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8/14/2019 MAL Report.pdf
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July 20, 2013
To
Mr. Managing Director
Matsuoka Apparels Ltd.
Plot 60, Road 07; Block A, Ward 07, Kumkumary, Ashulia, Savar, Dhaka.
Subject: Structural Condition Assessment of 6 Storied Industri al Building.
Dear Sir,
We are pleased to provide this report on our structural condition assessment of the 6-story industrial
building located at Ashulia, Dhaka. Our work is completed in accordance with your request.
The purpose of our work is to provide a structural evaluation of the industrial building to compare its
current condition to standard performance criteria.
From this study it can be concluded that the 6 storied industrial building requires retrofitting work.
If you have any questions regarding this report, please do not hesitate to contact us.
Thank you.
Sincerely yours
Engineer Md. Najmul HudaManaging PartnerAL-Famous Engineers
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Table of Contents
Table of Contents .............................................................................................................................. 2
List of Figures .................................................................................................................................... 3
1. SUMMARY ................................................................................................................................. 5
2. INTRODUCTION ........................................................................................................................ 5
3. BUILDING DESCRIPTION.......................................................................................................... 6
4. MODELING AND ANALYSIS TECHNIQUES .............................................................................. 6
5. LOAD CONSIDERATION ........................................................................................................... 7
5.1 Dead load .......................................................................................................................... 7
5.2 Live load ............................................................................................................................ 7
5.3 Live load Reduction .......................................................................................................... 10
6. MATERIALS ............................................................................................................................. 11
7. RESULTS................................................................................................................................. 11
7.1 Gravity Loads Assessments ............................................................................................. 11
7.1.1 Evaluation of Foundations ................................................................................................ 11
7.1.2 Evaluation of Columns...................................................................................................... 12
7.1.3 Evaluation of Beams ........................................................................................................ 14
7.1.4 Evaluation of Slabs........................................................................................................... 14
7.2 Seismic Performance Assessments .................................................................................. 15
7.2.1 Capacity Curve ............................................................................................................. 15
7.2.2 Collapse Mechanism .................................................................................................... 16
7.2.3 Seismic Performance ................................................................................................... 18
8. CONCLUSION ......................................................................................................................... 18
9. RECOMMENDATIONS............................................................................................................. 19
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List of Figures
Figure-1: Typical floor plan of Matsuoka Apparels Ltd Factory Building .............................................. 6
Figure-2: Live Load for Various Occupancies ..................................................................................... 8
Figure-3: Provision for Live Load Reduction ....................................................................................... 9
Figure-4: Compressive Strength Test Result .................................................................................... 10
Figure-5: Support Reaction (Showing Column Axial Force Unit: Kip) ................................................ 12
Figure-6: Ground Floor Column Layout Plan (Showing Column Axial Force and Moment, Unit: Kip, ft)
........................................................................................................................................................ 13
Figure-7: Ground Floor Column Layout Plan (Showing Demand Capacity Ratio) ................... ........ ... 14
Figure-8: Capacity Curve ................................................................................................................. 15
Figure-9: Collapse Mechanism at Grid Line (1) ................................................................................ 16
Figure-10: Collapse Mechanism at Grid Line (3) .............................................................................. 17
Figure-11: Collapse Mechanism (Grid Line 5) .................................................................................. 17
Figure-12: Performance Point Evaluation ......................................................................................... 18
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DESIGN EVALUTION OF 6- STORY MATSUOKS APPARELS INDUSTRIAL BUILDING AT
ASHULIA.
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1. SUMMARY
Elastic Analysis and Nonlinear Pushover analysis has been performed on a six story, reinforced
concrete building located in Ashulia, Dhaka with a gross area of 62,500 square feet. The building was
designed in the year 2008. The gravity load carrying capacity of this building is evaluated as per
current Bangladesh National Building Code (BNBC-1993). The finite element model of this building is
developed by using the software ETABS V9.7.4 and SAP 2000 V15.0. To evaluate the seismic
performance of this building non-linear pushover analysis has been performed by using the same
software. Procedure followed for carrying out the analyses and results are presented in this report.
