Some considerations on shear and torsion in R/C structural members in fire

Abstract

Purpose This study aims to provide a factual justification of the extension to fire conditions of the well-known design models for the calculations of R/C members at the ultimate limit state in shear and torsion. Both solid and thin-walled sections are considered. In the latter case, the little-known topic of shear-transfer mechanisms at high temperature is introduced and discussed. Design/methodology/approach Both the effective-section method and the zone method are treated, as well as the strut-and-tie models required by the analysis of the so-called D zones (discontinuity zones), where heat-enhanced cracking further bears out the phenomenological basis of the models. Findings The increasing role played by the stirrups in shear and by the rather cold concrete core in torsion stand out clearly in fire, while high temperatures rapidly reduce the contributions of such resisting mechanisms as concrete-teeth bending, aggregate interlock and dowel action. Originality/value On the whole, beside quantifying the side contributions of web mechanisms and section core in fire conditions, this study indicates a possible approach to extend to fire the available models on the coupling of shear and bending, and shear and torsion in R/C members.

Failure characteristics of reinforced concrete circular slabs subsequently subjected to fire exposure and static load: An experimental study

“…Therefore, the investigation and understanding of RC structures exposed to fire has always been a challenge. [1][2][3][4][5][6][7][8] Comprehensive experimental research at material level has been carried out in recent decades to test normal-strength concrete (NSC) subjected to elevated temperatures. [9][10][11][12][13][14][15][16][17][18][19][20] The use of high-strength concrete (HSC) has become increasingly popular compared to NSC due to its greater stiffness and strength (70-120 MPa).…”

Calculation of reinforced concrete beams’ shear strengths at ambient and fire conditions according to Russian design standards

“…However, there are only prescriptive rules specified in the Vietnam national code [12] and design standard [7] whereas there is still a need of more rational approaches for the structural fire design for RC structures. Various studies on shear strength of RC structures at elevated temperatures have been published in the world [13][14][15][16][17][18][19][20][21]. However, in the literature of RC structures in fire in Vietnam, there is limited related information since most of them are for RC members under the effects of compression and bending moments [22][23][24][25][26][27][28][29].…”

Shear capacity of indirectly loaded reinforced concrete beams under and after fire exposure

“…To address this shear capacity problem, the structural design of indirectly loaded RC beams usually requires additional transverse reinforcement to strengthen the junction between the primary and secondary beams. However, exposure to high temperatures is well known to have detrimental effects on the mechanical properties of concrete and steel materials, resulting in the severe redistribution of internal forces and deterioration of the capacity of members fabricated using such materials; accordingly, the occurrence of a fire can endanger the safety of an RC building (Bamonte et al, 2018; Dong, 2001; Fu et al, 2018; Gabriela et al, 2018; Kodur and Naser, 2018; Wu, 2003). Upon exposure to fire (such as a common fire on three or four sides), the mechanical properties of the primary beam in the tension zone can be seriously degraded, making the indirect loading mode even more unfavourable and further increasing the risk of shear failure.…”