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

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 www.iitk.ac.in/nicee/RP/2007_Masonry_Properties_ASCE.pdf

TEST SETUP

The test setup consists of -:A load cellA device to measure the

deformation of the specimen.Saw for cutting out the

specimen.

SOURCE https://nees.org

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.

PREPARATION OF SPECIMEN

LABORATORY FIELD

PREPARE MORTAR AND CONSTRUCT

PRISM

SAMPLING

TRANSPORTING

CURING

CAPPING

LABORATORY Build prism on a flat surface.

Cover the specimen in an open moisture tight bag for curing of the specimen

SOURCE ASTM C1314 − 16

SOURCE https://ceen.et.byu.edu/sites/default/files/snrprojects/640-juan_m_salguero_mendizabal-2011-fsf.pdf

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.

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.

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 https://ceen.et.byu.edu/sites/default/files/snrprojects/640-juan_m_salguero_mendizabal-2011-fsf.pdf

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 C1314 − 16

CONTINUED…

The strength of the masonry is obtained as fmt =correction factor X Strength of prism

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.

SOURCE ASTM C1314 − 16

FLAT JACK TEST BY-SHIVAM DUBEY

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

TEST SETUP

GAUGE POINTS

PUMP

CONNECTION OF FLAT JACK

DETACHABLEMECHANICAL GAUGE EXTENSOMETER SOURCE -google images

FLAT JACK TEST

FOR MEASUREMENT OF IN FIELD SUBJECTED

STRESS

FOR MEASUREMENT OF MECHANICAL

PROPERTIES

TYPE-1 TYPE-2

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.

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.

.

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.

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 intervalsCalculate the stress by multiplying the readings with

suitable calibration constants..

CUTTING OF SLOTS

With the help of drilling machine.

With the help of circular saw with special guiding equipment.

SHIMS

REGULAR SLOTS OR SLOTS HAVING

UNIFORM THICKNESS

IRREGULAR SLOTS OR SLOTS HAVING NON-UNIFORM THICKNESS

Source ASTM c1197-14aSource ASTM c1197-14aSource ASTM c1197-14a

CALLIBRATION SETUP

Source ASTM c1197-14a

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

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

INTRODUCTION Prism test was conducted on 84 masonry specimens Displacement control compression loading was

applied Different grades of mortar used were

Size of bricks used were L=230mm B=110mm H=75mm

MORTAR CEMENT LIME SAND

Type 1 1 0 6Type 2 1 0 3

Type 3 1 0.5 4.5

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 400– 410 mm

Epsilon extensometers were used to record the displacement response across 3 mortar joints

OBSERVATIONSType of mortar

ffMpa

fbMpa

f’mMpa

FailureStrain

EmMpa

Type 1 3.1 20.8 4.1 0.0059 2300Type 2 20.6 20.8 7.5 0.0053 4200Type 3 15.2 20.8 6.6 0.0080 3800

f’m = Prism strength

ff = Strength of mortar

fb = strength of bricks (Avg.)

Em = Elatic modulus of prism

CONTINUED….

Modes failure were observed as And the stress strain curve which

was observed

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

Em 550 *fm

With CR=0.63

CONTINUED... 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...

Prism strength was given by

After regression analysis

d=0.32

c=0.49

K=0.63

With standard error=0.48

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 = 0.0001

STANDARDIZED STRESS STRAIN CURVE

MECHANISM OF FAILURE

THANK YOU

REBOUND HAMMER TEST AND MECHANICAL PULSE VELOCITY TEST

REBOUND HAMMER TEST

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

TEST SETUP

The test setup consist of Schmidt Rebound Hammer(Type L)Calibration chart

There are 4 types of hammer Type L (impact energy - 0.075 kgm) Type N (impact energy -- 0.225 kgm) Type M (impact energy = 3 kgm) Type P (pendulum type, impact energy =

0.09 kgm)

Source-http://www.extratech.it

Source-http://www.matest.com

TEST PROCEDURE

Source-http://www.scielo.br

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 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-http://www.scielo.br

MECHANICAL PULSE VELOCITY TEST

INTRODUCTION

It is a field test Non destructive test Test consists of impacting a wall with a

hammer blow andMeasuring 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

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

TEST SETUP

Source http://www.extratech.it Source http://www.extratech.it

ACCELEROMETERHAMMERSource http://www.sensorsmag.com

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

hp/tp ratio for indian conditions

QUESTIONS

Source IS 1905 (1987)

SOURCE ASTM C1314 − 16

DIFFERENT CLASSES OF BRICKS

AA CLASS 14 Mpa

A CLASS 10.5Mpa

B CLASS 7.0Mpa

C CLASS 3.5Mpa

DIFFERENT GRADES OF MORTAR

CONSTANT PRESSURE IN HYDRAULIC PUMP