钢与预应力混凝土后结合法组合梁的受力特性研究

为了明确大跨度后结合预应力组合梁桥的受力性能，以一主跨70 m的预应力组合梁桥为例，采用空间有限元模型详细模拟了组合梁的施工过程，计算从施工到成桥初期及长期运营情况下组合梁的受力情况。计算结果表明：中支点钢梁上翼缘和底板在施工阶段的最大应力分别为118 MPa和-133 MPa，后结合法和顶升/回落法在中支点混凝土桥面板内产生7.33～10.33 MPa的预压应力储备；中支点钢梁上翼缘和底板在短期运营阶段的最大应力分别增长了22 MPa和13 MPa，而中支点混凝土桥面板在曲线外侧的边缘只剩下3.33 MPa的预压应力储备，满足全预应力状态的要求；在第10年的长期运营阶段，中支点钢梁上翼缘和主跨跨中钢底板的最大拉应力分别减少17%和35%，中支点钢底板和主跨跨中钢梁上翼缘的最大压应力分别增加10%和42%。收缩徐变在长期运营阶段降低负弯矩区混凝土桥面板的预压应力储备，负弯矩区混凝土桥面板在运营第2年由全预应力构件变成A类部分预应力构件，在运营第13年变成B类部分预应力构件。

Study on Mechanical Characteristics of Steel and Prestressed Concrete Post-combined Composite Girder

To clarify the mechanical characteristics of long-span post-combined prestressed composite girder bridge, taking a prestressed composite girder bridge with the main span of 70 m as an example, the construction process of composite girder is simulated in detail by using the spatial finite element model to calculate the mechanical characteristics of the composite girder from the construction stage to the initial stage of finished bridge and in the long-time operation stage. The calculation result shows that the maximum stress of the upper flange and bottom plate of the middle fulcrum steel girder are 118 MPa and -133 MPa respectively during the construction stage. The 7.33 ~ 10.33 MPa preloaded stress reserve is produced within the middle fulcrum concrete bridge deck by the post-combined method and the jacking/fallback method. During the short-term operation stage, the maximum stress of the upper flange and bottom plate of the middle fulcrum steel girder are increased by 22 MPa and 13 MPa respectively, while the middle fulcrum concrete bridge deck has only 3.33 MPa of preloaded stress reserve left at the outer edge of the curve, which meets the requirements of full prestressing state. During the long-term operation of the tenth year, the maximum tensile stress of the upper flange of the middle fulcrum steel girder and the steel baseplate in the middle of main are reduced by 17% and 35% respectively, and the maximum compressive stress of the middle fulcrum steel baseplate and the steel girder upper flange in the middle of main span are increased by 10% and 42% respectively. The shrinkage and creep will reduce the preloaded stress reserve of the concrete bridge deck in the negative bending area during the long-term operation stage. The concrete bridge deck in the negative bending area will change from the full prestressed component to Class A partially prestressed component in the second year of operation and to Class B partially prestressed component in the 13th year of operation.