Welcome to Raftsoftware^®

Residential slabs on reactive soil

Design by engineering principles

Developed by RAFTsoftware Pty Ltd with Premier Software Group Pty Ltd

World-first computer program introducing a cost-effective alternative to current practice.

Current practice is to select slab designs prescribed in Australian Standard AS-2870 Residential slabs and footings (1996). The Standard permits alternative design by engineering principles using analysis which allows for an interaction of the structure with some representation of the stiffness of the foundation and the assumed mound shape.

RAFTsoftware^® is based on a major break-through in understanding the true nature of soil-structure interaction. Like "The strength of a chain is that of its weakest link", the strength of a slab is that of its weakest failure mechanism. RAFTsoftware^® identifies the governing failure mechanism of slabs on reactive soil. The program produces a performance chart (as shown to the right) of ultimate strength versus surface movement at which the slab fails. Interpolation of the performance chart determines the design ultimate strength to resist failure at the design surface movement applicable to the building site.

RAFTsoftware^® designed slabs are up to 20% cheaper in material construction costs than standard designs, and up to 50% stronger. The difference in costs is that standard designs rely on concrete with low tensile strength to sustain the flexural stresses in slabs, whereas RAFTsoftware^® designs rely on the much higher tensile strength of reinforcing steel. This saves a lot of concrete and requires only a little extra reinforcing. The difference in strengths is that standard designs provide only the minimum strength to resist cracking, whereas RAFTsoftware^® designs provide the ultimate strength to resist failure.

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