A Computational Model for Prestressed Concrete Hollow-Core Slab Under Natural Fire

R Pečenko,I Planinc,S Bratina,T Hozjan

doi:10.1186/s40069-019-0373-9

R Pečenko, I Planinc + Show 2 more

Open Access

https://doi.org/10.1186/s40069-019-0373-9

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Abstract

Performance-based approach, introducing a new two-phase computational model for determining the response of prestressed hollow-core concrete slab exposed to natural fire including heating and cooling phase, is presented. Firstly, the two-dimensional coupled hygro-thermo-chemical model is used to determine time dependent temperature and moisture field in the characteristic cross-section of the concrete hollow-core slab during fire. In addition, the influence of opening on the temperature distribution over prestressed hollow-core concrete slab is accounted for. Secondly, stress–strain state of prestressed concrete hollow-core slab is determined with a newly developed one-dimensional geometrical and material non-linear model, which includes a slip between concrete and tendon. Temperature dependent mechanical properties of concrete, tendon and bond stiffness are accounted for in the model. Model validation showed that the presented two-phase computational model is suitable for the analysis of prestressed hollow-core concrete slab exposed to natural fire. Furthermore, parametric studies revealed that heat exchange between the concrete section and the opening has a significant influence on the development of temperatures in the slab, particularly in the cooling phase, and consequently also on the development of slab displacements. In addition, it was identified that accounting for the slip between concrete and tendon enables the determination of the bond stress distribution and evaluation of the load bearing capacity of the contact.

Highlights

Prestressed hollow-core concrete slab is known as one of the most frequently built-in precast concrete elements nowadays
The main objective of this paper is to present a new developed two-phase numerical model based on the precise physical description of the phenomena occurring in the HC slab during natural fire, providing more accurate determination of fire resistance and response of the HC slab exposed to fire for both heating and cooling phase
5 Conclusions The paper presents a new two-phase numerical model to determine the response of the HC slab exposed to natural fire

Summary

Introduction

Prestressed hollow-core concrete slab (hereinafter HC slab) is known as one of the most frequently built-in precast concrete elements nowadays. In order to consider the influence of moisture transfer and dehydration of chemically bound water on the behaviour of the HC slab in fire, own developed coupled hygro-thermo-chemical model (Hozjan et al 2010; Kolšek et al 2014), adopted from Davie et al (2006), is used in the first phase of the numerical model, where, in addition, the influence of the opening within the HC slab geometry on temperature distribution is considered. In the last section numerical example, model validation and parametric studies are given

Basic Equations of Coupled Hygro‐Thermo‐Chemical Model

Numerical Solution

Numerical Example

Findings

Conclusions