ABSTRACT
ABSTRACT: Precast concrete spandrel beams are commonly used in parking structures to transfer vertical loads from deck members to columns. These beams typically have slender, unsymmetrical cross-sections and are often subjected to heavy, eccentric loading. These factors produce a complex internal structural mechanism including significant out of plane behavior. Traditionally, slender spandrel beams have been reinforced using the torsion and shear provisions of ACI-318. These provisions assure torsional strength by requiring heavy closed reinforcement and well-distributed longitudinal steel to provide torsional resistance after face shell spalling. The need for such complex and expensive reinforcement in slender spandrel beams is questionable. From as early as 1961, extensive field observations and limited full-scale testing have documented a lack of face shell spalling and spiral cracking in slender spandrel beams. Rather, out of plane bending appears to dominate slender spandrel behavior. More recently, extensive full-scale testing has confirmed that the classically assumed mode of torsional distress is not realized in precast slender spandrels. This paper provides background information and argument for simplifying the reinforcement detailing requirements for slender spandrel beams. The paper presents an overview and selected results to date of research currently in progress to develop alternative, more efficient reinforcing schemes and a rational design approach.
