Monolith of Murten
In 2000 the Swiss National Exhibition (EXPO) organization approached us about assisting them in the evaluation of the safety aspects of the so-called “Monolith of Murten” exhibition building.
This building had been designed to float on a large number of coupled pontoons, on Lake Murten in Switzerland, in 12 to 15 m of water. The building was to be a regular cube with sides 35 m long. Our work was originally to be an audit of the design work carried out by the engineering office of Emch + Berger in Bern, but later expanded to include a full assessment of the forces and motions of the building in wind and wave conditions such as occur once in every 50 years and, also, a full mooring line assessment.
We first performed a full weight-distribution analyses, hydrostatics and stability calculations for the total floating structure, looking at the effects of a large wind force on the structure and the movement of a large number of people inside the building. We then arranged an agreement with the Maritime Research Laboratory (MARIN) for assisting us in the dynamic motion and mooring force analyses.
The results of all of the calculations carried out led to the result that the motions of the Monolith are relatively small, due mainly to the limited size of lake Murten, with the wave period being no greater than 3.4 seconds.
Considerable discussion ensued concerning the best mooring arrangement and, based on our calculations of the maximum load in each of the many mooring cables of around 270 kN, we were able to assist in defining the best (and cheapest to build) arrangement. A particular factor of great influence on this project was the fact that after the exhibition, at the end of 2002, the total building and mooring system needed to be removed. This necessitated that the costs of the mooring system had to be as small as possible, necessitating that steel cables be used and not anchor chains. To increase the damping of the mooring motions we recommended that these steel cables be weighed down with weights at specific locations.
A jetty was attached to the building and specially-designed catamaran ferries were built to ferry the people from the city of Murten to the Monolith and back. Every trace of the Monolith has now been erased from the lake in accordance with the requirements of the local Canton.