Timber-only Structures & Architecture - Exploring the Potential of Using Salvaged Timber and Wooden Nails
By Dr. Ruan Gengmu
Supervised by Fink, Gerhard, Assoc. Prof., Aalto University, Department of Civil Engineering, Finland ; Filz Günther H., Prof., Universität Innsbruck, Austria
Abstract
In light of the serious environmental challenges, it is urgent to ease the current dramatic increase of CO2 emissions. The building sector, as one of the major contributors to global CO2 emissions, is on the move to a more conscious and environmentally compatible thinking. The use of natural resources, short transport, low processing of raw material, and prolonging life cycles of existing building components, are some of the keywords in this context. In this thesis, a concept of timber-only structures and architecture was proposed to explore possible sustainable solutions for future building construction. Specifically, salvaged timber and wooden nails were used as the only material and connector for building structures. This research consists of three main research phases: The first phase was initiated by a pedestrian trail project, which searched for a more cost-efficient and more sustainable solution to replace the traditional trail-making in Finland. The solution was mainly based on two individual parts – (i) an investigation on the wooden nails in terms of usage, nailing arrangements, and structural behavior, and (ii) an investigation on salvaged timber in terms of availability, planar arrangements, and resulting patterns. The outputs from the individual investigations were merged in the trail design, where full-scale prototypes were built up and an exhibition was performed. The second phase rethought the design process of the trail. A systematic review of integrated design concepts was conducted. Inspired by the review, a concept of using feedback loops was proposed to reinterpret the design process of the trail. This feeding-back process also informed a more complex structure to be studied in the following phase. In the third phase, a planar rectangular slide-in reciprocal frame (RF) system was proposed. A systematic investigation was carried out regarding structural performance, assembly logic, possible layouts, and resulting architectural spaces. As a showcase, a canopy was designed and built by applying the outputs from the investigation, and then exhibited to the public. According to the overall process of the exploration using salvaged timber and wooden nails, the concept of timber-only structures and architecture showed its potential in various aspects: (i) wooden nails can provide sufficient load-bearing capacity for structural applications, at least for less-loaded structures or structures with low safety requirements; (ii) salvaged timber brings both structural and aesthetic values for new constructions; (iii) using feedback loops to interpret the building design process can bring more holistic solutions compared to the traditional linear design approach; and (iv) the planar rectangular slide-in RF system brings unique architectural features and structural benefits, but they are associated with large deformations and a brittle failure mode in terms of structural behaviour.