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建筑工程中用得最多的是Ⅰ级钢筋和Ⅱ级钢筋。现行《混凝土结构设计规范》GBJ10—89对钢筋的锚固长度作了新的规定:当计算中充分利用纵向受拉钢筋强度时,其锚固长度不应小于下表规定的数值:纵向受拉钢筋的最小锚固长度la 表1注:(1)当月牙纹钢筋直径d>25mm时,其锚固长度应按表中数字增加5d采用;(2)当螺纹钢筋直径d≤25mm时,其锚固长度应按表中数值减少5d采用;(3)当混凝土在凝固过程中易受扰动时(如滑模施工),受力钢筋的锚固长度宜适当增加;(4)在任何情况下,纵向受拉钢筋的锚固长度不应小于250mm。从表1及附注中可以看出,现行规范比原规范(TJ10-74)对钢筋的锚固长度规定得更加具体、更加严格了。就是现行规范给出的钢筋锚固长度,不但与混凝土的强度等级、钢筋外形有关,而且还考虑了变形钢筋直径的影响、钢筋表面形状的影响以及施工条件的影响。
The most widely used in construction projects are grade I steel and grade II steel. The current “Specifications for Design of Concrete Structures” GBJ10-89 makes new provisions for the anchoring length of steel bars: When the strength of longitudinal tensioned steel bars is fully utilized in calculations, the anchorage length should not be less than the value specified in the following table: Longitudinal tensile reinforcement The minimum anchorage length la Table 1 Note: (1) When the crescent rebar diameter d> 25mm, the anchorage length should be increased by 5d in the table; (2) when the rebar diameter d ≤ 25mm, the anchorage length should be The numerical value in the table is reduced by 5d; (3) When the concrete is easily disturbed in the solidification process (such as sliding mode construction), the anchorage length of the stressed steel bar should be appropriately increased; (4) In any case, longitudinally reinforced steel The anchorage length should not be less than 250mm. From Table 1 and the notes, it can be seen that the current specification is more specific and stricter than the original specification (TJ 10-74) for the length of anchorage of reinforcing bars. The anchorage length given by the current specification is not only related to the strength grade of the concrete and the appearance of the steel bar, but also the influence of the diameter of the deformed bar, the influence of the surface shape of the steel bar and the influence of the construction conditions.