Reanalysis of structures with varying cross‐sectional values based on influence functions

Abstract

AbstractDigital building data models are increasingly employed in the design and construction planning of buildings, so that almost the entire planning process is covered with three‐dimensional (3D) models. Starting with available detailed CAD data it is easy to generate 3D models for the design analysis. However, this comes with a price since the complexity of the 3D models requires a high computational effort. Considering the fact that the structural engineer often must investigate numerous design variants and system modifications during the planning stage to reach an optimal solution it makes sense to facilitate the multitude of these recalculations by an easy‐to‐use reanalysis technique.The approximation method we use for reanalysis is referred to as the Sensitivity Analysis with Green's functions (SAGF). The basic principles of the SAGF method can be found in [2,3]. It can be used very advantageously for reanalysis purposes, especially in the presence of complex computational models, and allows for a quick comparison of different design variants. In this paper, the method is used to determine how the system responses (internal forces, displacements) are affected by local changes in the stiffness of frame elements as they are typical for modifications of cross‐sectional values in steel structures such as when haunches are added at nodes.In [1] Abdank already presented an approach to determine the changes in structural response of beams from the subsequent consideration of haunches without performing a complete recalculation. In comparison to this, the presented SAGF method is applied very beneficially in connection with 3D models.Furthermore a 2D implementation of the presented reanalysis technique can be found in the program BE‐FRAMES [4]. It allows for a fast and simple “one‐click”‐reanalysis of various design variants since the designer can traverse the different designs forward and backwards – in a blink of an eye, with simple mouse clicks. An additional benefit is that the program can display influence functions for any displacement and force component so that with this graphical tool the engineer can predict the effects of design changes quite easily.