Dottorato in INGEGNERIA STRUTTURALE E GEOTECNICA

Titolo della tesi: Next generation of multi-storey laminated timber buildings to enhance community resilience and sustainability

The impact of catastrophic events like earthquakes and the challenges posed by climate change on the built environment have become of growing concern worldwide. New high-(multi-)performance buildings, relying on advanced technological and sustainable solutions, are necessary to satisfy both the societal expectations of engineered seismic performance and to build up a sustainable building portfolio. Furthermore, enhancing resilience in the built environment requires designing adaptable, flexible buildings that can accommodate evolving societal needs and functions over time, while minimizing disruptions throughout their life cycle. In recent years, the use of engineered timber has garnered increasing attention as a sustainable alternative in the construction sector. It offers a significant reduction in the high environmental impact related to constructions, while providing structural performance that is comparable to traditional materials such as concrete and steel. In addition to the widely used traditional timber structures (e.g., platform-type cross-laminated timber CLT panels), the low-damage post-tensioned timber system (known as Pres-Lam) offers a promising cost-efficient technology for a damage-control approach in building design, using low-carbon modular components. Alongside low-damage advanced façade systems, Pres-Lam has the potential to drive a paradigm shift in building design, promoting a safer, sustainable, energy-efficient, and resilient built environment. Besides the technology employed, the design phase is crucial for optimizing overall building performance. To define a truly high-(multi-)performance building system, all its features and their interdependence must be considered simultaneously. Additionally, effective interdisciplinary collaboration among the various stakeholders involved in the design phase should be supported by user-friendly yet advanced methodologies. Based on these considerations, this Thesis aims to build on the most recent developments for low-damage timber buildings, integrating key aspects such as energy efficiency, architectural flexibility, structural/seismic performance and overall sustainability. An integrated approach is proposed through the development of a multi-performance parametric design/assessment framework for Pres-Lam buildings, leveraging the computational power and intuitive visual programming environment of Grasshopper, along with its various plug-ins. A probabilistic approach is used to evaluate the seismic performance of Pres-Lam frames, expressed as the exceedance of specific damage states, while the building's sustainability and energy efficiency are assessed at the whole-building level, performing the Life-Cycle Assessment methodology and dynamic energy simulations. The framework is validated though different building case-study archetypes, but its parametric and automated nature enables the evaluation of a wide range of solutions, enhancing the early-stage design process. The framework is further extended and refined by incorporating the Multi-Objective Optimization technique, which addresses conflicts among the considered building performances in the search for optimal solutions that ensure architectural flexibility and adaptability, with high seismic performance, and low embodied and operational carbon emissions. The algorithm is able to identify a set of Pareto-optimal solutions, highlighting not only the effectiveness of the proposed methodology, but also the significant potential of Pres-Lam technology in delivering sustainable and resilient buildings across various seismic and climate conditions. Finally, through an Academic-Industry research partnership, a case-study of a Pres-Lam adaptable building in Italy is presented. A real CLT platform-type building is redesigned using the Pres-Lam structural system (in the form of both post-tensioned frames and walls), and its cost is assessed and compared with the original solution through a bill of quantities. The seismic performance is evaluated through numerical analyses, along with the building’s environmental impact and its flexibility to accommodate changes in use. The building is designed at a definitive-design stage, by developing all the constructive details for both the seismic-resistant systems and the gravity-only systems. The detailed design, along with the first-ever cost assessment of a Pres-Lam building in Italy, aims to address the lack of awareness and information about this technology in the country, together with its perceived high costs.