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进行了4根编号分别为B1、B2、B3和B4的体外预应力混凝土简支梁受力全过程的试验研究。其中B1、B3和B4梁的体外预应力筋为碳纤维筋,B2梁的体外预应力筋为带塑料套管的无粘结钢绞线。全部试验梁采用三分点加载方式。试验表明,体外预应力混凝土梁的跨中荷载-挠度曲线呈现为三折线的形状,分别以受拉区混凝土开裂、梁内非预应力受拉钢筋屈服及混凝土压碎为特征点。试验还表明,无论是钢绞线体外筋还是CFRP体外筋,从开始加载到构件破坏的过程中,体外预应力筋应力增量与跨中挠度基本呈直线关系。这些现象均与相应的体内无粘结预应力混凝土梁的现象一致。试验结果为建立统一的既适用于体外预应力钢筋又适用于体外预应力CFRP筋的极限应力计算方法提供了基础。
The experimental research on the whole process of four external prestressed concrete beams supported by B1, B2, B3 and B4 respectively was carried out. The external prestressing tendons of B1, B3 and B4 beams are carbon fiber reinforced tendons, and the external prestressing tendons of B2 beams are unbonded steel strands with plastic casing. All test beams using three points load mode. The test shows that the mid-span load-deflection curves of the externally prestressed concrete beams show the shape of a tri-fold line, and are characterized respectively by cracking of the concrete in the tension zone, yielding of the non-prestressed tensile steel beams and crushing of the concrete. The experiment also shows that the external stress of prestressing tendons and the mid-span deflection are in a linear relationship from the initial loading to the failure of the components. These phenomena are consistent with the corresponding in vivo unbonded prestressed concrete beams. The test results provide the basis for establishing a unified method for calculating the ultimate stress of both externally prestressed steel bars and externally prestressed CFRP bars.