桁架外形对其次应力的影响分析

理想桁架的计算模型一直是桁架截面设计的依据,但实际桁架的结点构造与此计算模型不符.实际桁架中广泛存在次应力,桁架外形对次应力的影响很大.利用有限元方法对各种不同外形的桁架因结点刚性而产生的次应力进行了计算,对它们的次应力的大小和分布特征进行了对比,从中分析了桁架次应力随桁架外形改变而改变的规律性.初步探讨了形成上述规律性的原因和减小桁架次应力不利影响的方法.指出了各种不同外形的焊接钢桁架因次应力而对截面设计产生的不同影响,并提出了考虑次应力时的设计改进建议.

Analysis for influence of the shape of trusses upon the secondary stress

The cross-section designing of trusses is always bases on the calculation model of ideal trusses. The structure of panel points of the real trusses is quite different from this model. There are secondary stresses in most real trusses. The shapes of trusses have significant influence upon them. the secondary stress of trusses with different shapes due to the rigidity of panel points is computed by the finite element method. The size and distribution of the secondary stresses in those trusses are compared. The variation of the secondary stresses with truss shapes is therefore analysed. The reasons resulting the secondary stress and the motheds decreasing its negative influence are preliminarily discussed. The different influence upon cross-section disigning of steel trusses with different shapes due to the secondary stress is illustrated. The designing improvement of the steel trusses is suggested on account of the secondary stresses.