Abstract

This article highlights the importance of construction stages in studying frame structures with transfer beams. For this purpose, a result comparison between Advance Design construction stages and classical full model single run analysis are presented for a steel frame model with a transfer beam.

Keywords: Advance Design, Construction Stages, Transfer Beam.

1. Introduction

In conventional structural analysis, all loadings are applied at once on the complete final structure before studying their effects in a single step calculation. In other words, no loading of any type is applied on the structure until the entire construction process is completed. However, in practice, structures are constructed in stages (story by story) and loadings such as self-weight, construction and finishing loads are present at each stage prior to structure completion. Therefore, at each construction stage, the distribution of displacements and internal forces in the completed parts of the structure (due to the existing loads) is not affected by elements of upper stories that do not exist yet.

Neglecting the construction stages effect in the classical analysis will sometimes yield wrong results.  A good example where this effect should not be overlooked is in analyzing frame structures with transfer beams.

2.Frame structure with transfer beam

A steel frame structure with a transfer beam in story 1 is considered. This structure is subjected to its self-weight and finishing dead loads at each story (refer to Figure 1).

2.1.            Construction stages

Construction stages are defined according to the actual story by story construction sequence (Refer to Figure 2).

2.2.            Results comparison

To highlight the importance of conducting construction stages analysis, results comparison between the Advance Design classical analysis (all loads applied at once on the complete final structure) and construction stages will be presented (refer to Figures 3, 4 and 5).

3.     Conclusion

The real structural behavior obtained by the construction stages analysis is very different from the results of the classical analysis. Neglecting the construction stages effect, will lead to a dangerous under dimensioning of the transfer beam and middle column.

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