MAL Report.pdf

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.

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