钢筋-GFRP筋增强混凝土梁的疲劳力学性能

Fatigue behaviors of steel bars-GFRP bars reinforced concrete beams

钢筋-玻璃纤维增强树脂复合材料(GFRP)筋增强混凝土(RC)梁设计结合了钢筋和GFRP筋的优点,可以提高构件承载力,同时改善纯纤维增强复合材料(FRP)筋构件使用性能存在的问题,但是关于其疲劳性能的研究十分有限。因此,本论文进行了7根钢筋-GFRP筋增强RC梁的疲劳试验,研究参数包括疲劳荷载幅、有效配筋率、配筋面积比。结果表明,钢筋-GFRP筋增强RC梁疲劳破坏始于钢筋的疲劳断裂,钢筋疲劳断口光滑平整,显著区别于静力拉伸破坏断口。疲劳加载过程中,截面平截面假定仍然满足。疲劳荷载幅对疲劳寿命有显著影响,随着疲劳荷载幅的增大,梁中钢筋、GFRP筋和混凝土应力和应力幅均随之增大,疲劳寿命减小。增大有效配筋率,跨中挠度和最大裂缝宽度均减小,正常使用性能改善。配筋面积比(Af/As)的增加不利于构件抵抗疲劳荷载,Af/As由0.25增大到2.0,疲劳寿命从36.6万次降低到8.3万次。对比了各种疲劳挠度计算公式,CEB-FIP 2010规范的预测结果较好,误差范围在7%以内,推荐作为钢筋GFRP筋增强RC梁疲劳挠度的计算公式。

Steel bars-glass fiber-reinforced polymer(GFRP)bars reinforced concrete(RC)beams combined the advantages of steel bars and GFRP bars.Flexural capacity was increased compared with RC beams and serviceability performance was improved compared with the pure fiber-reinforced polymer(FRP)reinforced concrete beams,however,the investigation of fatigue behaviors was limited.In this study,seven beams were fabricated for fatigue tests,and the test parameters were load amplitude,effective reinforcement ratio and area ratio of FRP to steel bars(Af/As).The test results show that fatigue failure of the steel bars-GFRP bars RC beams start with fatigue fracture of steel bars and the fracture surface is significantly different from that of static tensile failure modes.Plane section assumption is verified under fatigue.The fatigue load amplitude has significant effects on the fatigue life.With the increase of fatigue load amplitude,strains in steel bars,GFRP bars and concrete increases,and the fatigue life decrease.The increase of effective reinforcement ratio contribute to decreasing mid-span deflection and crack width,and improve the serviceability.The increase of area ratio of FRP to steel bars(Af/As)has negative effects on the fatigue behaviors of steel bars-GFRP bars RC beams.The fatigue life decrease from 366 thousand cycles to 83 thousand cycles with Af/As increasing from 0.25 to 2.0.Different theoretical models for the midspan deflection of beams under fatigue load are compared and the CEB-FIP 2010 presented satisfactory prediction,and thus is recommended.