Numerical assessment of fatigue life of concrete frame using PZT sensors

Progressive damage to any structure causing the decrement in material strength when subjected to alternate cyclic loading condition is termed as fatigue. The present work deals with numerically assessing the life of concrete frame under the influence of flexural fatigue load using ANSYS Mechanical computer program. Stress life analysis is considered for analyzing the life and fracture parameters of two broadly classified 3-D solid models (1) without edge notch, and (2) with edge notch at critical locations for the given loads in concrete frame. Further the notch opening width to depth ratio (a/d) has been varied to understand the effect of crack propagation onto the fatigue life and stress intensities build up in the concrete models. Six PZT-5H sensor patches were modelled on the frame surface with glue interface at different symmetrical locations. The PZT output in form of admittance signatures is gathered and analysed for different damaged states to develop a mathematical model that relates these variation with respect to stiffness loss of the concrete frame. Further the results revealed the degrading trend of fatigue life and growth of alternating stresses with increase in magnitude of applied cyclic loads and flexural stiffness losses. Plots for variation of maximum directional deformation and equivalent von-mises stress set up in the model are devised relative to applied sinusoidal cyclic accelerations and are discussed briefly along with describing the advantages of using PZT transducers for structural health monitoring applications in concrete framed structures under the action of low-strain loads causing high cycle fatigue.