structural lab. facility at iitg direction of … · • failure in tension mainly due to shear...

STRUCTURAL LAB. FACILITY AT IITG IN THE

DIRECTION OF TRADITIONAL/LOCAL HOUSING

by

Sandip Das

Department of Civil Engineering

Indian Institute of Technology Guwahati

Guwahati- 781039, India

A Presentation

Sandip Das IIT Guwahati, Assam 21/07/2017

• Overview of Structural Lab. Facility

• Traditional Assam-type house

– Material Characterization

– Slow cyclic testing of Full-Scale walls

– Specimen for Shake Table testing

• Local Masonry building

– Material Characterization

– Slow cyclic testing of Full-Scale walls

– Full-scale house testing

2

Presentation Outline


Overview of Structural Engg. Lab.

3

Strong floor-wall Testing Platform

• Designed for 1000 kN with deflection

limit1mm

Structural Engg. Lab


Lab Facility in IIT Guwahati

4

No. of Hydraulic actuators: Four

• 1000 kN load capacity and 500 mm

stroke length


stroke length


stroke length


stroke length


Shake Table at IITG

5

Shake table with size: 2.5 m × 2.5 m

• Pay load 5 tonnes

• Capacity120 kN and Stroke length 500 mm

• Accelation +/-2g and Frequency 10 Hz


Universal Testing Machine

6

Hydraulic displacement controlled UTM

Capacity:250 kN and 160 mm stroke lengthLoad controlled UTM

Capacity: 1000 kN


Compression Testing Machine

7

Capacity 2000 kN Capacity 3000 kN and rate controlled

Sandip Das IIT Guwahati, Assam 21/07/2017 8

Assam-type houses

– Among very few systems that performed exceptionally well in earthquake

– In use since many decades (North Eastern India)

Uniqueness lies in its

– Material used in structural component

– Easy construction methodology

– Excellent joint and infill behavior

– Cost effectiveness and low maintenance

In spite of exceptionally good features, these houses

– Not received due attention

– Performance under seismic action not studied so far

Objective: Evaluation of lateral load performance by means of

systematic experimental and analytical studies

Assam-type house


Material Testing: Compression parallel to grain

9

Inclined plane failure

0

10

20

30

40

50

60

0 0.02 0.04 0.06 0.08 0.1 0.12

Co

mp

ress

ive

Str

ess

(MP

a)

Strain

Test 1 Test 2Test 3 Test 4Test 6 Test 7Test 8 Test 9Test 10 Test 11Test 12 Test 13Test 14 Test 15Average

• Specimens were tested as per IS 1708 (BIS

1986) and ASTM D-143 (2014) standards

• Tests performed using displacement

controlled UTM at a loading rate of 0.6

mm/min.


Material Testing: Compression perpendicular to grain

10

0

5

10

15

20

25

30

35

40

45

0 0.05 0.1 0.15 0.2 0.25 0.3 0.35

Str

ess

(MP

a)

Strain

Test 1 Test 2

Test 3 Test 4

Test 5 Test 6

Test 7 Test 8

Test 9 Average

• Specimen size 50 mm × 50 mm × 150

mm

• Load applied through a steel plate as

specified in IS 1708 (BIS 1986) and

ASTM D-143 (2014) standards


Material Testing: Tensile strength parallel to grain

11

0

20

40

60

80

100

120

0 0.002 0.004 0.006 0.008 0.01 0.012 0.014

Str

ess

(MP

a)

Strain

Test 1 Test 2

Test 3 Test 4

Test 5 Test 6

Test 7 Test 8

Test 10 Test 9

Average

• The tensile strength parallel to grain carried out on specimen size as specified in IS

1708 (BIS 1986)

• Failure in tension mainly due to shear failure between fibers or cells.


• Tensile strength perpendicular to grain carried out on a specimen size as specified in IS 1708 (BIS 1986)

Material Testing: Tensile strength perpendicular to grain

12

0

0.5

1

1.5

2

2.5

3

3.5

4

0 0.005 0.01 0.015 0.02 0.025 0.03 0.035 0.04

Str

ess

(MP

a)

Strain

Test 1 Test 2 Test 3

Test 4 Test 5 Test 6

Test 7 Avg.


