桁架结构强度计算研究

The investigation of the strength calculation of the truss

分别采用轴力杆单元、弯曲-轴力梁单元和三维实体单元的有限元法对桁架结构进行静力分析.计算结果表明:采用轴力杆单元和采用梁单元的轴向应力接近,采用实体单元节点处的最大等效应力远高于杆单元模型和梁单元模型的应力,采用实体模型的位移大于杆单元和梁单元的位移;理想桁架中应力为零的杆件,用梁单元和实体单元计算应力并不为零;桁杆两端和节点存在应力集中,等效应力数值远大于杆件的应力.理想桁架的计算方法的杆件轴向应力虽然计算精度较高,但是不能反映节点的应力集中,桁架的强度计算应该考虑节点的应力集中.文中研究结果可以用于井架及电塔结构的强度设计.

The numerical analysis for truss is conducted using link element,beam element and the 3D element respectively.Numerical results have shown that the axial stresses of the members are close when using link element or beam element,the maximum equivalent stress at the joints of 3D solid model is much higher than the stress of both link element model and beam element model.The displacement of the solid model is larger than the displacement of both the link element and the beam element.In the ideal truss model,the stress of some members is zero,but it＇s not the same in both the beam element model and 3D element model.Meanwhile the stress concentration are existed at the end of the members and the nodes,the value of the stress obtained from solid model is much greater than those from the link element model or beam element model.The axial stress are of high precision by the traditional method,but the stress concentration both at the end of the members and the nodes can not be reflected,the stress concentration should be considered in the strength condition of the truss.The results of the paper can be used to the design of the derrick and the electric-tower.