Parametric Study of Posttensioned Inverted-T Bridge System for Improved Durability and Increased Span-to-Depth Ratio

Rehabilitation of the existing bridges is one of the most pressing needs in maintenance of the transportation infrastructure. As an example, more than 2,000 bridges in Kansas alone need to be replaced during the next decade. The majority of these bridges have spans of 30 m (100 ft) or less, and shallow profiles. The inverted-T (IT) bridge system has gained increasing popularity in recent years due to its lower weight and relatively larger span-to-depth ratio compared to the prestressed I-girder bridges. However, there are some limitations in replacing the existing cast in place (CIP) bridges with IT system. Implementation of posttensioning, which is the focus of this paper, is a promising solution for these limitations. This leads to a higher span-to-depth ratio and reduces potential transverse cracks in the CIP deck which is a major concern for corrosion of the reinforcement. An analytical research was conducted to identify the major parameters influencing the performance of a posttensioned IT bridge system. This was followed by a parametric study to explore the scope of these parameters and specify the design limits in terms of posttensioning stages, timing scenarios, and posttensioning forces. Concrete strength and different methods for estimating time-dependent restraining moments were addressed in this parametric study.