高强钢筋轻骨料混凝土梁短期受弯刚度计算方法研究

Study on calculation method of short-term flexural stiffness of high strength reinforced lightweight aggregate concrete beam

为研究配置高强钢筋轻骨料混凝土梁短期受弯刚度特点及其计算方法,分别进行了5根配置400MPa和5根配置500MPa级纵筋的陶粒轻骨料混凝土梁受弯性能试验。结合收集到的22根高强钢筋轻骨料混凝土梁的试验结果,评估了相关规范中短期受弯刚度计算公式的适用性。试验结果表明,试件在纵筋屈服前的跨中弯矩-平均曲率曲线先近似呈直线,开裂后呈微凹曲线;与普通混凝土梁相比,轻骨料混凝土梁的短期受弯刚度较小。根据《轻骨料混凝土结构技术规程》(JGJ 12—2006)和《混凝土结构设计规范》(GB 50010—2010)短期受弯刚度计算公式得到的试件刚度计算值均比试验值偏小。利用试验数据,基于跨中弯矩-平均曲率曲线特点给出了配置高强钢筋轻骨料混凝土梁的短期受弯刚度一般计算模式,并基于该计算模式下的特例(双折线法)构建了与预应力混凝土构件刚度公式统一的修正计算公式,按该公式所得刚度计算值与试验值吻合较好。

In order to study the short-term flexural stiffness characteristics and calculation method of high-strength steel reinforced lightweight aggregate concrete beams,five ceramsite lightweight aggregate concrete beams each with 400MPa and 500MPa longitudinal reinforcements were carried out respectively.Combined with the collected test results of 22 highstrength reinforced lightweight aggregate concrete beams,the applicability of the short-term flexural stiffness calculation formulas of relevant codes was evaluated.The test results show that the mid-span bending moment-mean curvature curve of the specimen is approximately straight before the longitudinal reinforcements yield and slightly concave after cracking.Compared with ordinary concrete beams,the short-term flexural stiffness of lightweight aggregate concrete beams is smaller.According to the Technical specification for lightweight aggregate concrete structure(JGJ 12—2006)and Code for design of concrete structures(GB 50010—2010),the calculated values of the stiffness of the specimens obtained from the short-term bending stiffness calculation formula are all smaller than the test values.Using test data,based on the characteristics of the mid-span bending moment-average curvature curve,a general calculation model for short-term bending stiffness of highstrength steel reinforced lightweight aggregate concrete beams was given.Based on a special case of this calculation mode(double broken line method),a general calculation model with prestressed concrete was constructed.The revised calculation formula is unified with the stiffness formula of prestressed concrete member,and the calculated stiffness value obtained according to it is in good agreement with the test value.