Typological evolution of the "roof as a trussed beam" (a-f) and the "rafter as a trussed beam" (g-i). Sources: Palladio 1650 (a); Demanet 1847 (b); Böhm 1911 (c, d, f & i); Oslet 1890 (e); Denfer 1892 (h); Krafft 1805 (g).

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... architect Palladio illustrated as early as 1570 what is certainly the first known example of a trussed bridge (Timoshenko 1965) (Fig. 3a). By connecting three simple triangular trusses, which he knew were not deformable, he understood that the strength of the whole truss "lies in the fact that each part is supporting each other" (Palladio 1650). To create a pitched roof, a small triangular frame resting on the Palladio truss could be added on top. Such a typology is ...

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... other" (Palladio 1650). To create a pitched roof, a small triangular frame resting on the Palladio truss could be added on top. Such a typology is represented in Demanet's lecture notes (1847), where the 19th-century improvements are clearly introduced: tensioned members are out of wrought iron while the assemblies are ensured by cast iron shoes (Fig. 3b). Because the contribution of the small upper frame to the overall truss' stiffness was unclear, more efficient roof trusses quickly replaced this ...

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... development of economical railway bridges in America during the second quarter of the 19th century had a great influence on European builders. Wellknown examples were illustrated in the literature. For example, the Howe's truss systems used in 1850 for Munich's Propylaea (Fig. 3c). In 1880, a version without all counter members (called "English roof truss" in Germany) was built for Frankfurt's opera house (Fig. 3d) (Böhm 1911). From the 1890s onwards, very efficient structures known as "American trusses" -already in widespread use in iron construction since the 1830s -appeared in the literature available in ...

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... the second quarter of the 19th century had a great influence on European builders. Wellknown examples were illustrated in the literature. For example, the Howe's truss systems used in 1850 for Munich's Propylaea (Fig. 3c). In 1880, a version without all counter members (called "English roof truss" in Germany) was built for Frankfurt's opera house (Fig. 3d) (Böhm 1911). From the 1890s onwards, very efficient structures known as "American trusses" -already in widespread use in iron construction since the 1830s -appeared in the literature available in Belgium and dedicated to timber construction (Fig. 3e). With a very clear structural behaviour, such trusses were ideal for a precise sizing ...

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... counter members (called "English roof truss" in Germany) was built for Frankfurt's opera house (Fig. 3d) (Böhm 1911). From the 1890s onwards, very efficient structures known as "American trusses" -already in widespread use in iron construction since the 1830s -appeared in the literature available in Belgium and dedicated to timber construction (Fig. 3e). With a very clear structural behaviour, such trusses were ideal for a precise sizing of all members.Their tensioned elements were usually connected by mean of iron straps or iron bolts. Sometimes, these members were replaced by iron (Fig. 3f). According to Pauporté (1907), the resulting mixed-trusses were, in the Belgian context of ...

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... since the 1830s -appeared in the literature available in Belgium and dedicated to timber construction (Fig. 3e). With a very clear structural behaviour, such trusses were ideal for a precise sizing of all members.Their tensioned elements were usually connected by mean of iron straps or iron bolts. Sometimes, these members were replaced by iron (Fig. 3f). According to Pauporté (1907), the resulting mixed-trusses were, in the Belgian context of the 1900s, advantageous for roofs spanning 10 to 20 meters. Beyond that, timber trusses were too expensive and too heavy; therefore, full-iron trusses were ...

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... of designing one single truss, another option was to build the rafters as two inclined trusses. This idea was already present in Krafft's treatise (1805) where each rafter was doubled and bounded to the other with perpendicular posts (Fig. 3g). A famous example is the Cirque d'Hiver built in 1852 in Paris, where the technique was applied on a much larger scale (Denfer 1892). The connection between the upper and lower chords was improved by several diagonal bracings which allowed the truss to work as a whole (Fig. 3h). The 19th-century advances in timber engineering are ...

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... rafter was doubled and bounded to the other with perpendicular posts (Fig. 3g). A famous example is the Cirque d'Hiver built in 1852 in Paris, where the technique was applied on a much larger scale (Denfer 1892). The connection between the upper and lower chords was improved by several diagonal bracings which allowed the truss to work as a whole (Fig. 3h). The 19th-century advances in timber engineering are obvious if one compares this last structure to the Dresden's feast hall built in 1900 (Fig. 3i). Each rafter forms a Warren truss made of thin planks which were bolted to the upper and lower ...

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... the technique was applied on a much larger scale (Denfer 1892). The connection between the upper and lower chords was improved by several diagonal bracings which allowed the truss to work as a whole (Fig. 3h). The 19th-century advances in timber engineering are obvious if one compares this last structure to the Dresden's feast hall built in 1900 (Fig. 3i). Each rafter forms a Warren truss made of thin planks which were bolted to the upper and lower ...