Soil-structure interaction of a permanent steel fibre reinforced underwater concrete floor system

Abstract

The focus of this research was the implementation of a permanent steel fibre reinforced underwater concrete floor (SFRUCF) as a permanent structural floor. A model was created that can describe the soil structure interaction of an SFRUCF including the highly non-linear behaviour of SFRC. The soil structure interaction of the UCF was modelled in Plaxis 2D with a plate element that includes the behaviour of SFRUC by means of an MN-κ diagram. This model was validated with measured data from the Albert Cuyp garage. It was shown that due to the uplift pressure heave occurred in the clay layer underneath the UCF, which increases the load on the UCF by 10%-30% and should be taken into account in the design. Also the heave from the deep Eemclay was considered. This heave had influence on the total deformations but hardly affected the internal forces in the UCF, justifying the fact that this heave is usually not included in the design of a UCF. A fictive E-modulus is often used to describe the cracked behaviour of steel fibre reinforced concrete. It was shown that using this fictive E-modulus in the building phase leads to an underestimation of the shear forces.
Additionally, a sensitivity analysis was done to show which parameters influence the calculation results, the design and the suitability of a permanent SFRUCF. The suitability of an SFRUCF is determined by the column loads in the final phase and the presence of a stiff raft. It was concluded that an SLS check should be included in the CUR 77 for water tightness, crack width and deformations if an SFRUCF is to be used permanently. The interaction between the raft can be modelled in Plaxis 2D with the plate element that has the behaviour of SFRC. For cases that do not include a stiff raft simpler models can be used such as the Plaxis model with springs or even a beam model with SFRC input.