Probabilistic Fragility Analysis of Smart Steel Moment-Resisting Frame Structure Subjected to Intentional Blast Loading

Abstract

The fragility functions are obtained for steel Moment Resisting Frame structures (MRFs) equipped with Nickle Titanium Shape Memory Alloy (NiTi SMA), named smart MRFs. Following the key design procedures proposed by the authors’ previous studies, [15–17], the smart MRFs are designed to serve as a blast protective smart structure. The fragility function genuinely considers the local and global stability of the smart structure. The global stability of the structure is determined by Inter-Story Drift Ratio (ISDR) performance function. On the other hand, the local stability of the columns and smart connections are checked by the global buckling of the columns and the connection rotation, respectively. To capture the global nonlinear performance of the structure under investigation, a simplified beam-element numerical model is developed in OpenSees. The behavior of the beam-to-column connections is represented by rotational spring elements with special characteristics. The characteristics of this spring element are calibrated against the results of a detailed solid-element numerical model. Blast reflected overpressure is applied through programmed and slightly modified simplified Kingery Belmush polynomial equations. The probabilistic auto-framework is formulated using Monte Carlo Latin Hypercube Sampling Strategy simulation (MC-LHS) to perform probabilistic fragility analysis. The extent of propagation of uncertain random variables is parametrized on charge weight, dead load, live load, geometrical properties, and material properties. OpenSees platform is used to simulate transient dynamic analysis of 4, 7, 10, and 15 story level smart MRF, which are used as case studies to develop the fragility function. The results confirm the efficiency of the proposed key design rules and developed numerical methodology. Finally, the sensitivity of the fragility function on global and local performance functions is presented.