Analysis of the roof trusses of Centrale Werkplaatsen in Kessel-lo (1863-1922): gradual transition of a traditional timber truss towards a full iron truss

Abstract

The case study of the Kessel-lo train workshops is a good example of new infrastructure that was built to satisfy needs of the booming railway industries in the 19th century. Train bridges, railway stations and maintenance facilities asked for bigger roof spans and the engineers were challenged to find solutions. Before this time period the roofs were supported by traditional timber trusses. Through this search for larger spans and the rush to follow the needs of the railroads, iron found its way in to the construction of trusses. Iron did not immediately take over the dominant position of timber and timber kept being used as a construction material. That is how many hybrid trusses were developed combining timber and iron. Later on iron did fully replace timber. There is however not a lot known about this transition period. One way to get to know more about this time is to look at buildings that were constructed during this transition period. The Kessel-lo workshops are chosen as case study because of their variety of different trusses from different periods. The building complex itself is, as it were, a reflection of this transition. After a detailed historical research to find out what the exact use of the buildings were and if the current structures were original, a structural analysis is carried out. The structural analysis clarified the working principles and load distribution of the trusses. For the structural analysis the same graphic statical methods that were used in the 19th century are applied to the trusses. This method helped to clarify the working principles and load distribution of the trusses. This was necessary to understand the reasoning behind the way the elements were connected and to be critical about the joints. Joinery is a very important aspect in analyzing a truss, if they are not well-designed the truss can fail. The further investigation of the joints and the comparison between historical handbooks showed that iron elements like washers, bolts and cast iron shoes, were commonly used to speed up the assembly of rather traditional truss forms. Because of the scale of the project, these elements could be produced in large amounts thus reducing the unit price of one element. The Howe truss, an advanced version of the traditional king post truss, also had some tension members made out of iron. Next to those traditional forms new forms were also developed. One that could be found in the case study was the Polonceau truss, a truly engineered truss that made use of iron tension rods and timber rafters only. It could be stated that there had been an evolution in the assembly method of this kind of trusses, by comparing the Polonceau trusses from different periods with each other and with the original documents of Polonceau, who invented the truss. The connection elements were simplified during time which demonstrates that the production of those elements was optimized. By analyzing this case it can be concluded that the transition period was rather gradual than drastical since different hybrid trusses were used and even optimized before full iron trusses took over. This research also provides a better insight into the assembly of trusses and how the type of joints evolved from traditional timber joinery to bolted connections.

Date of Award	2017
Original language	English
Awarding Institution	BRUFACE Brussels Faculty of Engineering
Supervisor	Ine Wouters (Promotor) & Louis Vandenabeele (Advisor)