Experimental study on flexural behaviour of rubber composite RCC beam

ABSTRACT

This paper attempts to compare the Experimental results such as Ultimate Load, Maximum Bending moment and flexural strength of PVC (Polyvinyl chloride) Rubber Composite RCC beams as both single and double layered with Conventional RCC beam to the results of Finite Element analysis in Abaqus CAE software. The Rubber-mat was used in RCC beam to resists some plastic deformation and increase the load carrying capacity of beam by reducing the Plastic Strain in tension zone area where the flexural crack appears and increasing the Flexural Strength of Structural Beam.

Keywords: Abaqus CAE; PVC Rubber-mat; Composite beams

1. INTRODUCTION

Composite materials were made from two or more constituent materials with significantly different physical or chemical properties. The goal of using composite materials is to achieve a combination of desirable characteristics such as strength, stiffness, low weight, corrosion resistance, and durability. Types of composite materials include Fiber Reinforced Composites, Particulate Composites, Structural Composites, Laminar Composites.

The tensile strength of PVC rubber mats is influenced by the reinforcing fibers or materials within the rubber component. Tensile strength is the ability of the material to resist being pulled apart. The inclusion of reinforcing elements, such as fabric or fibers, enhances the overall strength of the mat. PVC rubber mats were designed to withstand compressive forces without significant deformation.

PVC rubber mats were designed to bear loads, and their load-bearing capacity depends on factors such as thickness, material composition, and overall design. This is important for ensuring the mats can support the intended use and weight requirements.

1.1. Objective

To compare the Experimental results such as Ultimate Load, Maximum Bending moment and flexural strength of Rubber Composite RCC beams as both single and double layered with Conventional RCC beam with results of Finite Element analysis in Abaqus CAE software.

2. MATERIAL PROPERTIES

2.1. Concrete

Property values were taken from tested design mix concrete

Density : 2.4 × 10⁻⁹ N/mm³

Youngs Modulus : 22360 MPa

Yield stress : 20 MPa

Poison Ratio : 0.2

Fe415 TMT Steel bars: [¹]

Density : 7.6 × 10⁻⁵ N/mm³

Youngs Modulus : 200000 MPa

Yield stress : 500 MPa

Poison Ratio : 0.3

PVC Rubber Mat:

Property values were obtained from the Oxford Reference shown in Figure 1

Figure 1
Book of mechanical Engineering.

“A Dictionary of Mechanical Engineering (2. ed)” by Author Marcel

Escudier and Tony Atkins [²]

Some referred citations for mechanical properties of Rubber and its behaviors: [³,⁴,⁵,⁶,⁷,⁸,⁹,¹⁰,¹¹].

Density : 1.419 × 10⁻⁹ N/mm³

Youngs Modulus : 3.7 GPa

Yield stress : 47 MPa

Poison Ratio : 0.4

Thickness : 15 mm Figure 2

Figure 2
Rubber mat.

2.2. Dimensions of RCC beam

Breath : 200 mm

Depth : 200 mm

Length : 1000 mm

Effective length : 800 mm (distance between supports)

Reinforcement details:

Main bar : 4 numbers of 10 mm diameter bars were provided with 150 mm spacings

Stirrups : 7 numbers of 8 mm diameter bars were provided with 153 mm spacings

The cross-sectional and longitudinal view of designed beam is inserted below as an image with reinforcement and dimensional details Figure 3.

Figure 3
Sectional view of casted doubly reinforced beam.

3. DESIGN OF SINGLE LAYERED RUBBER COMPOSITE RCC BEAM IN ABAQUS

In the phase of designing and analyzing the single layered rubber composite RCC beam in ABAQUS software different trails had conducted with various placements of rubber. And the various placements of rubber mat as single layer in RCC beam were added as an image in the following Figure 4, Figure 5, Figure 6, Figure 7.

Figure 4
Rubber mat placed 30 mm from bottom of beam.

Figure 5
Rubber mat placed 45 mm from bottom of beam.

Figure 6
Rubber mat placed 75 mm from bottom of beam.

Figure 7
Rubber mat placed 105 mm from bottom of beam.

Trial 1: Rubber mat placed 30 mm from bottom of beam

Trial 2: Rubber mat placed 45 mm from bottom of beam

Trial 3: Rubber mat placed 75 mm from bottom of beam

Trial 4: Rubber mat placed 105 mm from bottom of beam

4. DESIGN OF DOUBLE LAYERED RUBBER COMPOSITE RCC BEAM IN ABAQUS

In the phase of designing and analyzing the double layered rubber composite RCC beam in ABAQUS software different trails had conducted with various placements of rubber. And the various placements of rubber mat as double layer in RCC beam were added as an image in the following Figure 8, Figure 9, Figure 10, Figure 11.

