Strength and performance evaluation of nepalese RC bridge pire using nonlinear dyanamic response analysis

Abstract

Nepal lies in one of the world’s most seismically active region. During the 1995 Hyogo-Ken Nanbu (Kobe) earthquake (M 7.8), highway structures were damaged or severely affected, particularly the single – column –type RC piers. During the 1989 Loma Pita earthquake (M 7.1) in California, widespread damage was reported to the region’s highways and bridges. Five different conditions of Bridge Pier have been considered with investigation of all the database of design available at the DOR. Available bore-hole soil database of the Bridge Pier have been utilized. The analysis showed that the RC Bridge Pier is safer in the event of earthquakes for simulating the ground conditions encircling the pier. The performance of the RC Bridge Pier was accessed in strong ground motion records. In this study it was intended to access the seismic performance of RC bridge piers under Gazali strong motion. It was observed in the field observation that most of the bridges in Kathmandu Valley were having lowered bed due to scouring. The effect of strong vertical ground motion was investigated for possible reduction in flexural and shear strength of the pier. For this purpose, fifteen models have been developed. These fifteen models are grouped into three sets. First set consists of the five models having only horizontal direction of earthquake is applied. Second set consists of five models with horizontal & Vertical direction of earthquake is applied and third Set consist of the five models with Scouring is considered. These studies have revealed that have got profound effect on the performance of the RC structures. The lateral extent of soil mass for each of the five different bridges were fixed based on trial computations until the percentage difference in consecutive response quantities were found within the limit of 0.4%. The lateral extent for the AO is fixed as 400 m ,AW is fixed as 500 m, AP is fixed as 400 m , IP is fixed as 500 m and BPis fixed as 400 m. The light damage, considerable damage and also failure damage of the Bridge pier at different bridges for different cases (AO, AW, AP and BP).The introduction of strong vertical ground motion increase the vertical displacement by 48 % all bridges. It means horizontal ground acceleration (0.71g) and vertical ground acceleration (1.37g) both applied horizontal displacement increases as well as vertical displacement increases. The Nepalese RC Bridge Pier (In 1990-2000) is over safe. The Nepalese RC Bridge Pier (After 2000 & Before 1990) is designed under safe.