Because of the phenomenon of deterioration of the aging structures and a high density of traffic, certain highway bridges need maintenance by replacement in United States. The projects that are done for the purpose of replacement cause troubles for the local traffic in form of non-convenient and possibly risky alternate routes. In order to reduce the time consumption of the construction works and reduce negative influence on the environment, and minimize quality control issues, a safer method against potential hazards is employed, that is incorporation of precast elements in the construction works, and this method is gaining popularity every next day.
This practice of using full depth pre-cast concrete decks in highway bridges started in 1965 AD in the United States. The idea behind usage of such method of construction is to accelerate the construction process in rehabilitation projects that leads to less inconvenience of local traffic, reduced costs of traffic closures especially in the areas where the traffic density is high. Through the experience of the design engineers over the years, they have realized that this method of construction has not only proven to be advantageous for rehabilitation projects but can also be equally beneficial for new construction projects.
The quality of the precast decks is relatively higher and have a longer service life than others, that is why those precast elements require less future maintenance and thus reducing costs.An economical and an effective design concept is made possible by the development of prefabricated, full depth precast concrete bridges, that can be employed for the rehabilitation of existing but also new construction of highway bridges. This solution if effective in case of reducing the reconstruction time and bridge closures. This practice minimizes the interference with the local traffic.
The building of prefabricated decks can be achieved in short periods of time like days or even hours in contrast to the traditional methods that take months at least. This accelerated building method reduces the influence on environment and provides a safer construction and less life cycle costs by increased life spans.The process is carried out in a controlled environment and is a combination of high strength prestressing cords with prefabricated full depth precast concrete panels of high performance. The resulted deck if high quality that is resistant to many environmental impacts.
The connection among the beams and precast panels is provided by the shear studs aligned in shear pockets that provides full composition of action. In order to achieve a simpler framework of precast concrete panels and erection technique, no typical reinforcement in the transverse joints of adjacent precast panels is provided during design process, that is no steel runs through the joints. Keeping in consideration of concrete creep and shrinkage under different kinds of loads, its is advised to carry out post-tensioning of the precast concrete panels in longitudinal axis that results into continuous and tight transvers joints among the adjacent joints, and eliminating tensile stresses in the deck.