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基于宁波市外滩大桥桥塔节段,采用预应力钢绞线自平衡加载方式进行1∶3.34桥塔节段缩尺模型荷载试验,采用非线性有限元方法,研究了考虑初始缺陷和局部屈曲的桥塔节段的传力路径、受力特性、实际承载能力和局部失稳机理。研究结果表明:外荷载主要由主塔两外箱各板件承担,从靠近截面突变处开始,外箱和内箱各板的应力分别呈现递增和递减的趋势,内箱承受的外荷载逐渐向外箱传递,各板应力最大值均出现在截面形状突变处;根据截面平均应力与测点应力的关系可将桥塔节段测点分成轴压、向钢箱内、外侧压弯三类;试验得到桥塔节段的强度折减系数大于0.90,且采用有限元分析得到节段模型的极限荷载是理论极限荷载的1.06倍;虽然纵向加劲肋和横隔板结构能有效防止桥塔结构中加劲板件的局部屈曲,但因截面突变处容易造成应力集中,是最易发生局部屈曲破坏的位置,因此,应注意截面突变处外箱顶底板与内腹板交接附近的纵向加劲肋的设计与施工;在极限荷载作用下,外箱各板件在截面突变处会因局部屈曲而导致无法继续承载。
Based on the section of the tower of Ningbo Beidai Bridge, the 1: 3.34 bridge tower section scale model load test was carried out by means of self-balanced prestressed strand loading method. The nonlinear finite element method was used to study the influence of initial defects and local buckling Pylon section of the force path, the force characteristics, the actual carrying capacity and local instability mechanism. The results show that the external load is mainly borne by the plates of the two outer boxes of the main tower. From the point of sudden change near the section, the stresses of the outer and inner boxes increase and decrease, respectively. The external load to the inner box gradually increases According to the relationship between average stress and measuring point stress, the measuring points of bridge tower section can be divided into axial compression and bending to the inside and outside of the steel box. The strength reduction coefficient of the pylon section is greater than 0.90, and the ultimate load of the section model is 1.06 times of the theoretical ultimate load by the finite element analysis. Although the longitudinal stiffener and the diaphragm structure can effectively prevent the pylon structure The local buckling of the stiffened plate is easy to cause the stress concentration due to the sudden change of the cross section, which is the most prone to local buckling damage. Therefore, attention should be paid to the design of the longitudinal stiffener near the junction of the top plate and the inner plate And construction; under the ultimate load, the outer box of each plate in the section of the sudden change due to local buckling and can not continue to carry.