This building has been designed for 5-story building but it has been constructed at 6 story building
with steel framing roof system. This building is safe for 5-story building under the current load but if
the owner would like to use the 5th
floor the column of this building need to strengthen. At the ground
floor level the demand capacity ratio of 8 columns out of 27 exceeds the code limit. From the
nonlinear elastic analysis it can be concluded that the building does not satisfied the seismic
requirement of the current BNBC.
2. INTRODUCTION
Design of civil engineering structures is typically based on prescriptive methods of building codes.
Normally, loads on these structures are low and result elastic structural behavior. However, under a
strong seismic event, a structure may actually be subjected to forces beyond its elastic limit. Although
building codes can provide reliable indication of actual performance of individual structural elements,
it is out of their scope to describe the expected performance of a designed structure as a whole,
under large forces. Several industries such as automotive and aviation, routinely build full-scaleprototypes and perform extensive testing, before manufacturing thousands of identical structures, that
have been analyzed and designed with consideration of test results. Unfortunately, this option is not
available to building industry as due to the uniqueness of typical individual buildings, economy of
large-scale production is unachievable.
With the availability of fast computers, so-called performance based seismic engineering (PBSE),
where inelastic structural analysis is combined with seismic hazard assessment to calculate expected
seismic performance of a structure, has become increasingly feasible. With the help of this tool,
structural engineers too, although on a computer and not in a lab, can observe expected performance
of any structure under large forces and modify design accordingly. Nonlinear response historyanalysis is a possible method to calculate structural response under a strong seismic event. However,
due to the large amount of data generated in such analysis, it is not considered practical and PBSE
usually involves nonlinear static analysis, also known as pushover analysis.
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E
D
C
B
A
1 2 3 4 5
SEWI
NG
MA
CHINE
SEWI
NG
MA
CHINE
SEWI
NG
MA
CHINE
B
31'-6" 2 7'-0" 2 7'-0" 27'-0"
22'-6"
22'-6"
22'-6"
22'-6"
C1
A
22'-6"
22'-6"
22'-6"
22'-6"
31'-6" 2 7'-0" 2 7'-0" 27'-0"
1 1' -1 " 3 '- 3"17'-2"
11'-6"
STAIR1
STAIR2
10'-0"
12'-6"
SEWI
NG
MA
CHINE
3. BUILDING DESCRIPTION
Building analyzed is a six story, 64 feet from plinth level reinforced concrete building located in
Ashulia with a gross area of 62,500 square feet. This building is first constructed in the year 2008.
This building has 27 columns and it is a frame structure building. The height of bottom story of this
building is 14 feet. The height of the other floors is 10 feet. This building contains two stair main beam
from column to column with size 12x24 and secondary beam with size 10x24. Figure 1 shows the
building outline with column grids.
Figure-1: Typical floor plan of Matsuoka Apparels Ltd Factory Building
After the catastrophic collapse of RANA Plaza at savar the people of the garments sector become
aware about the capacity of their building. For this reasons the owner of this building invited us to
evaluate this building.
4. MODELING AND ANALYSIS TECHNIQUES
To evaluate the present status of the building under gravity load and under seismic load two different
models have been developed. One model has been developed by using software ETABS V9.7.4 and
other model has been developed by using software SAP 2000 V15.0. For gravity load analysis ACI
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318-99 code has been used to check the performance. To evaluate the performance under seismic
load plastic hinge are defined in the beams and columns. After performing pushover capacity curve is
compared with the standard performance criteria.
Nonlinear hinge assignment
In order to model nonlinear behavior in any structural element, a corresponding nonlinear hinge must
be assigned in the building model. Nonlinear hinges were assigned to the following structural
elements expected to undergo inelastic deformation:
Beams
Beam section has been used in this study having cross section 12x24 and 10x 124 and this
section are used as per the existing structural drawing. Beams were modeled pin-ended and M3
hinge is assigned at each end of the beam.
Columns
Columns were modeled as frame element and P-M-M hinge are assigned at two end of the column for
pushover analysis.
5. LOAD CONSIDERATION
A building structure is usually design so that it can carry both gravity load and lateral loads. Gravity
loads include dead load, live loads, floor finish, super impose dead load etc.
5.1 Dead load
Self-weight of slabs, beams and columns are considered as dead load. In addition to this load 1.45
kN/m2 has been considered for floor finish. 5.83 kN/m line loads has been considered on the
perimeter beam as a dead load. For roof these line load and uniformly distributed load has not been
considered.
