Effect of spalling on predicted temperature gradients and flexural capacity: numerical model

Abstract

Purpose

The paper aims to present an advanced 2 D transient heat transfer analysis capable of accounting for the effect of spalling in terms of amount, location and time. The model accounts for moving thermal boundary conditions to comply with the changing member cross section. The discussed numerical model provides a tool to quantify the effect of spalling on the flexural capacity of reinforced concrete beams.

Design/methodology/approach

The implementation of the presented numerical model in an in-house code and its validation has been discussed. The thermal subroutine has been sequentially coupled with the mechanical subroutine (sectional-analysis) to compute the variation of sectional moment carrying capacity with exposure time.

Findings

The temperatures predicted while considering spalling were in good agreement with experiments available in literature. The presented results also emphasise the importance of considering the time of spalling. The results also show that the fire rating of simply supported beams is also affected by spalling in the compression zone.

Research limitations/implications

It should be acknowledged that the model does not predict spalling, rather is developed as a tool to study the effect of spalling. The model takes the information related to spalling in terms of the location, amount and time, as user input.

Originality/value

The paper quantitatively presents the effect of spalling on the predicted temperature variation across the beam cross section and the moment carrying capacity.

Citation

Lakhani, H. and Hofmann, J. (2020), "Effect of spalling on predicted temperature gradients and flexural capacity: numerical model", Journal of Structural Fire Engineering, Vol. 11 No. 2, pp. 151-165. https://doi.org/10.1108/JSFE-01-2019-0010