Design of Reinforced and Prestressed Concrete Inverted T Beams for Bridge Structures

Abstract

P refabricated concrete stringers with cast-in-place slab are frequently used to achieve economical and speedy bridge construction schemes. Beams constructed in the form of an inverted T possess on each side of the web a bracket or flange overhang that provides a convenient shelf or supporting surface for the precast stringers. Hence, castin-place, post-tensioned, prestressed concrete (PC) and reinforced concrete (RC) inverted T beams are frequently used in bridges as bentcap girders as indicated in Fig. 1. Inverted T beams can he simply supported, cantilevered over simple supports, or they can be constructed monolithically with columns or piers. They reduce overall floor depth by avoiding deep cross members beneath prefabricated stringers, resulting in lower abutments and shorter approaches for the bridges. Despite its frequent use for at least the past two decades, the inverted T shape remains as one of the least investigated cross sections. At present, no guidance for handling design problems specifically associated with the inverted T section is available in current North American standards. Consequently, engineers have tended to rely on per,sonal judgment and discretion for design of inverted T girders. This paper summarizes design recommendations that are based on observations and analyses of cast-in-place normal weight, PC and RC laboratory test specimens reported in studies of inverted T beams °-' The paper is directed