In this project, a progressive collapse assessment was carried out for a typical ten-story reinforced concrete framed structure, with and without a masonry infill wall, designed according to codes for minimum design loads for buildings and other structures. Three different types of analysis were carried out namely linear static analysis, nonlinear static analysis and nonlinear dynamic analysis using SAP2000. It was found for the studied case that, the infilled masonry walls have a valuable contribution in mitigating progressive collapse of the reinforced concrete framed structures.

1. Effect of Masonry Walls in the
Progressive Collapse of a Ten
Storied RC Building
Under the Guidance of
Dr. Yamini Sreevalli I
Kunal Sahu 12BCL1034
Nataraj Sai Charan 12BCL1053
Harshit Kumar 12BCL1010

2. Abstract
 The collapse that progresses from the failure of a local member to the entire
structure or major portion of the structure is called progressive collapse.
 In this project the behaviour of Masonry wall aided structure towards progressive
load, will be studied for a ten storey reinforced concrete OMRF (Ordinary moment),
designed according to Indian standards.
 The analysis methods followed for this are Linear Static, Non-Linear Static and
Non-Linear Dynamic analysis. These analysis are done as per the GSA guidelines for
Progressive Collapse Analysis.

3. Introduction
 The propagation of damage occurred in a
local member of a structure to a majority or
complete structure is known as progressive
collapse.
 Many events including overload due to
change in utility of structure, structural
modifications, deterioration and degradation
of structural member, accidents or attacks like
impact or explosion can trigger the local
damage which may lead to progressive
collapse.
Fig 1 The Partial Collapse of Ronan Point structure

4. Objectives
The main consideration from the structure perspective to resist progressive collapse is
ductility and redundancy. Generally seismic resistance structure is considered to
behave in a ductile manner during seismic events. Hence the main objective of the
study is:
 To compare the behaviour of the structure during linear static analysis, non linear
static analysis and non linear dynamic analysis.
 To study the effect of infill on the structure towards resistance of progressive
collapse.

5. Progressive collapse analysis
 Guidelines set by different agencies, General Service administration (GSA) and
Department of Defense (DoD), for progressive collapse analysis are threat
independent i.e., the analysis is independent of the cause of local damage.
 GSA has provided certain guidelines for the progressive collapse analysis of a
structure which consists of analyzing a structure for different column removal
scenarios. The analysis can be performed as linear static, non linear static, non
linear dynamic for the column removal scenarios.

6. Column removal Scenarios suggested by GSA are as follows:
 Instantaneous loss of an exterior column of ground storey located at or near the
middle of the short side of the building.
 Instantaneous loss of an exterior column of ground storey at or near the middle of
the long side of the building.
 Instantaneous loss of an exterior column of ground storey located at the corner of
the building.
 Analyses for the instantaneous loss of one column that exceeds from the floor of
the underground parking area or uncontrolled public ground floor area to the next
floor. The column considered should be interior to the perimeter column line.

7. Fig 3 Column removal scenario

8. Design of Building
To achieve the objective a ten storey RC structure was designed according to Indian
Standards IS456 and IS1893. Methodology followed is given below:
 Preliminary analysis for gravity and seismic loads using STAAD pro V8i.
 Structure is designed according to IS 456.
 Load combinations taken from IS1893.
 The frames are then modeled in SAP2000.
 Linear Static, Non linear Static and Non linear Dynamic analyses is done for various
column removal cases.

9. StaadPro model and Design of Sections
RC structure model is analysed for
different load combinations in
STAADPro V8i, the members are
designed using Limit State method
according to IS 456, as number of
elements designed is very large.
The layout of the structure and
design reinforcement detail for one
column and one beam is shown in
next slide.
Fig. 4 Layout of structure in STAADPro V8i

10.  Design of Beam

Fig. 5 Design of Column Fig. 6 Design of Beam

11. Load Cases and Loadings:
Dead Loads:
 Self weight of Column 6.25 kN/m2
 Self weight of beam 3.5 kN/m2
 Self weight of Slab 2.5 kN/m2
 Floor Finish 1 kN/m2
 Water proofing (terrace) 2 kN/m2
 Brick wall 3.5 m high(110 mm thick) 8.99 kN/m2
0.11x19(wall)+2x0.012x20(plaster)
Imposed Loads:
 Typical floor 2 kN/m2
 Terrace 1.5 kN/m2

12. Linear Static Procedure
 The linear static analysis procedure is performed using an amplified (by a factor of
2) combination of service loads, such as dead and live, applied statically, Load = 2
x(DL + 0.25LL).
 This analysis procedure is the simplest and easiest to perform. However, it is limited
to relatively simple structures where both nonlinear effects and dynamic response
effects can be easily and intuitively predicted.
 Response is evaluated by demand to capacity ratios (DCR), which for our study
shall not exceed a value of 2.