5.2 Live load
Live load has been considered as a uniformly distributed load on the floor element and the magnitude
of this load is 6.0 kN/m2for cutting and finishing floor, and 4.0kN/m
2for sewing floor and 3 kN/m
2for
office floor. These loads have been considered as per Table 6.2.3 of Bangladesh National Building
Code (BNBC-1993). The table 6.2.3 of BNBC-1993 is given in Figure 2.
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Figure-2: Live Load for Various Occupancies
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Figure-3: Provision for Live Load Reduction
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Figure-4: Compressive Strength Test Result
5.3 Live load Reduction
As per BNBC-1993 there are 3 load groups to reduce live load for designing a structure. The provision
of live load reduction as per BNBC-1993 is presented in Figure 3. As per this figure this building is
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under the group-2. The interior column has contributing area 55m2. From figure it can be concluded
that the Live load reduction factor for this building is, R=0.97.
6. MATERIALS
In the process of design and evaluation the properties of material play an important role. Compressive
strength of concrete has been considered as 3.5 ksi or 25 MPa. To evaluate the compressive strength
of existing concrete we did the core cutting test. The test has performed by BRTC BUET and test
result is is shown in the Figure-4. As per this result the average value of 4 tests is 3.5Ksi. Steel has
been considered as 60 grade deformed bar..
7. RESULTS
In this study two different types of analyses have been performed to evaluate the building. Elastic
analysis and nonlinear static pushover analysis has been performed to evaluate the building under
gravity load and to evaluate the performance under seismic load respectively.
7.1 Gravity Loads Assessments
We have evaluated this building under gravity load and the results of this evaluation are presented
here one by one like the foundation, column, beam and slab.
7.1.1 Evaluation of Foundations
Foundation has been evaluated under service load. Figure-5 has shown the support reaction of the
column. From the soil test report supplied by the client it is observed that the allowable soil bearing
capacity at foundation level is 4.25ksf and from the structural drawing supplied by the client it is
observed that the considered allowable soil bearing capacity is 4Ksf. From the SPT value and Using
the principles of plastic equilibrium, the ultimate bearing capacity, qf , of a shallow strip footing, with a
depth of D, from the surface and with a width of Band length L, is given by Terzaghi (1967) as,
qf= c Ncsc + D Nq + 0.5 B N s (1)
From this equation it can be concluded that with factor of safety 2.5 we can use allowable soil bearing
capacity at foundation level 5.5Ksf. Few of the footings found inadequate however we believed that
the clay soil is now over consolidated and its capacity increase. So the foundation is safe under the
current loading condition.
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P= 5 37 P= 830 P= 7 63 P= 7 43
P= 5 37 P= 830 P= 7 63
22'-6"
22'-6"
22'-6"
22'-6"
3 1'- 6" 2 7'-0" 27'-0" 27'-0"
11'-1"
12'-1"
3'-3"17'-2"
11'-6" 15'-6"
WA
TER
TAN
K
9'-0"
P= 319
C4 C4
C1A C2C C1A C3
C2B C2B C2A C2B C3
C2B C2A C2C C2A
C1 C2A C2 C1C2A
C2B
C2B C2A C2C C2C2B
C2C
E
D
C
B
A
1 2 3 4 5
P= 533 P= 4 83 P= 4 88 P= 283
P= 5 37 P= 830 P= 7 63 P= 7 43 P= 467
P= 462
P = 6 0 8 P = 2 8 5
P= 3 16 P= 747 P= 7 57 P= 408 P= 150
P= 1 90 P= 160
Figure-5: Support Reaction (Showing Column Axial Force Unit: Kip)
7.1.2 Evaluation of Columns
The exiting building has been evaluated under factored loads. The factored axial load and moments
for columns at ground level are shown in Figure-6. From the factored load analysis and design it is
observed that at the Ground floor level out of 27 columns 8 columns are overstressed. The demand
capacity ratio of the columns at the ground floor level is shown in Figure-7. In this case the strength
reduction factor has been considered as 0.9, 0.7, 0.75, 0.85 for tension-bending, compression tied,
compression spiral, and shear forces respectively. The overload factor has been considered as 1.4
and 1.7 for dead and live load respectively.
