A quite general base connection modeling capable of accurately representing material and geometrical nonlinear behavior of the base plate and arbitrary nonlinear contact with concrete foundation has been demonstrated and its implementation in a finite element nonlinear seismic analysis is presented. A time domain finite element methodology for nonlinear dynamic analysis problem that accounts for base connection lift-off and the inelastic behavior of anchor bolts through an incremental-iterative procedure is developed. A representative problem of cable-stayed bridges tower subjected to strong ground motion is analyzed. The maximum bearing stress on the concrete foundation as well as the tension force per anchor bolt that necessary to design the anchorage system is computed.