Concrete slabs on grade are mainly subjected to mechanical loads and restrained loading. The designer could easily treat mechanical loads by using various tools. Restrained loading caused by restrained shrinkage or thermal movements are, however, often dealt with in a very approximate way. Swedish guidelines have suggested two possible ways to handle restrained loading in steel fibre reinforced concrete (SFRC) slabs. If the ductility of the SFRC is sufficiently high, Losberg's hypothesis stating that restrained stresses vanish as soon as the reinforcement yields is used also for the SFRC slab. Solely mechanical loads have to be treated in the design. Contrary, for lower fibre contents, the SFRC slab is in principle treated as an un-reinforced concrete slab. Here, the effects of mechanical and restrained loads must be combined. The paper describes the Swedish method to compute stresses due to restrained loading. In indoor climate, the restrained shrinkage stresses are predominant. They depend on developed free shrinkage, modulus of elasticity, creep, and the degree of restraint. The degree of restraint is the most difficult parameter to determine, but the guidelines propose different values for different circumstances, e.g., material and treatment of the uppermost layer beneath the concrete slab, joint spacing, slab thickness, and locking effects.
2004. 975-984 p.