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近年来,国内外对预应力混凝土技术及预应力损失作了大量试验研究工作,并取得了很大进展。预应力钢筋长期应力松弛试验结果表明,应力松弛损失经过数年后才趋向终止。然而,过去许多国家的预应力混凝土结构规范中,应力松弛损失值一般都是按照1000小时试验结果而规定取值的。但在实际上,如法国的松弛试验资料表明,延续七年的应力松弛损失值约为100天(即2400小时)松弛值的两倍。第六届国际预应力混凝土会议文献中指出,缺乏长期试验的松弛值,可假设长期的松弛值为1000小时的两倍。通过我们对钢绞线应力松弛的试验研究,采用双对数座标外推法,求
In recent years, a large number of experimental studies on prestressed concrete technology and prestress losses have been made at home and abroad, and great progress has been made. The long-term stress relaxation test results of prestressed steel bars show that stress relaxation loss tends to end after several years. However, in many countries in the past, in the specification of prestressed concrete structures, the value of the stress relaxation loss was generally determined according to the results of the 1000-hour test. In practice, however, data from relaxation tests in France indicate that the value of stress relaxation loss over seven years is approximately twice the relaxation value of 100 days (ie, 2400 hours). The sixth International Prestressed Concrete Conference document pointed out that the lack of long-term test relaxation values can assume that the long-term relaxation value is twice that of 1000 hours. Through our experimental study on the stress relaxation of steel strands, a double logarithmic coordinate extrapolation method was used to