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22'-6"
22'-6"
22'-6"
22'-6"
3 1 '- 6" 27 '- 0" 2 7 '- 0" 27 '- 0"
11'-1"
12'-1"
3'-3"17'-2"
11'-6" 1 5'-6"
WA
TER
TANK
9'-0"
P= 440
M 2 = 2 3
M 3 = 8 2
C4 C4
C1A C2C C1A C3
C2B C2B C2A C2 B C3
C2B C2A C2C C2A
C1 C2A C2 C1C2A
C2B
C2B C2A C2C C2C2B
C2C
E
D
C
B
A
1 2 3 4 5
P= 731
M 2 = 2 7
M 3 = 7 3
P= 667
M 2 = 2 6
M 3 = 6 3
P= 679
M 2 = 2 5
M 3 = 6 7
P= 375
M 2 = 3 6
M 3 = 5 8
P= 743
M 2 = 7 4
M3= 135
P= 1198
M 2 = 2
M3= 120
P= 1102
M 2 = 3
M 3 = 1 2 8
P= 1120
M 2 = 2
M 3 = 1 1 2
P= 668
M 2 = 6 7
M 3 = 9 9
P= 1087
M 2 = 1
M 3 = 1 0 8
P= 573
M 2 = 5 7
M 3 = 9 3
P= 744
M 2 = 7 4
M3= 135
P= 1201
M 2 = 3
M3= 120
P= 1107
M 2 = 2
M 3 = 1 5 1
P= 896
M 2 = 8 7
M 3 = 3 0
P= 441
M 2 = 4 9
M 3 = 5
P= 419
M 2 = 4 0
M 3 = 8 5
P= 792
M 2 = 2 3
M 3 = 7 9
P= 671
M 2 = 2 3
M 3 = 6 7
P= 470
M 2 = 4 5
M 3 = 4 5
P= 198
M 2 = 1 5
M 3 = 5 6
P= 156
M 2 = 2 2
M 3 = 4 8
P= 132
M 2 = 1 0
M 3 = 5 2
P= 743
M 2 = 7 4
M3= 135
P= 1198
M 2 = 2
M3= 120
P= 1102
M 2 = 3
M 3 = 1 2 8
Figure-6: Ground Floor Column Layout Plan (Showing Column Axial Force and Moment, Unit: Kip, ft)
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22'-6"
22'-6"
22'-6"
22'-6"
31 '- 6" 27'- 0" 2 7 '- 0" 27 '- 0"
11'-1"
12'-1"
3'-3"17'-2"
11'-6" 15'-6"
WA
TER
TAN
K
9'-0"
D/C= 0.65
D/C= 0.76 D/C= 0.75 D/C= 0.75D/C= 0.80 D/C= 0.60
D/C= 1.26 D/C= 1.16 D/C= 1.05D/C= 0.82 D/C= 0.76
D/ C
= 0.92
D/ C
= 0.82
D/C= 0.79 D/C= 0.67
D/ C
= 0.61D/C= 0.62
D/ C
= 0.48
D/C= 0.35D/C= 0.35
C4 C4
C1A C2C C1A C3
C2B C2B C2A C2B C3
C2B C2A C2C C2A
C1 C2A C2 C1C2A
C2B
C2B C2A C2C C2C2B
C2C
E
D
C
B
A
1 2 3 4 5
D/C= 1.26 D/C= 1.16 D/C= 1.05
D/C= 0.82
D/C= 1.26D/C=
1.16D/C= 0.82
Figure-7: Ground Floor Column Layout Plan (Showing Demand Capacity Ratio)
From the factored load analysis and design it is also observed these 8 columns are overstressed up
to 2nd
floor level. Column C2B at gridline B1, C1, D1 are overstressed at 1stand 2
ndFloor level.
7.1.3 Evaluation of Beams
From this analysis it is also observed that the reinforcement required in the beams is less than the
provided. The reinforcement detailing in the beam is not appropriate. Like in Beam B5 at top 5 no.
25mm bar placed within 12 which does not satisfied the code detailing requirement. Over
reinforcement in the beam make the structure strong beam-weak column situation which is not
desirable situation in structural engineering.
