Comparing alternative flood mitigation strategies for non-engineered masonry structures using Demand and Capacity Factored Design

A closed-form performance-based safety-checking format known as the Demand and Capacity Factored Design (DCFD) is used in order to compare alternative flood mitigation strategies for non-engineered masonry structures. The structural fragility is evaluated by adopting an efficient and simulation-based method yielding the so-called "robust" fragility curve and an associated plus/minus one-standard deviation interval. The structural performance is measured by the (critical) demand to capacity ratio for the weakest element of the weakest wall within the structure, subjected to a combination of hydro-static, hydro-dynamic and accidental debris impact loads. Analogous to the incremental dynamic analysis method proposed for seismic demand assessment, an incremental hydraulic analysis has been implemented in order to monitor the structural performance as a function of increasing water height. In particular, the incremental hydraulic analysis has been employed in order to calculate the critical water height corresponding to a demand to capacity ratio of unity. This procedure has been illustrated for comparative evaluation of the factored demand and factored capacity for the case-study building hypothetically subjected to various flood mitigation strategies. The case-study application focuses on a one-story cement-brick non-engineered building located in Dar es Salaam, Tanzania.