Revised code provisions for long-term deflection calculations

Serviceability uncertainties in flat slabs

“…Tension stiffening can have a significant effect on member deformations [4] so successful modelling of the Cardington slab was very dependent on assumptions made concerning tension stiffening effects. A brief summary of the approaches used in the codes to accommodate tension stiffening now follows (a more detailed discussion may be found elsewhere [4–10, 12]).…”

“…Research at the Universities of Durham and Leeds [3–8] has indicated that tension stiffening effects decrease much more rapidly than was previously thought, plus there is no recovery on unloading. A consequence of this is that for virtually all situations that were previously regarded as long‐term parameters should be used even when calculating short‐term effects.…”

“…Thus, with Eurcode 2, β = 0.5 is recommended for virtually all situations, whereas with BS 8110, using a stress of 0.55 MPa at the level of the tension steel is usually the most appropriate approach. The TN372 Method was also developed further [4–6] and the revised version now used in ADSEC, known as the TN372 Revised Method (or TN372R for short), is also shown in Fig. 7.…”

“…The floors and the roof of the building were all flat slabs and, soon after construction was completed, the author and colleagues conducted a series of static service load tests on the 6th floor of this building [1, 2]. Since then, considerable research into tension stiffening behaviour of reinforced concrete structural elements has been completed [3–8], which prompted the programme of numerical modelling described in this paper.…”