13. This analysis procedure involves the following steps:
1. Build a finite-element computer model;
2. Apply the amplified static load combination as defined by Load = 2 x(DL
+ 0.25LL;
3. Perform static linear analysis, a standard analysis procedure in SAP2000; and
4. Evaluate the results based on demand to capacity ratios (DCR).
Now that the member forces are known, the DCR can be found by taking the ratio of the
maximum moment in the beam to its ultimate capacity as illustrated in equation below:
𝐷𝐶𝑅 =
𝑀𝑚𝑎𝑥
𝑀𝑝

14. Instantaneous loss of an exterior column of ground
storey located at or near the middle of the short side
of the building

15.  Mp value is calculated using IS 456-2000 (Annex G). It comes as 253 kNm.
 Mmax comes as 802.78 kNm.
So the ratio comes as 3.17, which is more
than 2.
We can conclude that this
structure does not satisfy the GSA
progressive collapse criteria. Additionally,
by examining calculated DCR values, it
can be seen that this structure exceeds by
58.5%.

16. Instantaneous loss of an exterior column of ground
storey at or near the middle of the long side of the
building

17. Maximum negative bending
moment comes as 808.3, so
the DCR value comes as 3.19.
Hence it is not safe.

18. Instantaneous loss of an exterior column of ground
storey located at the corner of the building

19. Maximum negative
bending moment
comes as 921.9, so the
DCR value comes as
3.64. Hence it is not
safe.

20. Column interior to the perimeter column
line

21. Maximum negative
bending moment
comes as 573, so the
DCR value comes as
2.26. Hence it is not
safe.

22. On adding Infill Masonry Walls
 Masonry is the building of structures from individual units laid in and bound
together by mortar; the term masonry can also refer to the units themselves.
 The common materials of masonry construction are brick, building stone such as
marble, granite, travertine, and limestone, cast stone, concrete block, glass block,
and cob. Masonry is generally a highly durable form of construction.
 The infill walls are usually considered as non-structural elements. In conventional
analysis and design, only considering the non-structural elements as loads, the
stiffness and strengthen are usually ignored throughout the processes.
 However, the infill wall may significantly change the collapse resistant potentials
and damage patterns. In addition, most of the practical frames contain infill walls
rather than bare frames.

23. These infilled masonry walls are provided
on the exterior of the structure assuming
that the building will be used for
exhibitions, as an art gallery or show room,
etc., so that there are no walls inside the
building. Only external walls 230 mm thick
with 12 mm plaster on both sides are
considered. The building with infilled
masonry walls model is as shown in Fig. 7.
Fig. 7 Structure with infill masonry walls

24. Instantaneous loss of an exterior column of
ground storey located at or near the middle of
the short side of the building
Mmax comes as 172.23 kNm. So the ratio
comes as 0.685, which is less than 2. We
can conclude that this structure satisfies
the GSA progressive collapse criteria.
Additionally, by examining calculated
DCR values, it can be seen that this
structure has DCR value nearly 4.63 times
less than previous structure.

25. Instantaneous loss of an exterior column of
ground storey at or near the middle of the long
side of the building
Maximum negative bending
moment comes as 172.33, so
the DCR value comes as
0.685. Hence it is safe.

26. Instantaneous loss of an exterior column of
ground storey located at the corner of the
building
Maximum negative
bending moment
comes as 167.94, so
the DCR value comes
as 0.66. Hence it is
safe.

27. Column interior to the perimeter column
line
Maximum negative
bending moment
comes as 282.66, so the
DCR value comes as
1.12. Hence it is safe.

