Introduction

One-way slabs

Theoretically, all slabs are two-dimensional systems with bending in two orthogonal directions or two-way bending. In practice, however, some slabs are supported on parallel and continuous (line) supports in one direction only. Figure 8.1(1)a shows a typical slab of this type, in which the line supports take the form of a continuous wall or a girder, which is supported on discrete columns. Note that the coordinate system adopted here is different from that used in the earlier chapters. This is to conform to AS 3600-2009 (the Standard) convention.

If such a slab is subjected to a uniformly distributed load only, then bending mainly occurs in the direction perpendicular to the support – the x-direction in Figure 8.1(l)a. The bending in the y-direction may be ignored. Such a slab is referred to as a one-way slab.

Since bending occurs only in the x-direction, the entire slab structure can be seen as a very wide beam running continuously in the x-direction. For analysis and design, it is convenient to consider a strip of a unit width, for example, one metre. This is illustrated in Figure 8.1(1)b. The strip can be further assumed to be continuous over standard (beam) supports. However, such an assumption is valid only if the column-supported girders are rigid enough to prevent significant bending in the y-direction.