MDOT Camber Program Description
The deformation of modern concrete bridge superstructures constructed in a sequential manner is highly influenced by the time dependent behavior of concrete (i.e. its ability to creep and shrink over time). Delayed deformations different than those predicted during design may affect the serviceability of concrete bridges or may result in increased cost and longer construction duration. A methodology to predict camber and displacement history 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 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. A computer program called MDOT Camber was developed to facilitate data input and summarize essential output.
Download from the link below: Link |
Variation of camber as a function of time and distance from the support up to midspan for a simply supported composite prestressed concrete beam
|
The research report that describes the development of the MDOT Camber program is provided at the following link:
Link
Link
The peer reviewed journal articles are listed below:
- Cakmak, F., Menkulasi, F., Eamon, C. (2022). "Time Dependent Flexural Deformations in Composite Prestressed Concrete and Steel Beams: Part I – Prediction Methodology", ASCE Journal of Bridge Engineering, February 2022. Link
- Cakmak, F., Menkulasi, F., Eamon, C. (2021). "Time Dependent Flexural Deformations in Composite Prestressed Concrete and Steel Beams: Part II – Comparison of Predictions", ASCE Journal of Bridge Engineering, February 2022. Link