FEM - Direction vector normalization - since SCIA Engineer 24.0

Introduction

This chapter is to provide a closer information about change originated from the FEM solver implemented in SCIA Engineer version 24.0. The direction vector within the seismic load case defined by user is being normalized in the background. The change would be observed if the direction type is set to general, and all the vector dimensions are explicitly defined by user.

This change is applicable for seismic load cases with direction of the vector set as general (as for the other direction cases, the vectors are already normalized).

The reason of this change is unifying the seismic load case definition work-flow between the cases, where the direction vector is defined by "general" and specific direction (x, y, z). As there are two factors to be defined by the user, direction (by x, y, z coordinates) and acceleration (by scalar value). It is assumed, the user intends to define only direction within the direction vector by definition of the vector components (x, y, z), hence the direction is considered by vector of size = 1. Afterwards, the seismic actions are altered by the value of the acceleration factor.

Example

In the figure below there is an example of the behaviour before SCIA Engineer version 24.0 and since v 24.0.

The meaning of these components for direction vector is to define the direction, not the size. So the size of the direction vector is considered as 1.0. The size is then modified by the "acceleration factor".