STRUCTURAL LAB. FACILITY AT IITG IN THE DIRECTION OF TRADITIONAL/LOCAL HOUSING

Transcription

1 STRUCTURAL LAB. FACILITY AT IITG IN THE DIRECTION OF TRADITIONAL/LOCAL HOUSING A Presentation by Sandip Das Department of Civil Engineering Indian Institute of Technology Guwahati Guwahati , India

2 Presentation Outline 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

3 Overview of Structural Engg. Lab. Structural Engg. Lab Strong floor-wall Testing Platform Designed for 1 kn with deflection limit1mm 3

4 Lab Facility in IIT Guwahati No. of Hydraulic actuators: Four 1 kn load capacity and 5 mm stroke length 25 kn load capacity and 5 mm stroke length 25 kn load capacity and 25 mm stroke length 1 kn load capacity and 125 mm stroke length 4

5 Shake Table at IITG Shake table with size: 2.5 m 2.5 m Pay load 5 tonnes Capacity12 kn and Stroke length 5 mm Accelation +/-2g and Frequency 1 Hz 5

6 Universal Testing Machine Load controlled UTM Capacity: 1 kn Hydraulic displacement controlled UTM Capacity:25 kn and 16 mm stroke length 6

7 Compression Testing Machine Capacity 2 kn Capacity 3 kn and rate controlled 7

8 Assam-type house 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 8

9 Compressive Stress (MPa) Material Testing: Compression parallel to grain 6 Inclined plane failure Specimens were tested as per IS 178 (BIS 1986) and ASTM D-143 (214) standards Tests performed using displacement controlled UTM at a loading rate of.6 mm/min Test 1 Test 2 Test 3 Test 4 Test 6 Test 7 Test 8 Test 9 Test 1 Test 11 Test 12 Test 13 Test 14 Test 15 Average Strain 9

10 Stress (MPa) Material Testing: Compression perpendicular to grain Specimen size 5 mm 5 mm 15 mm Load applied through a steel plate as specified in IS 178 (BIS 1986) and ASTM D-143 (214) standards Strain Test 1 Test 2 Test 3 Test 4 Test 5 Test 6 Test 7 Test 8 Test 9 Average 1

11 Stress (MPa) Material Testing: Tensile strength parallel to grain Test 1 Test 2 Test 3 Test 4 Test 5 Test 6 Test 7 Test 8 Test 1 Test 9 Average Strain The tensile strength parallel to grain carried out on specimen size as specified in IS 178 (BIS 1986) Failure in tension mainly due to shear failure between fibers or cells. 11

12 Stress (MPa) Material Testing: Tensile strength perpendicular to grain Tensile strength perpendicular to grain carried out on a specimen size as specified in IS 178 (BIS 1986) Test 1 Test 2 Test 3 Test 4 Test 5 Test 6 Test 7 Avg Strain 12

13 Material Testing: Flexural test 3-point specimen size -5 mm 5 mm 75 mm and 4-point specimen size -5 mm 5 mm 1 mm as per IS 178 (BIS 1986) Deflection values determined by the LVDT placed at the bottom of the specimen at specified locations 3-Point loading 4-Point loading 13

14 Load (kn) Material Testing: Flexural test results Load (kn) Test_1 Test_2 Test_3 Test_4 Test_5 Test_6 Test_7 Test_8 Average Displacement (mm) 3-Point Loading Displacement (mm) 4-Point loading Test 1 Test 2 Test 3 Test 4 Test 5 Average Large displacement was achieved in the specimens before failure 14

15 Material Testing: Ikra panel test Load (kn) To characterize the Ikra panel for analytical modelling, the diagonal compression test of Ikra panels were conducted Two different full scale sizes of Ikra panels were adopted Specimen 1 Specimen 2 Specimen 3 Specimen 4 Specimen 5 Specimen 6 Average Displacement (mm) 15

16 Slow-cyclic Test set up and sensor locations Hydraulic Actuator LVDT 7 Displacement (mm) Time (s) LVDT 1 LVDT 6 Strong wall LVDT 2 LVDT 5 LVDT 3 LVDT 4 Base plate Strong floor 16

17 29 Specimens tested Joint B B Joint B B Bamboo mesh with cement mortar plaster C 95 Joint B Joint C Joint E Joint E Joint D Joint E C 165 Joint D Joint C Joint E Joint E Joint D Brick wall A A 68 Joint C Joint A Base plate Joint A Section A-A Section B-B 75 Section C-C Joint A 17

18 Test specimens in the study Frame 1 Frame 2 Frame 3 Frame 4 18

19 Damages in Frames after Cyclic Loading Frame 1 Frame 2 Frame 3 Frame 4 19

20 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 2

21 Actuator Load (kn) Hysteretic Response Frame 1 vs Frame 2 Actuator Load (kn) Drift (%) 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 21

22 Actuator Load (kn) Hysteretic Response Frame 2 vs Frame 3 Actuator Load (kn) Drift (%) Drift (%) Frames experienced severe pinching Frames exhibited a progressive loss of stiffness, even though the ultimate load 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 22

23 Actuator Load (kn) Hysteretic Response of Frame 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 23

24 Full Scale Specimen house for Shake-Table Test At Construction Stage Specimen Ready For Testing Shake Table at IIT Guwahati Evaluation on Dynamic Characteristics, Failure Patterns, Damage Pattern, etc 24

25 Local Masonry building and its Strenghening Post-Earthquake Reconnaissance Visits (26 Sikkim EQ) (211 Sikkim EQ) Concentration of masonry buildings 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. 25

26 Masonry constituents: Compression Test Stress (MPa) Strain specimen 1 specimen 2 specimen 3 specimen 4 26

27 Masonry constituents: Shear Test Shear stress (MPa) Two LVDTs and laser extensometer positioned to measure the deformations along both the diagonals. Shear stress and shear strain calculated as per ASTM E519/E519M (21) The formula is as follows Shear strain 27

28 Stress (MPa) Masonry constituents: Z test (Tensile bond strength) Fig. 5 (a) Z Test Fig.5 (b) Force-Displacement plot of Z test Strain 28

29 Stress (MPa) Masonry constituents: Triplet Shear Test Stress(MPa) Sample 1 Sample 3.2 Sample 1 Sample Sample 5 Sample 6 sample 7 Average Sample 5 Sample 6 Sample 7 Average Strain Strain Full brick joint specimen sets Partially full brick joint specimen sets 29

30 Slow cyclic testing of Full-Scale walls Lateral Load (kn) Model 1:Wall without any opening Displacement (mm) Failure occurred at the base of the wall along the mortar joints Fig.8 (a). Damage state 3

31 Lateral Load (kn) Slow cyclic testing of Full-Scale walls Model 2:Wall with door opening Fig. 11 (a). Damaged states of Model 2 Fig. 11 (b). Numerical Damaged Model Displacement (mm) 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

32 Lateral Load (kn) Slow cyclic testing of Full-Scale walls Model 3:Wall with window opening 3 Fig. 14 (a).wall Model Fig. 14 (c). Damaged Model 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 Displacement (mm) 32

33 Lateral Load [kn] Slow-cyclic test of pure Unreinforced Brick Masonry Building Hysteresis Curve Capacity Curve Damage originated from corner of the opening Combined shear and flexural failure has been observed Displacement [mm] 33

34 Lateral Load (kn) Cyclic Test of Strengthened Masonry building 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

35 Thank You 35