Moment redistribution capacity in prestressed concrete continuous beams

Abstract

In prestressed concrete continuous beams, building code provisions often allow for a reduction in the moment at a critical section (calculated through elastic analysis). This reduction is permitted as long as the moments in all other sections are adjusted to maintain equilibrium and support the designated loads. However, the allowable moment redistribution percentage (MRP) for prestressed concrete beams (PCBs) remains a topic of debate. Many codes currently assign a similar MRP limitation to both PCBs and reinforced concrete members. This approach might be over-simplistic for PCBs due to their unique behaviour. This paper proposes a method for identifying the maximum available MRP. An in-depth study was conducted on the maximum available MRP of PCBs based on calibrated finite element models. The results show that the parameters such as passive reinforcement ratio, steel yield strength, slenderness ratio, eccentricity of prestressing tendons, concrete grade, and load pattern, which were not considered in the codes, influence the maximum available MRP to an extent. Using the same permissible MRP as reinforced concrete beams may be inappropriate. Finally, an equation is proposed to estimate the maximum available MRP for PCBs.