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非预应力混凝土梁和部分预应力混凝土梁在使用荷载作用下通常都是带裂缝工作的。全预应力混凝土梁在理论上是不开裂的,然而,由于某些原因(例如K_f略大于1.0,偶然超载,材料强度偏低等),也有可能在使用荷载作用下出现裂缝。因此,各种钢筋混凝土梁都存在一个开裂的问题。在设计中,除应保证构件具有足够的强度外,还需考察和验算构件在不同荷载组合作用下的工作性能,诸如变形,受拉钢筋应力增量,裂缝开展以及截面材料的疲劳强度等。这些问题都与截面开裂后的受压区高度有关。因此,寻求一个简单实用的开裂截面受压区高度的计算方法,是设计和验算各种钢筋混凝土梁的一个重要问题。
Non-prestressed concrete beams and partially prestressed concrete beams usually work with cracks under the use of loads. Fully prestressed concrete beams are theoretically non-cracked. However, due to certain reasons (for example, K_f slightly greater than 1.0, accidental overload, low material strength, etc.), it is also possible that cracks occur under the use of loads. Therefore, all kinds of reinforced concrete beams have a problem of cracking. In the design, in addition to ensuring that the components have sufficient strength, it is necessary to examine and verify the working performance of the components under different load combinations, such as deformation, tensile stress of tensile steel reinforcement, crack development, and fatigue strength of the cross-section materials. These problems are related to the height of the compression zone after the cracking of the section. Therefore, the search for a simple and practical calculation method for the height of the compression zone of the cracked section is an important issue in the design and verification of various reinforced concrete beams.