28. Column Location DCR initially DCR with masonry
Exterior Short Side Column 3.17 0.685
Exterior Long Side Column 3.19 0.685
Exterior Corner Column 3.64 0.66
Interior Column 2.26 1.12
DCR values of selected columns

29. 3.17
3.19
3.64
2.26
0 0.5 1 1.5 2 2.5 3 3.5 4
Exterior Short Side
Exterior Long Side
Exterior Corner Column
Interior Column
DCR without infills
0.685
0.685
0.66
1.12
0 0.2 0.4 0.6 0.8 1 1.2
Exterior Short Side
Exterior Long Side
Exterior Corner Column
Interior Column
DCR with infills

30. 4.63
4.66
5.5
2.02
0 1 2 3 4 5 6
Exterior Short Side
Exterior Long Side
Exterior Corner Column
Interior Column
Change in DCR values after introducing infills
3.17
3.19
3.64
2.26
0.685
0.685
0.66
1.12
Exterior Short Side Exterior Long Side Exterior Corner Column Interior Column
Comparison for each column cases
DCR without infills DCR with infills

31. Nonlinear Static Procedure
 For progressive collapse analysis, a nonlinear static analysis method implies a
stepwise increase of amplified (by a factor of 2) vertical loads, as prescribed by
given Eq. Load = 2 x(DL + 0.25LL), until maximum amplified loads are attained or
until the structure collapses.
 This means that in most cases vertical pushover analysis would be load controlled;
in analysing for progressive collapse potential, structural performance under
amplified service loads is evaluated.

32. Nonlinear static analysis procedure is limited to structures where dynamic behavior patterns
can be easily and intuitively identified and involves the following steps:
1. Build a finite-element computer model;
2. Define and assign nonlinear plastic hinge properties, which involve estimating element
capacities and force-displacement relations;
3. Apply static load combinations, defined by given Eq. Load = 2 x(DL + 0.25LL),
4. Perform nonlinear static analysis, a standard procedure available in ETABS; and
5. Verify and evaluate the results based on the maximum load resisted as well as maximum
ductility and rotation values.

33. Instantaneous loss of an exterior column of
ground storey located at the corner of the
building without infill.
Pushover
curve

34. Instantaneous loss of an exterior column of
ground storey located at the corner of the
building with infill.

35. Instantaneous loss of an exterior column of
ground storey at or near the middle of the long
side of the building without infill.
Pushover
curve

36. Instantaneous loss of an exterior column of
ground storey at or near the middle of the long
side of the building with infill.

37. Instantaneous loss of an exterior column of
ground storey located at or near the middle of
the short side of the building without infill.
Pushover
curve

38. Instantaneous loss of an exterior column of
ground storey located at or near the middle of
the short side of the building with infill.

39. Column interior to the perimeter column
line without infill.
Pushover
Curve

40. Column interior to the perimeter column
line with infill.

41. The performance of structure under different
column removal case in pushdown analysis with
and without infill.
0
5000
10000
15000
20000
25000
30000
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
Base
force
(kN)
Displacement (cm)
Corner Column removed
with infill
without infill

42. 0
5000
10000
15000
20000
25000
30000
35000
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23
Base
force
(kN)
Displacement (cm)
Interior column removed
with infills
without infills

43. 0
5000
10000
15000
20000
25000
30000
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22
Base
force
(kN)
Displacement (cm)
Long side column removed

44. 0
5000
10000
15000
20000
25000
30000
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23
Base
force
(kN)
Displacement (cm)
Short side column removed
with infill
without infill

45. Combined results of the four column
removal cases without infill.
0
5000
10000
15000
20000
25000
30000
0 0.9 1.8 2.7 3.6 4.5 5.4 6.3 7.2 8.1 9 9.9 10.8 11.7 12.6 13.5 14.4 15.3 16.2 17.1 18 18.9 19.8 20.7
Base
force
(kN)
Displacement (cm)
Four column cases without infill
corner column
interior column
long side column
short side column

46. Combined results of the four column
removal cases with infill.
0
5000
10000
15000
20000
25000
30000
35000
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23
Base
force
(kN)
Displacement (cm)
Four column removal cases with infill
corner column
interior column
long side column
short side column

47. Non Linear Dynamic Procedure
The nonlinear dynamic procedure for progressive collapse is the most thorough
method of analysis in which a primary load-bearing structural element is removed
dynamically and the structural material is allowed to undergo nonlinear behavior. This
allows larger deformations and energy dissipation through material yielding, cracking,
and fracture. Dynamic analysis procedures, especially nonlinear dynamic, are usually
avoided due to the complexity of the analysis.
Nonlinear dynamic analysis is performed similarly to linear dynamic analysis with the
exception that now the structural elements are allowed to enter their inelastic range.
We have used the initial conditions methodology to perform this analysis.

