Auen school complex, conversion, renovation, and expansion
Frauenfeld, Switzerland
Competition 1st prize 2014
Start of planning 12/2014
Commencement 01/2018
Completion 05/2020
Launch: Gymnasium 11/2019, school complex 08/2020
Auen
School.
Overview
Client
Sekundarschulgemeinde Frauenfeld, Switzerland
Architecture
jessenvollenweider architektur, Basel, Switzerland
Construction Management
Roland Grandits, Architect HTL, Frauenfeld, Switzerland
Awards
Prix Acier 2021 - Swiss prize for steelworks
Team ZPF
Konstantinos Adamakos, Isak Buljubasic, Heike Egli-Erhart, Antje Käser-Wassmer, Franck Mahler, Kata Aletta Orbán, Nico Ros, Robert Vögtlin, Manuel Wehrle
The 1960s Auen school complex in Frauenfeld by architects Barth and Zaugg is an exemplary work from the so-called “Solothurn School” and is listed under “noteworthy post-1959” in the Canton Thurgau Heritage Preservation Office’s reference inventory. The renovation and extension of this complex enhance the pre-existing ensemble and make its original concept perceptible again.
Along the complex’s central axis, three pavilion-like new structures sit between the pre-existing buildings. This “third lane” leads to a densification, in which the ensemble’s original composition is preserved and simultaneously reinforced.
The architecture of the new structures (pavilion, break shelter and bicycle shelter) incorporates the structural logic of the pre-existing buildings. However, as open steel pavilions placed in the open space, they do not have a corporeal presence, but appear primarily as roofs supported by columns. Also to emphasise the relationship between the two new buildings, both pavilions’ steel support structures are on the outside. Consequently, the steel columns are shifted away from the corners and, despite all the similarities, make the different nature of the new structures in comparison to the pre-existing ones apparent.
New structures
Between the pre-existing above-ground buildings from 1967, three single-storey structures were built. These were designed to fit into the site’s grid system.
Pavilion. The pavilion is both a kiosk/bistro for use during breaks and an assembly hall / multi-purpose room. This new structure was designed in the style of the pre-existing buildings, as a steel construction with reinforced-concrete walls. The load-bearing structure consists of slender bend-resistant steel frames that are clamped in sleeve foundations. The frames’ cross-sections are adapted to the flow of forces. The steel structure was delivered to the construction site prefabricated, which enabled construction work to proceed quickly. The pavilion is founded on point foundations. In the area of the underground intermediate structure, loads are transferred to the ground via the intermediate structure’s reinforced-concrete slab, its reinforced-concrete walls and its columns.
Break shelter. The load-bearing structure is the same as that of the pavilion. There is a large opening in the centre. The flow of forces within the frame structure matches that of the assembly-hall building. The roof pane acts like a ring and transfers the horizontal forces. The result is a clear and efficient construction.
Bicycle shelter. The load-bearing structure of the bicycle shelter also matches that of the pavilion.
Intermediate structure. The single-storey intermediate structure in reinforced concrete lies underground and connects the school building Auen 1 with the gymnasium. It accommodates equipment rooms, changing rooms, sanitary facilities etc. The intermediate structure replaces a 1967 connecting structure.
Pre-existing structures
Auen 1. The school building designed by the two architects Alfons Barth and Hans Zaugg, dating back to 1967, has one underground level and three above ground. The load-bearing structure above ground was dimensioned and built by the company Tuchschmid AG from Frauenfeld, using the CROCS system of bend-resistant steel frames. Seismic analysis showed that the steel structure did not need to be made more earthquake-resistant, as the αeff compliance factors are above 1.0. The pre-existing steel structure is very pliant. The more pliant a load-bearing structure, the lower the forces acting on the building elements as a result of earthquakes. Ideally, the load-bearing structure should yield to an earthquake like a spring, so the forces applied to the building elements remain low. The structure was not given extra bracing by adding new walls, but was left pliant.
Gymnasium. The underground third of the gymnasium’s height is in reinforced concrete. Above ground, the gymnasium is a purely steel structure. Transverse bend-resistant steel frames are arranged along the main axes of the steel construction. The columns are clamped within the reinforced-concrete outer walls. The outer transverse frames’ columns are articulated, and the transverse frames are braced by wind braces in the edges of the roof level. The main beams consist of plate girders, the main columns of rolled sections with cross-section class 2, and the frames and auxiliary beams of non-rolled sections with cross-section class 2. The bend-resistant frames and clamped columns brace the structure transversely and longitudinally, respectively. The roof level’s wind braces serve as tilt mounts for the plate girders and transfer wind loads. The gymnasium was extended by adding a main axis, which was structurally designed like the pre-existing bend-resistant frames. Seismic analysis calculations showed the αeff compliance factor of the transverse bend-resistant frames and of the roof bracing to be greater than 1.0, so no earthquake-proofing measures were required. These calculations already took the planned extension of the gymnasium into account.