Finding the roots of a technical evolution of architecture at the beginning of the modern period in Iran: examining the late Latif Abolghasemi's hypothesis about the technique of Iranian Jack Arch

The roofing technique called Jack Arch in English that means a brick arched roof on top of steel I-beams, is one of the first special building techniques of Iran's modernization period, which has not been properly researched so far. While recent structural engineers in Iran saw it as a lay technique of no importance, architects have a growing attention toward it. Many years ago, in defense of this technique, the late Latif Abolghasmi (the late professor of Tehran University) has introduced it as an Iranian technology; but his statement was not properly documented by him. This research has investigated the hypothesis proposed by him with a historical interpretation approach. The findings of the research show that this technique has three different origins in the early modern Europe in the nineteenth century: England (Jack Arch), Germany (Prussian arch) and Spain (Catalan roof). The so called Jack arch was introduced for fire proofing of textile factories while the Prussian vault find its origin in traditional water proofing of wooden structures at the level of basement. The catalan vault could be considered as continuation of a traditional system from two separate origin (of Islamic period of Spain or Mexican red Indians). Its entry into the Iranian building construction has two different source: popular origin which was continued from very developed system of vaulting in Iran and engineering origin that introduced in the factories of the first Pahlavi period (mostly by German engineers) and governmental buildings (of English-American engineers). Before the arrival of foreign engineers, this method was common with a wooden beam, and practically a historical intersection has linked it to steel; Therefore, in comparison with the Jack arch, the Iranian counterpart is distinguished from it by construction without form-working; In comparison with Prussian vault, the Iranian type has more elaborated brickwork while from point of view of formwork the German type, is rarely constructed without formwork. The Catalan vault has much more common features with Iranian vault, not only in formworking but also from point of view of mission of the technology; but the catalan vault has no common real history with contemporary Iran as well as its features of brickwork are very simpler than Iranian vault. In addition, thin brick layering (called ‘LaPoush’ in Iran) that is in some catalan vault, is not based on resistance of the brick itself unlike Iranian vault. As a result, Abolghasemi's hypothesis partially confirmed i.e. this technique is not specified to Iran althoug the Iranian type has not foreign origin but the introduction of western engineering catalyzed its development. The main impact of engineers can be pursued in factories where the brickwork is exposed without plastering while in residential works it is flattened and plaster. In addition to the technical superiority of Iranian works, the Iranian type used in popular buildings such as local mosques and trading centers, shows a very fine brickwork as well as elaborated techniques for hiding steel beams that deserve more attention as cultural heritage of early modern era of Iran.