Safe Upgrading: Tailor‑Made Reinforcement for the La Tourelle Shopping Centre
The upward extension of the La Tourelle shopping centre in Geneva resulted in a significant increase in the loads on the floor slabs and the corresponding foundations, exceeding the load-bearing capacity of the existing structure. To meet these new requirements, S&P developed a bespoke FRP strengthening solution that combined both prestressed and non‑prestressed carbon fibre laminates with carbon fibre fabrics, enabling the structure to resist bending, shear and point loads – all without altering the geometry of the building
Project Description
Situation
As part of this upward extension project, the loads acting on the slabs and concrete beams increased significantly. To determine the material properties and to verify the load-bearing capacity of the structure, the project engineer provided the S&P specialist team with the calculated actions as well as the results from material tests, exploratory investigations, and on‑site measurements of the existing reinforcement and concrete.
The most affected element was the ground‑floor slab, specifically the existing central downstand beam, which rests on three columns and spans two bays of nine metres each.
Problem
The existing condition of the load‑bearing structure was not sufficient to safely accommodate the additional actions resulting from the upward extension. For this reason, targeted strengthening was required, in particular for the ground‑floor slab and the central downstand beam.
In the anticipated final state, the concrete beam will be subjected to additional concentrated point loads. As a result, the positive and negative bending moments increased by approximately 20% to 80%, clearly exceeding the reserve capacity of the existing reinforcement. Consequently, the reinforcing steel would have reached its yield limit rapidly.
A purely flexural tensile strengthening using externally bonded carbon laminates would therefore not have been adequate. Additional shear strengthening of the beam was required to safely transfer the increased shear forces.
Solution
To meet the various requirements of the project, S&P developed several solutions in close collaboration with the design office:
Strengthening of the floor slabs
The floor slabs were strengthened using CFRP laminates applied to either the underside or the top surface, depending on the direction of loading. This ensured adequate capacity to resist the newly introduced positive and negative bending moments.
Strengthening of the central downstand beam
To address the project’s specific challenges, S&P developed several tailored solutions in close cooperation with the design office. The strengthening works were carried out by Marti Construction SA of Geneva.
- Active strengthening: In collaboration with the structural repair specialists at Marti SA, the S&P team installed prestressed CFRP laminates on both the underside and the top of the beam. The objective was to reduce the stresses in the existing steel reinforcement and to achieve a significant increase in the beam’s load‑bearing reserves. Throughout the intervention, the cross-sectional dimensions of the beam remained unchanged, ensuring that the clear room height was preserved.
- Additional strengthening: In addition, the specialists installed non‑prestressed, externally bonded CFRP laminates—using end anchorages where necessary—along with CFRP fabrics to take up the shear forces. S&P C‑Anchors provided reliable anchorage into the slab.
This project highlights the expertise of the S&P specialists in delivering turnkey, innovative, and efficient strengthening solutions that meet even the most demanding boundary conditions and the highest levels of technical complexity.
