Non-Rectangular Reinforced Concrete Walls: Assessing Effective Stiffness and Influence of Axial Load Ratio and Eccentricity with Beam-truss Models
(2024) Journal of Earthquake Engineering — (2024)
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- Equivalent lateral forces or response spectrum analyses are regularly employed worldwide to perform seismic design and assessment of buildings, where demand and capacity are expressed in terms of forces. However, most international codes and standards now also include, in addition to these force-based (FB) approaches, alternative and more accurate displacement-based (DB) methods based on static or dynamic nonlinear analyses. Recent research has shown that unsatisfactory estimations of the effective stiffness of vertical lateral-load-resisting members is at the heart of potentially significant inaccuracies in FB approaches, as well as of discrepancies between FB and DB formulations. The enhancement of the accuracy of FB and DB approaches, and their harmonisation, hinges fundamentally around the use of accurate and practice-compatible nonlinear models, for DB approaches, and of reliable effective stiffness estimates, for FB approaches. The effective stiffness is calculated, in most design codes, via factors that reduce the uncracked member stiffness. Most have been derived for rectangular cross-section walls although many key lateral-resisting walls in buildings are non-rectangular, such as core walls. Using the experimental results of a series of walls with varied cross-section geometries, the current research shows that the existing stiffness reduction factors are not applicable to non-rectangular walls. It goes on to assess the ability of nonlinear beam-truss models to, firstly, simulate the response of non-planar walls along their minor and major axes, as well as diagonally, and secondly, to determine the corresponding effective stiffness. Additionally, this research puts forward the effect of the axial load ratio on the effective stiffness of non-planar walls and the equally considerable, although usually neglected, influence of the axial load eccentricity.
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Saraiva Esteves Pacheco De Almeida, J., Payen, B., Hoult, R., & Correia, A. A. (2024). Non-Rectangular Reinforced Concrete Walls: Assessing Effective Stiffness and Influence of Axial Load Ratio and Eccentricity with Beam-truss Models. Journal of Earthquake Engineering. Submitted. https://hdl.handle.net/2078.5/273046 (Original work published 2024)