Limit state behavior and response sensitivity analysis of endplate steel connections with shape memory alloy bolts

Abstract

Shape memory alloys have been used in developing self-centering steel moment connections. This article presents a numerical study aiming at evaluating the cyclic response sensitivity and limit states of extended endplate steel connections with shape memory alloy bolts. Three-dimensional finite element models are developed and validated against a recent experimental study. Using a statistical design-of-experiment method, the effects of 21 design factors and their interactions on the cyclic response of shape memory alloy connections are assessed. The sensitivity of six response parameters is studied. In addition, four limit states for shape memory alloy connections are discussed, including beam local buckling, bolt excessive axial strain, endplate yielding, and column flange yielding. Results show that endplate thickness, shape memory alloy bolt diameter, beam web slenderness ratio, and shape memory alloy maximum transformation strain are the most influential factors. Furthermore, endplate yielding is found to be the governing limit state in almost 80% of the analyzed connections, whereas shape memory alloy bolt excessive strain and column flange yielding are observed in less than 20% and 5% of the connections, respectively. Beam local buckling is not governing in the analyzed shape memory alloy connections designed as per the AISC 358-16 and AISC 341-16 seismic design requirements for extended endplate connections and highly ductile members.

Performance‐based optimum seismic design of self‐centering steel moment frames with SMA‐based connections

“…The supports of the first story columns in conventional and SC‐MRFs are considered fixed. The effect of panel zones is not explicitly considered in the numerical modeling 3,8 . According to the results of a statistical sensitivity analysis, 8 the panel zone effect on the hysteretic response of the endplate connections with SMA bolts is insignificant.…”

“…As shown in Figure 4, these response parameters include rotation and moment at point B (i.e., θ B, and M B ) when the SMA enters a forward transformation phase, point C (i.e., θ C, and M C ), when the outermost SMA bolts reach their fracture strain, and point E (i.e., θ E, and M E ), when the second‐row SMA bolts fracture, as well as a β factor that characterizes the self‐centering response. Ten parameters that are known to influence the nonlinear behavior of the SMA connections serve as inputs 8 . These factors include the martensite start stress, $${\sigma }_{Ms}$$, martensite finish stress, $${\sigma }_{Mf}$$, austenite start stress, $${\sigma }_{As}$$, austenite finish stress, $${\sigma }_{Af}$$, maximum transformation strain, $${\varepsilon }_L$$, SMA bolt pretension strain ratio, $${\varepsilon }_{pt}$$, SMA bolt length, L bolt , SMA bolt diameter, D bolt , beam depth, H beam , and beam length, L beam .…”

“…Past experimental studies (e.g., 6,7 ) have demonstrated the excellent self‐centering capability of SMA endplate connections. Parametric sensitivity analyses have also been used to determine the most influential design factors in endplate connections with SMA bolts 8 . Surrogate models have also been proposed for predicting the response of these self‐centering connections 9 .…”

“…Parametric sensitivity analyses have also been used to determine the most influential design factors in endplate connections with SMA bolts. 8 Surrogate models have also been proposed for predicting the response of these self-centering connections. 9 Other types of SMA-based connections, such as those with SMA plates, 10 can be found in the literature.…”

Artificial Neural Network–Based Predictive Tool for Modeling of Self-Centering Endplate Connections with SMA Bolts

“…Finally, the accuracy of the developed predictive modeling and optimization results is confirmed. were selected to idealize the backbone and self-centering response of endplate connections with SMA bolts on the basis of experimental (e.g., Fang et al 2013) andFE analysis results (e.g., Mohammadi Nia andMoradi 2020). To create a response curve for the connections, SMA materials were assumed to fracture upon reaching strain ε fr (Mohammadi Nia and Moradi 2021;Sabouri Ghannad et al 2021):…”