Deterministic and Probabilistic Forced Response Analysis of a Railway Coach

Dynamic response studies of railway vehicle or any other ground vehicle include free as well as forced vibration analysis. In free vibration analysis of railway coach, the natural frequencies and mode shapes are extracted. Forced vibration analysis consists of harmonic, transient dynamic and random response analyses. The harmonic response of a railway vehicle is a predictable property of a vibratory system caused by a known-frequency dynamic load. Harmonic response analysis predicts persistent dynamic behavior of structures. Random response analysis is a probabilistic dynamic response examination of a moving rail car using random inputs. The harmonic and random response characteristics of an Indian railway ICF carriage are presented in this paper. The harmonic response results indicate that in both unladen and laden conditions of the railway coach, the middle or center portion of the coach is subjected to lower displacements indicating the uniform and balanced distribution of dynamic forces at the middle of the coach due to its proximity to center of gravity of the coach. PSD vertical irregularities as a random function of time are used as base excitation input for rail-way coach response spectrum analysis. PSD response spectrum analysis is carried out on the ICF railway coach model using FEA. Under the random excitations in the form of vertical PSD of acceleration inputs, the response of the coach lies within ISO ride comfort limits for a short duration of four hours. The bounce mode significantly influences the passenger ride.