Modeling shape memory alloys with applications to seismic design of structural systems
Mishra, Shashi Kant
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Two distinct specimen-based macroscopic constitutive models of shape memory alloys were considered in this thesis for unidirectional cyclic loading. The first one was adapted from an existing grain-based microscopic model and comparison with major specimen-based macroscopic models was discussed, under a unifying approach based on the driving energy and required transformation energy pair. However, temperature changes and strain rates were not considered. In the second approach a new state-space shape memory alloy model was proposed. Though temperature changes again were not considered, for this approach, however in this latter case, an incremental formulation was employed. Stress-strain relationships were simulated for some representative strain cycles using both models. Due to the greater limitations with the first approach, the second incremental approach model was further used for the analysis of a 3-story building using SMA dampers with a state-space transient dynamic analysis code. Numerical results showed that the proposed simple model behaved accurately enough to be applied for smart structural design. The same model was further used for the evolutionary design of the same 3-story building for a more robust design.