Keywords: structural walls, openings, lateral forces, numerical analysis, equivalent static, dynamic linear, dynamic non-linear.

Reinforced concrete shear walls are commonly used as a main resisting system for both gravitational loads and lateral forces due to earthquakes [1]. Plain walls or walls pierced by small openings connected by floor slabs, behave as vertical cantilevers [2]. Several factors may modify the wall cantilever behavior, namely the variation in opening sizes, locations, and shapes. The current study considers the effects of these variations, for vertically aligned openings, on the structural response of the shear walls to seismic forces. For this purpose, numerical analysis was conducted considering the different variations for three methods: (1) equivalent static load, (2) dynamic time-history, and (3) dynamic non-linear.

The walls in the numerical models were represented using three dimensional finite shells and volumetric elements. The material behavior was considered perfectly elastic in the two first methods, and non-linear in the third. The material non-linear stress-strain relationship included some phenomena related to damage under dynamic effects.

The analysis results showed for the different variations the following:

1. Along with the increase in the size of central openings, the plain wall is transformed gradually into a coupled wall system, where the external moment is distributed among the wall piers, and a couple moment is created from the piers axial forces.
2. The lateral displacements of the central openings toward the wall edge decreases as the stiffness of the smallest pier, and consequently its contribution to resisting the lateral forces. Large displacements of the openings may result in early large damage in the smallest pier.
3. The variation in shape with largest opening sides parallel to the lateral force direction, led to an inadequate structural behavior of the system, with an increase in the horizontal wall segment stiffness and decreases in wall pier stiffness. A storey mechanism may be developed.
4. The variation in shape with smallest opening sides parallel to the lateral force direction, led to more adequate structural behaviour than the previous case.
5. The comparison of the elastic and non-linear analysis results showed the similarities of the structural responses of the walls for the different variations in openings. Nevertheless, the magnification of the elastic results to account for non-linear behavior [3], as per the code requirements, proved to be conservative.
6. At higher intensities of seismic forces, significant damage in the wall piers and wall horizontal segment were observed, leading to more important differences between the elastic and non-linear analysis results.

1

B.S. Smith, A. Coull, "Tall Building Structures: Analysis and Design", John wiley and son, Scotland, January 1991.

2

G.G. Penelis, A.J. Kappos, "Earthquake-Resistant Concrete Structures", E & FN Spon, London, 1992.

3

C. Pontirolli, "Comportement au soufle des structure en béton armé, analyse experimentale et modélisation", Thèse de l'ENS Cachan, Cachan, France, 1995.

purchase the full-text of this paper (price £20)

go to the previous paper
go to the next paper
return to the table of contents
return to the book description
purchase this book (price £140 +P&P)