1. ‘Seismic Analysis and
Response of Bare Vs. Masonry
In-filled Frame Structures’
Researcher: Mr Constantinos Chris Andreou
BEng, MSc Civil- Subsea Graduate Engineer

2. RESEARCH PROPOSAL
 Several countries lie in areas susceptible to earthquakes and their structures
need to be designed to withstand seismic loads.
 Infill panels are not considered in the design process but treated as
architectural (non-structural) components.
 This study assessed the seismic performance of RC buildings by utilizing
dynamic analysis to obtain predictions of the infill panels used in their design.
 The present study may assist in reducing risks of collapsed structures in case
of earthquake disasters
‘ B a r e f ra m e a n d M a s o n r y I n - f i l l e d s t r u c t u r e s ’

3. Research AIMS and OBJECTIVES
 To analyse and demonstrate the importance of masonry
infill walls against seismic loads.
 To compare the available seismic design methods
proposed by Structural Eurocodes.
Research on structural seismic performance.
Evaluation of structural seismic performance of buildings using
linear structural analysis methods proposed by Structural Eurocodes
Estimation of Masonry Infill Stiffness.
Comparison of Bare and Infilled framed structure using analytical
and computer techniques.

4. PROPOSED MODELS FOR ANALYSIS
 Bare Frame
 Partially-Infilled
 Fully-Infilled
 Masonry infill configurations modelling
o Medium Class Ductile
Reinforced Concrete
o Regular building in Plan
and Elevation
o 6 Stories with known
heights
o 4 x 4 Frames

5. METHODS OF SEISMIC RESPONSE ANALYSIS
The following two types of linear-elastic analysis were contacted:
I. Equivalent static method {Lateral Force Method}
o The system response is derived by applying equivalent lateral seismic
load to the model.
o These lateral forces are applied as static loads at the position of
concentrated mass of the structure at each floor.
II. Response Spectrum Method
o Is one of the most popular methods in modern earthquake engineering.
o Offers logical results and it is more economical.
o Requires the determination of a response spectrum from measured seismic
activity.
‘Spectral
acceleration against
Periods’

6. MASONRY INFILL STIFFNESS VERIFICATION
Infill Wall panels are not included in structural design
 Such assumption may lead to inaccurate approximation of strength,
ductility and stiffness of concrete framed buildings.
‘Research has proved that the i nfi ll system behave as a braced
frame with the wall forming ‘co m pressio n stru ts’
Equivalent diagonal compression ‘STRUT’

7. MASONRY INFILL STIFFNESS VERIFICATION {cont’d}
 Infill walls replaced by Equivalent Diagonal Strut.
 By determinate the diagonal strut AREA using the brick and masonry
properties, the stiffness of the wall were estimated.
Z= 0.175 [ λ . ℎ)− 0.4
] dm
𝐀𝐞 = 𝐙 . 𝐭
λ =
4 𝐸𝑚 . 𝑡𝑚 . 𝑠𝑖𝑛 (2θ)
4 . 𝐸𝑓. 𝐼 𝑐 ℎ𝑚
Area of STRUT = Width (Z) x Thickness
 SLIDING and COMPRESSION SHEAR failure
 DISPLACEMENT AT YIELDING
Initial wall Stiffness = 2 x [Min. Initial shear / Displacement]
(Madan et al., 1997)
(Das and Murphy,2004)
(Mainstone,1971)

8. MASONRY INFILL STIFFNESS VERIFICATION
 There are many investigations and proposed verifications of masonry infill stiffness
that impediment to a reliable modeling
 Limited amount of research has been undertaken on Infilled frames with openings
The initial stiffness of the masonry infill panel was defined and used in linear-elastic
analysis methods
RESULTS TAKEN FROM BARE FRAME AND MASONRY INFILL CASE WERE COMPARED

9. • Masonry Infilled Frames and their Seismic Behaviour at Structures
 Increase Stiffness of structures
 The fundamental period is decreased
 The Base Shear is increased
 The structural system is more reliable at seismic action as part of the load is
consumed by the infills
 Energy capacity of the structure is significantly increased
RESEARCH DELIVERABLES
Comparison of
Displacements of Bare
and Infill cases

10. Distribution and Comparison of Results
 Comparison of Seismic Analysis Methods
BASE SHEAR (KN)
MODEL T = Ct x H3/4 T = 2.(d)^0.5
Bare Frame 373.3 472.60
Partially Infilled F. 373.3 601.50
Fully Infilled 373.3 696.50
o Equivalent Static method
1. Carried out in less time by doing few and simple calculations
2. Temporal variations were neglected.
3. Considers only maximum possible responses.
4. Gives an initial idea for magnitude that will be acted due to a possible earthquake.
1) Consider the Height
2) Lateral elastic
displacement (F / k)
 Can be used for preliminary design situations and for buildings up to
10 storey as mentioned by EC8.

