Seismic risk assessment through non-linear time-history analysis of template buildings in Nepal

: RC with infills and stone masonry

Abstract

The implicit risk of unreinforced template masonry (URM) and reinforced concrete (RC) with masonry infill structures is assessed. Template design is an approach used by non-governmental organisations (NGOs) in developing countries where a single design is replicated at many sites as a method of reducing design and approval costs. Pahar Trust has provided the design of a template RC with infill school and a URM health centre for this research. These structures are used as benchmark cases for assessing the implicit risk to template across Nepal, allowing the assessment of the suitability of the template approach. Implicit risk is the unavoidable seismic risk to a structure built according to local design codes.
A detailed finite element (FE) model of the template RC with infill school is developed, and non-linear time history analysis is used to find the fragility curves for various limit states. These fragility curves are integrated with up-to-date seismic hazard maps to assess the varying risk across Nepal. This showed that the risk values for the code-compliant structure were below threshold values from Europe at all locations across Nepal.
The spectral-based FAST method is adapted and verified for the Nepalese context. The FAST method was initially conceived for Southern European RC buildings with hollow clay brick infills. It is updated for Nepal by reviewing the local code prescriptions, construction practices and material properties for RC masonry infills. The input parameters are updated, and the method is validated using numerical models and a building dataset with damage information from Gorka 2015. The method captures the dominance of the low damage states in the specific Kathmandu neighbourhood considered but still overestimates the overall damage.
Continuous micro-modelling of an unreinforced irregular masonry pier is verified. An FE model of an experimental campaign carried out by (Senaldi et al., 2018) is developed, and the shear capacity of the numerical model is compared to the experimental values. The code-based approach from CNR-DT 212/2013. (2014) is used as a further point of comparison. The comparisons show that continuous micro-modelling can accurately capture the shear capacity and failure mechanism.
Finally, a continuous micro-model of the Pahar Trust template health centre is developed, and NLTHA is used with a cloud analysis to derive fragility curves. An established equivalent SDOF approach is also used for deriving fragility curves as a point of comparison. The risk assessment is then carried out, which shows that the URM health centre exceeds European benchmark risk thresholds in some areas of Nepal. 

Date of Award	27 Sept 2022
Original language	English
Awarding Institution	University of Bristol
Supervisor	Flavia De Luca (Supervisor) & Raffaele De Risi (Supervisor)