In longitudinal multi-mode pushover analysis of bridges with elevated pile foundation systems, the inelastic contributions of the second mode cannot be neglected. Generalized pushover analysis cannot be applied directly in this condition. A modified generalized pushover procedure is developed for estimating seismic demands of bridges with elevated pile foundation systems. Modified generalized pushover procedure, modal pushover analysis and incremental dynamic analysis of a bridge with elevated pile foundation systems are conducted. The results show that the modified generalized pushover procedure can provide reasonable estimations of moments and predict more accurate plastic hinge rotations compared with modal pushover analysis. KeywordsPushover analysis; Modified GPA; bridges with elevated pile foundation system; Contributions of higher modes; MPA.Modified generalized pushover analysis for estimating longitudinal seismic demands of bridges with elevated pile foundation systems INTRODUCTIONFor seismic evaluation of structures, nonlinear time-history analysis (NL-THA) could be used. However, NL-THA is time-consuming. As an efficient and economic method for seismic performance evaluation of structures, pushover analysis is favored by current structural engineers (Akhaveissy, 2012;Forcael, 2014).Pushover analysis in many cases will provide much more relevant information than an elastic static or even dynamic analysis, while in some other cases it will provide misleading results (Krawinkler, 1996). Traditional pushover analysis procedures are conducted with common lateral force patterns, such as first mode, inverted triangular, uniform, etc (Applied Technology Council, 2005). The procedures are applicable for regular structures which vibrate primarily in the fundamental mode. However, they are not suitable for irregular structures, in which the contributions of higher modes are significant (Krawinkler and Seneviratna, 1998

According to the research fruits of the diverse damages of bridge in the past, bearings' invalidation is the main reason of the damage of isolated bridges and causes oversized relative displacements between pier and girder. Eventually, it may lead to severe collision of superstructure. It is extremely dangerous when near-fault motion occurs, because it has obvious velocity pulse effect and increases the risk of colliding between girders.Aiming at this problem, this paper puts forward a device named cable-sliding modular expansion joints (CMEJs) that can control the relative displacement and avoid collision. The working principle and mechanical model are described, and then based on a triple continuous seismic isolation bridge which has different heights of piers, a 3D model with or without CMEJs is established. The responses of continuous beam bridges using the CMEJs are comprehensively inspected under the consideration of the velocity pulse effect, and then a real simulation of limit performance of CMEJs is made, focused on CMEJs' restraining effect.The calculation shows that velocity pulse effect would magnify the seismic response of isolation bridges. In addition, the device can well control the displacement and prevent collisions. And the isolation technology combined with CMEJs can be more effective to play their respective roles. The advantage in controlling displacement is obvious. Keywords near-fault ground motion, the effect in limiting relative displacement; cable-sliding modular expansion joints (CMEJs), seismic isolation bridge, velocity pulse effect