预应力钢绞线松弛试验研究

Experimental Study on Relaxation of Prestressed Steel Strands

摘要: 本文针对预应力长期损失核心因素——钢绞线应力松弛，依据国家标准开展试验研究。结果表明：钢绞线松弛呈初期速降、后期趋稳特征，0~50 d衰减最快；1 h内数据离散性大，以60 min后数据外推精度最高，120 h实测推算的1000 h松弛率为2.51%，满足规范要求，且长度对松弛率无显著影响。对比发现，规范低松弛模型虽趋势吻合，但因未考虑锚具回缩等初期短期效应，存在早期损失低估问题。实测长期损失较规范计算值低约35.7%，建议将锚具回缩控制在8 mm以内并结合实测修正模型，以提升预应力损失预测精度。

Abstract: This study focuses on stress relaxation of steel strands—the dominant factor governing long-term prestress loss—and conducts experimental investigations in accordance with relevant national standards. The results indicate that strand relaxation exhibits a distinct pattern: a rapid initial decline followed by gradual stabilization, with the most significant attenuation occurring within the first 0~50 days. Data collected within the first hour show high dispersion; consequently, extrapolation based on measurements taken after 60 minutes yields the highest accuracy. The 1000-hour relaxation rate, extrapolated from 120-hour test data, is 2.51%, satisfying code requirements. Furthermore, specimen length was found to have no significant effect on the relaxation rate. Comparative analysis reveals that while the low-relaxation model specified in the code captures the general trend, it underestimates early-stage losses due to its omission of short-term effects, such as anchorage set. The measured long-term loss is approximately 35.7% lower than the code-predicted value. It is recommended that anchorage set be limited to within 8 mm and that the predictive model be calibrated using empirical data to enhance the accuracy of prestress loss forecasting.