斜拉桥U形预应力索塔锚固区受力与抗开裂试验研究

Experimental Study on Force and Crack Resistance Test of Cable-pylon Anchorage Zone with U-shaped Prestressed Tendons on Cable-stayed Bridge

为研究斜拉桥U形预应力索塔锚固区的受力与抗裂特性,采用ANSYS有限元软件建立了淮沭新河大桥桥塔8节段有限元模型。分析了应力分布规律,并选取最不利索力节段开展了足尺模型静载试验研究索塔锚固区的实际受力特性,进一步提出了索塔锚固区抗裂系数以探讨其抗开裂性能。结果表明:在U形预应力工况下,索塔塔壁及锚固区整体呈受压状态,索塔短壁外部和长壁内部区域存在-7.41~-6.1 MPa的预压应力;U形预应力筋锚固处和圆弧段外侧区域处于复杂应力状态,出现1.5~2.0 MPa的局部集中拉应力;在索力组合工况下,塔壁压应力降低至-4.43~-2.78 MPa,此时塔壁内应力水平较均匀;索塔短壁外部和长壁内部区域相对U形预应力工况出现约为3.0 MPa的拉应力增量,即预压应力很好地抵消了索力产生的拉应力;斜拉索锚固区存在一定应力集中,锚固面出现最大压应力-14.58 MPa,锚固区凹槽侧面出现1.53 MPa的最大拉应力,为受力最不利位置;在模型加、卸载过程中,模型各测点实测应力与荷载等级基本呈线性关系,模型整体处于弹性受力状态;数值计算值与试验实测值相对误差在15%以内,吻合良好;锚固区抗裂系数最小为1.38,大于1.0限值,表明U形预应力筋为索塔锚固区提供有效的预压应力储备,索塔锚固区具有良好地受力与抗开裂性能。

In order to study the force and crack resistance characteristics of the cable-pylon anchorage zone with U-shaped prestressed tendons on cable-stayed bridge,a finite element model containing 8 pylon segments of Huaishu New River Bridge is established with ANSYS software.The stress distribution rule is analyzed,the most unfavorable cable section is selected,a full-scale static model test is carried out on site to study the actual mechanical characteristics of the cable-pylon anchorage zone,and the crack resistance coefficient of the cable-pylon anchorage zone is further proposed to discuss the crack resistance performance.The result shows that(1)under the U-shaped prestressing working condition,the entire pylon wall and the anchorage zone are in a compressed state,and the compressive stress at the external side of the short pylon wall and the internal side of the long pylon wall is in the range from-7.41 to-6.1 MPa;(2)the anchorage area of U shaped prestressed tendons and the external area of the arc section are in a complex stress state,and display local concentrated tensile stress of 1.5-2.0 MPa;(3)under the working condition of combined cable forces,the compressive stress of the pylon wall decreases to the rang from-4.43 to-2.78 MPa,the stress of the pylon wall is relatively uniform;(4)the external side of the short wall and the internal side of the long wall of the cable pylon have a tensile stress increment of 3.0 MPa compared to the U-shaped prestressing working condition,which indicating that the pre-compressive stress effectively counteracted the tensile stress generated by the cable force;(5)there is a certain stress concentration in the anchorage zone of the cable,and the maximum compressive stress-14.58 MPa appears on the anchorage surface,the maximum tensile stress of 1.53 MPa appears on the side of the groove in the anchorage area,which is the most unfavorable position;(6)during the loading and unloading process of the model,the measured stresses at various points of the model showed a nearly linear relationship with the load level,indicating that the model worked in an elastic state;(7)the relative error between the numerical and experimental stresses is within 15%,which is in good agreement;(8)the minimum crack resistance coefficient of the anchorage zone is 1.38,which is greater than the limit value of 1.0,indicating that the U-shaped prestressed tendons provide an effective prestress reserve for the anchorage area of the pylon,and the cable-pylon anchorage zone has good force and crack resistance performance.