engleski

Problems of vaulting the eastern part of the Gothic cathedral of Zagreb (Croatia)

The cathedral of Zagreb is the most important and the largest Gothic building in Croatia: ca 75 m long, ca 35 m wide, with vaults of the nave and choir spanning 13 m. It was begun in the 13th century, and its last major repair and reconstruction was carried out at the end of the 19th century, following the earthquake in 1880, which caused the collapse of the vault of the choir of the Cathedral. This vault had late Gothic stylistic characteristics, with ribs forming patterns typical of Central-European late Gothic vaults. From the contract of 1647 it is known that this vault was built by master Hans Alberthal "exactly in the form of the old vault" which had collapsed a year before. This was the only vault of the Zagreb cathedral with the late Gothic formal characteristics. All the other vaults of the cathedral were of the quadripartite type, typical of early and high Gothic. Therefore it might be concluded that the choir vault was built later than the other vaults of the cathedral – even later than the vaults of the hall-type nave, constructed in the 15th c. From historical sources it is known that the side apses and the aisles of the eastern part of the cathedral were vaulted by the end of the 13th century, but the completion of the main apse and the choir has not been mentioned in any historical source. Structural analysis discovers serious flaws of the structural concept of the eastern part of the cathedral, which might have caused constructional problems and even collapse of the high vaults of the choir. The eastern part of the building has a basilican section, with the choir higher than the aisles. In this type of structures, the horizontal thrust of the high vaults of the choir is usually assumed by flying buttresses, constructed high up over the aisles. In the preserved structure no traces of vertical substructure of flying buttresses can be observed. Because of the inadequate buttressing system, the attempts of vaulting the high choir must have caused dangerous displacements of the substructure. Maybe that is why the existing choir is relatively low (compared to the usual proportions of Gothic basilican buildings). The constructors of the cathedral, not familiar with Gothic vaulting system, were not able to vault a choir with high clerestory, and therefore constructed a choir lower than planned.

Gothic vaulting system ; buttressing system ; cathedral of Zagreb ; structural flaw ; construction history

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