Concentrated load test at the Poptahof project in Delft (NL)
In previous posts on this blog we have shown few examples of actual application of CRC i2® – so I thought it was time for a couple of cases to show how we utilise the material properties.
In this post, I will show a couple of examples utilising the ability to handle large concentrated loads through internal force redistribution.
CRC i2® deviates from conventional high strength concrete by having a large tensile capacity because of the steel fibres. This enables CRC i2® to effectively “redirect” forces and allows small sections (with a lot of conventional reinforcement) to absorb large internal moment, shear and torsion loads.
The best example of this is the helical staircase, where a helical parapet carries cantilevered steps – resulting in very large combined moment, shear and torsion loads on the parapet, especially at the supports.
Overview of section force distribution of an asymmetrical helical staircase with a restrained straight wall section in one end. Characteristic values.
The analysis is in itself relatively complex – see below combination analysis to determine the moment distribution.
Combination plot to establish total moment distribution in the helical parapet of a complex stair.
The large forces require a lot of reinforcement – both main reinforcement for bending, but also for the shear and torsion loads in the form of stirrups.
Reinforcement for a helical staircase under preparation – the steps are easy to reinforce (l) – it is fitting in the required bars and stirrups in the helical beam that is the issue. Work in progress shown (r).
However, when utilising the ability to absorb the large forces in limited sections, beautiful examples such as the Sidney Stringer academy staircase in Coventry (UK), the Hotel La Tour staircase in Birmingham (UK), the Aggersvold Estate in Jyderup (DK) and the PTCG staircase in Groningen (NL) may be realised.
Completed Hotel La Tour staircase. The parapet beam is restrained at the wall in the upper right corner of the image (B on the section force curve) and then revolves around the column without touching it and ends resting on the floor deck with a specially reinforced base step absorbing the torsion (A on the section force curve).
I hope you found this interesting. We will post more examples on how the unique properties of CRC i2® can be utilized to realize unique structures.
If you are curious how one or more of the projects in our reference section has been realized, don’t be shy to ask for it, and it may end up in a post such as this!
Tommy Bæk Hansen
Group Product Development Manager
Read about Tommy’s 20 years of experience with UHPC right here