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

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

Presentation Outline

Overview of Structural Engg. Lab.

Strong floor-wall Testing Platform

• Designed for 1000 kN with deflection

limit1mm

Structural Engg. Lab

Lab Facility in IIT Guwahati

No. of Hydraulic actuators: Four

• 1000 kN load capacity and 500 mm

stroke length

Shake Table at IITG

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

Hydraulic displacement controlled UTM

Capacity:250 kN and 160 mm stroke lengthLoad controlled UTM

Capacity: 1000 kN

Compression Testing Machine

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

Inclined plane failure

0 0.02 0.04 0.06 0.08 0.1 0.12

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

0 0.05 0.1 0.15 0.2 0.25 0.3 0.35

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

• 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

0 0.002 0.004 0.006 0.008 0.01 0.012 0.014

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

0 0.005 0.01 0.015 0.02 0.025 0.03 0.035 0.04

Strain

Test 1 Test 2 Test 3

Test 4 Test 5 Test 6

Test 7 Avg.

Material Testing: Flexural test

• 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

• Large displacement was achieved in the specimens before failure

0 5 10 15 20 25 30 35

Displacement (mm)

Test_1 Test_2

Test_3 Test_4

Test_5 Test_6

Test_7 Test_8

Average0

0 5 10 15 20 25 30 35

Displacement (mm)

Test 1

Test 2

Test 3

Test 4

Test 5

Average

3-Point Loading 4-Point loading

Material Testing: Ikra panel test

• 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 5 10 15 20 25 30 35 40 45

Displacement (mm)

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

Slow-cyclic Test set up and sensor locations

LVDT 7

LVDT 4

LVDT 5

LVDT 6 LVDT 1

LVDT 2

LVDT 3

Hydraulic

Actuator

Base plate

Strong floor

0 500 1000 1500 2000 2500 3000 3500 4000

Time (s)

Joint B Joint B

Joint C

Joint D

Joint E

Joint EJoint E

Section B-B

Section C-C

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

Specimens tested

Joint B

Joint D

Joint E

Joint A

Joint C

Test specimens in the study

Frame 1 Frame 2

Frame 3 Frame 4

Damages in Frames after Cyclic Loading

Frame 1 Frame 2

Frame 3 Frame 4

Deformational Behavior under Monotonic Load

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

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

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

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

Drift (%)

Hysteretic Response Frame 2 vs Frame 3

• 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

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

Drift (%)

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

Drift (%)

Hysteretic Response of Frame 4

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

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

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

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 0.005 0.01 0.015 0.02

Strain

specimen 1

specimen 2

specimen 3

specimen 4

• 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 0.0001 0.0002 0.0003 0.0004 0.0005 0.0006 0.0007 0.0008 0.0009

Shear strain

Masonry constituents: Z test (Tensile bond strength)

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

0 0.001 0.002 0.003 0.004 0.005 0.006 0.007

Strain

Masonry constituents: Triplet Shear Test

0 0.005 0.01 0.015 0.02 0.025

Strain

Sample 1

Sample 3

Sample 5

Sample 6

sample 7

Average

0 0.002 0.004 0.006 0.008 0.01 0.012

Strain

Sample 1

Sample 3

Sample 5

Sample 6

Sample 7

Average

Full brick joint specimen sets Partially full brick joint specimen sets

Slow cyclic testing of Full-Scale walls

Model 1:Wall without any opening

Fig.8 (a). Damage state

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

)Displacement (mm)

• Failure occurred at the base of the wall

along the mortar joints

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

Fig. 11 (b). Numerical Damaged Model 2

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

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

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

-15 -10 -5 0 5 10 15

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

-30 -20 -10 0 10 20 30

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

Cyclic Test of Strengthened Masonry building

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

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

• This strengthened model have

shown higher displacement capacity

without any increase in load

carrying capacity

Thank You

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

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