摘要
受弯构件的稳定性对其承载力往往起着决定性的作用,也是钢结构设计领域的一个重要课题。实际工程中,由于荷载偏心等影响,使得钢梁常常同时承受弯矩和扭矩的联合作用。我国《钢结构设计规范》(GB 50017-2003)给出了集中荷载,均布荷载,以及端弯矩作用下简支梁的整体稳定计算方法,但没有对弯扭联合作用下钢梁的整体稳定性计算进行规定。我国《冷弯薄壁型钢结构技术规范》(GB50018-2002)虽然给出了弯矩和扭矩共同作用下冷弯薄壁型钢梁的整体稳定计算方法,但仅适用于冷弯薄壁型钢结构。对于工字型钢梁在弯扭联合作用下的整体稳定承载力计算,目前的研究还很少。因此,对于此种情况下工字形钢梁的整体稳定承载力研究具有一定的科研意义和应用价值。
本文首先采用能量法,给出了工字形钢梁在三种荷载作用下的整体稳定系数,结合《冷弯薄壁型钢结构技术规范》中对冷弯薄壁型钢梁在弯矩和扭矩共同作用下的整体稳定计算公式,分别给出了偏心均布荷载、跨中偏心集中荷载、1/3、2/3跨偏心集中荷载作用下考虑不同荷载偏置时工字形简支钢梁的整体稳定承载力计算公式,荷载的偏置分别为作用于上翼缘或下翼缘。以有限元分析软件ANSYS为分析工具,按照不同截面尺寸、不同跨度、不同荷载作用类型、不同荷载偏置及不同荷载偏心距建立有限元模型,对三种截面绕弱轴对称的工字形钢梁——双轴对称工字形钢梁、加强受压翼缘和加强受拉翼缘的单轴对称工字形钢梁在弯矩和扭矩联合作用下的整体稳定承载力进行非线性屈曲分析,共计算了180根钢梁。通过对有限元计算结果和理论计算结果的比较,对理论公式在弹性和弹塑性范围的合理性和适用性进行了多方位的验证和评价,并考察扭矩、荷载偏置、截面尺寸和跨度等变化时对弯扭联合作用下工字形钢梁整体稳定承载力的影响。
The stability of thin-walled steel beams is often a decisive role to their carrying capacity, and it's an important aspect in structure design. Steel beams are often suffering combined bending and torsion as the influence of eccentric load in actual projects. In our country, the method to calculate the overall stability of simply supported beams under concentrated load, uniformly distributed load or fixed end moment is introduced in Code for design of steel structures (GB 50017-2003). But there are not any relevant rules for calculating the overall stability of steel beams under combined bending and torsion in this code. Technical code of cold-formed thin-wall steel structures (GB 50018-2002) has introduced the method to calculate the overall stability of cold-formed thin-wall steel beams under bending and torsion, but it's only suitable for the cold-formed thin-wall steel structures. Nowadays, the research on the overall stability of steel I-beams under combined bending and torsion is steel rare. So, it's necessary to research the overall stability of steel I-beams under combined bending and torsion. It has some scientific research meaning and applied value.
In this paper, it presents the overall stability factors of steel I-beams under three typical loads by using energy method firstly. The formulas for calculating the overall stability of simply supported steel I-beams under three eccentric loads is proposed in combination with the formulas for calculating the overall stability of cold-formed thin-wall steel beams under bending and torsion while loads on the compression flange or the tension flange. The loads include uniformly distributed eccentric load, concentrated eccentric load in the midspan and concentrated eccentric load in one-third and two-thirds of the span. The paper uses finite element software ANSYS to analyze the overall stability of steel I-beams under combined bending and torsion according to different parameters, such as section dimension, span, load type, load bias and load eccentricity. The section shapes include doubly symmetric I-section and monosymmetric I-section with compression flange enhanced or tension flange enhanced. It has calculated one hundred and eithty models in all. We can check and evaluate the theoretical formulas in elastic range or elastoplastic range by comparing finite element results with theoretical results. And it studies the influence to the overall stability of simply supported I-beams under combined bending and torsion while torsional moment, load bias, section dimensions and span vary.
引文
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