7.1.4 Evaluation of Slabs
The designer designed the slabs as a two way slabs. The thickness of the slab is adequate. The
reinforcement of this slabs are adequate except the cutting floor where 5kN/m2load is considered as
per BNBC 1993.
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0
100
200
300
400
500
600
700
800
900
1000
0 2 4 6 8
Base
Shear(Kip)
Roof Displ acement (Inch)
Capacity Curve
Design Base Shear
7.2 Seismic Performance Assessments
After publication of 1st Edition of Bangladesh National Building Code in the Year 1993 the seismic
design becomes popular in Bangladesh. In the current code the whole country is divided in the three
seismic zones. The considered building is located in the seismic zone-2. The seismic zone coefficient
for this zone is 0.15 as per current BNBC. Pushover analysis is a useful tool of Performance Based
Seismic Engineering to study post-yield behavior of a structure. It is more complex than traditional
linear analysis, but it requires less effort and deals with much less amount of data than a nonlinear
response history analysis. Pushover analysis was performed on a six story frame building. From the
pushover analysis capacity curve is developed. By using the capacity curve the performance of the
building has been evaluated as per ATC-40 by using BNBC response spectrum. The hinge formation
pattern also observed to identify the week element of the building.
7.2.1 Capacity Curve
Capacity curve has been constructed after performing pushover analysis. To develop a capacity curve
the horizontal displacement at roof level and base shear capacity building are observed. The capacity
curve for this building is shown in the Figure-8. From the Capacity curve it is observed that the
capacity of this building dose not satisfy the seismic requirement. This building need to design for a
base shear 710 Kip and the maximum capacity of this building is 910 Kip.
Figure-8: Capacity Curve
The over strength factor for this building is 1.28. As per National Building Code of Canada (NBCC
2005) for special moment resisting concrete frame building the required over strength factor is 1.7. To
get this over strength factor the required maximum base shear capacity is 1210 Kip. So the maximum
base shear capacity of this building is not sufficient.
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7.2.2 Collapse Mechanism
From the pushover analysis the collapse mechanism of this building is observed and these are shown
in the Figure 9 to 11. From these figures it can be observed that the beam at the grid line 1 and 5
reached at collapse state at performance point. We also observed that the performance point does
not satisfy the BNBC requirement. For frame structures most of the hinge formed in the bottom four
stories. The columns are need to strengthening for these stories.
Figure-9: Collapse Mechanism at Grid Line (1)
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Figure-10: Collapse Mechanism at Grid Line (3)
Figure-11: Collapse Mechanism (Grid Line 5)
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7.2.3 Seismic Performance
The seismic performance of this building has been evaluated as per ATC-40. After developing
pushover curve the design spectral acceleration as per BNBC has been developed for Seismic Zone-
2 and soil class C. The building need to design for a spectral acceleration value Sa=0.12g but from
figure-12 it is observed that the building can cope with spectral acceleration value Sa=0.086g which is
71%of the code requirement.
Figure-12: Performance Point Evaluation
8. CONCLUSION
The current status of the building does not comply with the current code requirements. It does not
also satisfy the seismic requirements for zone-2 as per BNBC-1993.
From the gravity load design approach it is observed that the vertical load carrying capacity of the 8
interior columns of the existing building is overstressed. Beam reinforcement is over reinforced. This
building is weak column strong beam condition. Weak Column strong beam condition is not desirable
condition for a building.
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From the pushover Analysis it is observed that the bottom four stories are the most vulnerable for
collapse. From this analysis it is also observed that the performance point does not satisfy the code
requirement for seismic design.
9. RECOMMENDATIONS
From gravity load assessment and seismic load assessment and visual inspection following
recommendations are mandatory before start any renovation work.
1. This building does not satisfy the current code requirement.
2. Strengthening of 8 interior columns and C2B at gridline B1, C1, D1 is required under gravity
load.
3. Seismic strengthening is also required. For this few share wall or steel bracing is need to
install.
4. We strongly recommend not adding any additional load in future for this building.
5. Generator Tower or any equipment shall not be installed in this building.
6. The over stressed column need to strengthening.
7. To increase the seismic capacity we recommend installing some shear wall or steel bracing
as per the engineer design.