CRC 528-D1 (II): Maintenance and shear strengthening of RC Members
Table of contents
Project data
| Titel | Title SFB 528-D1: Instandsetzung und Verstärkung von Stahlbetonbauteilen für Querkraft | CRC 528-D1: Maintenance and shear strengthening of Reinforced Concrete Members Förderer | Funding Deutsche Forschungsgemeinschaft (DFG) / SFb 528 Zeitraum | Period 01/2006 – 03/2009 Leiter | Project manager Prof. Dr.-Ing. Dr.-Ing. E.h. Manfred Curbach Bearbeiterin | Contributor Dipl.-Ing. Anett Brückner |
Report in the yearbook 2009
Textile Reinforcement for Shear Strengthening
Shear test on a T-beam
Since the average use of engineered structures is from 80 to 100 years, it is not possible to anticipate and predict every type of the use and form of applied load that a structure will undertake during its lifetime. Unplanned loads, as well as inappropriate calculation assumptions; faulty execution of construction work; or environmental factors can lead to the structural damage of members. Rehabilitation or strengthening measures are required if a structure of this age is to be preserved.
Various methods can be used to increase the shear bearing capacity of a structural member. One option is to strengthen by applying textile reinforced concrete (TRC). TRC combines the material properties of steel reinforced shotcrete with the geometric properties of externally bonded reinforcement (EBR). This means that the textile reinforced concrete has properties comparable to reinforced concrete; however, the thickness of the strengthening more closely resembles that of EBR. These minimal layer thicknesses are possible to achieve by the use of non-corrosive reinforcement from AR-glass, carbon, or other high-performance fibres in a fine-grained concrete matrix with a maximum aggregate size of 1 mm. TRC is then applied in alternating layers of fine-grained concrete and textile reinforcement. The thickness of the strengthening is between 1 and 2 cm and is dependent on the amount of reinforcement required.
The experimental research of structural members, with practical, relevant dimensions, has shown that the load-carrying capacity of an RC member can be increased considerably by application of textile reinforced shear strengthening. The strengthening is particularly effective if the textile reinforcement works in conjunction with available steel stirrups. In this case, it is expected that the increase in ultimate load would correspond to the shear resistance of the textile reinforcement added. Compared to unstrengthened RC members, however, the actual increase in load-carrying capacity, relative to the shear resistance is lower since strengthening changes the web stiffness. This can be verified by measuring the deformations of each web surface.
The shear strengthening was anchored outside the compression zone in all tests. Strengthening layer and RC members were connected only by the adhesive tensile bond so as to ascertain the load-carrying capacity of the bond joint. The failure of the adhesive tensile bond was stated by measuring the relative displacements between the web and the applied strengthening layers.