杭州湾大桥梁上运梁过程仿真分析

对杭州湾大桥非通航孔滩涂区的50 m箱梁上运梁过程进行空间仿真分析。按照实际工况荷载,考虑预应力空间效应,施加等效节点力,并合理考虑支座等细部建模,建立精密的三维实体有限元仿真模型。混凝土的材料特性按现行公路桥梁设计规范取值,考虑最不利计算荷载,支座底部按刚性单元模拟,而与梁相接触层的弹性模量满足梁端回转变形时不出现拉应力,在结构离散时尽可能细分单元网格,由于梁端的应力相对复杂,采用比跨中更密的单元网格。计算承重箱梁整体变形和空间应力分布特性,结果为,由于载荷位置在支座附近,变形相对较小,最大挠度在反拱位移之内。支座截面的最大主拉应力发生在底板上表面侧,超过混凝土的开裂强度,因此,对该区域的混凝土应采取加劲处理,以防止混凝土拉裂;最大主压应力发生在架桥机肢腿处附近,小于混凝土的抗压强度。

Simulation Analysis of Girder Transport Process on the Box Girder of Hangzhou Bay Bridge

The 50 m box girders in the tidal flat section of unnavigable channel bridge in Hangzhou Bay Bridge adopt the approach of trolley on the under bridge to transport and erect the girder. Based on the actual working and load conditions, a precise 3D solid FEM simulation model is established by taking account of the space effects of prestressing force, applying equivalent node force and taking reasonable consideration of support details, etc. The values for concrete characteristics are determined according to current specifications for the design of highway bridge. The load is calculated with the consideration of the worst factors. The bottom of the support is simulated as rigid element. Modulus of elasticity for girder contact layer will not appear tensile stress when rotations and deformations occur at girder end. Element mesh should be as subdivided as possible when the structure is discretized. Owing to the relative complexity of the stress at girder end, thicker than span intermediate element mesh is adopted for girder end. The integral deformation and the space stress distribution of weight-bearing box girder are calculated. Results indicate that the deformation is relatively small and the maximum deflection is within the reversed arch because the load is quite close to the support. The maximum main tensile stress of the support section occurs at the side of bottom plank surface, which exceeds concrete cracking strength. Consequently, concrete in this area should be treated and stiffened so as to avoid it from cracking. When the maximum main compressive stress occurs near the stabilizer of girder-erecting machine, its value is less than the compressive strength of concrete.