Seismic Evaluation of Cost-Effective Houses around Addis Ababa Due to Current Earthquakes in Awash Region (Case Study of Condominium Building)
No Thumbnail Available
Date
2025-09
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Addis Ababa University
Abstract
Ethiopia, particularly the Afar region, has experienced a significant increase in seismic activity, including frequent tremors in the Awash region. This heightened seismic risk necessitates a comprehensive evaluation of seismic performance of buildings, especially low-cost housing structures. Seismic evaluation of constructed buildings is mandatory especially in Ethiopia region where the great east African rift valley crosses our country Ethiopia. Studies shows or predicts that the country Ethiopia inclusive of Africa will bisect into two different continents. Recently starting from September to end of October 2024 unusual weekly repeating earthquakes making its initial (epicenter) from awash region is occurring and the ground shake vibration is felt in 10km radius including in Addis Ababa.
The performance of existing building in seismic evaluation area mainly affected by ground excitation. Ground acceleration is the principal cause of collapse in reinforced concrete structures developed in seismically active zone. This might be owing to either the unanticipated nature of the seismic excitation or due to lack of suitable structural design, detailing and construction. It is mandatory to accurately assess the response of the structure during seismic excitation. Codes are unable to foresee the real-time reaction of structures when it comes to response determination. Therefore, the existing structural performance assessment should be done using a reliable and easily applicable analysis procedure.
The revised Ethiopian building code shows a major change on Ethiopia’s hazard map in terms of peak ground acceleration. The expected peak ground acceleration (from 0.05g to 0.1g) for Addis Ababa [1]. And also incorporate two types of spectra that depends the surface wave magnitude (Type 1 and Type 2) that happen recently earth quick fluctuate in those two ranges. Many buildings have been designed and build in accordance with the previous building code for the past few years. This change has the significant impact on these structures’ performance. Therefor it is necessary to evaluate the effectiveness of the current structures using the revised code’s provisions. Because condominiums are built on a large scale across the nation and are places where people congregate, this study focus on them. Premature failures are not anticipated to occur, according to the study's premise. The main objective of the study is to assess the seismic performance of residential condominium buildings that have been built in Addis Ababa for earthquake design. The existing residential condominium buildings have been chosen for the study.From the existing 40/60 high rise condominium houses located in Addis Ababa, four samples (Building Typology of B+G+7, B+G+9,2B+G+12 and 2B+G+18) were chosen for the assessment. Architectural, structural as built structural detail and some design reports were taken from CITY GOVERNMENT OF ADDIS ABABA SAVING HOUSING HOUSE DEVELOPMENT ENTERPRISE for modeling purposes. The structural modeling was analyzed and designed by linear static and nonlinear static pushover analysis using ETABS 22.0.0 (cracked) Engineering software. Furthermore, damage limitation limit state and ultimate limit state have been considered for the linear static analysis.
Base shear, story displacement, story drift, and design spectra were compared in this study in order to analyze the building; The findings base shear, story displacement and story drift significantly changed as the result of revision but spectrum type in the performance evaluation did not significantly change. Lastly, push over analysis was used to evaluate the case study building's performance level. All four typologies used for the study—Building TypologyB+G+7, B+G+9, 2B+G+12, and 2B+G+18)—had sufficient capacity to withstand damage limiting earthquakes, according to the results of linear static analysis. And going additional investigation on nonlinear static analysis showed Only two structures (structure Type B+G+9 and 2B+G+18) had sufficient capacity to ensure life safety but 2B+G+18 has good performance in Y direction between (A and Io), while the other one building (Building Type B+G+7 and 2B+G+12) had inadequate for IO it is in the range of LS(life safety) near Cp (collapse preventive). But the most important discovery was that every type of building did not pass ultimate limit state evaluation, which is a crucial criterion outlined in the code.
The majority of house construction in the town area is from this construction type and the performance of the buildings against earthquake forces was shown to be poor. Accordingly, it is important to seismically retrofit the existing buildings to mitigate potential disasters to be caused by future earthquakes.
Description
Keywords
Seismic Performance, Pushover Analysis, Plastic Hinge, Fiber Hinge, performance point, Capacity Curve, Demand Curve