Monotonic Pushover analysis of Externally Reinforced Welded I-column to foundation Connection

Abstract

This study presents an improved understanding of the stress distribution in the joint region of weak-axis connections in steel MRFs, and based on this understanding, connection configurations have been proposed for the column-to-foundation connections Columns in MRFs are subjected to lateral forces along their strong and weak axes. To ensure ductile response, analysis, and requisite provisions of column foundation connections along the strong axis have been dealt with in detail. In this study, preliminary inelastic finite element analyses are conducted to study the flow of forces near the weak axis column-to-foundation connection. Theoretical axial load P in the column that produces the worst V-M (shear-moment) loading is identified. Based on these loads a cover plated and ribbed configuration is proposed for the weak- axis column-base (WACB) connection. Nonlinear finite element analyses are performed under monotonic, and FEMA recommended multi-cycle loadings using ABAQUS software to evaluate the performance of the proposed connection configurations and the associated design procedures. The performance of the new weak-axis connections (WACs) is compared with that of the existing connections in terms of von Mises stress, shear stress, normal stress, load deformation response, energy dissipated, and cumulative plastic strain excursion. It was observed that WACB connections in steel MRFs need to be reinforced to keep the stress in CJP welds connecting the column to the base plate below the yield stress even at the lateral drift levels much lower than those expected of about 4–6% lateral drifts. The proposed configuration results in increased moment of inertia of the column about the weak axis and hence enhances the seismic response.