A note on the earthquake performance of reinforced concrete shear walls

A great many one and two story buildings as well as many buildings as tall as 10 stories or higher have cast in situ reinforced concrete walls designed to act as shear walls for resisting seismic forces. Allowable design stresses in reinforced concrete shear walls have been increased in recent years in many building codes, although in one major code they have been drastically reduced. Concurrently, modern architectural trends have often resulted in the reduction of certain reserve strength features neglected in seismic design such as "non-structural" panel walls of brick or of reinforced concrete since these elements are often replaced by glass or by insulated metal panels. This, in effect, results in greater applied seismic forces on the shear walls. The frequent elimination of deep spandrel beams in favor of thin slabs which may meet glass or metal walls also tends to increase stresses in the shear walls since the strength and stiffness of the spandrels were often neglected when interior shear walls existed. In summary, it has been the experience in the United States and in many other countries in the world that the effective factor of safety in reinforced concrete shear walled structures has often been substantially reduced for seismic loadings. In many cases, inadequate methods of analysis have neglected critical stresses at boundaries and openings.