The 2010–2011 Canterbury earthquakes in New Zealand revealed (1) improved structural response resulting from historical design advancements, (2) poor structural performance due to previously identi...

https://lib.dr.iastate.edu/cgi/viewcontent.cgi?article=1210&context=ccee_pubs

Understanding Poor Seismic Performance of Concrete Walls and Design Implications

Experimental results gained from quasi-static cyclic tests on 34 slender structural reinforced concrete walls available in the literature are used to examine the shear deformations for displacement demands in the inelastic range. Based on these results the distribution of shear strains within the walls and the variation of shear deformations with top displacements is discussed. It is shown that for shear walls whose shear transfer mechanism is not deteriorating significantly the ratio of shear to flexural deformations remains approximately constant over the entire range of imposed displacement ductilities while for walls whose shear transfer mechanism is degrading significantly the ratio of shear to flexural deformations is increasing. For the former a simple model is proposed which allows estimating the ratio of shear to flexural deformations.

Shear deformations of slender reinforced concrete walls under seismic loading

A three-dimensional nonlinear cyclic model for nonplanar reinforced concrete walls is presented. Nonlinear Euler-Bernoulli fiber-section beam elements are used to represent steel and concrete in the vertical direction, and nonlinear trusses are used to represent the steel and concrete in the horizontal direction and the concrete in the diagonal directions. The model represents the effects of flexure-shear interaction by computing the stress and strains in the horizontal and vertical directions and by considering biaxial effects on the behavior of concrete diagonals and accounts for mesh-size effects. The model is validated by comparing the experimentally measured and numerically computed response of three reinforced concrete T-shape, C-shape, and I-shape section wall specimens, respectively, with the response of the latter two characterized by crushing of the concrete in the diagonal direction. The overall force-deformation and local strain responses are presented. Finally, the computed response u...

Three-Dimensional Cyclic Beam-Truss Model for Nonplanar Reinforced Concrete Walls

Nonlinear line-element modeling of flexural reinforced concrete walls

Although core structures are often used in reinforced concrete buildings as members providing lateral strength and stiffness, experimental and numerical studies on their inelastic behavior are scarce. In an experimental program recently completed at the ETH Zurich, two U-shaped walls were subjected to a bi-directional quasi-static cyclic loading regime. In this article, inelastic wide-column models for these two test units are developed. The wide-column analogy was chosen because it combines the merits of representing the U-shaped wall as a three-dimensional structure with inelastic properties while still being relatively simple and easy to set up when compared to shell or solid element models. It is therefore a tool which is not only available to researchers but also to design engineers. The article commences with the analysis of wide-column models that have been built according to recommendations found in the literature. Since these recommendations had been derived from analyzes of elastic systems, they are then revisited in a sensitivity study in which the effects of different modeling assumptions on the inelastic behavior of wide-column models are investigated. Finally, comparing the numerical results with the experimental evidence from the tests, the article concludes with practical recommendations for setting up wide-column models of U-shaped walls subjected to large inelastic deformations.

Inelastic wide-column models for U-shaped reinforced concrete walls

U-shaped or channel-shaped walls are frequently used as lateral strength providing members in reinforced concrete (RC) buildings since their form does not only provide strength and stiffness in any horizontal direction but is also well suited to accommodate elevator shafts or staircases. Despite this popularity, experimental results on the seismic behavior of U-shaped walls are scarce. For this reason a research program with the objective to provide additional experimental evidence for such walls under seismic loading was developed. It included quasi-static cyclic testing of two U-shaped walls at the structural engineering laboratories of the ETH Zurich. The walls were built at half-scale and designed for high ductility. The main difference between the two walls was their wall thickness. The project was chiefly focusing on the bending behavior in different directions and therefore the walls were subjected to a bi-directional loading regime. This article discusses the design of the test units, the test set...

Mjn Priestley

Papers

Quasi-Static Cyclic Tests of Two U-Shaped Reinforced Concrete Walls