FAQ 000632 ZH

计算 RFEM RSTAB

Although there is no external force, there is a jump right before the support in the internal forces diagram for the shear force.

What is the explanation for this?

回答

The internal forces jump right before the support, because imperfections are considered at these locations.

Imperfections from initial sway and/or precamber are applied as equivalent loads to the members. The equivalent load results in additional moments and shear forces. The moments also result in support moments from the inclination.

However, the shear forces may not result in support reactions, because the system would loose its equilibrium.

The pictures explain the issue in more detail.

Figure 1 is a restrained column subject to a axial force.

In the second load case, a precamber is applied to the column.

In the results of the load combination, you can see the resulting shear force from the equivalent load N x Phi0: 10 x 1/282 = 0.035 kN. This new shear force is, however, not an action-effect and therefore not considered as support reaction. The appearing concentrated shear force is therefore always to be regarded as equivalent load form the imperfection.

Also, compare the following Figure 2 of an inclined member with vertical loading. The inclination results in only one support moment.

A horizontal support reaction cannot arise due to reasons of equilibrium (sum of loading = sum of support reactions).

The described above is also true if the system is converted to a member with equivalent loading.

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RFEM 主程序 RFEM
RFEM 5.xx

主程序

结构设计与有限元­分析软件(FEA)可以用于建立平面与空间结构模型,适用于由杆件、面、板、墙、折板、膜、壳、实体以及接触单元等的建模与分析计算。

RSTAB 主程序
RSTAB 8.xx

主程序

空间结构设计与分析软件,主要用于框架、梁与桁架等空间结构的建模与计算。可以输出内力、变形与制作反力的线性与非线性的计算结果。