ABSTRACT
Presence of trucks and other heavy vehicles on bridges during earthquakes has been observed in past events. Furthermore, frequent traffic congestion on highways increases the probability of truck presence on a bridge during earthquakes. However, the effect of these vehicles and their interaction with the bridge on the seismic performance of bridges has received little attention in the literature. Therefore, this study determines the effect of vehicle-bridge interaction on the seismic response of bridges. For this purpose, a multi-span simply supported concrete girder case study bridge is subjected to earthquake ground motions with and without trucks. Herein, trucks are modeled in two different ways, firstly as point loads with masses and secondly by a 19 degree of freedom model with springs and dampers representing tires and suspension systems in the vehicle. The first truck model only includes the effects of additional loads and masses while the second truck model includes the effect of vehicle-bridge interaction as well. Therefore, the effect of the vehicle suspension system can be distinguished from the effects of the additional masses and loads. Furthermore, in this study the position of the truck is varied and the response of the bridge is simulated for three ground motions representing different characteristics and three intensities, 0.5 g, 1.5 g and 2.5 g spectral acceleration at 0.5 seconds. Thus, the results of this study enable comparison of the bridge’s seismic response, i.e. the response of columns, bearings and abutments, due the presence of additional loads and the vehicle suspension system as the position of the truck and the ground motion characteristics vary. The results of this study provide several insights in to the seismic behavior of the bridge in presence of the truck and present several opportunities for future work. Firstly, large differences are observed in the responses of the bridge components when subjected to earthquake ground motions in presence and absence of the second truck model atop the bridge. Furthermore, the differences in the responses of components are highly influenced by the truck’s position and the intensity of the ground motions. In order to differentiate the influence of additional masses and loads from the influence of suspensions the seismic response of the bridge components is compared with each of the two truck models atop the bridge at all 31 bridge locations. The results show large differences highlighting the importance of modeling suspension systems to incorporate effects of vehicle bridge interaction. Further studies are necessary to uncover the systematic trends in the differences observed from the response of the bridge components. Also, this study focused on an individual bridge with a truck model with predetermined weight. Future work may focus on bridges with different geometries, different truck models, a suite of ground motions with a variety of ground motion characteristics and a variety of vehicle suspension parameters.
