GGU-CANTILEVER: Structural system

The structural analysis required to determine the state variables (displacement, moment, shear force and normal force) is by means of a rod construction module, which treats the cantilever wall and any anchors and struts as a single structural system. The wall is taken into consideration as a rod construction, running along the centroid of the cantilever wall. The base of the structural system corresponds to the top of the footing as shown in the 2 figures in “Theoretical principles: Determination of wall loads for reinforced concrete design” (Base of wall (stem) Example 1/Example 2). Full fixation is assumed.

The wall is analysed using the finite-element method. The size of the finite elements (rods) can be defined in the menu item "System/Depth subdivisions".

The setting in the dialog box assumes subdivision into 0.05 m long rods. Empiricism indicates that this produces sufficiently accurate results. A reduction in these values is not necessary.

The stiffness EI of the wall is acquired from E·d³/12, where d is the horizontal thickness of the wall in the section under consideration. The stiffness of each element is assumed as constant, where the thickness is the thickness at the centre of the section. The remaining values of any anchors or struts can be specified before beginning the analysis. If anchors or struts exist in the system, the point of acting is automatically placed in the centroid axis.

Using FEM produces equation systems in which the number of unknowns is a function of the number of rods. The solution to the equation system is acquired in GGU-CANTILEVER using Cholesky's method, which is also employed in other GGU programs and is numerically highly stable.