Cidect 2W: Hollow section columns embedded in concrete

1. Introduction and background


Architectural trends today show an increase in the use of hollow section members, for both building and bridge structures.
This is primarily due to their advantageous characteristics for structural as well as aesthetic aspects of design as compared to conventional open-section members.
Many advancements were made, but there are still areas which need some improvements.
In investigations carried out in the scope of ECSC-Project 7210-SA/511, the design embedded length of open sections could be reduced to 40 up to 50 % of the previously allowed values.
It is proven in Munich by Heimershof, that for circular and rectangular timber sections, a smaller embedded length is adequate for design.
The lower embedded length and the corresponding economic benefits not only reduce the volume of earth excavation, but also the foundation dimensions. Also, erection of such columns is simplified.
More advantages are expected in areas where the ground water level is very high.
At present, hollow sections are designed very conservatively, which presents a disadvantage in the use of hollow sections as a result of deeper foundation requirements than for other sections.
Appropriate turnovers may be expected, when columns of steel structures made of hollow sections are just as economically designed as columns made of open sections.
This research project may be considered as an extension of

  • CIDECT Research Project 2J and
  • ECSC Project 7210-SA/511 for rolled open sections

to hollow sections.


2. Aim of the project


This research programme considers the following aspects:

  • Investigation whether the existing design formulae determined for open sections can also be used (with possible modifications) for circular and rectangular hollow sections
  • Theoretical work (financial support of the German Research Foundation, DFG, is applied for) substantiates the low number of tests.
  • Especially for circular hollow sections, a more favourable mechanism of load shedding and failure is expected, where the embedded length to be selected or designed is reduced again, in comparison to open sections.
  • Including the modified design formulae in existing standards.


In the framework of these tests additional information about the load carrying behaviour of these elements will be achieved using strain and deformation measurements. With this, a more detailed view about

  • Failure mode
  • Strain distribution inside and outside of the foundation
  • Distribution of forces
  • Crack pattern

will be possible.