In the construction of the arch of the reinforced concrete arch bridge,the self-weight of the cantilever-cast segments and weight of form travelers induce oversized tensile stresses in partial arch cross-section and offsets of the tie-up towers.This paper presents the methods to determine the forces of forestay and backstay cables,which is developed from the stress superimposition principle and influential matrix to determine forestay cable forces,and derive the method to judge the timing to dismantle forestay cables when the stresses in the arch cross-section do not meet the requirements.It is suggested to utilize the correction coefficients of backstay cable forces to actively adjust the forces of the forestay and backstay cable forces,to allow the tie-up tower to generate the backstay cable forces that approximate the data in the cantilever casting of the arch,but in the opposite direction.And a calculation procedure for the forestay and backstay cable forces that could simultaneously meet the requirements of arch stresses,tie-up tower offset and alignment of the completed arch is proposed.The presented methods have been applied to an aqueduct crossing Baifuhe River,a concrete arch bridge spanning 180 m.The calculated and measured values of the forestay cable forces,backstay cable forces,stresses in arch,completed arch alignment and the offsets of the two tie-up towers were compared.It is shown that the maximum tension difference between the forces of forestay and backstay cables calculated by the presented methods and the actual tensioning forces is 6.02％.During construction,five pairs of forestay cables can be dismantled in sequence to make the tensile stresses in the arch cross-section meet the design requirements.The measured maximum offset of the tie-up tower is 3.3 cm,smaller than the maximum allowable limit offset of 4.0 cm.The measured maximum tensile stress in the arch cross-section is 1.74 MPa,below the design value of 1.8 MPa.The bias between the alignment of the completed arch and bare arch alignment is 0.5 cm,indicating a sound arch alignment and proving that the presented methods are applicable.
关键词
混凝土拱桥/斜拉扣挂/悬臂浇筑/扣索力/锚索力/塔架偏位/锚索力修正系数/有限元法
Key words
concrete arch bridge/cable-stayed cantilever casting system/cantilever casting/forestay cable force/backstay cable force/tie-up tower offset/correction coefficient of backstay cable force/finite element method
维普
万方数据