TORSIONAL RESPONSE OF FIXED BASE CONNECTION UNDER COMBINED CYCLIC BENDING- TORSIONAL LOADING

There is a lack of study concerning the torsional effect on the torsional response of column base especially cyclic behavior under combined torsional-flexural loading; many unknowns exist on this topic. A study for the torsional performance of the base connection for C-bent column subjected to seismic in the traffic direction is necessary to address the effect of the complex combination of cyclic flexural-torsional action on such a type of connection; for this purpose an extensive numerical parametric study was conducted to evaluate the torsional performance of the fixed base connection of C-bent bridge pier against combined cyclic bending and torsional loading following SAC phase II protocol. After verifying results with previous experimental works a Finite Element Analysis (FEA) using Strand7 is performed for Finite Element Models (FEM) which simulates force transfer at major contact interfaces in the connection, and a total of six base plate connection sub-assemblages with variable base plate thicknesses (three for stiffened connection and three for un-stiffened connection) anchored by 10 bolts, were configured and analyzed to support double cantilever pier subjected to eleven loading schemes that reflect different pairs of gravity moment and axial loads along with cyclic loading in the traffic direction eccentric from pier center of rigidity to guarantee the application of combined flexural-torsional action on the base connection. The study provided a curves for the following performance terms; strength (ultimate torsion), deformation (ultimate twisting angle), and stiffness (torsional stiffness); the seismic torsional performance of the base connection under the previously mentioned loading package was evaluated by plotting the variation of the mentioned terms against the parametric values of the base plate thickness for different loading condition considered in the analysis.