A study on seismic behavior of scour-vulnerable bridges


Thesis Type: Postgraduate

Institution Of The Thesis: Orta Doğu Teknik Üniversitesi, Faculty of Engineering, Department of Civil Engineering, Turkey

Approval Date: 2016

Student: HALE SEMA KIZILDUMAN

Co-Supervisor: ALP CANER, ALİ MELİH YANMAZ

Abstract:

Scour under bridge foundations typically causes serious defects or failures. The studies on seismic behavior of bridges scoured prior to earthquake are very limited. Although earthquakes are not one of the top reasons for bridge failures or damages, when the effects of earthquakes and scour are combined, the structure can become highly vulnerable to failure. In Turkey, during the design process of bridges, the earthquake effects are seriously considered, but the combined effect of scour and earthquake is not normally analyzed. This study aims to evaluate differences of structural behavior proportionally in scoured and not scoured bridges. In this context, a two-span reinforced concrete bridge is selected for this study. For six different flood conditions, water surface profiles are obtained via hydraulic analysis and response spectrum analyses are made for earthquakes with four different return periods. There are two ground structure scenarios studied in analyses; two layers with sand and clay and one layer of sand. The results have shown that the moments vi on columns and the fundamental periods of the structure are decreased. As a result, an increase in column capacity is observed to be dependent on the scour depth. On the other side, it is seen that pile capacities decrease and shear force and moments on piles increase due to scour. The stability of the bridge becomes more questionable as the pile load carrying capacity decreases due to loss of skin friction.