Static and seismic design of one-way and two-way jack arch masonry slabs

Abstract

Steel I-beam, brick jack arch slabs have long been used to floor and roof industrial and residential buildings in many parts of the world. Collapse of a large number of these non-homogeneous one-way slabs during past earthquakes has highlighted their poor seismic performance. However, due to their easy construction together with low cost, the jack-arch slab is still widely used in many countries. In this article, the weaknesses inherent in the traditional one-way jack-arch slabs are explored. To overcome these shortcomings, a new two-way system is proposed. Results of static and dynamic tests on full scale two-way and one-way jack-arch slabs and finite element numerical analyses, aimed at investigating the effectiveness of the proposed two-way system, are presented with favourable conclusions. Following these investigations the static and seismic design of jack arch slabs are discussed. The proposed, allowable stress design method is based on designing for the steel grid and controlling the stresses in brick arches. Parameters necessary for an equivalent static seismic load calculation are first determined. Finite element numerical analyses are then conducted to investigate the effects of a number of parameters on the design of the slab and the necessary design factors are evaluated. In addition, appropriate tables and figures are presented to facilitate the design of the one-way and two-way jack arch slabs. It is concluded that the jack arch slab system, designed and constructed as presented in this article, provides a viable, low cost alternative to other forms of flooring in seismic zones and elsewhere.