11. 0
100
200
300
400
500
600
700
800
900
Bare Frame Partially
Infilled
Frame
Fully Infilled
Frame
Equivalent static method(T =
2.(d)^0.5)
472.613 601.507 696.482
Response spectrum method 560.82 732.42 819.96
BASESHEAR(KN
Equivalent static
method(T =
2.(d)^0.5)
Response spectrum
method
o Response Spectrum method
 Comparison of Seismic Methods {cont’d}
1. Approximates better the fundamental period of vibration (T)
2. Yields more accurate and responsible results
3. Involves simplifying assumptions
4. Errs on the side of safety
Difference varies
from 15 - 18 %
 Response spectrum analysis provides significant information about real-world
applications when considering a linear, elastic system that is exposed to a forcing
function (earthquakes).
WASTE OF MATERIALS
equal to
15 - 18 %

12. Infill Panels Behaviour
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
0 1 2 3 4 5 6
MAXIMUMDISPLACEMENT(mm)
FLOOR LEVELS
Bare Frame
Partially Infilled Frame
Fully Infilled Frame
 Design Codes should NOT neglect the effects of masonry infills
• 2 Times smaller
(Increase in stiffness)
• P.I.F displacement at first and
second floor is bigger compared
to B.F
(Presages Soft storey effect)
• F.I.F has very small storey
displacements
(presence of infill walls)
o Displacement

13. o Measured Envelope of Base Shear Vs. Displacement
0
20
40
60
80
100
120
140
160
180
200
0 1 2 3 4 5
BASESHEAR(KN)
DISPLACEMENT (mm)
Fully Infilled Frame
Partially Infilled
Frame
Bare Frame
Maximum
Displacements
at TOP storeys
BASE SHEAR (KN)
Story Bare Frame Partially Infilled
Frame
Fully Infilled
Frame
0 0 0 0
1 47.441 93.539 77.437
2 60.745 105.405 103.375
3 81.244 122.396 134.377
4 97.656 135.562 158.472
5 123.54 140.127 171.972
6 127.058 133.264 166.855
ΣFBi 537.7 732.4 812.5
• F.I.F presented to be
34% stronger compared
to B.F
• P.I.F presents 26%
difference from B.F
• Higher amount of Shear
force is needed to
displace equal each
models top storey.
*An estimation of the overall
ductility demand can be obtained.

14. COMPUTER COMPUTATION TECHNIQUES
 Using SAP 2000 the RESPONSE SPECTRUM ANALYSIS was carried
out for Bare model case.
 Results were compared to analytical results
SAP 2000 (Linear Dynamic Procedure)
Model simulation

15. o SAP 2000 {cont’d}
Story SAP 2000 ANALYTICAL
1 10.3 0.178 0.27
2 18.48 0.319 0.38
3 27.9 0.481 0.527
4 37.19 0.642 0.647
5 50.19 0.866 0.881
6 57.96 1 1
T (s) 0.476 0.488
Story DISPLACEMENT
0 ANALYTICAL SAP 2000 Percentage
difference (%)
1 1.118 1.5 25
2 1.576 2.63 40
3 2.185 3.78 42
4 2.682 4.8 44
5 3.654 6.07 40
6 4.147 6.91 40
Base Shear
537.7 363.9 47
The large percentage difference caused
from:
• The different method of structural element’s
stiffness calculation .
• The reduction moment of inertia at beams
and columns equal to33% and 50%
respectively.
There is only a 4% variation of results at first vibration mode
Vibration mode shapes

16.  The behaviour of infill frames depends on the properties of infill and
frame.
 The proposal analytical procedure can be implemented in the design and
used by available computational tools.
 Infilled frames can be improved by applying recommended guidelines
during their construction to achieve a better behaviour.
 The non-structural infills walls can change the global seismic behaviour
of framed buildings
 Masonry infill walls have major influence to the structure’s performance
ALL project Deliverables were PROVED…
CONCLUSION

17. REFERENCES
I. Structural Eurocodes, 2010. ‘Extracts from the
Structural Eurocodes for students of structural design’.
Third edition.
II. Thesis on ‘Seismic Analysis and Response of Bare and
Masonry In-filled Reinforced Concrete Frame
Structures’.
III. ‘Literature Survey Report’ of thesis.