CFRP has high strength and elastic modulus but low ductility. GFRP is supplementary for CFRP and mixed CFRP/GFRP sheet in the same layer and is the new material for the consolidation of the civil engineering. When the concrete beam is strengthened by the prestessed CFRP/GFRP sheet, the stress relaxation of the sheet appears and prestress loss comes into being. Experimental results showed that the prestress loss was distinct after 3 hours after the CFRP/GFRP sheet was tensioned and then the prestress loss became slow. After 9 hours from tension, the residual prestress kept almost constant. The residual prestress was 22% of the total prestress and the degree of the prestress loss was acceptable. The prestress loss at the 3 hours after tension was 87% of the total prestress loss and the main prestress loss was finished in 3 hours after tension.%层内混杂CFRP/GFRP纤维布是一种用土木工程加固的新材料.CFRP具有高强度、高弹性模量的特点,但延性较差,GFRP相对于CFRP可起到互补作用.预应力CFRP/GFRP混杂纤维布加固混凝土梁,纤维布施加预应力后出现应力松弛,产生预应力损失.试验表明,在纤维布张拉结束后的3h内预应力损失较为明显,其后预应力损失变化缓慢而逐渐趋于平稳.张拉结束约9h后,预应力损失基本不再继续增大,最终的预应力损失占到张拉预应力约22％,损失程度在正常范围之内;张拉结束后3h的预应力损失占到总共预应力损失约87％,预应力损失主要在张拉结束后的3h内完成.
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