The present work aims to define horizontal joint dimension tolerances for newly proposed prefabricated façade systems for applications in tall cross laminated timber (CLT) buildings based on the compression perpendicular to grain characteristics of the component. This requires a thorough understanding of structural settlement under vertical loads which can vary at each floor height. An experimental program has been carried out with reference to the case of a platform frame building construction, where major perpendicular to grain compression of the floor can occur under high loads. Five-layer CLT specimens have been tested under compression via the application of a line load with steel plate as well as actual CLT wall specimens. Strengthening contribution using full threaded self-tapping wood screws has also been investigated. Results of deformation characteristics have been validated through a non-linear finite element analysis and further elaborated in order to outline implications in the design of a prefabricated façade.
Cross-Laminated Timber is one of the most widely used engineered wood products, thanks to its numerous advantages, among which construction speed is the most appreciated, both by clients and by designers. However, construction scheduling compression refers exclusively to CLT structures, while the rest of the construction process still requires a longer phase to complete vertical enclosures. The aim of the research work presented in this paper is to outline advantages brought about when the degree of envelope prefabrication of tall timber buildings is increased. Results are presented in two sections. The first includes the definition of a case study together with an overview of possible technical details for entirely prefabricated façade solutions, ready to be installed without the need to work via scaffolds. The second deals with construction site management analysis for the case study building, where the determination of specific factors having an influence on time and costs is achieved by varying the prefabrication degree of the various façade configurations and repeating the analysis process. The main findings of this research work demonstrate that comprehensive façade prefabrication allows not only consistent compression of construction scheduling to be achieved, but also for immediate protection of wooden elements from weather agents.
Prefabrication of timber envelope components is a constantly developing research field, which attracts interest from various sectors of expertise thanks to the conspicuous advantages it can confer in terms of resources savings, as well as quality management and safety for all actors involved in the process. The present paper goes through the design of a newly conceived external wall system for tall CLT buildings, entirely preassembled off-site and so able to be installed on his final position via crane, renouncing to scaffolds for the façade completion. This not only allows for the construction phase to speed up but also for immediate protection of loadbearing timber elements from weather agents exposure. The work follows three main phases: the functional analysis and layer definition, component design through bi-dimensional study of joint operating mechanism and tri-dimensional validation of the system. Main author findings outline how success of prefabricated systems and their durability over service life is strongly dependent on the effectiveness of joint design.