Harmonious “Dreiklang” in Aarau

A hospital is coming into being with the help of BIM and MEVA formwork

The hospital building of the Kantonsspital Aarau with a surface area of 145 x 120 m is almost 50 m high and consists of two staggered basements and ten upper floors plus an equipment floor. In future, 472 inpatient beds, 130 places in the day clinic and 18 operating rooms will be available. The hospital will be build in accordance with Minergie P-ECO, the highest building standard presently in use, thus ensuring that high demands on quality, comfort and energy consumption are fulfilled. Once it has been opened in 2026, the plan is to demolish the existing building and to enlarge and redesign the park in the hospital’s grounds.

The building as a whole is called “Dreiklang”, German for the musical term “triad”, as the three main areas form a single harmonious unit. The outpatient clinics are directly connected to the four-storey base with functional areas. On top of this sits a six-storey, square superstructure (75 x 75 m) for the wards.

Tablet computers instead of paper
The building shell was completed in less than two years. Up to 140 people worked on the construction site at the same time and two in-situ concrete plants delivered 62,000 m³ of concrete. 9,300 tons of rebar material and 235,000 m² of formwork were used. This is all the more astonishing as the construction site planning was performed without paper using 3D models by means of building information modelling (BIM). 20 tablet computers were in use on the construction site, thus enabling team supervisors and foremen to access the latest plans at all times. Five “BIM planning huts” spread over the construction site served as information and meeting points.

The Marti employees responsible were very enthusiastic about the improvements achieved with regard to efficiency, precision and communication thanks to the use of BIM. To date, the cantonal hospital is the total contractor’s, i.e. Implenia AG’s, largest project to be implemented using the BIM-to-field method. Approximately 200 submodels were merged to form a single overall model. MEVA was responsible for planning the wall formwork and working platforms and also had a supplementary order for the creation of BIM-compatible models for all the shaft walls. This was achieved together with our partner company BIM².

Strong formwork for strong walls
To construct walls with storey heights up to 5.30 m, Marti used a MEVA formwork system that has already proved its worth during numerous projects performed by the well-known construction company. The high-performance wall formwork system Mammut 350 with a full-surface fresh concrete load capacity of 100 kN/m² allows for short pouring cycles for heights up to 4 m and thus rapid construction progress. The simple assembly with several corner configurations for a variety of floor plans also speeds up the work.

The large-format formwork panels (350/250) with a surface area of 8,75 m² were combined with the SecuritBasic safety system with working platforms. This is easily installed on the Mammut 350 panels using a single part, the flange screw, and, with a load-bearing capacity up to 200 kg/m², guarantees safety throughout the assembly and concrete pouring work.

With support frames below ground level
The basements were partly planned and built using single-sided wall formwork – once again using Mammut 350. The task of safely transferring the concrete pressure via the formwork panels into the foundation was performed by MEVA’s STB 450 support frames. They are the idea solution when pouring against earth walls and the sides of temporary construction pits, and take up large loads in restricted spaces. STB 450 support frames are only 2.45 m deep, fit on every truck, can be stored in a space-saving manner, and can be easily transported by crane or moved on swivel-type castors.

Bespoke shaft platforms

The building has ten stairwell and elevator cores. To enable the work to be performed under comfortable conditions and in accordance with the most stringent safety requirements, two to three – a total of 23 – bespoke shaft platforms were used for each core, in some cases with trailing platforms. They were planned by MEVA and delivered to the construction site as pre-assembled units.

The Dreiklang’s stairwells shine in architectural concrete quality as do the entrance area and other areas of the building that are publicly accessible. Due to offset tie holes, Mammut 350 with its symmetrical tie hole and joint pattern is ideally suited for this purpose and enhances the overall architectural appearance. The system, like all MEVA formwork systems, is equipped with alkus all-plastic facings as standard. These can be cleaned in a resource-conserving manner, repaired on the construction site and are suitable for about 1,500 high-quality applications over the course of their long service life.

Own material and RentalPlus
The material used came mainly from Marti’s own stock. This was supplemented by rental equipment supplied by MEVA Switzerland in Seon. The construction company chose the comprehensive ­RentalPlus package and thus enjoyed costing certainty right from the start, as alongside rental equipment and logistics, this package also includes all other services such as cleaning and repairs.

MEVA systems:

• Mammut 350 wall formwork
• SecuritBasic safety system
• Shaft platforms

Project:
Replacement hospital building “Dreiklang”, Aarau, Switzerland

Total Contractor:
Implenia AG

Contractors:
Marti AG, Zurich, Switzerland

Civil engineer:
WaltGalmarini AG, Zurich, ­Switzerland

Architects:
Burckhardt + Partner AG, wörner traxler richter

Engineering and support:
MEVA Schalungs-Systeme AG, Seon, Switzerland