Study of stress loss in fibreglass reinforcement under relaxation and creep

Introduction. Stress loss of polymer-composite reinforcement in prestressed concrete is one of the main problems affecting their crack resistance and stiffness. However, to date this issue has not been sufficiently studied. The paper proposes methods for determining losses from relaxation of fibreglass reinforcement, and also provides experimental studies of stress losses in fibreglass reinforcement at different levels of initial tension. The results of the study show the nature of the reduction in forces in fibreglass rods, and the dependences of stress loss over time are also proposed.Materials and methods. The results of the analysis and systematic synthesis of data obtained from domestic and foreign sources on the issues of force loss in prestressed composite rods from relaxation and creep are used as a basis. Based on the results of experimental data, logarithmic dependences of voltage losses over time are proposed.Results. As a result of the experiment, it was possible to record the nature of the change in forces in prestressed fibreglass rods. A logarithmic dependence is well suited to describe the relaxation component of stress losses in a fibreglass rod over time.Conclusions. The study of stress losses in fibreglass reinforcement during relaxation and creep showed that stress losses are most pronounced in the first days after tensioning the reinforcement, with a subsequent decrease in the rate of losses over time. Relaxation losses in fibreglass reinforcement were quantitatively determined based on the experiments conducted, which confirmed that the logarithmic dependence describes well the nature of stress losses in the material. The scientific novelty of the study lies in obtaining experimental data on the relaxation of reinforcement made of domestic fibreglass, which complements existing knowledge and allows us to clarify regulatory documents, such as CP 295.1325800.2017. The practical significance of the work lies in the fact that the results obtained allow us to predict the durability and performance characteristics of structures using fibreglass reinforcement, as well as make adjustments to existing engineering solutions to minimize stress losses. Recommendations for practice include the need for further research to refine the relaxation factors as a function of initial stress and to develop more accurate calculation methods for engineering applications.

polymer composite reinforcement, fibreglass reinforcement, stress losses, relaxation, creep, prestressing