Average reinforcement strain in reinforced concrete structures loaded until failure - An experimental study on the effect of reduced interaction and reinforcement ratio on plastic deformation capacity
Examensarbete för masterexamen
Reinforced concrete and its behavior have a significant role in structural engineering. Reinforced concrete structures are usually designed based on Eurocode for static loading which is not sufficient in case of dynamic loading situations such as explosion. For a structure subjected to impulse loading, plastic deformation capacity is of higher importance rather than the load capacity. The regulations provided by the Swedish Fortification Agency, FKR 2011, provides certain design regulation to fulfill requirements for structures subjected to impulse load. According to these regulations for which a revision is needed, average tensile strain of reinforcement at failure is an effective factor representing plastic deformation capacity. The aim of this project was to study the effect of reinforcement amount and decreased interaction between steel and concrete on reinforcement average strain and plastic deformation capacity of reinforced concrete beams subjected to static loading. Therefore, nine beams in three different categories were constructed and subjected to a four-point bending test as: three beams with 10 reinforcement, three beams with 12 reinforcement, and three beams with 12 reinforcement with PVC tubes placed in the middle of the reinforcement to decrease the bond. The number of bars and the dimensions were the same for all beams. Before casting, the reinforcement were marked every 50 mm and then remove after testing to measure the elongation of the bars. Also some bars were 3D scanned as another method to measure the elongation and to analyse the cross-sectional changes. During the tests, the structural response of beams was recorded using Digital Image Correlation (DIC). Although there were some scatter in test results, in general it can be concluded that beams with 12 reinforcement provided a larger plastic deformation capacity compared to beams with 10 reinforcement. Also, application of PVC tubes to reduce the bond between the concrete and the steel resulted in a larger plastic deformation capacity and average reinforcement strain. The utilization rate for strain values was estimated and the reinforcement bars with PVC tubes showed a increase utilization rate.
Reinforced concrete, plastic deformation capacity, average tensile strain , bond interaction, DIC, four-point bending test, FKR