无背索斜拉桥钢-混凝土组合脊骨主梁的关键受力分析

根据无背索斜拉桥中大悬臂钢-混凝土组合脊骨主梁的结构和受力特点,采用空间有限元法分析了混凝土桥面板徐变对组合脊骨梁内力分配的影响、钢箱梁扭转效应、组合悬臂挑梁受力及荷载横向分布、桥面板剪力滞效应等几个关键性受力问题,并利用外国规范验算了钢箱梁承压板的局部稳定性。由分析可知,混凝土徐变导致脊骨梁中钢箱梁应力增加,混凝土板应力下降;钢箱梁的扭转翘曲正应力可达到弯曲正应力的10%;大悬臂组合行车道板的横向分布计算取3片梁模型即可,且施工中采取预弯措施可防止组合挑梁的混凝土板受拉开裂;《本四桥规》中承压板容许应力计算公式约具有2.0的安全度;混凝土行车道板的剪力滞效应明显,塔梁固结处的行车道板还出现了负剪力滞现象。上述结论可为同类结构设计提供参考。

Key Force Analysis of Steel-concrete Composite Spine Main Girder on Cable-stayed Bridge without Back Stays

Based on the structural and force properties of steel-concrete composite spine main girder with long cantilevered beams in cable-stayed bridge without back stays,several key loading problems of the structure were analyzed by means of spatial finite element method,including the influence of creep on internal force distribution between steel box girder and concrete deck of composite spine girder,torsion effect of steel box girder,force behaviors and load lateral distribution of composite cantilevered beams and shear lag effect of concrete deck.Local stability of bearing plates in steel box girder was also verified in terms of appropriate foreign specifications.The following conclusions were concluded:(1) concrete creep would lead to the stress increase of steel box girder and decrease of concrete deck;(2) the torsion warping stress is about 10% of bending normal stress;(3) three-beam model is accurate enough to calculate the load lateral distribution of composite carriageway plates with long cantilevered beams and crack of concrete slab due to tensile stress could be avoided by using the preflex measure in construction;(4) the safety degree of the allowable stress formulas of bearing plates in the Specifications and Commentaries for Design of Honshu-Shikoku Bridge is about 2.0;(5) shear lag effect in concrete carriageway plates is serious and the negative shear lag is found at consolidation position between the girder and the tower.These conclusions educed from the analysis could be referenced in design of similar structures.