Behaviour of concrete beam without shear reinforcement.
Objective:
To study the behavior of reinforced concrete beam without shear reinforcement in flexure.
Materials required before starting the experiment:
1. RC beam of the shown cross section, casted at least 28 days before the experiment.
2. fck of the concrete mix used.
3. Load cell
4. Hydraulic Jack
Specimen type:
Concrete Beam
STEP
1
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PLACEMENT OF BEAM:
Choose the simply supported beam setup to be used in the experiment.
CLICK ON THE CORRECT IMAGE TO MOVE FORWARD
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STEP
2
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EXPERIMENTAL SETUP:
Choose the four point loading setup to be used in the experiment.
CLICK ON THE CORRECT IMAGE TO MOVE FORWARD
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Specimen Preparation
Make RC beam with given geometric and material properties.
Concrete cubes for compressive strength test – 3 nos.
Steel reinforcement, same as used in beam specimen for tensile strength test.
Steel reinforcement, same as used in beam specimen for tensile strength test.
| L' | 2000 |
| L | 1800 mm |
| LAA | 600 mm |
| b | 150 mm |
| D | 200 mm |
| Cover | 25 mm (to shear reinforcement) |
| Ast | 2-12φ |
| Steel Grade | Fe500 |
| Concrete Grade | M25 |
STEP
1
Test three cube specimens in compression testing machine and determine the average value
of compressive strength.
of compressive strength.
| Specimen | Compressive strength(MPa) |
| 1 | 35.11 |
| 2 | 34.44 |
| 3 | 30.88 |
| Average Cube Strength (fcm) | 33.50 |
STEP
2
Perform tensile strength test on the reinforcement and determine the average value of the yield strength
| Specimen | Yield strength (MPa) |
| 1 | 532 |
| 2 | 518 |
| 3 | 522 |
| Average Yield Strength (fym) | 524 |
STEP
3
Attach the loading arrangment and load cell to the specimen.
STEP
4
MEASURING DIMENSIONS OF THE BEAM Click on the measuring tape to measure the length of the beam.
Total Length(L)
MEASURING DIMENSIONS OF THE BEAM Click on the measuring tape to measure the length of the beam.
Total Length(L)
2012 mm
STEP
4
MEASURING DIMENSIONS OF BEAM Click on the measuring tape to measure width of the beam.
2012 mm
Total Breadth(b)
MEASURING DIMENSIONS OF BEAM Click on the measuring tape to measure width of the beam.
2012 mm
Total Breadth(b)
150 mm
STEP
4
MEASURING DIMENSIONS OF BEAM Click on the measuring tape to measure the depth of the beam.
2012 mm
150 mm
Total Depth(D)
MEASURING DIMENSIONS OF BEAM Click on the measuring tape to measure the depth of the beam.
2012 mm
150 mm
Total Depth(D)
205 mm
STEP
5
Click on the measuring tape to measure the distance between the supports and the points of application of load.
Measure the distance between support 1 and 2 when the measuring tape is placed as shown.
Measure the distance between support 2 and 3 when the measuring tape is placed as shown.
Measure the distance between support 3 and 4 when the measuring tape is placed as shown.
Measure the distance between support 1 and 2 when the measuring tape is placed as shown.
2012 mm
150 mm
205 mm
1800 mm
603 mm
598 mm
599 mm
A
B
C
D
Length between the supports
AB
BC
CD
A
B
C
D
Length between the supports
1800 mm
Length between Support and point of application of loadAB
603 mm
Length between Support and point of application of loadBC
598 mm
Length between Support and point of application of loadCD
599 mm
STEP
6
Apply the load using the hydraulic system uptill failure.
STEP
6
The following types of cracks are observed.
Flexure Crack
Shear Crack
Flexure Crack
Shear Crack
STEP
7
Load at failure
Record the load (from load cell) and mark the shear and flexure cracks.
Record the load (from load cell) and mark the shear and flexure cracks.
STEP
8
1. Start increasing the load after marking the cracks.
2. After marking once keep increasing the load till failure or the time when beam fails and shear crack appears as shown in next slide.
3. Note down the failure load as P
(kN) = 6.3 T
2. After marking once keep increasing the load till failure or the time when beam fails and shear crack appears as shown in next slide.
3. Note down the failure load as P
(kN) = 6.3 T
Observation
Left Cracks
Right Cracks
Select the observed failure crack.
Click any one image:
✗ ✔
Left Cracks
Right Cracks
Observation
1. Mark the shear crack as shown below (at approximately 45 degrees)
2. Measure the distance La and Lb as shown below to determine the location of the shear crack.
La
Lb
La =
Lb =
2. Measure the distance La and Lb as shown below to determine the location of the shear crack.
La
Lb
La =
460 mm
Lb =
640 mm
Observation
| Grade of concrete(fck) | = M25(GIVEN) |
| Grade of steel(fy) | = Fe500 |
| Area of tension steel(Ast) | = 339.29200 mm2 |
| Length of Beam Between Supports | = 1800 mm |
| Depth of Beam(D) | = 200 mm |
| Width of Beam(b) | = 150 mm |
| Effective depth of beam (d) | = 169 mm |
| Location of the crack (La) | = 460 mm |
| Location of the crack (Lb) | = 640 mm |
Calculation
| Density of reinforced concrete = ρconc = 2400 kg/m3 | |
| Shear force applied at failure (including self weigth) = | |
| Weigth of the approximate section considered to estimate the applied shear force at the location of the crack = W | |
$$ W = \left(\frac{{La + Lb}}{2}\right) \times b \times \text{Dρconc} $$ |
|
| Experimental shear force at failure (Vobs)= 59.606 kN | |
| Percentage tension reinforcement : 100Ast/bd = 1.33843 | |
| fck = 25 | |
| Shear force at failure as per IS:456-2000 = 18.10355 kN | |
| Factor of safety is defined as the ratio of | |
| Vobs and Vpred FOS = Vobs/Vpred | |
Result
The Factor of Safety for the experiment is = 3.2931
The load at failure is = 59.606 kN
The Predicted value of the beam section is =18.10355 kN Failure Load(kN)(obs)
The load at failure is = 59.606 kN
The Predicted value of the beam section is =18.10355 kN Failure Load(kN)(obs)
59.606 kN
Failure Load(kN)(Theo.)
18.1035 kN
FoS
3.2931
6.3 T
Report
- Grade of concrete = M25
- Mean cube strength of concrete = 33.5 MPa
- Grade of reinforcement = Fe500
- Mean yield strength of steel (MPa) = 524 MPa
- Estimated ultimate moment of resistance as per IS:456 (2000) = 18.32 kN-m
- Observed ultimate moment of resistance = 19.35 kN-m