More than 40% of the bridges in mountainous areas of Southwest China are constructed with piers having a height of over 40 m. Such piers are characterized by large structural flexibility and distributed mass. To investigate the effects of higher modes on the seismic performance of this class of bridges, shake table tests on two 1/7-scale, tall-pier models were conducted at Tongji University, Shanghai. This paper describes the design, instrumentation, and loading protocols for the tests and discusses and compares the results. Due to the higher-mode effects, the curvature at the pier base and displacement at the pier top of were found to be weakly correlated, indicating that displacement is not a reliable damage measure for tall piers. Moreover, results indicated that the contribution of higher modes can lead to the formation of an additional plastic region at midheight in the piers. However, current seismic design code guidelines are for short to medium-height piers, where the midheight region of piers is assumed to respond elastically; code guidelines are not provided for tall piers. This paper explores the effect of higher modes on the seismic performance of bridges with tall piers and suggests two methods to improve the seismic performance: (1) eliminating the midheight plastic response by including more longitudinal steel, and (2) using more confinement in the midheight region to improve pier ductility and prevent shear failure.

Typical small-to-medium–span highway bridges in China are often installed with economical laminated-rubber bearings that allow for thermal movement of girders and concrete shear keys that restrain transverse girder displacement. However, the damage investigation after the 2008 Wenchuan earthquake had shown that sliding between the girder and the laminated-rubber bearings was a common phenomenon that caused excessive girder displacement and damage to shear keys, expansion joints, and abutments. The bearing sliding can actually act as isolation for the piers, which suffered from a small amount of damage during the earthquake. Therefore, a new seismic design strategy for typical girder bridges has been proposed in which the bearing sliding acts as a fusing mechanism to mitigate the seismic demands of piers, and unseating-prevention devices are used to control the bearing displacement. This paper investigates the seismic performance of three transverse unseating-prevention devices (concrete shear keys...

To investigate the efficiency of passive energy dissipation devices in protecting cable-stayed bridges from severe damage when subjected to high-intensity ground motions, a 1/20-scale bridge model from a typical medium-span concrete cable-stayed bridge was designed, constructed, and tested on shake tables. Yielding steel damper (YSD) and viscous fluid damper (VFD) were used as passive energy dissipation devices in the transverse and longitudinal directions, respectively. The bridge models were then excited by two ground motions with different spectral characteristics in transverse and longitudinal directions accordingly, including the Chi-Chi earthquake wave and a site-specific artificial wave. The seismic responses of the bridge models with and without the passive devices were analyzed and compared. Both numerical and test results show that the YSD applied in the transverse direction could reduce the seismic responses of the towers effectively, and the VFD applied in the longitudinal direction co...

Long-span cable-stayed bridges often have a design service life of more than a hundred years, during which they may experience multiple earthquake events and accumulate seismic damage if they are located in seismic-prone regions. Earthquake occurrence is discretely and randomly distributed over the life cycle of a long-span cable-stayed bridge and often causes sudden drops in the structural performance instead of yearly fixed seismic performance degradation. This study thus proposes a digital twin-based life-cycle seismic performance assessment method for long-span cable-stayed bridges. The major components of this method include: (1) a seismic hazard analysis-based generation method of earthquake occurrence sequence; (2) a digital twin-based structural response prediction method considering lifetime earthquake occurrence and sequence; and (3) a service life quantification method. The proposed method is applied to a scaled long-span cable-stayed bridge with a series of shake table tests. The results show that the digital twin can closely reproduce the life-cycle seismic response of the bridge under sequential earthquakes. The proposed assessment method provides a more intuitive presentation of the life-cycle seismic damage accumulation process and a more accurate estimation of the service life of a long-span cable-stayed bridge.