PRISM TEST, FLAT JACK TEST, REBOUND HAMMER, & MECHANICAL PULSE VELOCITY

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1 PRISM TEST, FLAT JACK TEST, REBOUND HAMMER, & MECHANICAL PULSE VELOCITY

2 PRISM TEST(Introduction) It is a laboratory test to calculate the compressive strength of a masonry prism. The prism can be obtained from site or can be manufactured in lab as a representative modal of site. It used to check that whether the masonry is providing sufficient strength or not. SOURCE

3 TEST SETUP The test setup consists of -: A load cell A device to measure the deformation of the specimen. Saw for cutting out the specimen. SOURCE

4 TEST PROCEDURE Preparation of specimen. Install deformation measuring device. Watch for the mode of failure of the specimen. Note down the observations from the test. Make report.

5 PREPARATION OF SPECIMEN LABORATORY FIELD PREPARE MORTAR AND CONSTRUCT PRISM SAMPLING TRANSPORTING CURING CAPPING

6 Build prism on a flat surface. LABORATORY SOURCE ASTM C Cover the specimen in an open moisture tight bag for curing of the specimen SOURCE

7 FIELD Select the place from where you want to take the sample according to your requirement. The order of sampling can be done in following ways Random sampling - Designate a numbering system associated with specimen locations and randomly select numbers.

8 CONTINUED. Location-Specific Sampling Select specimens sample locations specific to a particular installed location. Condition-Specific Sampling Select specimen sample locations specific to a physical condition of the masonry, such as units or mortar visually assessed to be deteriorated.

9 CAPPING Cap the specimen with high strength gypsum cement material. Use glass made casting plate for placing the capping material on the specimen. Casting plate Capping material SOURCE

10 TESTING Place the specimen in the test setup and load the specimen at a convenient rate. At the time of failure match it from the fig. SOURCE ASTM C

11 CONTINUED The strength of the masonry is obtained as fmt =correction factor X Strength of prism SOURCE ASTM C We can obtained modulus of elasticity from the stress strain curve obtained from the test. And if we install extensometer in the lateral direction we can also get poisson s ratio.

12 FLAT JACK TEST BY-SHIVAM DUBEY

13 FLAT JACK TEST (INTRODUCTION) It is a field test It is a relatively non-destructive testing technique to assess the in situ mechanical properties of masonry. It is used to measure the load to which the masonry in field is subjected to. SOURCE -google images

14 TEST SETUP CONNECTION OF FLAT JACK GAUGE POINTS DETACHABLE MECHANICAL GAUGE EXTENSOMETER SOURCE -google images PUMP

15 FLAT JACK TEST TYPE-1 FOR MEASUREMENT OF IN FIELD SUBJECTED STRESS FOR MEASUREMENT OF MECHANICAL PROPERTIES TYPE-2

16 TYPE-1 TEST PROCEDURE Select the location of masonry to be tested. Mark the position of slot. Mark the gauge points on the masonry wall, equal no. above and below the slot. And measure the distance between the gauge points. Make the slot. Allow the slot to be partially close.

17 CONTINUED. Allow the slot to get partially close. Again note the distance between the gauge points. Insert the flat jack in the slot. Insert shim in the slot. Apply pressure into the flat jack with the help of the hydraulic pump. Calculate the pressure at which the gauge points initial position is restored by multiplying the reading with suitable calibration constants..

18 TYPE-2 TEST PROCEDURE Select the location of masonry to be tested. Mark the position of slots. The slots should be marked parallel to each other. Mark the gauge points on the masonry wall between the two marks(of slots). And measure the distance between the gauge points. Make the slots.

19 CONTINUED. Insert the flat jack in the slot. Insert shim in the slot. Apply pressure into the flat jack with the help of the hydraulic pump. Note the readings of the load cell and extensometer at suitable intervals Calculate the stress by multiplying the readings with suitable calibration constants..

20 CUTTING OF SLOTS With the help of drilling machine. With the help of circular saw with special guiding equipment.

21 SHIMS REGULAR SLOTS OR SLOTS HAVING UNIFORM THICKNESS IRREGULAR SLOTS OR SLOTS HAVING NON- UNIFORM THICKNESS Source ASTM c a Source ASTM c a Source ASTM c a

22 CALLIBRATION SETUP Source ASTM c a

23 CALLIBRATION Stress in the masonry between the flatjacks is given by Where Km = pressure applied by flat jack against wall pressure pumped in the flat jack Ka = bearing area of flat jack area of slot

24 STRESS STRAIN MODEL FOR BRICK MASONARY AND BEHAVIOUR OF MASONRY PRISM ON LOAD APPLICATION

25 INTRODUCTION Prism test was conducted on 84 masonry specimens Displacement control compression loading was applied Different grades of mortar used were MORTAR CEMENT LIME SAND Type Type Type Size of bricks used were L=230mm B=110mm H=75mm

