Abstract

With the introduction of new building products made of planar glued board lamellas, the CLT, the restriction of load-bearing structures to linear and thus additively used load-bearing members was abolished. As a result, new, technically determined boundary conditions for moisture management in the interior of buildings have arisen. Due to the emergence of massive, planar wall and floor components as in concrete construction, the integration of building services technology in timber construction must now take place differently than was traditionally the case. In addition, it can be observed that the damage to building components is increasing, the detection of moisture damage is becoming more difficult and, ultimately, the consequences and risks are not yet foreseeable. The study focuses on the cause-effect relationship of increased water input and uses selected examples to reveal the problem of moisture exposure in the interior of buildings with planar load-bearing structures, the damage mechanisms and direct consequences set in motion. This paper shows the necessity for moisture protection measures in modern timber structures in comparison to traditional ways to construct with timber. It shows where moisture intake with modern structures must be considered and avoided from the engineering perspective in order to minimize the risk of moisture damage.

Abstract

Deep renovation interventions on existing buildings remain currently unattractive due to technical, financial and cultural/social barriers. Now that the European Union 2018 Energy Performance Directive aims to “reach the long-term greenhouse gas emission goal and decarbonize the building stock”, Member States may use their long-term renovation strategies to address risks also related to fire hazards and seismic loads in addition to energy renovation. This opens a wider market for innovative approaches in retrofit of existing buildings. The current paper illustrates the primary outcomes of an ongoing multidisciplinary Horizon 2020 research project (called e-SAFE), tackling the integration of energy, seismic and architectural renovation interventions through an innovative and combinable technological solution, applicable to non-historic RC framed buildings (i.e. built after 1950) and easily adaptable to specific climatic conditions, seismicity levels and other boundary conditions. Hence, the proposed solution will contribute to the de-carbonization of the EU building stock, reducing the occurrence of natural hazards related to climate changes, and, at the same time, to the improvement of the social resilience against earthquakes and to the enhancement of buildings architectural image. The seismic retrofit technology consists in the external application of modular prefabricated Cross Laminated Timber (CLT) panels on the existing perimetral walls. These panels are connected to the beams of two consecutive floors by means of friction dampers and provide additional lateral stiffness and strength to the existing structure, thus reducing the storey drift demand in case of earthquake. The friction dampers cut the force transmitted by the CLT panel to the structure and dissipate energy, which further reduce the drift demand. Strength, stiffness and dissipation capacity provided by the system are controlled by modulating the thickness and the number of CLT panels, as well as the friction dampers size. In this research phase, friction damper prototypes have been designed in order to optimize both mechanical performance and production process. Detailed numerical models allowed to investigate the stress distribution in the dissipative connections. The results of the preliminary testing campaign will be presented and discussed in this paper, also in relation with the findings of the numerical analysis and future tests.