Novel model for the determination of stress redistribution in GFRP reinforced concrete members under long-term compression based on experimental results

Reinforcement bars based on glass fibre reinforced polymers (GFRP) show good mechanical properties and advantageous durability properties compared to conventional steel reinforcement. The increasing use of GFRP reinforcement can, therefore, also be seen against the background of an advised resource-efficient adoption of materials in the construction industry. However, the mechanical properties of GFRP reinforcement are still not sufficiently researched, currently leading to regulatory restrictions. More specifically, regarding the compressive material properties of GFRP reinforcement bars under long-term loading, there is a significant lack of information. This paper introduces a novel model for predicting the stress redistribution in GFRP reinforced concrete members subjected to long-term compression. A comprehensive examination of the mechanical background and a brief summary of existing literature on relevant test results form the basis for the initial development of an extensive test program to be applied. In the first part of the experimental investigations, GFRP reinforcement bars are statically loaded for an experimental period of 1000 hours in order to determine creep rates. Subsequently, GFRP reinforced concrete specimens are subjected to compression for 190 days at three different load levels. The results show a significant stress increase in the GFRP reinforcement due to creep and shrinkage. The high ultimate loads of preloaded specimens demonstrate that the long-term loading did not lead to any damage. The proposed analytical model combines the two parts of the experimental program and provides a practical method for determining the load redistribution in GFRP reinforced concrete members under permanent compressive loading. •Experimental determination of GFRP compressive creep behaviour.•Determination of a GFRP compressive creep model.•Investigation of creep induced GFRP load share to compressive capacity.•Assessment of shrinkage induced GFRP load share to compressive capacity.•Model proposal for the load-redistribution in compressed GFRP RC members.