PSI - Issue 70

Blessy Grant C J et al. / Procedia Structural Integrity 70 (2025) 247–254

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4. Experimental results and discussion A G+4 frame with pinned support was modelled in STAAD.Pro software, considering the dead load, including the self-weight of the structure, and a floor finish load of 1 kN/m². A live load of 4 kN/m² was applied, in accordance with relevant building standards. The seismic load was defined based on the provisions of IS 1893:2016, ensuring compliance with the seismic design requirements. After performing the analysis, the shear force distribution and bending moment distribution. 4.1 Hysteresis loop The load deflection variation of beams LRC 45, LRC 60 and RC 90 tested under reverse cyclic load are shown as hysteresis response curve in Fig. 5.

LRC 45 C1 LRC 45 C2 LRC 45 C3 LRC 45 C4 LRC 60 C1 LRC 60 C2 LRC 60 C3 LRC 60 C4 RC 90 C1 RC 90 C2 RC 90 C3 RC 90 C4

-80 -70 -60 -50 -40 -30 -20 -10 0 10 20 30 40 50 60 70 80 90 100

-26 -24 -22 -20 -18 -16 -14 -12 -10 -8 -6 -4 -2 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 Load (kN)

Displacement (mm)

Fig. 5. Hysteresis response curve of the specimens

The load applied and its displacement are varying in the directions of push and pull because of the Bauchinger effect in steel reinforcement. The Bauchinger effect can manifest during reverse cyclic loading in beam due to the material’s history-dependent behavior. Specifically, if the material has undergone prior plastic deformation during previous loading cycles, its mechanical properties, including strength and ductility, may be altered. This altered state can affect the materials response during subsequent loading cycles, leading to changes in the hysteretic loop. All the beams displayed nearly similar behavior, except for differences in the initial crack load and the maximum load capacity. The load-deflection response of all the specimens exhibited linear behavior initially, up to the point where concrete cracking occurred. Post cracking, it is found that secant stiffness is indirectly proportional to the deflection. i.e., slope of the hysteresis curved degrades as the deflection is increased. Notably, none of the beams showed any pinching in their hysteresis loops. The maximum load carrying capacities of LRC 45, LRC 60 and RC 90 are 90 kN, 62.5 kN and 75 kN respectively. The corresponding displacements are 25.8mm, 12mm and 14.85 mm respectively.