Überprüfung der zusätzlichen Regeln für ∅︁40 mm nach EC2 - Teil 2: Rissbreiten und Oberflächenbewehrung

Checking of additional rules for Ø40 mm according to EC2. Part 2: Crack widths and surface reinforcement

In highly reinforced concrete elements, it might be reasonable to use bars with large bar diameters Ø >32 mm. Only one bar Ø 40 mm (12,56 cm²) can replace the cross section areas 2Ø28 mm, 4Ø20 mm, 8Ø14 mm, 11Ø12 mm, 16Ø10 mm or 25Ø8 mm. Due to the use of large bar diameter, economic advantages but also disadvantages concerning the crack width limitation may occur. Verified rules for the crack width limitation are still missing. Eurocode 2 requires a cross-the-board surface reinforcement with bar diameters Ø = 10 mm to limit crack widths. In a research project, tests were conducted that display the fact that the crack width calculation according to EC2, where large bar diameters and surface reinforcement are considered by an equivalent diameter, gives inadequate results. Based on 60 tensile strength tests and more than 30 000 crack widths measurements, a calculation suggestion was developed that considers the coaction between large bar diameters and surface reinforcement realistically. The research project was carried out together with RWTH Aachen (Prof. Dr.-Ing. Josef Hegger) and the Technical University of Braunschweig (Prof. Dr.-Ing. Martin Empelmann). The results of the work packages "bond behaviour" and "colums" are documented in [1, 2].