Optimizing Connections for the Reuse of CLT Elements

Abstract

The construction and real estate sector significantly contributes to greenhouse gas emissions and waste generation in Sweden. Replacing heavy CO2-emitting materials like concrete and steel with alternative wood-based products like cross-laminated timber (CLT) can be an effective measure. However, this will result in higher demand for timber, which may increase the challenge in maintaining sustainable forestry. By designing its connections with reuse in mind, a CLT panel could be used in multiple iterations, mitigating the demand and prolonging carbon storage. The objective is to provide overall guidelines for design when reusability is to be considered. To develop an effective connection for the reuse of the CLT panel, interviews were conducted with respondents from the construction industry, and insights regarding reusability and its practical application were gained. Furthermore, a parametric study was performed to find how different connection configurations affect the governing failure mode. The connection type and kind of fastener were found to have the greatest impact on reusability. Screws with larger diameter in a bracket configuration is preferable compared to long construction screws and nails if reuse of the CLT panel is intended. Moreover, to ease disassembly, the connection must be designed to fail in the bracket and not in the timber or the fasteners. From the parametric study it was found that the aspect of rope effect in screws have a large impact on governing failure modes in some cases, highlighting the importance of its consideration. With this knowledge, a genetic algorithm (GA) was constructed to obtain optimized connections, with regard to cost and reusability.