Seismic performance of retrofitted reinforced concrete bridge piers : laboratory testing of the proposed Thorndon Overbridge retrofit scheme

Abstract

This thesis describes the experimental set-up and testing of two scale models of particular piers of the Thomdon Overbridge incorporating the proposed retrofit measures to be included in the structure. Each test specimen represented the structural model developed for the analysis of the Overbridge structure incorporating the proposed retrofit designs for each pier. Modelling of the boundary conditions of the structural model were incorporated into the test specimens by including elements to represent the variable stiffness properties of the piles in the structure under tension and compression.

Testing revealed potential deficiencies with the original structure and the proposed retrofit designs which would have limited the seismic performance of the retrofitted piers. Repairs to the test specimens showed improved seismic performance could be obtained and recommendations for the proposed retrofit designs are included. A method for assessmg the capacity of bridge columns containing curtailed longitudinal reinforcement is proposed following the results of the test programme. This method provides a lower bound strength for columns which compares well to the experimental results from the two test specimens. Flexural strength enhancement over the ACI ideal moment is known to occur due to assumptions made when determining the ACI ideal moment. Expressions are presented which predict the ACI ideal moment and the maximum flexural strength of rectangular shaped columns. The observed shift in the critical section of a column, when confined by an adjacent member, and its influence on the flexural strength enhancement is investigated. A statistical analysis of a number of experimental colunm tests has indicated this to be a significant component of the flexural strength enhancement observed during testing.