Figure 8
Rubber mat placed 30 mm and 60 mm from bottom of beam.

Figure 9
Rubber mat placed 60mm and 90mm from bottom of beam.

Figure 10
Rubber mat placed 30 mm and 100 mm from bottom of beam.

Figure 11
Rubber mat placed 80 mm and 105 mm from bottom of beam.

Trial 5: Rubber mat placed 30 mm and 60 mm from bottom of beam

Trial 6: Rubber mat placed 60 mm and 90 mm from bottom of beam

Trial 7: Rubber mat placed 30 mm and 100 mm from bottom of beam

Trial 8: Rubber mat placed 80 mm and 105 mm from bottom of beam

5. COMPARISON OF CONVENTIONAL AND RUBBER COMPOSITE TRIALS RESULTS FROM FEA

6. SELECTED POSITIONS OF RUBBER-MAT IN RCC BEAMS

From the above results shown in Table 1 and Table 2, Two trial specimens were selected for experimental study which gives good results among all of the trials had analyzed in Abaqus software.

Table 1
Load vs Deflection Graph for comparison of FEA and Experimental results.

POSITION OF RUBBER MAT	MAX. LOAD (kN)	MAX. BENDING MOMENT(kN-m)	FLEXURAL STRENGTH (MPa)	PLASTIC STRAIN
Without Mat	114.29	30.47	11.43	0.177
30 mm from Bottom	115.42	29.98	11.54	0.168
45 mm from bottom	116.23	30.99	11.62	0.159
75 mm from bottom	115.42	29.98	11.54	0.168
105 mm from bottom	116.10	30.11	11.61	0.161

Table 2
Comparison of conventional and double layered rubber composite beam.

POSITION OF Rubber Mat	Max. Load (kN)	Max. Bending Moment (kN-m)	Flexural Strength (MPa)	Plastic Strain
Without Mat	114.29	30.47	11.43	0.177
30 and 60mm from Bottom	116.39	30.81	11.64	0.155
60 and 90mm from bottom	117.72	31.24	11.77	0.145
30 and 100mm from bottom	117.39	31.12	11.73	0.140
80 and105mm from bottom	116.39	30.81	11.64	0.155

Specimens which gave Comparatively good results in ultimate load, maximum bending moment, flexural strength and also decreased plastic strain have chosen for experimental study.

From both single and double layered rubber composite beam trials each one specimen was chose.

Those specimens were 45mm from bottom of beam from single-layered rubber composite beam Figure 5 and 60,90 mm from bottom of beam from double-layered rubber composite beam. [¹²]

And the casting process of RCC beam with Rubber-mat placings were added as an image in following Figure 12.

Figure 12
Casting of RCC beam with rubber.

7. EXPERIMENTAL SET-UP FOR 2 - POINT FLEXURAL TESTING OF SPECIMENS

Loading Frame Machine: A 1000-ton capacity loading frame machine with hydraulic actuators used for applying the load.

Support Conditions: The beam placed horizontally on two simply-supports (Rollert at one end and hinged at other end) spaced at 800 mm apart, allowing for two-point loading was shown in Figure 13. [¹³–¹⁴]

Figure 13
Experimental set-up.

Displacement Measurement: Linear variable displacement transducers (LVDTs) were installed at mid-span to measure deflections.

Load Application: Hydraulic jacks connected to load cells used to apply loads gradually and uniformly to the beam.

$${\text{Flexural strength formula has calculated using PL/BD}}^{\text{2}}$$

$$\text{Maximum bending moment}=\text{PA}$$

Were,

P-Applied load

L-Effective span length of beam (800 mm)

B- Breadth of the beam (200 mm)

D- Depth of the beam (200 mm)

A- L/3 = 266.66 mm

8. TESTED SPECIMENS CRACK COMPARISON OF EXPERIMENTAL AND FEA RESULTS OF CONVENTIONAL RCC BEAM

9. COMPARISON OF EXPERIMENTAL AND FEA RESULTS OF SINGLE-LAYERED RUBBER COMPOSITE RCC BEAM (45mm- From Bottom)

10. COMPARISON OF EXPERIMENTAL AND FEA RESULTS OF DOUBLE-LAYERED RUBBER COMPOSITE RCC BEAM (60 and 90mm- From Bottom)

11. RESULTS AND DISCUSSION

11.1. Maximum bending moment of beam (as per flexural test set-up Figure 13)

R_a + R_b = 2P

R_a(0) – P(a) – P(L−2a+a) + R_b(L) = 0

− Pa –PL + Pa + R_b(L) = 0

R_b = P R_a = P

M_max = R_a (L/2) – P(L/2 – a)

