Assessment of toughness of concrete subject to elevated temperatures from complete load-displacement curve - Part I: General introduction

The fracture and toughness of concrete is significantly influenced by heari ng scenarios, including heating temperature and exposure time; however, inf ormation on the quantitative assessment of the concrete toughness is very l imited. In this paper, six energy-based and deformation-based toughness ind exes were summarized and compared for assessing the concrete toughness. A t wo-portion complete load-displacement relationship containing load, charact eristic displacements, and geometric coefficients was also proposed, and th e physical meanings of these parameters were illustrated. Meanwhile, the ef fect of self-weight of the beam specimen under three-point bending an the c oncrete toughness was considered. In general, the energy-based toughness indexes were more appropriate than t he deformation-based indexes, and toughness indexes covering the whole fail ure process were more appropriate and applicable than those only covering t he ascending branch. In Part II of this paper; the relationships of these p arameters with heating temperature, exposure time, and even curing age will be determined based on the three-point bending tests on preheated concrete beams. Thus, the effects of these influencing factors on the concrete toug hness can be quantitatively assessed by using the six proposed toughness in dexes.