26 CONTINUED The bricks were manufactured by 4 different manufacturers Designated as M, B, S, and O Approximate height of 5 brick high masonry prism with 10 mm thick mortar joints was about mm Epsilon extensometers were used to record the displacement response across 3 mortar joints

27 Type of mortar f f Mpa OBSERVATIONS f b Mpa f m Mpa Failure Strain E m Mpa Type Type Type f m = Prism strength f f = Strength of mortar f b = strength of bricks (Avg.) E m = Elatic modulus of prism

28 CONTINUED. Modes failure were observed as And the stress strain curve which was observed

29 ANALYSIS Modulus of elasticity is calculated from stress strain curves By measuring the slope of secant between ordinates corresponding to 5 and 33% It was observed that Em lies between 250 and 1100 times f m for the present dataset By regression analysis Em can be found from the equation With C R =0.63 E m 550 * f m

30 Control points on curve: 0.33f m : Point up to which the stress strain curves remain linear 0.75f m : Vertical splitting cracks in bricks start developing at about this stress 0.90f m : Vertical splitting cracks in bricks propagate excessively throughout masonry f m : Ultimate stress level in masonry (prism strength) 0.2f m : Maximum residual compressive stress in masonry (on descending curve) CONTINUED...

31 CONTINUED... Prism strength was given by After regression analysis d=0.32 c=0.49 K=0.63 With standard error=0.48

32 STANDARD CURVE FOR STRESS STRAIN The ascending portion of the curve is given by the parabola m denotes the peak strain Again by regression analysis we have peak strain With standard error =

33 STANDARDIZED STRESS STRAIN CURVE

34 MECHANISM OF FAILURE

35 THANK YOU

36 REBOUND HAMMER TEST AND MECHANICAL PULSE VELOCITY TEST

37 REBOUND HAMMER TEST

38 INTRODUCTION It is a field test Non destructive test Less time consuming By calculating the rebound number we can calculate the compressive strength by using calibration table

39 TEST SETUP The test setup consist of Schmidt Rebound Hammer(Type L) Calibration chart There are 4 types of hammer Type L (impact energy kgm) Type N (impact energy kgm) Type M (impact energy = 3 kgm) Type P (pendulum type, impact energy = 0.09 kgm) Source- Source-

40 TEST PROCEDURE Source- After getting the reading from the test by calibration chart we should calculate the compressive strength

CALIBRATION For calibration rebound hammer test is conducted on 5-10 samples(masonry prisms) On the same samples prism test is conducted A graph is plotted between the compressive

41 CALIBRATION For calibration rebound hammer test is conducted on 5-10 samples(masonry prisms) On the same samples prism test is conducted A graph is plotted between the compressive strength obtained from the prism test and rebound number from rebound hammer test Fit a straight line on graph for various test points Tabulate the graph Source-

42 MECHANICAL PULSE VELOCITY TEST

43 INTRODUCTION It is a field test Non destructive test Test consists of impacting a wall with a hammer blow and Measuring the travel time of a sonic wave across a gage distance to measure the velocity It is used to asses the condition of Masonry i.e. crack width and quality of construction materials

TEST SETUP An impact hammer equipped with a load

44 TEST SETUP An impact hammer equipped with a load cell or accelerometer to detect the time of impact A distant accelerometer is fixed to a wall to detect the arrival time of the pulse Source ACCELEROMETER Source HAMMER Source

PROCEDURE Hit the hammer on the surface of the masonry on the pre decided point Attach the accelerometer at a known gauge distance from the point of hitting the hammer Note down the time interval

45 PROCEDURE Hit the hammer on the surface of the masonry on the pre decided point Attach the accelerometer at a known gauge distance from the point of hitting the hammer Note down the time interval between generation of pulse and reception of pulse Obtain the velocity of sonic wave by Wave velocity = Gauge Distance Time elapsed For correlating it with the conditions of masonry, firstly it should done with destructive tests like prism test

47 hp/tp ratio for indian conditions QUESTIONS Source IS 1905 (1987) SOURCE ASTM C

48 DIFFERENT CLASSES OF BRICKS AA CLASS A CLASS B CLASS C CLASS 14 Mpa 10.5Mpa 7.0Mpa 3.5Mpa

49 DIFFERENT GRADES OF MORTAR

50 CONSTANT PRESSURE IN HYDRAULIC PUMP

CHAPTER 5 COMPRESSIVE STRENGTH AND MODULUS OF ELASTICITY OF MASONRY PRISMS

68 CHAPTER 5 COMPRESSIVE STRENGTH AND MODULUS OF ELASTICITY OF MASONRY PRISMS In this chapter, after many trials, the mix ratio of metakaolin based geopolymer brick to attain a compressive strength of