The Design of precast concrete segmental bridge piers in New Jersey, USA

Abstract

The $ 900 million Rt. 295 Direct Connect Project in New Jersey, USA is a major highway and bridge construction project currently under design. This project is to be built in several stages and in four separate contracts in one of the busiest corridors in the country where three major highways meet. It has numerous long span bridges that weave through the interchange at four separate levels. For the I-295 Direct Connect Project, the New Jersey Department of Transportation (NJDOT) required the use of precast post tensioned segmental piers where appropriate to expedite construction and to relieve motorists from construction related delays. In precast concrete construction, much of the pier fabrication can be done in an off-site pre-casting plant. This shortens the on-site labor and construction time, thereby reducing traffic delays and detours during construction. A pre-casting plant allows for both the efficiency of mass production and a high level of quality control. Consequently, the cost of the precast substructure will be reduced. With the high level of quality control attainable in a precast plant, high performance concrete can be used. This results in more durable substructure units with higher quality and better finish. The higher strength of high performance concrete allows the use of hollow sections. Hollow sections result in material savings, lower hauling and erection weights, and decreased foundation costs. In this paper, the design of post tensioned segmental straddle bent type piers is presented. An Excel Spreadsheet was developed for the design. The features of the spreadsheet discussed also describe the design procedure adopted. The efficient use of the spreadsheet shows that these piers can be routinely designed without complicated and expensive computer programs. The sequence of pier construction is also provided.