# On the Role of Seismic Damage Tolerance on Costs and Life Cycle of CLT Buildings
## 4 Discussion of Results
### Construction Costs and Life Cycle Assessment  
This section reports some observations on the influence of the costs and LCA aspects related to the different structural schemes and types of mechanical connections investigated in this paper. A comparison from an economic point of view of the different structural systems of Group G1 and those of Group G2 requires analyzing many factors, concerning design and technological aspects. All the solutions of Group G1 (designed according to Approach A1 or A2) are particularly massive because the CLT seismic-resistant walls are distributed all over the perimeter and in the inner of the building while few internal partitions are present. Such solutions require a higher number of walls and larger quantities of material, whereas the technology of Group G2 needs few seismic-resistant walls. In addition, non-structural lightweight timber infill panels (or glass facades) are used to close the perimeter of the buildings, as well as internal partitions. As only the structural components are concerned, the weight of timber in cases of Group G1 resulted in being greater than 30% with respect to Group G2. Obviously, this aspect also has an impact on the construction costs involving transportation and installation costs, material and energy used in the production as well as building phases. For the case study herein analyzed, the impact of the costs of the structural system on the total building costs of Group G1 is about 30%, while in the case of the post-tensioned solution (Group  
Figure 12: Construction technologies for CLT buildings: (**a**) platform technology, (**b**) balloon technology. G2) is about 20%. In Figure 13, the total costs of the solutions relative to Groups G1 and G2, with an indication of the impact of costs of the structural elements, are summarized. Furthermore, despite the fact that costs related to the non-structural component are not directly evaluated in this paper, those attributable to Group G2 are surely greater than those relative to Group G1. As far as the LCA is concerned, it measures the environmental impact associated with all stages of a building's Life Cycle, as provided by the International Organization for Standardization ISO 14040 [50] and the European Standard EN 15978 [51]. LCA consists of five different phases, which should be correctly considered to assess the environmental impact of the construction process: processing and extraction, production, packaging and transports, use and end of life (Figure 12). Depending on the type of material, technological features of the buildings, structural behavior after a seismic event (e.g., damage level) and recyclability of materials, different environmental impacts can be achieved. In Figure 14, the impact of the different structural solutions on the LCA is represented through red, blue and black circles. The thickness of the circles indicates the relevance of the impact of the structural solutions on each phase of the Life Cycle. A first consideration concerns the structural solutions of Group G1, where the advantages of Approach A2 with respect to Approach A1 can mainly be referred to as the repairing phase after the seismic event (i.e., use and end of life). In fact, the low damage-based Approach A2, avoiding removal and disposal of damaged CLT walls, reduces demolition and reconstruction costs, material and energy use and pollution due to transport and fabrication. In fact, solutions that provide permanent damage to the connecting zones (e.g., Group 1-A1) require the demolition of the structure involving additional costs. A detailed LCA being out of the scope of this paper, some remarks can be proposed based on the comparative analysis of the design procedures described herein:  
* The structural solution of Group G1 involves higher quantities of structural material than that of Group G2, and consequently high environmental impact on the phases of extraction, production, packaging and transport is expected in the first case (red circles). Figure 13: Comparison between construction costs.