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在轴向压力和弯矩作用下,平行四边形闭口截面薄壁杆件的受力机理不明确,为确保该种结构的安全可靠性,指导结构设计,以某公铁两用大桥斜主桁的弦杆为原型,建立0°、5°、10°、14.036°、20°、25°6种腹板倾角的杆件有限元模型,计算轴向压力、弯矩作用下杆件横截面的正应力;制作1∶2.4缩尺模型,进行静力试验,测试杆件横截面的正应力,并将实测值与计算值进行对比。结果表明:轴向压力作用下,杆件横截面的正应力分布均匀,腹板倾角对正应力分布的影响非常小;弯矩作用下,随着倾角的增加,杆件横截面的正应力不均匀程度加剧,钝角角点正应力绝对值增加,锐角角点正应力绝对值减小,各角点正应力有限元计算值和理论计算值吻合较好;轴向压力和弯矩单独作用下,随着倾角的增加,杆件的弹性稳定系数降低;杆件横截面的正应力实测值和计算值吻合较好,说明计算值可作为设计依据。
Under the action of axial pressure and bending moment, the force mechanism of parallelogram thin-walled bar with closed cross-section is not clear. In order to ensure the safety and reliability of this kind of structure, The chord was taken as the prototype to establish the finite element model of the web with 6 web inclinations of 0 °, 5 °, 10 °, 14.036 °, 20 ° and 25 °. The axial compressive force and the positive Stress; making 1: 2.4 scale model, static test, test bar cross-section of the normal stress, and the measured values and calculated values were compared. The results show that under the action of axial pressure, the normal stress distribution in the cross section of the bar is uniform and the influence of the web inclination on the normal stress distribution is very small. With the increase of the incline angle, the normal stress of the bar cross section The absolute value of normal stress at obtuse angle increases, the absolute value of normal stress at acute angle decreases, and the calculated value of normal stress at each corner coincides well with the theoretical value. Under the action of axial pressure and moment alone, As the inclination increases, the elastic stability coefficient of the rod decreases. The measured values of the normal stress in the cross section of the rod agree well with the calculated values, indicating that the calculated value can be used as the design basis.