大跨径预应力混凝土梁桥孔道摩阻试验研究

Experimental study on channel friction resistance test of long span prestressed concrete beam bridge

为更精确地进行施工监控,结合某三跨连续梁桥,通过现场试验得出实际孔道摩阻系数。对实测得到的短、长预应力束的摩阻系数和管道偏差系数对比分析,并根据实测数据修正有限元模型,对比分析修正后支座截面顶板的应力理论计算值与现场实测值。试验得出不同长度预应力束的摩擦系数μ分别为0.254和0.282,偏差系数k分别为0.002 0和0.001 7。结果表明,实际施工过程中的摩阻系数大于规范上限值1.6%~33.3%,不同长度的预应力束的摩阻系数存在较大离散性,随着预应力束的增长,曲线处由于法向挤压力导致的摩阻损失占整体预应力摩阻损失的比重增加,长束预应力束相比较短束μ值增加了11%,k值减小了15%。支座截面顶板应力实测值与理论计算值变化趋势一致,采用实测值修正后误差减小,两次修正误差分别减少了10%和9%。

The friction in a post-tensioning system has a significant effect on the distribution of prestressing force in a prestressed concrete structure. One of the major causes leading to the deteriorations like the deflect ion and cracking of current long span prestressed concrete beam bridge was underestimating the prestressing loss. The failure or destruction of bridge structure was caused by excessive prestress loss. For more precise construction monitoring, combined with a three span continuous beam bridge, the actual frictional coefficient of the channel was obtained through field test. This paper made a contrast between friction coefficient of prestressing tendon at different lengths and pipeline deviation coefficient that measured, then modified finite element model with measured data. Finally, the comparison between modified theoretical calculation value and field measured value of support section roof stress was analyzed. The friction coefficients of prestressing tendons with different lengths were 0.254 and 0.282, respectively, and the deviation coefficient K were 0.002 0 and 0.001 7, respectively. The results showed that the friction coefficient of the actual construction process was 1.6%-33.3% higher than the upper limit value of the norm, and friction coefficients of prestressing tendon at different lengths have obvious discreteness. Moreover, friction losses caused by normal extrusion force at the curve section increased with the increase in prestressing tendon length. Compared with the short prestressed tendons, μ value of long prestressed tendons increased by 11%, and k value reduced by 15%. The changing trend of theoretical calculation values and measured values of roof stress was consistent. Errors decreased by 10% and 9% after parameter correcting based on measured values.