Office building in Bilbao

IDOM Consulting Engineering Architecture – Spain

Building use

Office building

Country/Region

Spain

Overview

The building is an office tower that occupies the site of a previously planned tall building, that was not built to the excessive costs. The tower is the headquarter for the energy supply company Iberdrola, which occupies 10 floors of the building, while the rest is rented to different tenants.

Basic information (construction date, number of stories, gross floor area, adopted design code, engineer(s), Contractor(s), etc.)

Construction date: 2007-2012
Number of stories: 41
Gross floor area: 50,000m2
Adopted design code: Eurocode
Engineer(s): Idom. Ingeniería y Consultoría, S.A
Contractor(s): UTE. Afer-Fonorte

Issue and/or innovation

Limiting the size of structural elements while maintaining concrete strength values at 45Mpa in Columns and 50MPa in the core.

Reason for composite solution

In the vertical columns, the composite solution was adopted to limit the size of the columns to a reasonable dimension, while keeping reinforced concrete use at 45MPa in the columns. In the core, the reason was connected to the limited size of the lintels, due to the need of large openings. The mechanical resistance of reinforced concrete lintels was not sufficient in the lower portion of the building.

Specific solution/technical details

Columns are formed with composite construction up to a certain floor of the tower. 45Mpa concrete is used in conjunction with heavy sections of S355 steel, ranging from HD 400X818 at the level of foundations to 260×172 at the 17th floor. Above this level columns are in reinforced concrete.
Also the concrete tower features some composite elements, notably in the lintels above the core openings. Below a certain floor level the distortions where not bearable by the simple reinforced concrete lintels, and the embedment of a heavy steel profile that works compositely thanks to shear studs.

Impact or effectiveness

The composite columns have been designed considering that the embedded metal profile exclusively supports the axial force that corresponds to it due to the homogenization of the section, while the reinforced concrete section supports the rest of the axial force and the entire bending moment. To prevent the metal profile from supporting torsion forces, the connections between consecutive sections of metal profile have been designed so that continuity of moments is not allowed in order to simplify the joints, although the existence of total contact at these points. These joints were located 1.50 m above each floor level. The transmission of the axial from the slabs to the metal profiles is carried out by the connectors welded to the profiles under each concrete slab. In the core, the use composite lintels resolved the problems to limit the horizontal deformation of the core and maintain the comfort limits, in addition to supporting the distortion of the profile itself without causing damage to the slabs.