DYNAMIC ANALYSIS OF BALANCED CANTILEVER CONCRETE BRIDGES WITH DIFFERENT PIER HEIGHTS UNDER NEAR-FIELD GROUND MOTIONS

The selected bridge is a balanced cantilever concrete bridge having three spans of 37, 68 and 37 meter and is constructed using form traveller method as shown in Figure 1-a. Construction begins at each bridge pier. The deck section height varies from 4.03 m at the pier location to 2.03 m at the middle of main span in parabolic form, Figure 1-b. Thedeck is implemented continuously with the middle piers and seats on elastomeric bearings at each end. The height of the middle pier is 18 m. The pier section is considered wall type pier with 1.5 m thickness. The pier section width varies from the 6.5 m at the deck level to 8 m at the base linearly.This paper presents seismic performance of a concrete bridge with equal pier heights (EPH) and unequal pier heights (UPH) subjected to a set of Near-Field ground motions (NFGM). Two bridges with concrete box girder (balanced cantilever construction method) having three spans (37+68+37 meter) were modeled using three-dimensional nonlinear dynamic finite element method (FEM). The first one having EPH (18 m) and the second one having UPH (18 and 21 m), which were monolithically connected to the deck. In order to evaluate the inelastic response of bridges to Near-Field and Far-Field ground motions and the effect of bridge irregularity, two types of nonlinear analysis were performed. 1) Nonlinear time series (NTS), 2) Nonlinear static analysis (Push-over). The sensitivity of time series analysis depends on selection of ground motion records. According to recommendations of FEMA P-695 report, The records were selected according to various ground motion characteristic such as the peak ground acceleration, duration, frequency content, fault type and earthquake magnitude. Suite of 28 compatible ground motion records with site soil type II (175