工形截面钢拱考虑腹板局部屈曲的承载力设计方法研究

Strength and design of I-sectional steel arches subjected to web local buckling

把工形截面钢拱的腹板做高做薄是提高其承载力的有效方法之一。该文采用大挠度弹塑性壳单元模型,研究焊接工形截面两铰圆弧钢拱在允许腹板局部屈曲条件下的平面内稳定承载力及其设计方法,其中考虑钢拱几何初始缺陷和残余应力的影响。首先,对钢拱在均匀轴压力作用下的承载力和破坏机理进行有限元数值分析和参数研究,考察拱截面腹板高厚比、钢拱几何长细比、截面翼缘腹板板厚比和翼缘宽厚比对钢拱稳定系数的影响。在设定的钢拱翼缘宽厚比范围内,基于大量的钢拱承载力数值分析结果,提炼出腹板高厚比和翼缘腹板板厚比组合效应的等效正则化腹板高厚比,进而获得钢拱稳定系数与等效正则化腹板高厚比以及钢拱正则化长细比之间关系的计算公式。其次,研究压弯组合作用下钢拱腹板高厚比变化对钢拱整体稳定承载力的影响,揭示钢拱压弯组合作用下的破坏机理及稳定承载力。最后通过对大量钢拱算例进行不同压弯组合工况下的极限承载力分析,提出了钢拱在一般荷载或组合荷载作用下承载力设计的计算公式。

A numerical investigation is presented to in-plane strength and design of the pin-ended circular steel arches with a welded I-section subjected to web local buckling. A number of numerical examples of the arches were analyzed by using a large deflection elastic-plastic shell element model considering the web local buckling, and initial geometric imperfections and residual stresses were also involved in the analysis. Key parameters affecting the stability coefficient of the arches are involved in the numerical analyses under uniformly axial compression, which include web height-to- thickness ratio, slenderness and flange-to-web thickness ratio in a required range of flange width-to-thickness ratio. It is found that the stability coefficients of arches under the uniformly axial compression are exclusively related to the equivalent normalized web height-to-thickness ratio and the normalized slenderness, where the equivalent normalized web height-to-thickness ratio is introduced as an integrated result from both the web height-to-thickness ratio and the flange- to-web thickness ratio. Accordingly the design formula of the stability coefficients of the arches is proposed. Additionally, the influence of the web height-to-thickness ratio on strength of the steel arches under combined bending and compression is investigated numerically and a generalized design formula of the arches is developed for predicting the in-plane strength under general in-plane loading.