Material Testing: Flexural test

13

• 3-point specimen size -50 mm × 50 mm × 750 mm and 4-point specimen size -50 mm × 50 mm× 1000 mm as per IS 1708 (BIS 1986)

• Deflection values determined by the LVDT placed at the bottom of the specimen at specified locations

3-Point loading 4-Point loading


Material Testing: Flexural test results

14

• Large displacement was achieved in the specimens before failure

0

2

4

6

8

10

12

14

16

0 5 10 15 20 25 30 35

Lo

ad (

kN

)

Displacement (mm)

Test_1 Test_2

Test_3 Test_4

Test_5 Test_6

Test_7 Test_8

Average0

5

10

15

20

25

30

35

0 5 10 15 20 25 30 35

Lo

ad (

kN

)

Displacement (mm)

Test 1

Test 2

Test 3

Test 4

Test 5

Average

3-Point Loading 4-Point loading


Material Testing: Ikra panel test

15

• To characterize the Ikra panel for analytical modelling, thediagonal compression test of Ikra panels were conducted

• Two different full scale sizes of Ikra panels were adopted.

0

10

20

30

40

50

60

0 5 10 15 20 25 30 35 40 45

Lo

ad (

kN

)

Displacement (mm)

Specimen 1Specimen 2Specimen 3Specimen 4Specimen 5Specimen 6Average


Slow-cyclic Test set up and sensor locations

16

LVDT 7

LVDT 4

LVDT 5

LVDT 6 LVDT 1

LVDT 2

LVDT 3

Hydraulic

Actuator

Str

on

g w

all

Base plate

Strong floor

-100

-75

-50

-25

0

25

50

75

100

0 500 1000 1500 2000 2500 3000 3500 4000

Dis

pla

cem

ent

(mm

)

Time (s)


Joint B Joint B

Joint C

Joint D

Joint E

Joint EJoint E

3030

29

00

680

1065

905

75

100

75

Section B-B

75

Section C-C

100

100

Section A-A

Brick wall

Joint D

Joint C

Joint E

Bamboo mesh with

cement mortar plaster

885 910 885

Joint A Joint ABase plate

B

B

C

C

A A

Specimens tested

Joint B

Joint D

Joint E

Joint A

Joint C


Test specimens in the study

18

Frame 1 Frame 2

Frame 3 Frame 4


Damages in Frames after Cyclic Loading

19

Frame 1 Frame 2

Frame 3 Frame 4


Deformational Behavior under Monotonic Load

20

Major damage occurred in the framing members of Frame 1, Frame 2 and Frame

3 during the monotonic testing only

Response of ikra panels, are mainly of sliding type and that of main posts

bending type

Masonry behaved as a block and detached from timber frame during cyclic

testing


Hysteretic Response Frame 1 vs Frame 2

21

-10

-8

-6

-4

-2

0

2

4

6

8

10

-9 -8 -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8 9

Actu

ato

r L

oad

(kN

)

Drift (%)

Hysteretic response of Frame 1 and Frame 2 significantly different from each

other due to presence of Ikra panels in Frame 2

Curves were closely spaced which lead to very less energy dissipation during the

cycles compared to Frame 2

-25

-20

-15

-10

-5

0

5

10

15

20

25

-9 -8 -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8 9

Actu

ato

r L

oad

(kN

)

Drift (%)


Hysteretic Response Frame 2 vs Frame 3

22

• Frames experienced severe pinching

• Frames exhibited a progressive loss of stiffness, even though the ultimateload does not differ much from the maximum one

• Hysteretic response significantly different from that of each other

– Lesser readjustment of infill panels in Frame 3 than Frame 2 due to presence of window

-25

-20

-15

-10

-5

0

5

10

15

20

25

-9 -8 -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8 9

Actu

ato

r L

oad

(kN

)

Drift (%)

-25

-20

-15

-10

-5

0

5

10

15

20

25

-9 -8 -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8 9

Actu

ato

r L

oad

(kN

)

Drift (%)


Hysteretic Response of Frame 4

23

-25

-20

-15

-10

-5

0

5

10

15

20

25

-9 -8 -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8 9

Act

uat

or

Lo

ad (

kN

)

Drift (%)

• The suddenly load dropped

– because of major damage in top level Ikra panels and initiation of

separation of various members.

