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利用拱构和杆件之间的相似之处,可确定下承式拱非弹性侧向弯曲的有效长细比。设计人员可以将该长细比代入杆的强度计算公式中,计算拱的极限应力。本文所推荐的计算公式通过与电子计算机的分析结果相比较;其适用性得到肯定。计算机的模拟分析是针对分离式箱形截面单肋拱(isolatedsingle arches of box-section)和由两根箱形截面拱肋组合而成的下承式桁拱桥(through—typebraced arch bridges composed of twin box-section ribes)这两种情况来进行的。本文所研究的拱,其拱轴线的形状有抛物线型的也有圆弧线型的;矢跨比在0.1～0.2范围以内,沿轴线方向拱肋横截面有等截面的也有变截面的,而且考虑了不同钢材、纵向残余应力及拱的初始侧向弯曲等多种因素的综合作用。公式推导过程中虽然受一些条件的限制。但最后提出的公式作为初步设计用还是足够精确的。
Using the similarities between the arch and the bar, the effective slenderness ratio of the inelastic lateral bending of the underfloor arch can be determined. The designer can substitute this slenderness ratio into the bar’s strength formula to calculate the ultimate stress of the arch. The calculation formula recommended in this paper is compared with the result of computer analysis; its applicability is affirmed. Computer simulations were performed for isolatedsingle arches of box-sections and through-typebraced arch bridges composed of twin boxes -section ribes) these two situations. The arches studied in this paper have the shape of parabola and arc of arch. The ratio of sag to span is within the range of 0.1-0.2, and the cross section of the arch along the axial direction is also of variable cross section. A variety of steel, the longitudinal residual stress and the arch of the initial lateral bending and other factors combined. Although the formula derivation process is limited by some conditions. However, the formula proposed at the end is still accurate enough as a preliminary design.