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The scope of this contribution is to provide and analyse a rehabilitation concept for typical brick residential buildings in Nepal damaged after the spring 2015 earthquake of magnitude 7.8. Development workers of Engineers Without Borders Germany travelled the same year to the village of Lurpung, southeast of Kathmandu to inspect damages and recommended primary approaches for the earthquake-resistant reconstruction of residential buildings [1].
A detailed restructuring concept is developed herein based on the aforementioned recommended approaches and optimized in terms of time and cost based on information reflecting site conditions and experience. For this purpose, a horizontal timber bracing has been designed, which consists to a large extent of local existing materials. It is demonstrated that the strengthening can be applied in an area of high seismic activity and to simple quarry stone masonry buildings typical for Nepal.
In a first stage, a detailed FE-model was developed, focusing on a realistic load-bearing behaviour of a representative typical structure. Thereby it is ensured that the most accurate internal forces and stresses can be obtained from the FEM analyses for further verification and retrofitting. Following the modelling, the equivalent static horizontal forces as a result
of the relevant response spectrum are generated using the FE-software. Based on this procedure and with reference to Eurocode EN 1995 [2] for timber structures, the bracing system has been dimensioned for the maximum normal force resulting from the earthquake with a return period of 225 years corresponding to a peak ground acceleration of 0.35g. The considered earthquake reflects the regional seismicity described herein by a respective response spectrum with regard to the seismic provisions of Eurocode EN 1998 [3]. The reduced return period of 225 years compared to 475 years applied in design is selected in order to reflect a more reluctant safety target for existing structures [4]. The respective seismic hazard analysis is taken from Pradhan [5] and Chaulagain [6] and represents site specific conditions.
The improvement of the overall load-bearing behaviour influenced by the bracing, is subsequently checked by verifying the masonry walls using the Eurocode for masonry EN 1996 [7]. The material resistance parameters are taken from local studies and related testing outcomes [8]. The obtained structural analysis results show that wall shear capacity is utilized up to a ratio of 65% and the wall bending capacity is exceeded by 72%. However, when compared with the original building, it can be determined that the mutual floor displacements can be reduced by a factor of up to 4.3 due to the proposed bracing system. Consequently, further retrofitting measures are recommended for the masonry. In that respect lower reliability levels can be of interest since a “discount” in the safety requirements for existing structures, however by fulfilling acceptable human safety levels, is usually unavoidable due to economical constraints.
The contribution leads to the conclusion that by retaining the static replacement system in the form of a truss, but adapting the building materials used, the basic functionality of the xamined system can be provided. Although the FEM calculations have demonstrated satisfactory results further experimental campaigns are necessary to define the material properties of the considered typical building structures with respect to the analysed failure modes. The proposed approach supports efficient design of interventions in post-earthquake phases.
One major issue when considering the effects of climate change is to understand, qualify and quantify how natural hazards and the changing climate will likely impact infrastructure assets and services as it strongly depends on current and future climate variability, location, asset design life, function and condition. So far, there is no well-defined and agreed performance indicator that isolates the effects of climate change for structures. Rather, one can mention some key considerations on how climate change may produce changes of vulnerability due to physical and chemical actions affecting structural durability or changes of the exposure in terms of intensity/frequency of extreme events. This paper considers these two aspects and associated challenges, considering some recent activities of members of the IABSE TG6.1.
The contribution presents a methodological procedure for the management and planning of interventions after earthquake events in small historic centres. Reference is made to the case study of Castelluccio di Norcia, a village in the Apennine Mountains affected by the seismic sequence that hit Central Italy in 2016. The earthquake risk of the area and the damaging events of 2016 are critically reviewed. The implementation of cognitive analysis and the application of advanced survey techniques involving the use of nmanned Aerial Vehicles (UAVs) for the purposes of emergency management and monitoring of damaged areas are analysed. The outcomes, combined with the direct involvement of the local population, represent a complete and integrated approach allowing the definition of a) possible intervention strategies, b) related decision criteria and c) practical recommendations for the reconstruction and regeneration of Castelluccio, and, in general, of small historic centres damaged by catastrophic events.