孔道线形复杂预应力损失及力筋伸长量的试验研究

在大型多跨连续梁施工中,预应力施工是最为重要的分项工程,对工程质量的影响最大。某大跨度连续梁工程预应力筋张拉时实际伸长值与理论伸长值偏差较大,超出规范设定的±6%的允许范围要求。分析查找原因,进行了现场孔道摩阻试验,发现锚具锚圈口和锚下垫板口预应力损失大,且变化范围也很大,张拉力损失率平均约为10%。经过分析及认真的核算,为了保证连续梁的工程质量,确定对已经张拉的钢绞线采取补拉的措施,并启用备用束张拉。可为类似工程提供借鉴。

An Experimental Study of the Loss of the Pre-Stressing Stress and the Lengthening Length of the Reinforcement in Linearity-Complex Channels of Pre-Stressed Concrete Beams

In the construction of large, multi-span continuous beams of many projects,the pre-stressing construction is the most important itemized project because it has the greatest effect on the quality of the whole project. Owing to the fact that the value of the real lengthening length of the reinforcement of a certain large-spanned continuous beam project is found to be much dif- ferent from that of the theoretical lengthening length and surpass the allowable value of ±6 % designated in the norm, the pos- sible causes are analyzed in the paper. Through the channel friction tests at the site,it is found that the loss of the pre-stressing stress at both the opening of the anchoring ring of the anchoring tools and the opening of the cushion plates under the anchoring tools is great and the variable range is very large, with the average loss rate of the pre-stressing force being about 10 %. Through analyses and serious check-calculations,it is decided that the make-up stressing be applied to the pre-stressed steel strands and the reserved steel strands be tensioned as well to ensure the engineering quality of the project. The project may serve as a useful reference for other projects of similar types.