Making sense of minimum flexural reinforcement requirements for reinforced concrete members

摘要

Minimum flexural reinforcement requirements have been a source of controversy for many years. The purpose of such provisions is to encourage ductile behavior in flexural members by providing a reasonable margin of safety between first cracking and flexural failure or, alternatively, a reasonable amount of overstrength beyond the applied factored loads. The primary objectives of this study were to summarize the apparent origin of current minimum reinforcement provisions, examine the margin of safety provided by existing provisions for reinforced concrete members of different sizes and shapes, and propose new requirements when they provide more-consistent results than those from existing provisions.rnFive existing or proposed methods were included in the study. Parametric analyses show that the proposed method provides the most reasonable margins of safety among the methods examined. The study focuses on determinate reinforced concrete beams, which include only mild tensile reinforcement and no prestressing. High-strength steel and concrete were included. The study also found that, in many cases, flexural failure at minimum reinforcement levels can be initiated by crushing of the concrete rather than the fracture of the reinforcing steel.