This paper deals with the modeling of beam–column connections in reinforced concrete (RC) buildings subjected to various seismic loadings based on a fracture mechanics approach using Python. A numerical approach framed within the fracture mechanics formulation is presented for evaluating crack initiation and propagation (fatigue life) at beam–column joints in a six-story MDOF building frame subjected to lateral cyclic loads. The performance of RC frames is significantly influenced by the response of beam–column joints, which cause partial or complete collapse of buildings during ground motion. High shear stresses are concentrated at beam–column joints; thus the present work deals with the modeling of RC beam–column connections for determining the number of loading cycles required for the nucleation of cracks leading to subsequent failure or fracture of reinforcing bars. The cross-sectional area, geometrical features, material characteristic strengths, stress–strain life parameters, and equivalent lateral forces due to earthquakes are used to determine the number of cycles for an initial crack of 1 mm. The Ramberg–Osgood relationship has been used to determine the true stress–strain curve by providing fatigue test data such as elasticity modulus (E), failure cycles, stress, and strain parameters of the material. The number of loading cycles for crack initiation and fracture is computed for joint members at every floor of the considered six-story MDOF frame building. The critical crack length and the number of cycles after which bars fractures is computed for all six floor beam–column joints with varying diameter steel bars. From the numerical model developed in Python, it was found that the cracks initiated in the joint rebars at 335.39 ≈ 336 cycles at the fifth floor where there are maximum lateral forces and 5030 cycles at the fourth floor. The critical crack length of different bar diameters (8–20 mm) for the 5th were found to be 0.62, 0.97, 1.37, 1.84, 2.35, 2.9, and 3.49 mm.