Effects of Vertical Motions on Seismic Response of Goltzschtal Masonry Arch Bridge

Previous researches have demonstrated that the effects of earthquake vertical component on main structural elements of bridges are very noticeable in near-fault seismic events. In the near distances of seismic source (D<10 to 15 km) the response spectrum of a vertical component has a great peak in short-period regions. Owing to geometrical shape and mechanical properties, masonry arch bridges have lower characteristic periods. It seems that, in this type of bridge, axial force response is considerable under vertical seismic events. In this article, a simple analytic model for masonry arch bridges is introduced. Vertical motions effects on seismic axial force response of masonry arch bridges are investigated through dynamic time history analysis of the world's largest masonry arch bridge simplified model. Vertical component effects on bridge structural elements are measured using a ratio computed by dividing the average values resulted from time history analysis based on applying three components of earthquakes simultaneously for seven selected records to responses of dead load applying. Then, the bridge's simplified model dynamic analysis results are verified by the results obtained from accurate finite element model dynamic analysis. Besides, in order to investigate the effects of low tension strength of masonry materials, the results obtained from nonlinear dynamic analysis in which tension strength of material is assumed to be zero, are compared with those obtained from linear dynamic analysis. This survey shows that vertical component effects in some structural elements of bridges are very considerable.