Abstract:
In most cases, buildings are constructed in Ethiopia without properly taking into account
the impact of lateral loads due to earthquakes. Design of buildings to earthquakes is not
given appropriate attention, even in areas where the bedrock acceleration has been
reported to be overestimated according to the revised Ethiopian Building Code. This is
evident in Dessie, where the bedrock acceleration (alpha) has increased by fifty percent. This necessitates assessment of the existing buildings – particularly residential buildings –
against their capacity to resist future earthquake events. To assess seismic vulnerability of
the existing residential condominium buildings, those constructed in Dessie town have
been selected for the case study. The objective of this study is to evaluate seismic
vulnerability of condominium buildings constructed in Dessie town for design earthquake.
From the existing condominium buildings in Dessie, six samples (Building Typology
ranging from A to F) were chosen for assessment. Structural, architectural and as-built
structural details were taken from the Amhara Building& Construction Enterprise at
Dessie branch office for modeling purposes. The structural modeling was analyzed &
designed by linear static and nonlinear static pushover analysis using ETABS 2015
engineering software. Furthermore, Damage Limitation limit state and Ultimate Limit
state have been considered for the linear static analysis.
The findings of linear static analysis showed that, of the six typologies taken for study,
only three (Building Typology A, E and F) have adequate capacity to resist damage
limitation earthquake. Further investigation using nonlinear static analysis showed that
only one building (Building Type F) has adequate capacity to life safety (near collapse),
while the other one building (Building Type D) had inadequate capacity i.e. bound
collapse prevention. However, the significant finding was that all building types failed to
pass the assessment for the ultimate limit state; which is a paramount requirement
stipulated in the code.
These building types represented the majority of housing projects that are underway in the
town of Dessie. It was shown that these buildings failed in their adequacy to resist
earthquake loadings. Therefore, there is an urgent need to retrofit the existing buildings
properly to avoid the prospect of catastrophes due to future earthquake events