悬臂拼装施工的预制节段箱梁桥预应力参数优化

Prestress parameters optimization of precast segmental box girder bridge by cantilever assembly method

为揭示预制节段箱梁桥预应力相关参数对悬臂拼装阶段和合龙阶段箱梁横截面应力及施工期线形的影响,选取某工程一联三跨预制节段箱梁桥,针对悬臂拼装阶段和合龙阶段不同预应力参数取值对桥梁受力状态及变形特征的影响进行数值模拟。研究结果表明:预制节段箱梁桥顶板钢束最优张拉控制应力为预应力钢束抗拉强度标准值的0.70~0.75倍,与此同时应控制预应力钢束截面积不低于0.000 98 m^(2)(7Ф15.2 mm)。顶板单侧钢束组预应力合力作用线与顶板中轴线之间的距离,即顶板预应力合力偏心距宜取箱梁宽度的0.22~0.26倍。合龙阶段采用先张拉底板、腹板通长钢束,再张拉中、边跨局部钢束的方式可使桥梁在不同张拉阶段之间的线形及横截面应力变化更加平缓,有利于施工期间结构的安全控制。

To elucidate the influence of prestress-related parameters of precast segmental box girder bridges on the stress distribution across the cross-section and longitudinal profile during the cantilever assembly and closure stages,a three-span prefabricated segmental box girder bridge was selected.Numerical simulations were conducted to investigate the effects of various prestress parameters during the cantilever assembly and closure stages on the structural responses and deformation characteristics of the bridge.The research findings indicate that the optimal tensioning control stress for the top slab tendons of precast segmental box-girder bridges is 0.70-0.75 times of the standard tensile strength value of prestressing tendons,concurrently necessitating the constraint that the cross-sectional area of the prestressing tendons should not fall below 0.00098 m^(2)(7Ф15.2 mm).The distance between the resultant prestressing force line of the single-side steel strand group in the top slab and its centroidal axis,namely,the eccentricity of the resultant prestressing force in the top slab,is recommended to be selected within the range of 0.22 to 0.26 times the width of the box girder.During the closure phase,the utilization of continuous steel tendons for both the bottom slab and the web was pretensioned,followed by the subsequent tensioning of localized tendons for midspan and edge spans,which facilitates a smoother distribution of alignment and cross-sectional stresses across various tensioning stages by promoting enhanced structural safety control throughout the construction period.