Influence of the Loading Ratio on the Creep Behaviour
To analyse the long-term behaviour of the cracked SFRSCC, the creep coefficient parameter in the creep stage (фС) was calculated by :
where w1t and winst are the long-term crack width and instantaneous crack opening width at the time of loading, respectively, see Fig. 3a.
Figure 5 depicts the variation of the creep coefficient for different loading ratios of Fa/Fcr, see Fig. 3b. This coefficient has increased with the load level ratio. Considering the influence of pre-crack width, the creep coefficient in wcr = 0.5 mm series has increased with the Fa/Fcr at a higher rate than in the case of the series of wcr = 0.3 mm. By considering the micromechanical behaviour of a single fibre, the wcr = 0.5 series was submitted to higher damage level of fibre/matrix interface, which led to a higher increase of the crack opening width under a creep load . This influence was more significant for a load level of 100 %. Therefore, sustained loads near to the maximum instantaneous bearing capacity of the specimen can lead to a significant increase of the creep coefficient values.
Fig. 5 Relationship between the creep coefficient and the loading ratio, Fa/Fcr