Browsing by Author "Nunes, Pedro"
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- Influence of the SMA constitutive model on the longitudinal seismic response of RC bridgesPublication . Nunes, Pedro; Lobo, Paulo SilvaSeveral studies indicate that the re-centring capacity presented by superelastic Shape Memory Alloys (SMA) can reduce the displacements of structures subjected to earthquakes. To quantify the errors of numerical predictions with different constitutive models, peak, relative and residual displacements of four two-framed reinforced concrete (RC) bridges, linked by SMA bars, subjected to seismic actions, were numerically assessed. Different ratios of the elastic natural period of vibration of the frames of the bridges were adopted. Lumped plasticity models were used to simulate the behaviour of the reinforced concrete columns. Five SMA uniaxial models were considered, combining linear, nonlinear, isothermal and nonisothermal conditions. The seismic action was modelled by real accelerograms. The results show that the relative displacements are more sensitive to the adopted SMA model than the peak and residual displacements. Significant relative differences, up to 70%, were obtained.
- Influence of the SMA Constitutive Model on the Response of StructuresPublication . Nunes, Pedro; Lobo, Paulo SilvaStrong earthquakes may impose significant displacements in structures, which can result in excessive displacements at structural joints. Previous numerical studies have shown that the recentring capability of shape memory alloys (SMA) can be applied to limit joint openings and maximum longitudinal displacements. However, these studies do not focus on the influence of the SMA constitutive model adopted on the estimated displacements. A sensitivity analysis was performed using simplified two-degree-of-freedom models, which represent two-frame reinforced concrete bridges with various ratios of natural periods of vibration, connected by SMA bars. These models were implemented in a MATLAB based program for nonlinear dynamic analysis. The obtained results show that the relative displacements are more sensitive to the SMA model than the absolute displacements.