Office building in Barcelona

Building use

Office building

Country/Region

Spain

Overview

The building serves as headquarter for the Telefonica company and at the same time hosts a public space in the lower portion of the tower. The diamond shape of the building is dictated by the shape of the lot area and by the high visibility that the building would have had if situated on the sharp corner. To reduce the core size as much as possible a tube in tube structure was adopted, with 65% of the horizontal loads carried by the core and 35% by the external grid, connected to the core by the floor slabs.

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

Construction date: 2008-2011
Number of stories: 24+3 below grade
Gross floor area: 33,650m2
Adopted design code: Eurocode
Engineer(s): Idom. MC2 Estudio de Ingeniería
Contractor(s): FCC+Martifer

Issue and/or innovation

The choice of creating a 40 meter tall internal void in the sharp edge of the tower floor plan (also dictated by the little usability of such a narrow floor plan) caused the problem of lateral instability and buckling of the perimetral columns. To prevent this, composite beams (called patio beams in the project) were added to brace the vertical and diagonal beams that form the external loadbearing frame of the tower.

Reason for composite solution

Composite construction was used for the patio beams in order to provide enough strength with a limited-size bracing element that had to match, for architectural reasons, the depth of the floor slabs in the adjacent areas.

Specific solution/technical details

The so called Patio Beams are composed by two C shaped profiles (260mm in height) connected one with the other by a thin bottom plate. The C shaped profiles are formed by welded plates made with S275 steel. A further T-shaped connector is welded on the bottom thin plate. All assembly happens at the workshop while the rebar reinforcement and concreting with HA-30 concrete happens on site. As they are inside the building façade all patio beams had to be protected with a 40mm thick vermiculite layer to achieve a 180m fire rating on the bottom profile. The vertical webs of such element and the top layer are protected with the same thickness but the upper face don’t require any fireproofing thanks to the concrete layer protecting the steel parts. The cross section ranges from 1200mm on the first floor to 760mm to the upper floors as the compression forces on the vertical columns braced by the patio beams decreases progressively.

Impact or effectiveness

The properties of the composite Patio Beam cross section were defined so as to limit its normal horizontal displacements to ic/20, being ic the radius of gyration of the vertical columns that they brace.