Evaluation of the effective parameters on the behavior of shallow RC shear walls considering soil-structure interaction

Authors
A. Sarvghad Moghadam 1
M. ghanizade
A. Sarvghad Moghadam 1
M. Farzam 2
1 Chairof Structural Engineering Faculty, International Institute of Earthquake Engineering and Seismology
2 Assistant Professor of Structural Engineering Department, Tabriz University
Abstract
Short reinforced concrete shear walls with aspect ratio less than 2 are commonly utilizes in strengthening of low rise structures. These walls demonstrate adequate lateral load strength while they have low ductility comparing with high rise walls with same lengths. Considering typical span length of such a walls– between adjacent column distances -there are no need to motivate all of lateral bearing strength of them and only taking to account a portion of strength will be sufficient for the purpose of strengthening of the structure. In this paper it will be shown that tacking into account the shape and length of foundation and interaction of the soil-structure the ductility of the wall is increased. Furthermore, effect of the soil stiffness on the behavior of the wall is studied.
The short shear wall which has been studied experimentally by the NUPEC of Japan is adopted for numerical simulation by the commercial nonlinear analysis software ATENA 3D. The wall has been subjected to the predefined level of axial load and the increasing cycling lateral deformations. Sensitivity of the behavior of wall to mesh dimensions and the affecting parameters of concrete models such as fracture energy, tension softening and tension stiffening coefficient, shear modulus reduction after cracking, fixed or rotating crack modeling among the other affecting parameters are investigated to verify the model. Because of symmetry only one half of the wall is modeled. Reinforcing bars are modeled discretely taking into account the bond-slip between concrete and bars.
The results of verified model are used to study the sensitivity of a proposed short shear wall by IIESE for strengthening of low rise masonry buildings, to the parameters of length and shape of the footing together with and foundation soil property.
It is shown that with increasing the length of footing, base reaction coefficient and the embedment depth of footing the bearing capacity of shear walls showing rocking behavior is increased but the ductility is decreased. For structures which need a limited level of strength increase or a demanded ductility, the length or embedment length of the footing may choose intentionally to motivate the rocking behavior of foundation.
Short reinforced concrete shear walls with aspect ratio less than 2 are commonly utilizes in strengthening of low rise structures. These walls demonstrate adequate lateral load strength while they have low ductility comparing with high rise walls with same lengths. Considering typical span length of such a walls– between adjacent column distances -there are no need to motivate all of lateral bearing strength of them and only taking to account a portion of strength will be sufficient for the purpose of strengthening of the structure. In this paper it will be shown that tacking into account the shape and length of foundation and interaction of the soil-structure the ductility of the wall is increased. Furthermore, effect of the soil stiffness on the behavior of the wall is studied.
The short shear wall which has been studied experimentally by the NUPEC of Japan is adopted for numerical simulation by the commercial nonlinear analysis software ATENA 3D. The wall has been subjected to the predefined level of axial load and the increasing cycling lateral deformations. Sensitivity of the behavior of wall to mesh dimensions and the affecting parameters of concrete models such as fracture energy, tension softening and tension stiffening coefficient, shear modulus reduction after cracking, fixed or rotating crack modeling among the other affecting parameters are investigated to verify the model. Because of symmetry only one half of the wall is modeled. Reinforcing bars are modeled discretely taking into account the bond-slip between concrete and bars.
The results of verified model are used to study the sensitivity of a proposed short shear wall by IIESE for strengthening of low rise masonry buildings, to the parameters of length and shape of the footing together with and foundation soil property.

Keywords

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. (In Persian)
Modares Civil Engineering journal
Volume 17, Issue 3
September and October 2017
Pages 90-102