ALBERT

Description: Properly designed wooden truss bridges are environmentally compatible construction systems. The sharp decline in the erection of such structures in the past decades can be led back to the great effort needed for design and production. Digital parametric design and automated prefabrication approaches allow for a substantial improvement of the efficiency of design and manufacturing processes. Thus, if combined with a constructive wood protection following traditional building techniques, highly efficient sustainable structures are the result. The present paper describes the conceptual design for a wooden truss bridge drawn up for the overpass of a two-lane street crossing the university campus of one of Vienna’s main universities. The concept includes the greening of the structure as a shading design element. After an introduction, two Austrian traditional wooden bridges representing a good and a bad example for constructive wood protection are presented, and a state of the art of the production of timber trusses and greening building structures is given as well. The third part consists of the explanation of the boundary conditions for the project. Subsequently, in the fourth part, the conceptual design, including the design concept, the digital parametric design, the optimization, and the automated prefabrication concept, as well as the potential greening concept are discussed, followed by a summary and outlook on future research.

Description: Wooden shingles are a traditional roofing material on many culturally important building artifacts. Currently, the roof space of many traditional buildings is used for residential purposes and, consequently, cold roof constructions with ventilation layers are applied. In this study, it is evaluated whether the moisture content of wooden shingles is adversely affected by such constructions, compared with unvented shingle roofs over cold attics and whether a temporary closing of the ventilation gaps at the eaves contributes to a lower wood moisture content. Various sensors were installed in and around a building with wooden shingles on a ventilated roof and temperature, air moisture, and air speed in the ventilation layer were measured throughout a year. The findings show that the air speed in the ventilation layer can be adjusted from 0.06 to 0.25 m/s depending on the layout of the eaves. A hygrothermal model was applied to evaluate the effects of different ventilation operation modes and cardinal orientations of the roof on the moisture content of the wooden shingles. The results show that roof ventilation results in a 1% lower shingle moisture content on average than an unventilated roof over a cold attic. Finally, it is shown that the wood moisture content repeatedly reaches dangerous levels above 25% throughout a year, which is worse on north-facing roofs and, hence, measures to increase the dry-out are relevant.