体外预应力加固预应力混凝土梁的静力试验

Static experiment on prestressed concrete beams reinforced by external tendons

为研究体外预应力加固对预应力混凝土梁(PC)抗弯刚度和中性轴变化规律的影响,设计并制作了2片预应力混凝土静载试验梁,详细测试了采用三折线体外预应力筋加固PC梁后的关键截面竖向和位移、钢筋及混凝土应变、预应力钢筋内力等静力参数;分析了其中性轴和刚度变化规律,并与规范公式进行对比,最后提出了刚度计算公式。结果表明:与未加固梁相比,加固后的PC梁弹性阶段延长,破坏阶段竖向挠度减小37.7%;加固后梁受拉侧钢筋应变在开裂后增幅较未加固梁减少66%;加固后梁钢筋受力均较未加固梁大,弹性阶段刚度提升,中性轴保持原有位置,采用实测钢筋和混凝土应变推算的中性轴变化规律基本一致;通过修正传统公式计算的刚度与实测结果吻合较好。

To study the flexural stiffness and neutral axis variation of PreStressed Concrete Beam(PSCB)influenced by the external prestressing reinforcement.Two PSCBs were designed and made.And the static parameters(such as vertical and displacement of main sections,strain embed in reinforcement and concrete,internal force of prestressed reinforcement)of PC beams with trilinear external prestressing tendons were tested in detail.The flexural stiffness and neutral axis were analyzed and compared with the formulas in code.Finally,the stiffness calculation formulas were proposed.The results show that:compared with the PSCB without external prestressing,the elastic stage of the strengthened PSCB is prolonged.The vertical displacement at the failure stage is reduced by 37.7%;The steel strain in tension zone suddenly increases after cracking.And the strain increment of the beam without external prestressing reduced by 66%compared with PSCB with external prestressing.The steel stress in beam with external tendons is larger than that of the PSCB without external prestressing.And the stiffness in elastic stage is improved.The neutral axis maintains its original location.The flexural stiffness prediction using the presented analysis model gives good agreement with experimental results.