CFRP板环向张拉摩擦预应力损失试验研究

Experimental Study on Loss of Prestressing by Friction in Annular Tension of CFRP Plates

预应力加固技术凭借其主动约束、发挥材料高强性能的特点得以广泛应用,现有的加固技术主要有预应力钢绞线加固、预应力碳纤维复合材料(Carbon Fibre Reinforced Plastics, CFRP)布加固等,但钢绞线易锈蚀且在高应力状态下疲劳性能差,会导致突然断裂,难以修复,CFRP布易出现张拉受力不均匀现象,且制作时树脂浸渍困难等问题。所以CFRP板凭借均匀性强、比强度远超钢材、耐腐蚀性能极佳、抗疲劳性能优异等性能更适合用于预应力加固技术。为了研究预应力CFRP板环向加固时的摩擦预应力损失情况,作者团队设计了一种新型环向张拉装置,对6组CFRP板环向张拉进行了预应力损失试验研究,试验的影响因素主要包括了单/双端张拉、不同的摩擦介质。试验得出了不同工况下预应力CFRP板的摩擦损失量,计算出不同摩擦介质的摩擦系数值,得出了预应力的损失规律,并提出了减少预应力损失的措施。试验结果表明,无摩擦介质工况下的摩擦预应力损失最大,双端张拉可有效降低CFRP板的摩擦预应力损失。在表面涂黄油为代表的润滑材料可有效降低CFRP板的摩擦预应力损失。试验结果对预应力CFRP板环向加固有重要意义。

Prestressed reinforcement technology is widely used because of its active restraint and high strength performance of materials. Existing reinforcement technologies mainly include prestressed steel strand reinforcement and prestressed carbon fiber composite material reinforcement, etc. However, steel strand is easy to rust and has poor fatigue performance under high stress, which will lead to sudden fracture and difficult to repair. CFRP cloth is prone to uneven tensile force. Moreover, resin impregnation is difficult during production. Therefore, CFRP plate is more suitable for prestressed reinforcement technology by virtue of its strong uniformity, specific strength far exceeding steel, excellent corrosion resistance and excellent fatigue resistance. In order to study the frictional prestress loss of prestressed CFRP plates during the toroidal reinforcement, the author’s team designed a new type of toroidal tensioning device, and carried out an experimental study on the prestress loss of 6 groups of CFRP plates. The influence factors of the test mainly include single/double end tensioning and different friction media. The friction loss of prestressed CFRP plate under different working conditions is obtained, the friction coefficient of different friction media is calculated, the loss law of prestressed is obtained, and the measures to reduce the loss of prestressed are put forward. The test results show that the frictional prestressing loss of CFRP plates is the largest under the condition of frictional medium, and the double-end tension can effectively reduce the frictional prestressing loss of CFRP plates. The friction prestress loss of CFRP plate can be effectively reduced by applying the lubricating material represented by butter on the surface. The test results are of great significance for the circumferential reinforcement of prestressed CFRP plates.