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

This paper introduces general principles and gives analytical clarifications of the stirrups design at ambient condition and shear strength analysis for reinforced concrete (RC) beams at fire condition according to Russian design standards SP 63.13330.2012 (SP 63) and SP 468.1325800.2019 (SP 468), respectively. The calculation method on inclined cross section (ISC) and the simplified approach on normal cross section (NSC) are clarified and developed so that the stirrups configuration can be directly designed at ambient condition and the deterioration of shear strength when the beam is exposed to ISO 834 fire can also be explicitly determined. Calculation results of a case study conducted in the paper show that although there are certain gaps between the designed results of stirrups using ICS and NCS methods, the fire resistances based on shear strength criteria obtained from the two methods are similar. With the systematic nature between the design standards TCVN 5574:2018, SP 63 and SP 468, it is rational to use SP 468 as a reference for RC structural fire design that is compatible with QCVN 06:2021/BXD and TCVN 5574:2018, before any advanced international code is decided to be applied in Vietnam.