Upload
voxuyen
View
278
Download
19
Embed Size (px)
Citation preview
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