Behavior of Precast Reinforced Concrete Ledger Beams

Abstract

he design of ledger beams, commonly used as spandrels in precast concrete structures, may not always be adequate under currently accepted criteria based on the ACI Building Code' and the PCI Design Handbook' due to insufficient accounting for minor axis bending effects, and potentially, secondary effects. This paper presents the results of a study investigating load-deformation behavior of slender ledger beams. The conclusions and design recommendations drawn may assist engineers in preventing unserviceable behavior of such members. To determine the load-deformation behavior of ledger beams, a program of experimental analysis was conducted. Six model beams were tested by progressive elastic range Ioading at seven different spans in three configurations. The configurations considered were braced major axis bending under pseudo-uniform loading, uniform torsion only, and unbraeed bending and torsion under uniform eccentric loading intended to simulate the loads on spandrel ledger beams met in practice. Measurements were made of the vertical and horizontal midspan deflections and the midspan rotation under the appropriate loading conditions. The differences between the unhraced bending behavior obtained experimentally, and those estimated by superposition of the other two loading conditions were examined for any identifiable secondary behavior, or other response of potential design interest.