近代钢筋混凝土结构的钢筋强度判别方法研究

Research on judging method of reinforcement strength in modern reinforced concrete structures

为了进一步解决对历史建筑钢筋材料强度缺乏了解的问题,对历史文献进行了调研,并对上海某近代混凝土建筑改造工程现场截取的不同规格型号的钢筋进行了拉伸试验及里氏硬度试验。结合历史文献调研结果及钢筋制造工艺、拉伸试验及里氏硬度试验结果,对近代混凝土建筑中实测钢筋里氏硬度进行统计分析,得到如下结论:在相当于我国当前标准的HPB235级和HRB335级钢筋之间尚存在屈服强度275MPa的钢筋;当采用表面硬度法对近代混凝土结构中的钢筋强度等级进行判别时,若实测钢筋里氏硬度代表值大于400,可判别为G40级;若实测钢筋里氏硬度代表值小于375时,可判别为G33级;在两者之间时,建议取样检测或偏保守判别为G33级;G33级钢筋屈服强度可按HPB235级钢筋取值,G40级钢筋屈服强度可按275MPa取值;扭钢属于冷扭钢筋,在进行承载力验算时扭钢的屈服强度可按335MPa取值。

In order to further solve the problem of lack of understanding of the strength of reinforcement in historical buildings, the historical documents were investigated, and the tensile test and Leeb hardness test of different specifications of reinforcement intercepted from a modern concrete building reconstruction project in Shanghai were carried out. Based on the investigation results of historical documents and the test results of reinforcement manufacturing technology, tensile test and Leeb hardness test, statistical analysis on the measured Leeb hardness of reinforcement in modern concrete buildings was maked. The following conclusions are drawn: there are still 275 MPa reinforcement with yield strength between HPB235 grade and HRB335 grade reinforcement in China′s current standards;when the surface hardness method is used to judge the strength grade of reinforcement in modern concrete structures, if the representative value of reinforcement′s Leeb hardness is greater than 400, it can be judged as grade G40;if the representative value of reinforcement′s Leeb hardness is less than 375, if it can be judged as grade G33;if between the two, it is recommended to take samples for testing or to identify it as G33 conservatively. The yield strength of grade G33 reinforcement can be taken as HPB235 reinforcement, and the yield strength of G40 reinforcement can be taken as 275 MPa;the torsional steel belongs to cold-torstorsional reinforcement, and the yield strength of the torsional steel can be calculated according to 335 MPa when the bearing capacity is checked.