48. The following steps are involved:
1. Build a finite-element computer model.
2. Find the deflected shape of the loaded, undamaged structure.
This involves static analysis of the undamaged structure (i.e., with missing column
present).
3. Apply dynamic load combinations as defined by Eq. Load = DL + 0.25LL
4. Perform nonlinear time history analysis with initial conditions, which is available as a
standard analysis type in SAP2000.
5. Verify and evaluate the results based on the maximum ductility and rotation values.
Verification of nonlinear analysis is a somewhat complicated process and may involve
several computer analysis re-runs with varying nonlinear integration parameters, until
a stable and physically possible solution is found.

49. -0.5
-0.4
-0.3
-0.2
-0.1
0
0.1
0.2
0.3
0.4
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
Displacement
(mm)
Time (sec)
Behaviour of building without Struts
Shorter Side Longer Side Interior Column Corner Column

50. The effects of masonry-infill walls
Masonry is the building of structures from individual units laid in and bound
together by mortar; the term masonry can also refer to the units themselves. The
common materials of masonry construction are brick, building stone such as marble,
granite, travertine, and limestone, cast stone, concrete block, glass block, and cob.
Masonry is generally a highly durable form of construction.
The infill walls are usually considered as non-structural elements. In conventional
analysis and design, only considering the non-structural elements as loads, the
stiffness and strengthen are usually ignored throughout the processes. However, the
infill wall may significantly change the collapse resistant potentials and damage
patterns. In addition, most of the practical frames contain infill walls rather than bare
frames. Unlike many researches on effects of infill walls in the seismic collapse, up to
now, there are only a few of researches had been done on effects of infill wall in the
progressive collapse.

51. -0.6
-0.4
-0.2
0
0.2
0.4
0.6
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
Displacement
(mm)
Time (sec)
Behaviour of building with Struts
Shorter Side Longer Side Interior Column Corner Column

52. -0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
Displacement
(mm)
Time (sec)
Behaviour of building without Adjacent Struts
Shorter Side Longer Side Corner Column

53. -0.25
-0.2
-0.15
-0.1
-0.05
0
0.05
0.1
0.15
0.2
0.25
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
Displacement
(mm)
Time (sec)
Behaviour of Shorter side Column
With Strut Without adjacent Strut Without Strut

54. -0.3
-0.25
-0.2
-0.15
-0.1
-0.05
0
0.05
0.1
0.15
0.2
0.25
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
Displacement
(mm)
Time (sec)
Behaviour of Longer Side Column
With Strut Without adjacent strut Without Struts

55. -0.006
-0.004
-0.002
0
0.002
0.004
0.006
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
Displacememt
(mm)
Time (sec)
Behaviour of Interior Column
Without Strut With Strut

56. -0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
Displacement
(mm)
Time (sec)
Behaviour of Corner Column
Without Strut Without adjacent Struts With Struts

57. Conclusion
 The effect of the infill masonry wall on progressive collapse on a RC building under four
different cases of column loss is evaluated under this study. Compression-strut
elements are used to simulate the brick infills.
 Linear static analysis gives the DCR value for different column removal cases. DCR
values has been found with bare frames and with infill masonry walls. It has been
observed that there has been a huge reduction in DCR values of structure with infill
masonry walls as compared to bare frame structure.
 Nonlinear dynamic analysis shows the displacement of that joint with respect to time
just after the removal of the column. As we can see in the presented graphs that the
introduction of infills has significantly reduced the displacement of that joint and
provides more stable position in lesser time duration. Combined graphs show that the
interior column is the most stable column as compared to other three columns.

58.  Nonlinear static analysis has shown the behavior of the building in presence of the
infill as resistant towards progressive collapse. The analysis results clearly indicates
that on the bare frame without the brick infill has given lesser value of the base
force, more load is required in the case where infill is present which helps to resist
the building towards progressive collapse. Out of all the column cases it is clear
that the loss of corner column may lead to greater damage to the building as it
becomes most vulnerable among the four cases.
 So by a careful observation of all the three analysis we can say that the infilled
frame action showed a significant role in collapse resistance. Neglecting
nonstructural masonry walls in progressive collapse analysis may lead to incorrect
structural behavior and uneconomic design.