Numerical investigations on post-fire bond performance of reinforcement in concrete

Author(s): Arunita Das, Josipa Bošnjak, Sharma Akanshu
Paper category: Proceedings
Book title: Proceedings of the International Conference on Sustainable Materials Systems and Structures (SMSS2019) Durability, Monitoring and Repair of Structures
Editor(s): Ana Baričević, Marija Jelčić Rukavina, Domagoj Damjanović, Maurizio Guadagnini
ISBN: 978-2-35158-217-6
e-ISBN: 978-2-35158-218-3
Publisher: RILEM Publications SARL
Publication year: 2019
Pages: 445
Total Pages: 848
Language: English

Abstract: A safe and efficient stress transfer between reinforcement and concrete can take place if adequate bond between them is ensured. Failure of bond between reinforcement and concrete could be controlled by pull-out behaviour (pure bond failure) or premature splitting of concrete. Under normal conditions, bond behavior was extensively investigated and the design guidelines are well-established (EC2, fib MC2010). However, this behavior is relatively less-investigated under fire and post fire scenario. The studies performed so far were mainly limited to the investigations on bond pull-out behavior using confined test conditions at elevated temperature (slow heating). These test conditions don’t replicate the realistic boundary conditions that involve fast heating due to fire, low covers and unconfined setup. Recently the authors have shown that the real conditions could be well-simulated using beam-end-specimen.
In this work, 3D FE numerical studies have been performed to investigate the influence of fire on residual bond capacity using beam-end specimen. A transient three-dimensional thermomechanical model utilizing the temperature dependent microplane model is employed as the constitutive law for concrete. Two heating types are considered to simulate the exposure conditions in a slab and beam, following ISO 834 fire scenario. First the numerical model is validated against the results of the tests performed by the authors. The validated numerical model was then used for parametric studies to investigate the influence of parameters such as concrete-cover, concrete strength, bond length etc. on the effective bond strength. The results clearly show that under realistic conditions of concrete cover, confinement and fire exposure, concrete splitting almost always governs the bond behavior before pull-out due to the irreversible damage caused in concrete owing to high thermal gradients generated during fire and during cooling. These results leads to a strong degradation of the effective bond strength and must be considered in the design recommendations.

Online publication :2019
Publication type : full_text
Public price (Euros) : 00