Effect of force-temperature paths on behaviors of reinforced concrete flexural members

Building structures subjected to fire will generally experience complex force-temperature paths. In this paper, these paths are expressed simply by two basic paths: the path of constant forces but subjected to elevated temperature (FT path), and the path of constant temperature but subjected to applying forces (TF path). A total of 13 beam specimens subjected to two such basic paths were tested. The results show that the fire resistance for the FT path is different from that for the TF path; the former is always greater than the latter, and the two are similar only when the temperature exceeds 525°C or thereabout. However, there are always great differences between their deformations. Therefore, the behaviors of reinforced concrete flexural members subjected to fire are closely dependent on the force-temperature paths they experience. Thus, in fire-resistant design, especially for statically indeterminate structures, to more accurately ascertain their fire resistances the force-temperature path factor cannot be neglected.