ZWANG - Minimum Reinforcement Influence of Thermal Active Curing on Restraint Stresses in the Hardening Phase and Superposition of Deformation Impacts

In the actual design code EN 1992-1-1 the estimation of minimum reinforcement for crack width control of restrained concrete members is regulated with a heuristic approach. The steel stress at taking up the cracking force of the cross section or relevant parts of it is limited. But with the simplification of a restricted view on the cross section, this approach is not able to cover the central problem of deformation impacts. Especially in cases of massive cross sections or large dimensions, where the minimum reinforcement for crack width control is often decisive, this approach provides implausible results and was therefore modified on base of empirical values to avoid uneconomic reinforcements. Altogether this pragmatic approach does not consider essential material properties or the real structural behavior. Especially in watertight constructions this leads to damages due to leakage often. In cooperation with the German Federal Waterways Engineering and Research Institute (BAW) therefore a new design concept based on deformation compatibility is going to be developed. The design model considers real deformation impacts and the real structural behavior when it comes to the restraint condition and the geometry of the construction (see Schlicke, doctoral thesis 2014). Thereby the collaboration of material technology, structural design and on-site construction is promoted. The design model also allows the explicit superposition of restraint stresses due to hardening with restraint stresses during service life. Hence, an economical and safe approach for estimating the minimum reinforcement for crack width control in jointless concrete structures will be established.