不同强度混凝土T形加固梁抗弯承载力试验研究

Experiment study of T beams poured with different strength concrete and strengthened with near surface mounted FRP

通过11根T形梁试验,研究了嵌入式FRP筋加固具有不同强度等级混凝土梁的破坏模式、内力和变形特征等力学性能,讨论了混凝土强度等级对加固梁性能的影响。结果表明:加固筋的表面特征影响加固梁的破坏模式,光圆FRP筋加固梁产生因FRP筋-黏结剂/黏结剂-混凝土界面的剥离引起的加固梁弯曲破坏,混凝土的强度对加固梁的破坏模式基本无影响;螺旋FRP筋加固梁可能产生沿轴线方向裂缝,并最终发生由混凝土保护层的劈裂、剥落引起的加固梁弯曲破坏,但随着混凝土强度提高,加固梁的破坏可能转变为局部保护层剥落破坏模式。加固筋的表面特征是影响加固梁黏结性能的重要因素,并导致对加固梁极限承载力的影响,FRP筋的材料种类对承载力的影响不明显。随着混凝土强度等级的提高,嵌入式FRP加固梁的局部黏结强度增大,但其对加固梁承载力的影响远小于FRP筋的表面特征(变形筋)对加固梁承载力的影响。并且,混凝土强度对加固梁的极限承载力影响不大。在破坏时,各加固梁的跨中挠度的变化也差别不大。

According to the orthogonal experiments result of 11 T shape concrete beams reinforced with FRP fibers,this paper mainly investigated the influence of concrete strength on failure mode,bearing capacity,deformation features of the beams.The characteristic of the fiber surface had great impact on the failure mode.The deconstructed causation of beams reinforced with round FRP fiber surface could attribute to debonding of the FRP fiber and concrete,the concrete strength had no obvious effect on the deconstruction mode.Beams with thread FRP fibers might have the longitude cracks,and finally lead to the split flaking of concrete layer and the deconstruction.Meanwhile,with the increasing strength of the concrete,the failure mode of the beam could transform into the local layer flaking mode.The character of the fiber surface could dramatically affect the bonding performance and the ultimate bearing capacity of the beam.Fibers with different materials had no obviously influence on the performance of the beam.bearing capacity with the increasing of the concrete grade,the beam reinforced with FRP fiber had higher local bonding strength,but the impact was less dramatic than that of the fiber surface character.However,the concrete strength had minute effect on the ultimate bearing capacity of beam.The deflection value in the middle of the beam varies tinily during the deconstruction experiments.