基于实测的锚下有效预应力时变效应模型研究

Study on the Time-varying Model of Effective Prestress Under Anchor Based on Measured Results

为了分析实桥预应力张拉以后的衰减规律,捕捉拉脱法测试时机,在预制梁上开展了35束钢绞线长时间的衰减测试,进行了锚下有效预应力时变规律研究.基于已有规范,将锚固后的预应力损失用松弛损失、收缩徐变损失及温度变化损失来表示,提出了一种预应力长期损失预测模型.利用获得的锚下有效预应力测试结果,得到了模型中参数的分布及取值,并进行了预测模型与实测结果的对比.将文中所提模型与已有文献结果进行了对比验证.研究结果表明:800 h内,锚下有效预应力的整体衰减主要由松弛、收缩徐变及温度变化引起,相比于收缩徐变,松弛及温度的影响相对较小.72 h内,锚下有效预应力的快速衰减主要是由于混凝土徐变的快速发展,而收缩、松弛及温度的影响较小.预应力损失与环境温度变化之间呈明显的滞后正相关性,滞后期均值为8.76 h.研究提出的锚下有效预应力长期损失预测模型与实测结果吻合较好.

In order to analyze the attenuation law of prestressed concrete bridge after tensioning and seize the testing opportunity of pull-off method,35 strands of steel strand were tested on precast beam for a long time,and the time-varying law of effective prestress under anchor was studied.Based on the existing codes,the prestress loss after anchorage was expressed as relaxation loss,shrinkage and creep loss and temperature change loss,and a prediction model of long-term prestress loss was proposed.Using the test results of effective prestress under anchor,the distribution and values of parameters in the model were obtained,and the predicted model was compared with the measured results.The model proposed in this paper was compared with the existing literature results.The results show that the overall attenuation of effective prestress under anchor is mainly caused by relaxation,shrinkage and creep and temperature change within 800 h,and the effects of relaxation and temperature are relatively small compared with shrinkage and creep.Within 72 h,the rapid attenuation of effective prestress under anchor is mainly due to the rapid development of concrete creep,while shrinkage,relaxation and temperature have little influence.There is an obvious lag positive correlation between prestress loss and environmental temperature change,and the average lag period is 8.76 h.The long-term loss prediction model of effective prestress under anchor is in good agreement with the measured results.