Design of retaining walls for earthquake action is traditionally performed by limit analysis procedures—notably the classical solution of Mononobe-Okabe and its variants. Fundamental assumptions of these methods are (1) the static nature of seismic excitation, (2) the compliance in sliding and/or rocking of the base of the wall, (3) the shear failure of the backfill and the soil-wall interface, and (4) the prespecified point of application of soil thrust. Given the restrictive nature of these assumptions, alternative solutions based on wave-propagation theory have been developed that do not require failure of the backfill and thereby are applicable to nonyielding walls. Because of the complex mathematics involved, the use of these solutions in practice appears to be limited. A special integration technique inspired from the seminal work of Vlasov and Leontiev is presented, which simplifies the analysis by providing closed-form solutions suitable for practical use.

Malawi is located within the southern branch of the active East African Rift System, where earthquakes of moment magnitude (M_w) 7.0 or greater can occur along major faults. The majority of dwellings in the country are non-engineered unreinforced masonry constructions, built by local artisans with little input from engineers. These constructions are highly vulnerable to seismic events due to poor-quality materials and lack of construction detailing. This study presents a new methodology to assess the seismic fragility curves of typical dwellings located in the Central and Southern Malawi. On-site inspections of buildings are carried out to assess geometrical and structural features of 646 façades, and an experimental campaign is performed to characterise the mechanical properties of local construction materials. The collected data allow the identification of different building typologies in terms of quality of materials and construction techniques. The critical failure modes for each of the inspected façade at their ultimate limit state are evaluated analytically. Damage limit states are defined and adopted to derive simplified Static Push-Over (SPO) curves, transformed into incremental dynamic analysis (IDA) curves by using SPO2IDA. The IDA curves are then used to obtain fragility curves for the specific damage limit states. The fragility curves presented herein are the first to be calculated for these building typologies, based on local data, and unfortunately, they show that buildings in Malawi are far more vulnerable to earthquakes than estimated from previously available international reference data. The fragility curves developed in this study may prove useful for assessing the seismic risk of these building typologies in Malawi and other East African countries.