– This is because of non-fixity of doorpost with the foundation


Full Scale Specimen house for Shake-Table Test

24

At Construction Stage Specimen Ready For Testing

Evaluation on Dynamic Characteristics, Failure Patterns, Damage Pattern, etc

Shake Table at IIT Guwahati


Local Masonry building and its Strenghening

25

Post-Earthquake Reconnaissance Visits

(2006 Sikkim EQ) (2011 Sikkim EQ)

Use of steel members in strengthening old masonry buildings

- Performed exceptionally well in seismically active regions- Few reported damage but no collapse

- Other buildings collapsed in the vicinity

- Detailed study required to be undertaken to understand the behaviour

of such buildings.

Concentration of masonry

buildings


Masonry constituents: Compression Test

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

0 0.005 0.01 0.015 0.02

Str

ess

(MP

a)

Strain

specimen 1

specimen 2

specimen 3

specimen 4

26


• Two LVDTs and laser extensometerpositioned to measure the deformations

along both the diagonals.

• Shear stress and shear strain calculated

as per ASTM E519/E519M (2010)

• The formula is as follows

Masonry constituents: Shear Test

0

0.05

0.1

0.15

0.2

0.25

0 0.0001 0.0002 0.0003 0.0004 0.0005 0.0006 0.0007 0.0008 0.0009

Sh

ear

stre

ss (

MP

a)

Shear strain

27


Masonry constituents: Z test (Tensile bond strength)

Fig. 5 (a) Z Test Fig.5 (b) Force-Displacement plot of Z test

0

0.005

0.01

0.015

0.02

0.025

0.03

0 0.001 0.002 0.003 0.004 0.005 0.006 0.007

Str

ess

(MP

a)

Strain

28


Masonry constituents: Triplet Shear Test

0

0.05

0.1

0.15

0.2

0.25

0.3

0 0.005 0.01 0.015 0.02 0.025

Str

ess

(MP

a)

Strain

Sample 1

Sample 3

Sample 5

Sample 6

sample 7

Average

0

0.05

0.1

0.15

0.2

0.25

0 0.002 0.004 0.006 0.008 0.01 0.012

Str

ess(

MP

a)

Strain

Sample 1

Sample 3

Sample 5

Sample 6

Sample 7

Average

Full brick joint specimen sets Partially full brick joint specimen sets

29


Slow cyclic testing of Full-Scale walls

Model 1:Wall without any opening

Fig.8 (a). Damage state

-40

-30

-20

-10

0

10

20

30

-10 -8 -6 -4 -2 0 2 4 6 8 10

Lat

eral

Lo

ad (

kN

)Displacement (mm)

• Failure occurred at the base of the wall

along the mortar joints

30



Fig. 11 (a). Damaged states of Model 2

Fig. 11 (b). Numerical Damaged Model 2

-25

-20

-15

-10

-5

0

5

10

15

20

25

-8 -6 -4 -2 0 2 4 6 8

Lat

eral

Lo

ad (

kN

)

Displacement (mm)

Model 2:Wall with door opening

• Cracks initiated at the top corner of

the door opening followed by crack

originated from the base of the wall

• Introduction of door opening shows

a significant decease in capacity

31



Fig. 14 (a).Wall – Model 3 Fig. 14 (c). Damaged Model

-40

-30

-20

-10

0

10

20

30

-15 -10 -5 0 5 10 15

Lat

eral

Lo

ad (

kN

)

Displacement (mm)

Model 3:Wall with window opening

• Introduction of window opening has

shown negligible increase in capacity

• Smaller size window opening have

less influence on the overall lateral

load carrying capacity of the wall

32


-100

-80

-60

-40

-20

0

20

40

60

80

100

-30 -20 -10 0 10 20 30

Lat

eral

Lo

ad [

kN

]

Displacement [mm]

Hysteresis Curve

Capacity Curve

Slow-cyclic test of pure Unreinforced Brick Masonry Building

• Damage originated from corner of

the opening

• Combined shear and flexural failure

has been observed

33


Cyclic Test of Strengthened Masonry building

-120

-100

-80

-60

-40

-20

0

20

40

60

80

100

-40 -30 -20 -10 0 10 20 30 40

Lat

eral

Lo

ad (

kN

)

Displacement (mm)

• Damage originated from corner of

the opening

• Combined shear and flexural failure

has been observed

• Cracks has been arrested by the

steel bands up to joint failure of

bands

• This strengthened model have

shown higher displacement capacity

without any increase in load

carrying capacity

34


Thank You

structural lab. facility at iitg direction of … · • failure in tension mainly due to shear...

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