External Timber-Based Low-Damage Exoskeleton Systems for Enhanced Structural Safety and Energy Efficiency

Abstract

The European building stock, mostly built post-World War II with no regard to seismic design and energy efficiency principles, is facing significant safety and sustainability challenges. The seismic vulnerability of existing buildings has been further confirmed by recent earthquake disasters, such as L’Aquila 2009, Centre Italy 2016, Turkey & Syria 2023, whereas the energy inefficiency is underscored by high energy consumption rates. An unprecedented effort is therefore required to increase seismic safety while achieving energy savings and decarbonization targets to meet the ambitious goals of the European Green Deal. Although several technical solutions are available in separate engineering domains, it is essential to adopt integrated renovation strategies (i.e., structural and energy efficient), especially when dealing with buildings located in zones with moderate-to-high seismicity. This work explores the application of exoskeleton-type solutions for integrated building renovation. Specifically, external load bearing systems consisting of low-damage timber-based structural members (the so-called Pres-Lam technology), that upgrade the seismic performance by reinforcing existing building. Such a solution is particularly attractive because the renovation interventions are entirely executed from outside the building, thereby reducing occupant disruption and avoiding relocation of inhabitants. This aspect is crucial in motivating owners to choose a combined low-invasive renovation that goes beyond simple energy retrofitting and improves the resilience of the energy upgrades, which on their own could become ineffective after future earthquakes. The proposed exoskeleton system has a dual role of operating as the support for a high-multi-performance “double-skin” facade system that improves the seismic resilience of the existing building and enhances its energy efficiency, thereby proving a holistic renovation. The main goal of this work is to prove the effectiveness of the proposed integrated renovation strategy through an illustrative case study. The overall performance of both the as built/retrofitted structures is assessed by means of seismic and energy analyses. Building on such results, a loss assessment procedure is implemented to quantify the overall economic and environmental impact in the building lifespan. It is found that the proposed strategy enhances the holistic performance of the building with a 54% reduction of the economic losses.