1. 1 About SMA Self-centring connections SMA Belleville washers SMA ring spring systems Tongji-UBC Conference Application of shape memory alloys (SMAs) in seismic engineering Dr Cheng Fang Department of Structural Engineering

2. 2 About SMA Self-centring connections SMA Belleville washers SMA ring spring systems Background NiTi SMA (Nitinol) normally consists of nickel (slightly over 50% by weight) and titanium (slightly under 50% by weight) Shape memory alloys are smart metals featuring either superelastic effect or shape memory effect. Popular applications: bones, reinforcement for veins, dental wires, golf clubs, eyeglass frames…

3. 3 About SMA Self-centring connections SMA Belleville washers SMA ring spring systems Background

4. 4 About SMA Self-centring connections SMA Belleville washers SMA ring spring systems Background SMA vs. Steel SMA vs. Steel: Typical PropertyAustenite NiTiSteel Density6.45 g/cm 3 7.85 g/cm 3 Recoverable Elongationup to 8%0.2% Young’s Modulus30-83 GPa200GPa Yield Strength195-690 MPa250-520 MPa Ultimate tensile strength895-1900 MPa450-830 MPa Elongation at Failure25%20% Corrosion performanceExcellentFair

5. 5 About SMA Self-centring connections SMA Belleville washers SMA ring spring systems Objectives The conventional design strategies for seismic resisting connections normally induce unrecoverable post- earthquake deformations, which could be costly and difficult to repair. To provide test evidence for the feasibility of extended end- plate connections with SMA bolts.

6. 6 About SMA Self-centring connections SMA Belleville washers SMA ring spring systems Test programme Test parameters: bolt diameter & bolt length

7. 7 About SMA Self-centring connections SMA Belleville washers SMA ring spring systems Comparisons: SMA connection Flush end plate connection Shi et al. (2005) Stiffened extended end-plate connection Deformation Test results

8. 8 About SMA Self-centring connections SMA Belleville washers SMA ring spring systems Ductility: Issues Shear capacity:

9. 9 About SMA Self-centring connections SMA Belleville washers SMA ring spring systems Improvements

10. 10 About SMA Self-centring connections SMA Belleville washers SMA ring spring systems Parametric studies

11. 11 About SMA Self-centring connections SMA Belleville washers SMA ring spring systems SMA Belleville washers

12. 12 About SMA Self-centring connections SMA Belleville washers SMA ring spring systems SMA Belleville washers Test results:

13. 13 About SMA Self-centring connections SMA Belleville washers SMA ring spring systems SMA Belleville washers Parametric studies and applications:

14. 14 About SMA Self-centring connections SMA Belleville washers SMA ring spring systems SMA ring springs

15. 15 About SMA Self-centring connections SMA Belleville washers SMA ring spring systems Thanks! Q&A