Bond Of Epoxy-coated And Uncoated Pre-stressing Strand Applicable In The Development Of A Pre-cast Concrete Bridge Bent System

The precast concrete bridge bent system developed at the University of Washington’s Civil Engineering department aims to speed up a bridge’s construction time, extend a bridge’s life-span, and make the bridge earthquake resilient. One aspect our lab focuses on is the columns’ six unbonded, pre-tensioned, epoxy coated strands that are meant to restore the column to its original position after the seismic load is removed. Although we have a mathematical model for the pull out force associated with different types of rebar at a given embedment length, none exists for epoxy-coated strand. My task is to evaluate test data from bond tests on epoxy-coated and conventional “black” strand in order to formulate and calibrate a numerical model using Excel and Matlab that will form the basis for a design equation for a strand’s embedment length. Given that the instantaneous bond stress at a point is expected to be a function of slip, we will create a plot of load vs. slip displacement for each test in order to calibrate the model. The model that we develop from this data will allow us to determine the embedment length needed for any size strand to ensure that it yields before slipping out in order to take advantage of the strand’s strength. This is particularly vital to the precast concrete bridge bent system that relies on the strand’s elasticity to counteract the column’s drift due to a seismic load.