M_max = P(L/2) – p(L/2) + Pa

$${\mathbf{\text{M}}}_{\mathbf{\text{max}}}=\mathbf{\text{Pa}}$$

Were,

R_a and R_b – Support reactions

P – Applied load

L – Effective length of beam (800 mm)

a – Distance from support to the nearest load apply point (266.66 mm)

11.2. Flexural strength of beam

$$\text{Flexural strength of beam}=\mathbf{P}\mathbf{L}\text{/}\mathbf{b}{\mathbf{d}}^{\mathbf{2}}$$

Were,

b – Breadth of the beam (200 mm)

d – Depth of the beam (200 mm)

P – Applied load

L – Effective length of beam (800 mm)

By using equations Equation 1 and Equation 2 the maximum bending moment and flexural strength of the beams calculated and mentioned in.

In the comparison of FEA results Figure 14 from Ultimate Load, Maximum bending moment and Flexural strength of beam of Single-layer rubber composite beam, Figure 15, Figure 16, Figure 17 had increased by 1.65% from Conventional RCC beam Table 3, Table 4. And for Double-layer rubber composite beam increased by 3.00% from Conventional RCC beam.

Figure 14
Comparison of Deformation picture from ABAQUS and Experimental for conventional beam.

Figure 15
Load vs Deflection Graph for comparison of FEA and Experimental results for conventional beam.

Figure 16
Comparison of Deformation picture from ABAQUS and Experimental for single layered beam.

Figure 17
Load vs Deflection Graph for comparison of FEA and Experimental results for single layer beam.

Table 3
Results of conventional beam.

RESULTS	FEA RESULTS	EXPERIMENTAL RESULTS
Ultimate Load (kN)	114.29	108.8
Maximum Bending Moment (kN-m)	30.47	29.00
Flexural strength (MPa)	11.43	10.88

Table 4
Results of single layer rubber composite beam.

RESULTS	FEA RESULTS	EXPERIMENTAL RESULTS
Ultimate Load (kN)	116.23	115.8
Maximum Bending Moment (kN-m)	30.99	30.88
Flexural strength (MPa)	11.62	11.58

In the comparison Experimental results from Table 5, Table 6, Table 7 Ultimate Load, Maximum bending moment and Flexural strength of beam of double-layer rubber composite beam had increased by 6.43% from Conventional RCC beam. And for Double-layer rubber composite beam increased by 12.70% from Conventional RCC beam.

Table 5
Results of double layer rubber composite beam.

RESULTS	FEA RESULTS	EXPERIMENTAL RESULTS
Ultimate Load (kN)	117.72	122.7
Maximum Bending Moment (kN-m)	31.24	32.72
Flexural strength (MPa)	11.76	12.27

Table 6
Comparison of conventional and rubber composite beam results from ABAQUS.

POSITION OF RUBBER MAT	MAX. LOAD (kN) (P)	MAX. BENDING MOMENT(KN-m) (Pa)	FLEXURAL STRENGTH (MPa) (PL/bd2)
Without Mat	114.29	30.47	11.43
45mm from bottom	116.23	30.99	11.62
60 and 90mm from bottom	117.72	31.24	11.76

Table 7
Comparison of conventional and rubber composite beam results from experiment.

POSITION OF RUBBER MAT	MAX. LOAD (kN) (P)	MAX. BENDING MOMENT(kN-m) (Pa)	FLEXURAL STRENGTH (MPa) (PL/bd2)
Without Mat	108.80	29.00	10.88
45mm from bottom	115.80	30.88	11.58
60 and 90mm from bottom	112.70	32.72	12.27

12. CONCLUSION

From the observation of results in both FEA and Experimental, Deformation and Crack formation Rubber mat which placed inside the RCC beam as a composite element causes Shear crack by observing Figure 18, Figure 19 Double layered Rubber mat reduced the depth of Flexural crack on beam. At the same time increased the flexural capacity of beam.

Figure 18
Comparison of Deformation picture from ABAQUS and Experimental for double layered beam.

Figure 19
Load vs Deflection Graph for comparison of FEA and Experimental results for double layered beam.

Due to the small diameter hole in rubber-mat the composition of coarse aggregate in concrete and rubber mat is weak and it causes comparatively large shear-crack width in beam. This problem can be resolve by using large diameter holes in rubber-mats which can provide more space for coarse aggregate in concrete to fill and bind with the rubber-mat.

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Publication Dates

• Publication in this collection
  09 Dec 2024
• Date of issue
  2024

History

• Received
  29 July 2024
• Accepted
  03 Oct 2024