In 2016, Voortman Steel Construction delivered in cooperation with Rottinghuis’ Aannemingsbedrijf B.V. the first 20 earthquake-proof houses in the province of Groningen (NL). The houses have been structurally strengthened by means of prefab steel structures. After this successful pilot, Rottinghuis and Voortman were assigned for the reinforcement of another 64 houses, divided over 15 housing blocks, last year.
Project manager Marc Staal of Rottinghuis’ Aannemingsbedrijf B.V. points out that the positive experience of the first project is the main reason for choosing Voortman Steel Construction again: “Voortman has the necessary in-house knowledge and expertise for this project. Moreover, they constructively think along with the customer.”
The houses have to meet the highest demands of the Dutch Code of Practice for earthquake-proof construction. The prefab steel structures of the first 35 out of 64 houses have been produced in the same way as the houses in the pilot project. However, recently the advisory body BORG came up with renewed insights, which enable an optimization of the design.
The engineers of Voortman Steel Construction, in cooperation with Rottinghuis, calculated the reinforcement frames using the Dutch Code of Practice. This results in a steel structure which is as flexible as the original design in case of an earthquake and at the same time contains less kilos of steel. As a result, the steel structures are easier to produce and can be mounted more efficiently. Molds are used to produce them. The production of the other 29 housing frames was finished at the end of March.
The assembly of the frames started this week. The steel structure is mounted to the existing carcass of the house. Then the façades, including the steel structures, are completely insulated. After that, the façade elements, the new prefab roof elements and the finishes are mounted. The assembly is done one housing block at a time, in order to fasten the assembly process and limit the inconvenience for the residents to a minimum.
The execution of the project is not, as usual, according to the just-in-time principle, when the assembly order determines the phasing of production. The materials for this project are delivered to a buffer location near the construction site and then sorted for each housing block. This enables us to respond flexibly to any changes in the building process of the housing blocks, so the chance of stagnation during assembly is reduced to zero.
After the structural strengthening the houses meet the Dutch Code of Practice for earthquake-proof construction. They have at the same time been made energy-efficient with solar panels and sustainable installations, so they are now safe, comfortable and future-proof.