Summary:

A methodology to predict each stage of camber and displacements in composite prestressed concrete and steel bridge superstructures from inception to end of service life including a prediction of rebound in deck replacement projects is presented. The methodology invokes the use of multiple creep curves and allows the proper simulation of various construction activities each of which feature unique loading events. The proposed method captures the influence of several factors, such as creep and shrinkage of beam and deck concrete as well as prestresses losses induced because of these phenomena. Additionally, the prediction methodology offers the capability to quantify the influence of temperature gradients on beam camber and displacements at any point in time. The proposed method can be used to predict beam rebound during a deck replacement activity by considering the removal of the deck as well as the removal of the locked-in time dependent internal forces. The overall framework for the prediction methodology is based on principles of engineering mechanics, although components of the methodology are based on empirical models such as the estimation of the modulus of elasticity at prestress release and 28 days, its variation with time, prediction of creep and shrinkage properties, and relaxation of prestressing strands. The proposed methodology has been evaluated using measured pre-erection camber data for a total of fourteen projects, which feature a total of 90 beams. An alternative simplified method suitable for preliminary design and based on time dependent multipliers is presented. Pre-erection camber predictions based on the proposed methodology and the Time Dependent Multiplier Method are more accurate than those based on the PCI Multiplier Method and the MDOT multiplier method. A computer program called MDOT Camber was developed to facilitate data input and summarize essential output.

Publications:

• Final Report
• Spotlight

Research Manager	Project Manager	Performing Organization
Michael Townley	Kyle Kopper	Wayne State University