Seismic performance of steel moment resisting frames utilizing superelastic shape memory alloys Papia Sultana, Maged A. Youssef ⁎ Western University, Civil and Environmental Engineering, London, ON N6A 5B9, Canada abstract article info Article history: Received 11 January 2016 Received in revised form 20 June 2016 Accepted 23 June 2016 Available online xxxx Steel structures dissipate the seismic energy through steel yielding, which results in residual deformations. Al- though conventional earthquake-resisting structural systems provide adequate seismic safety, they experience significant structural damage when exposed to strong ground shaking. Seismic residual drifts complicate the re- pair of damaged structures or render the structure as irreparable. Therefore, systems that can minimize the seis- mic residual deformations are needed. Superelastic shape memory alloys (SMAs) have the ability to undergo large deformations and recover all plastic deformations upon unloading. Their utilization in steel structures can significantly reduce seismic residual deformations, which will facilitate post-seismic retrofitting. Although the literature provides few research data on using SMA in steel beam-column connections, previous research did not address their optimum use. This paper identifies the required locations of SMA connections in a typical steel moment resisting frame to enhance its seismic performance in terms of maximum inter-storey drift, resid- ual deformations, and damage scheme. © 2016 Elsevier Ltd. All rights reserved. Keywords: Steel moment resisting frame Shape memory alloy Inter-storey drift Residual drift Seismic performance Dynamic analysis 1. Introduction Structural steel is widely used in moment resisting frames of mid- and high-rise buildings. Modern code provisions categorize buildings according to their configurations, structural systems, materials and con- struction details [1–3]. A structure is assumed to behave in a ductile manner if it can experience large inelastic deformations without signif- icant degradation in strength. Steel moment resisting frames are one of the popular seismic load resistance systems because of their ductility. During a seismic event, they are expected to experience large inelastic deformations, while maintaining the life safety level for the occupants. Plastic hinges are expected to form in the beams, which may exhibit large yielding deformations leading to localized damage in the floor slabs and columns. Those yielding deformations are not recovered after the seismic event, which results in permanent residual deformations. Researchers are innovating to find design solutions that minimize the seismic residual deformations. Special post-tensioned partially re- strained connections were designed to provide recentering capability after a seismic event [4–6]. Shape memory alloys (SMAs) had also wide- ly attracted the attention of researchers in recent years because of their self-centering capability as well as energy dissipation features. Nickel Titanium (NiTi) SMAs were the most researched [7]. The two fundamental and characteristic properties of SMA are: shape memory effect (SME) and superelasticity (SE). SME is the ability of the material to recover from large mechanically-induced strains via moderate in- crease in its temperature. SE is the ability of the material to support rel- atively high inelastic strains and return to its original shape upon load removal. Ocel et al. [8] tested an external beam-column connection that uti- lized martensite SMA rods. The connection showed high energy dissipa- tion, large ductility and no strength degradation up to 4% drift level. The connection was also able to recover 76% of the experienced drift when the SMA tendons were heated. Ma et al. [9] investigated the behaviour of extended end-plate connections consisting of long shank Nitinol superelastic SMA bolts, continuity plates, beam flange ribs and web stiff- eners using a 3D finite element model. The connections experienced cy- clic elongations of the SMA bolts, however the traditional beam local buckling was avoided. The deformations of the SMA bolts were recover- able upon unloading. Ma et al. [10] conducted a quasi-static test of an extended end-plate connection utilizing long shank SMA bolts. The con- nection exhibited high deformation capacity with maximum inter-sto- rey drift (MID) angle beyond 0.02 rad. Sepúlveda et al. [11] tested a connection that utilized 3 mm-diameter copper-based (CuAlBe) SMA bars. The proposed connection experienced self-centering behaviour, dissipated moderate amount of energy, and showed no strength degra- dation up to 3% drift ratio. Speicher et al. [12] tested four half-scale inte- rior beam-column connections that utilized steel tendons, superelastic NiTi SMA tendons, martensitic NiTi SMA tendon, or combination of superelastic NiTi tendons and aluminum tendons. The superelastic Journal of Constructional Steel Research 125 (2016) 239–251 ⁎ Corresponding author. E-mail addresses: psultana@uwo.ca (P. Sultana), youssef@uwo.ca (M.A. Youssef). http://dx.doi.org/10.1016/j.jcsr.2016.06.019 0143-974X/© 2016 Elsevier Ltd. All rights reserved. Contents lists available at ScienceDirect Journal of Constructional Steel Research