某重载铁路连续刚构桥梁体外预应力加固设计

External Prestressing Reinforcement Design of a Heavy-duty Railway Continuous Rigid Frame Bridge

某重载铁路预应力混凝土连续刚构桥(96+132+96)m,在张拉底板预应力阶段出现底板混凝土大面积崩裂等现象。其成因主要有:(1)对波纹管的固定约束不够,部分波纹管上浮、移位,张拉时对混凝土产生较大拉力,导致保护层混凝土剥落;(2)箱梁底板上下层钢筋网缺失部分联系筋,钢绞线弯起处防崩钢筋数量不足及安装位置稍有偏差,在预应力张拉时抵抗下崩力不足,梁底混凝土出现崩裂。针对该病害,从安全有效、经济适用、思患预防等方面出发,提出采用凿除部分底板混凝土并重新浇筑、增加顶板厚度以及体外预应力加固等方法提高桥梁结构承载力。结果表明:(1)静力荷载作用下,边跨最大挠度20.2mm,中跨最大挠度21.8mm,挠度校验系数在0.64~0.88之间,加固后桥梁满足抗弯刚度要求;(2)动力荷载作用下,实测一阶振动频率大于理论频率,表明桥梁加固后的刚度大于理论刚度,满足设计要求。

In a heavy-duty railway prestressed concrete continuous rigid frame bridge(96+132+96)m,large-area cracks of the floor concrete occurred during the prestressed stage of the tension floor.The main reasons are as follows:(1)The corrugated pipes are not fixed and restrained enough,and some of the corrugated pipes float up and shift,which will generate a large tensile force on the concrete during tension,causing the protective layer of concrete to peel off;(2)The upper and lower layers of the box girder floor steel mesh Missing part of the contact bars,insufficient number of anti-collapsing bars at the bending of the steel strands,and a slight deviation in the installation position,insufficient resistance to collapse during prestressing,and cracks in the concrete under the beam.In response to this disease,from the perspectives of safety,effectiveness,economy,and risk prevention,it is proposed to remove part of the bottom plate concrete and re-pouring,increase the thick ness of the roof and strengthen the external prestress to restore the integrity of the bridge and improve the bearing capacity of the structure.Reinforcement method.The results show that:(1)Under static load,the maximum deflection of the side span is 20.2mm,the maximum deflection of the mid-span is 21.8mm,and the deflection check coefficient is between 0.64 and 0.88,which all meet the requirements of beam rigidity;(2)dynamic load effect Below,the measured first-order vibration frequency is greater than the theoretical frequency,indicating that the rigidity of the bridge after reinforcement is greater than the theoretical rigidity,which meets the design requirements.