| Sumario: | Abstract: This study is concerned with the computational modeling of energy absorption (fatigue) capacity of reinforced concrete bridge columns by using a cyclic dynamic Fiber Element computational model. The results are used with a smooth hysteretic rule to generate seismic energy demand. By comparing the ratio of energy demand to capacity, inferences of column damageability or fatigue resistance are made. The complete analysis methodology for bridge columns is developed starting from basic principles. The hysteretic behavior of steel reinforcement is dealt with in detailed: stability, degradation and consistency of cyclic behavior is explained. An energy based universally applicable low cycle fatigue model for steel is proposed. A hysteretic model for confined and unconfined concrete subjected to both tension or compression cyclic loading is developed, which is also capable of simulating gradual crack closure. A Cyclic Inelastic Strut-Tie (CIST) model is developed, in which the comprehensive concrete model proved to be suitable. The CIST model is capable of assessing inelastic shear deformations with high accuracy, within the context of a Fiber Element (FE) program. A parabolic fiber element with parabolic stress function element for uniaxial flexure developed, as well as a rectangular fiber element with a quadratic interpolation function suitable for biaxial flexure. A smooth rule-based macro model for the simulation of the hysteretic behavior of reinforced concrete elements is developed. The model is capable of accurately simulating cyclic behavior when compared with actual experimental data, through use of an automated system identification procedure which proved to be very effective in finding the model parameters to best approximate member behavior. The macro model was calibrated to simulate the behavior of a full size bridge pier and then implemented into a SDOF non-linear dynamic analysis program to generate inelastic response spectra. In addition to the usual ductility-based inelastic spectra, several additional energy spectra are also generated which include: viscous damping, hysteretic energy, cyclic (fatigue) demand. These spectra are used as part of a rational methodology in which the cyclic demand on bridge columns is compared with the capacity predicted by Fiber-Element analysis.
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