提出把混凝土受压区用**矩形应力块（Whitney rectangular stress block）**来近似的是 Charles S. Whitney（C. S. Whitney），通常记作 Whitney stress block，文献上常写成 1930s（常引 1937 年的工作）。
参考：
Design of Reinforced Concrete Beams per ACI 318-02：
- 尽可能准确预测构件的实际承载能力
- 还应采用尽可能简易的计算方法
Teaching the Equivalent Rectangular Stress Block：
ACI 318-19 (ACI Committee 318 2019) defines the maximum permissible strain at the extreme compressive fiber as 0.003, which essentially defines the strain condition at nominal moment strength. In addition, ACI 318-19 requires that equilibrium be satisfied at each section. Furthermore, Section 22.2.2.3 of ACI 318-19 notes that, “The relationship between the concrete compressive stress and strain shall be represented by a rectangular, trapezoidal,parabolic, or other shape that results in prediction of strength in substantial agreement with results of comprehensive tests.” The most used stress block, and the one that is sanctioned by ACI 318-19, is the equivalent rectangular stress block originally proposed by Whitney (1937). The intention of Whitney’s paper was to simplify the design process and “result in more efficient and economical use of reinforced concrete.” The use of the rectangular stress block in flexural strength analysis has been validated with experimental data through several studies dating back to the early 1900’s (Mattock et al. 1961).
- 任何理由都要经得起实验验证。
Whitney Rectangular Stress Distribution：
- \beta 并不总是0.85。