短期荷载作用下600MPa级超高强钢筋混凝土梁裂缝宽度试验研究

Experimental study on crack width of concrete beam with 600MPa ultra-high strength steel bars under short-term loading

为研究600MPa级超高强钢筋混凝土梁受弯性能,进行18根配置600MPa级高强钢筋和1根配置HRB400钢筋的混凝土梁受弯静载试验,分析600MPa级超高强钢筋对混凝土梁裂缝分布、承载力、平均裂缝间距、最大裂缝宽度等影响。研究结果表明:配置该类型钢筋的受弯构件开裂弯矩和极限弯矩仍然可以按照现行规范公式进行计算;短期荷载作用下平均裂缝间距、最大裂缝宽度等参数计算值与现行混凝土结构设计规范公式计算值存在一定差异,平均裂缝间距计算值偏大,最大裂缝宽度计算值与试验值相比偏小。最后根据试验数据对配置该类型钢筋的受弯构件裂缝宽度计算公式进行适当修正,第一种方法是在现行规范计算公式基础上引进裂缝宽度综合调整系数,第二种方法是对现行规范裂缝宽度计算公式中的平均裂缝间距采用修正公式代替,短期裂缝宽度扩大系数采用修正值。修正结果表明第一种修正方法得到的计算值与试验值吻合度高,同时考虑到规范的连续性,建议采用第一种方法进行裂缝宽度修正。

In order to study crack width distribution and calculation method of flexural member with ultra-high strength reinforcement of 600 MPa,tests were carried out for the flexural properties of 18 concrete beams with ultra-high strength steel bar of 600 MPa and 1 concrete beam with HRB400 reinforcement.Based on the tests,the influences of ultra-high strength reinforcement of 600 MPa under short-term loading on crack distribution,bearing capacity,average crack spacing and maximum crack width were analyzed.The results show that the cracking bending moment and ultimate bending moment of flexural members with such type of reinforcement can still be calculated according to the formula in current code;the calculated values of those parameters such as average crack spacing and maximum crack width under short-term load are different to some extent from those calculated according to the formula in the design code of current concrete structure.More specifically,the calculated values of average crack spacing are relatively large,and the calculated values of maximum crack width are smaller compared to the test values.Based on the test data,the formulas for calculating crack width of flexural members with such type of reinforcement were modified.In the first method,the formula of crack width is modified based on the calculation formula of the current code by introducing the comprehensive adjustment coefficient;In the second method,the average crack spacing in the current formula for calculating crack width is replaced with a modified formula,and a modified value for the short-term crack width enlargement coefficient is used.The results show that the calculation values obtained by the first modification method are in good agreement with the test values.Hence,in view of the continuity of the codes,the first method is recommended for modifying the crack width.