicates that there is not a clear
$

18. %

19. % )
!

20. 01-

21. % )
106
tendency for these types of displacements to be increased or decreased by increasing the degree
of elongation (Figs. 6, 7).

22. ''()
*'
!
!

23. '
Fig. 6: Diagram of maximum residual transverse displacement [max(mm), max/max,0‰] –
elongation [h /h(‰), h (mm)].
+,,-
./-
2/,-
0/3-

24. *'
!
!

25. '
''()
Fig. 7: Column diagram of maximum residual transverse displacement [max/max,0‰, max(mm)]
– elongation and type of longitudinal reinforcement [h /h(‰)].

26. International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 – 6308 (Print),
ISSN 0976 – 6316(Online), Volume 5, Issue 6, June (2014), pp. 101-107 © IAEME
The following conclusions have derived from the analysis and evaluation of experimental results:
107
5. CONCLUSIONS
1. Behaviour of test specimens during the second semi cycle of the compressive loading are
drastically affected by the imposed degree of tensile strain during the first semi cycle of tensile
loading when imposed tensile deformation exceeds a certain value (in our case this value is
30‰).
2. As far as transverse displacements (maximum residual transverse displacements) are
concerned, it seems that there is not a clear relation between degree of elongation and
transverse displacements. So, no clear conclusion has been derived on this matter.
REFERENCES
[1] J.W. Wallace, J.P. Moehle (1992), Ductility and detailing requirements of bearing wall
buildings, ASCE Journal of Structural Engineering, Vol. 116, No. 6, pp. 1625-1644.
[2] European Committee for Standardization (2004), EN 1998-1:2004, Eurocode 8: Design of
structures for earthquake resistance - Part 1: General rules, seismic actions and rules for
buildings, Brussels, Belgium.
[3] Standards New Zealand (2006), NZS 3101:2006, Concrete structures standard: Part 1 – The
design of concrete structures, Wellington, New Zealand.
[4] Ministry of Environment, Planning and Public Works (2000), Greek Code for the Design
and Construction of Concrete Works. Athens, Greece. (In Greek).
[5] Y.H. Chai, D.T. Elayer (1999), Lateral stability of reinforced concrete columns under axial
reversed cyclic tension and compression, ACI Structural Journal, Vol. 96, No. 5,
pp. 780-789.
[6] T. Paulay (1986), The design of ductile reinforced concrete structural walls for earthquake
resistance, Earthquake Spectra, Vol. 2, No. 4, pp. 783-913.
[7] T. Paulay, M.J.N. Priestley (1993), Stability of ductile structural walls, ACI Structural
Journal, Vol. 90, No. 4, pp. 385-392.
[8] T. Chrysanidis, I. Tegos, G. Pallogos, S. Christodoulou (2008), Lateral instability of
alternating tensile and compressive flanges of RC shear walls due to intense seismic flexure,
Proceedings of 3rd Panhellenic Conference on Earthquake Engineering, Athens, Greece, ID
1818. (In Greek).
[9] T. Chrysanidis, I. Tegos, V. Gkagkousis (2009), The influence of longitudinal reinforcement
ratio of boundary edges of R/C shear walls in their lateral stability, Proceedings of 16th
Greek Concrete Conference, Pafos, Cyprus, ID 131005. (In Greek).
[10] T. Chrysanidis (2014), Size of seismic tensile strain and its influence on the lateral buckling
of highly reinforced concrete walls, IOSR Journal of Mechanical and Civil Engineering,
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[11] T. Chrysanidis (2014), The influence of tensile strain of the high-reinforced end sections of
seismic walls to their displacements and mode of failure, Proceedings of the International
Conference on Recent Trends in Engineering and Technology – 2014 (IJBRMM’s ICRTET
2014), Cochin, Kerala, India, ID CC1266.
[12] Prerna Nautiyal, Saurabh Singh and Geeta Batham (2013), “A Comparative Study of the
Effect of Infill Walls on Seismic Performance of Reinforced Concrete Buildings”,
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