翼缘纵向变厚度焊接工字形截面钢梁整体稳定性能试验

为研究翼缘纵向变厚度焊接工字形截面钢梁的整体稳定性能，共设计了11个变厚度梁和2个等厚度梁并进行无侧向约束整体稳定试验，包含三点弯和四点弯两种加载方式，0、2、4、6、8mm/m共5种厚度变化率。试验结果表明：钢梁均发生弹塑性弯扭失稳破坏，卸载后仍有明显残余变形；相比四点弯加载，翼缘厚度变化对三点弯加载钢梁承载性能的影响更为明显。对现有等厚度梁的整体稳定设计方法和稳定系数曲线进行总结，结合精细化有限元分析得到，变厚度梁的弹性失稳临界弯矩随着翼缘厚度变化率增大而降低。基于现有等厚度梁规范稳定曲线进行变厚度梁稳定承载力计算时，建议采用有限元分析或者以平均截面尺寸下的等厚度梁近似计算弹性失稳屈曲临界弯矩，由此可得相比按跨中最大截面设计相对安全的稳定承载力。最后将试验结果与规范计算所得稳定承载力对比，结果表明欧洲规范BS EN 1993-1-1最为安全，中国规范GB 50017—2017次之，美国规范ANSI/AISC 360-16最不安全。变厚度梁整体稳定设计方法的提出还需进一步深入研究。

Experimental study on overall stability behavior of welded I-section steel beams with longitudinally profiled flanges

To investigate the overall stability behavior of welded I-section steel beams with longitudinally profiled (LP) flanges, eleven LP beams and two counterparts with constant thickness were designed and tested on a setup with no lateral restraint, including three-point and four-point loading, as well as five kinds of thickness changing rate (0, 2, 4, 6, 8mm/m). The results show that all specimens fail with elasto-plastic lateral-torsional buckling and have significant residual deformation after unloading. The influence of varied thickness on bearing capacity is much more obvious for LP beams under three-point loading than that for beams under four-point loading. The design methods and buckling curves for beams with uniform thickness were summarized. Referring to the finite element numerical analysis, the elastic critical moment of LP beams decreases with the increase of flange thickness change rate.When the stability curves in uniform thickness beam design standard is prepared be applied for LP beams, the FE analysis or approximate calculation with average section dimension is recommended to get the elastic critical moment of LP beams. Compared with design based on the critical mid-span section, a relatively conservative moment is obtained. Finally, the test results were compared with the design values, the results show that BS EN 1993-1-1 is the safest, followed by GB 50017—2017, and ANSI/AISC 360-16 is the least safe. The overall stability design method of LP beams needs further study.