PSI - Issue 70

Saravanakumar P. et al. / Procedia Structural Integrity 70 (2025) 533–539

537

(N/mm 2 )

(kN)

(kN)

(N/mm 2 )

Control beam

128 121 125

4.26 4.03 4.16 2.5

42 35 38 40

1.4 1.16 1.26 1.33

Single-Legged stirrup Inclined stirrup beam Alternate X stirrup beam

75

From the experimental study the first cracking load and the Ultimate load was identified and the corresponding stress values were calculated and reported in Table 3. While stirrups mainly influence shear capacity, their configuration can indirectly affect flexural behavior, particularly by influencing crack control, deflection behavior, and load redistribution. Inclined and Single-Legged Stirrups offer good flexural performance while using less reinforcement. Their ability to delay and control cracking contributes to better load distribution and enhanced flexural performance under ultimate loads. The Alternate X stirrup beam went through a shear failure at quite lesser load of 75kN and this may be due to the space between the two lateral stirrup reinforcement exceeded the nominal stirrup spacing length 130mm. From the above experimental results it was conclude that, the inclined stirrup beam presents the best balance between reinforcement efficiency and shear performance, closely matching the control beam in both cracking and ultimate behavior. The alternate X stirrup, despite a favorable cracking stress, falls short in ultimate strength, indicating a need for design refinement. The single-legged stirrup beam provides moderate performance with reduced reinforcement, making it a viable option when optimizing for cost and weight. Inclined stirrups (placed at 45°) are aligned more directly with the direction of diagonal tension (shear forces), which helps in resisting shear more efficiently. As a result, the inclined stirrup beam generally exhibits less deflection under load compared to conventional vertical stirrups, particularly after the onset of cracking. The single-legged stirrups are less aligned with the principal shear stress direction, so they provide less restraint against diagonal cracking and the beam tends to show higher deflection under the same load.

Fig.3. LoadvsDeflectiongraph

7. Crack Study Crack study was conducted to find the pattern of crack formation. In beforehand preparation grid lines were drawn at an interval of 5cm interval both horizontally and vertically. At the initial stages of loading, hairline flexural cracks were observed forming between the two loading points across all beam types. With further increase in load, these flexural cracks propagated vertically upward toward the compression zone of the beam. As the load continued to increase, diagonal shear cracks began to appear near the support regions , indicating the onset of shear stress effects. By