Effects of Skewed Angle Abutments on the Seismic Response of a Bridge with Hybrid Sliding-Rocking Columns
Abstract
This study computationally investigates the performance of bridges with hybrid sliding-rocking (HSR) columns and skewed angle seat type abutments, and experimentally explores the frictional response of interfaces for application in HSR joints. The HSR columns are segmental columns with end rocking joints, intermediate sliding joints (also termed HSR joints) along their length, and internal unbonded posttensioning tendons. A two-span bridge with a single column bent and an original abutment skew of 33o was selected for this study. The original monolithic cast-in-place column bridge and the HSR bridge, i.e. the same bridge with an HSR column instead of monolithic one, were modeled with five different abutment skew angles (0o , 15o , 30o , 45o and 60o ) in the OpenSees structural analysis software. Time history analyses were performed on both bridges using the 1994 Northridge Earthquake ground motion for two hazard levels; one with a return period of 1000 years and another with 2500-year return period; termed DE and MCE hazard levels, respectively. The analyses results showed higher demands of column drift, abutment seat length and shear key strength for bridges with abutment skew compared to bridge designs without abutment skew for both monolithic and HSR column bridges. All the analyses results showed a lesser damage to HSR columns than the monolithic column. The damage was in the form of concrete spalling for the HSR column at the MCE hazard level. No tendon yielding was observed for the HSR column.
An experimental program was also carried out to investigate the frictional behavior of PTFE-on-PTFE interfaces that are used in HSR joints. The variation of the coefficient of friction with contact pressure, sliding velocity and type of lubrication was studied by testing four types of specimen. The first two types of specimens had dry concrete-to-concrete interfaces, while the third and fourth specimen types had lubricated interfaces with two different grades of the same grease. Two different sliding and pressure protocols were considered, combining different sequences of pressures and sliding velocities. The contact pressures covered a range between 250 and 2000 psi, while, the peak sliding velocities vary between 0.39 in/sec and 4.71 in/sec. The test results showed that the coefficient of friction decreases with contact pressures and increases with the sliding velocity. Lubrication decreased the coefficient of friction approximately by 50%. A friction model was developed based on the test results that can be used in HSR joint modeling.
Subject
Hybrid Sliding-Rocking ColumnsCoefficient of friction
Skewed angle bridges
monolithic column
Citation
Goli, Hareesh Reddy (2019). Effects of Skewed Angle Abutments on the Seismic Response of a Bridge with Hybrid Sliding-Rocking Columns. Master's thesis, Texas A&M University. Available electronically from https : / /hdl .handle .net /1969 .1 /186522.