Mechanistic Behavior of Historical Masonry Assemblages of Fasil Ghenbe and Structural Response Assessment of Mentwab Castle Under Vertical Loading; A Case Study
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Date
2018-07
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AAU
Abstract
For a country like Ethiopia, one of the pivotal issue, from economic as well as cultural point
of view, is a conservation of heritage buildings. In that regard, understanding the structural
behavior of historical structures is immensely beneficial to design and implement effective
conservation and rehabilitation schemes. A comprehensive structural behavior assessment
requires for a knowledge of the material properties and the use of advanced numerical tools.
This study presents the experimental investigations carried out to characterize the
mechanistic properties, compression and shear, of the historical masonry assemblages of
Fasil Ghenbe with a FE analysis of Mentwab castle under vertical loading.
Replicas of historical masonry wall units were built in Gondar, by a well experienced
masons and by the use of representative construction materials. The construction materials
used for the masonry wall units were basaltic stone, slacked lime aged for six years and
aggregates extracted from traditionally made quick lime. After eight months of their
construction the mockups were tested for shear and compression behaviors. Additionally,
index tests and chemical tests were conducted to characterize the lime mortar.
For the shear test five masonry mockups were tested on a set-up arranged to conduct a triplet
shear test. The tests were executed under three different levels of confinement. For each test
the confinement level or the state of stress (0.1MPa, 0.3MPa, and 0.5MPa) was kept
uniform. As for the compression test, two specimens were tested. In both cases, load versus
displacement behaviors were acquired from the instrumentations used.
The mechanistic nature of the masonry assemblages is characterized for compression and
shear behaviors. Simple model using the Coulomb friction model is proposed for the shear
behavior, using coefficient of friction and cohesion parameters. The compression behavior
is mainly characterized by the peak strength and elastic modulus parameters. The results,
only available experimental data, can serve for the structural analysis of the historical
masonry structures of Gondar, under static loading.
The preliminary structural analysis conducted on Mentwab castle resulted in the static
structural response of the castle under vertical loads only, own weight and loads from the
roof/floor slabs. For this particular loading condition, the resulted stress levels were below
the capacity of the masonry. Above all the numerical analysis is a breakthrough in the
investigation of the historical masonry structures, on a finite element model based study.
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Keywords
Historical Masonry, Assemblages of Fasil Ghenbe, Vertical Loading, Mentwab Castle